Digital chest drainage is better than traditional chest drainage following pulmonary surgery: a meta-analysis

Digital chest drainage is better than traditional chest drainage following pulmonary surgery: a... Abstract In this systematic review with meta-analysis, we sought to determine the current strength of evidence for or against digital and traditional chest drainage systems following pulmonary surgery with regards to hard clinical end points and cost-effectiveness. PubMed, EMBASE and Web of Science were searched from their inception to 31 July 2017. The weighted mean difference (WMD) and the risk ratio were used for continuous and dichotomous outcomes, respectively, each with 95% confidence intervals (CIs). The heterogeneity and risk of bias were also assessed. A total of 10 randomized controlled trials enrolling 1268 patients were included in this study. Overall, digital chest drainage reduced the duration of chest tube placement (WMD −0.72 days; 95% CI −1.03 to −0.40; P < 0.001), length of hospital stay (WMD −0.97 days; 95% CI −1.46 to −0.48; P < 0.001), air leak duration (WMD −0.95 days; 95% CI −1.51 to 0.39; P < 0.001), and postoperative cost (WMD −443.16 euros; 95% CI −747.60 to −138.73; P = 0.004). However, the effect differences between the 2 groups were not significant for the duration of a prolonged air leak and the percentage of patients discharged home on a device. The stability of these studies was strong. No publication bias was detected. It may be necessary to use a digital chest drainage system for patients who underwent pulmonary surgery to reduce the duration of chest tube placement, length of hospital stay and air leak duration. Chest drainage , Digital drainage , Traditional drainage , Pulmonary surgery INTRODUCTION Air leakage is one of the most common complications after pulmonary surgery, affecting both the patient’s quality of life and hospital costs [1, 2]. Despite preventive measures such as fissureless surgery [3], fibrin sealants [4] and buttressing the incision with staples [5], about 20% of pulmonary surgical patients still have postoperative air leaks [6]. Therefore, the choice of chest drainage system is important for postoperative success [7]. Currently used systems include the conventional water seal, suction [8] and a combination of the water seal and suction [9]. These are controlled by a traditional analogue system or a digital monitoring system [10]. In the past, the measurement and assessment of an air leak relied mainly on a traditional chest drainage system [11]. Since the first digital drainage system with continuous air leak monitoring was introduced in 2007 [12], several companies have manufactured new chest drainage systems [13]. However, it is unclear if it is better to use a digital or a traditional drainage system to reduce air leaks. To answer this question, we focused on postoperative results including duration of chest tube placement, hospital stay, duration of air leak, postoperative costs, occurrence of prolonged air leak (PAL) and percentage of patients discharged on a device. MATERIALS AND METHODS Information sources We used the PubMed, EMBASE and Web of Science databases (through 31 July 2017). Search strategy Two researchers independently conducted a search with the following terms: ‘pulmonary surgery’ ‘lung surgery’ ‘video-assisted thoracic surgery’ ‘lobectomy’ ‘sublobectomy’ ‘lung resection’ ‘pulmonary resection’ ‘thoracic surgery’ ‘segmentectomy’ or ‘wedge resection’ and ‘chest drain’ ‘chest tube’ ‘chest drainage’ ‘drainage system’. The language was restricted to English. Both researchers also manually found papers referenced by eligible papers to identify potential eligible studies. Eligibility criteria The inclusion criteria were (i) randomized controlled trials (RCTs); (ii) participants of the RCTs had undergone pulmonary surgery; and (iii) the studies compared postoperative outcomes. The studies were excluded if they met one of the following criteria: (i) were reviews, letters, case reports, animal experiments and conference abstracts; (ii) the patients did not undergo surgery; (iii) essential basic information was incomplete; (iv) the article was not written in English. Two independent reviewers assessed the suitability of studies based on the inclusion and exclusion criteria. Any disagreement was solved through discussion, and if necessary, by arbitration by a third party. Data items The following data items were collected from each study: the first author, publication year, country, ethnicity, enrolled year, participants’ characteristics, disease type, surgery type, number of chest tubes, tube removal criteria and postoperative data including air leak duration, duration of chest tube placement, length of hospital stay, postoperative cost, occurrence of PAL and discharged on device and complications. Data collection process Two independent reviewers extracted the data. When there was disagreement regarding data, a third reviewer checked the data and made the final decision. From each study, we extracted patient characteristics, study design and outcomes. The PRISMA flow diagram of literature retrieval is shown in Fig. 1. Figure 1: View largeDownload slide The PRISMA flow diagram of literature retrieved. Figure 1: View largeDownload slide The PRISMA flow diagram of literature retrieved. Risk of bias in individual studies Included studies were assessed with the Risk of Bias Tool found in the Cochrane Handbook for Systemic Reviews of Interventions [14]. The characteristics assessed included sequence generation and concealment of allocation (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessors (detection bias), incomplete outcome data addressed (attrition bias), freedom from selective reporting (reporting bias) and other biases. This work was independently assessed by 2 reviewers (J.Z. and M.L.). When there were disagreements regarding the risk of bias, a third reviewer checked the data and made the final decision. Summary measures The main summary measures were the weighted mean difference (WMD) for duration of chest tube placement and length of hospital stay. For each summary measure, we calculated the 95% confidence interval (CI) and P-values (considered statistically significant when P < 0.05). Synthesis of results We used Cochran’s Q statistics and I2 statistics to characterize the heterogeneity of the included studies. If I2 was >50%, we would synthesize these data with the random effect model; otherwise, we used the fixed effect model. Subgroup analyses were performed to identify and explain the potential heterogeneity of the studies, including age (less than or over 60 years old), the digital drainage system types (Thopaz or Digivent or Drentech) and number of chest tubes (1 or 2). Risk of bias across studies To assess publication bias, a funnel plot was generated for each outcome and statistically assessed by Begg’s test. All statistical analyses were performed by Review Manager V.5.3 (The Cochrane Collaboration, Software Update, Oxford, UK). Sensitivity analysis We investigated the influence of a single study on the overall effect—by sequentially removing 1 study at a time—to test the robustness of the main results, allowing us to verify whether any study had an excessive influence on the overall results. RESULTS Study selection A total of 2994 articles were identified, of which 10 RCTs [15–24] were included with 1268 participants. Study characteristics A total of 1268 patients were included in 10 RCTs published between 2008 and 2017, with sample sizes ranging from 31 to 381. The ages of the participants ranged from 17 to 70 years. All recruited patients underwent pulmonary surgery for lung cancer, spontaneous pneumothorax or other lung diseases. The major types of surgical procedures were lobectomy, wedge resection and segmentectomy. Only Jablonski et al. [22] mentioned pleurectomy and lung resection. One or 2 tubes were applied in the different trials. There were 3 main brands of digital chest drainage systems: Thopaz® (Medela AG, Baar, Switzerland), Drentech® (REDAX, Mirandola, Italy) and Digivent® (Millicore AB, Danderyd, Sweden). Traditional chest drainage systems included Pleur-evac A-6002-08 (Teleflex Inc., Research Triangle Park, NC, USA) and Thora-Seal® (Covidien, Mansfield, MA, USA). The major criteria for the removal of the chest tube were no air leak detected and abnormal findings on a chest radiograph (sufficient lung expansion was shown); however, the drainage volume threshold varied among the studies. The compared outcome parameters comprised duration of chest tube placement, length of hospital stay, air leak duration, occurrence of PAL, postoperative cost, occurrence of patients discharged home on device and complications. The main characteristics of the 10 RCTs are presented in Table 1. Table 1: Main characteristics of the randomized controlled trials included in the study Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  EPR: elective pulmonary resection; NA: unavailable; NCT: number of chest tubes; SP: spontaneous pneumothorax. Table 1: Main characteristics of the randomized controlled trials included in the study Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  EPR: elective pulmonary resection; NA: unavailable; NCT: number of chest tubes; SP: spontaneous pneumothorax. Risk of bias across studies Two independent investigators assessed the risk of bias of the included studies. Seven of the 10 articles contained a low risk of bias in every aspect assessed. Cho et al. [18] had an unclear risk of bias for sequence generation. Filosso et al. [20] had an unclear risk of bias for sequence generation and concealment of allocation. Jablonski et al. [22] had an unclear risk of bias for sequence generation, concealment of allocation and incomplete outcome data addressed. The results of analyses of the risk of bias of the included studies are shown in Table 2 and Fig. 2. Table 2: Assessment of risk of bias Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Table 2: Assessment of risk of bias Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Figure 2: View largeDownload slide Assessment of risk of bias. (A) Graph of the risk of bias for the included studies; (B) graph of the risk of bias summary for the included studies. Figure 2: View largeDownload slide Assessment of risk of bias. (A) Graph of the risk of bias for the included studies; (B) graph of the risk of bias summary for the included studies. Synthesis of results Duration of chest tube placement Ten studies measured the duration of chest tube placement (chest tube duration) with 642 individuals having digital chest drainage systems whereas 626 were connected to traditional chest drainage systems. Patients with digital chest drainage systems had significantly shorter chest tube durations (WMD −0.72 days; 95% CI −1.03 to −0.40; P < 0.001) (Fig. 3). Figure 3: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on duration of chest tube placement (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Figure 3: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on duration of chest tube placement (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Length of hospital stay Nine studies measured the length of hospital stay, with 612 patients on digital chest drainage systems and 597 on traditional chest drainage systems. Patients who were on a digital chest drainage system had significantly shorter hospital stays (WMD −0.97 days; 95% CI −1.46 to −0.48; P < 0.001) (Fig. 4). In subgroup analyses, we found that digital devices reduced the length of hospital stay of patients who underwent lung resection (WMD −0.87 days; 95% CI −1.37 to 0.36; P < 0.001). Figure 4: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on length of hospital stay (weighted mean difference). Figure 4: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on length of hospital stay (weighted mean difference). Air leak duration Three studies measured the duration air leaks, with 316 patients on digital chest drainage systems and 309 patients on traditional chest drainage systems. Digital chest drainage systems were associated with shorter durations of air leaks (WMD −0.95 days; 95% CI −1.51 to −0.39; P < 0.001) (Fig. 5). No significant differences were observed in the subgroup analyses. Figure 5: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on air leak duration (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Figure 5: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on air leak duration (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Occurrence of prolonged air leak Three studies assessed the effect of the digital drainage system on the occurrence of a PAL, which was defined as a persistent air leak for more than 5 days. The difference between the effects of the digital and the traditional drainage systems on the occurrence of PAL is inconclusive (risk ratio 0.36; 95% CI 0.04–3.17; P = 0.36), and no meaningful discoveries were observed in the subgroup analyses. Postoperative cost Two studies comprising 219 patients measured postoperative costs. Digital chest drainage may significantly lower postoperative cost (WMD −443.16 euro; 95% CI −747.60 to −138.73; P = 0.004). Patients discharged home on a device Three studies measured the number of patients discharged home on a device: a total of 147 individuals were on digital drainage systems whereas 143 individuals were on traditional drainage systems. Results indicated that the difference between the 2 groups was not significant (risk ratio 0.67; 95% CI 0.25–1.79; P = 0.43; I2 0%). Other: percent air leak on postoperative days 1, 2 and 3 To identify any other factors that may affect the prognosis, we looked at the percentage of the occurrence of an air leak on postoperative days 1, 2 and 3. However, we found no significant difference among them. All of the main results of our analysis are shown in Table 3. Table 3: Main results of our analysis Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  CI: confidence interval; P-value: P-value of overall effect; P.H: P-value of heterogeneity; PAL: prolonged air leak; RR: risk ratio; WMD: weighted mean difference. Table 3: Main results of our analysis Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  CI: confidence interval; P-value: P-value of overall effect; P.H: P-value of heterogeneity; PAL: prolonged air leak; RR: risk ratio; WMD: weighted mean difference. Sensitivity analysis and publication bias From derived forest plots, we did not notice any outcomes out of the estimated range, and no significant results were identified in sensitivity analyses. Furthermore, we found no significant publication bias by visual inspection of the funnel plot and Begg’s test. DISCUSSION Summary of evidence Our meta-analysis showed that, compared to the use of analogue drainage systems, the use of digital drainage systems following pulmonary surgery is associated with a shorter duration of chest tube placement, air leak duration and hospital stay and lower postoperative costs. However, there was no significant difference regarding occurrence of pronged air leak, air leak on postoperative day 1, 2 or 3 or percentage of patients discharged with a device. Reasons for using a digital chest drainage system Digital drainage systems have several benefits over traditional systems. First, they allow continuous recording of air leaks [25, 26]. An abundance of well-recorded data enhances medical research in this field [27, 28]. Second, digital devices decrease the variability caused by physician judgments regarding when a chest tube should be removed [10]. Third, digital chest drains provide precise, stable negative pressure without the influence of position changes or obstruction of tubes. Fourth, digital devices maintain a stable intrathoracic pressure more effectively. Fifth, digital drainage systems, especially the Thopaz (Medela AG), are portable and quiet. Patients with a non-complicated pneumothorax can be discharged earlier if they are placed on this system (compared to traditional systems) [29, 30]. Adoption of the digital chest drainage system: perspectives from China Physicians have been slow to adopt the digital drainage systems. There are several possible reasons. The first is the large number of choices and the lack of clear guidelines for when to use each system. Price is another factor. Resistance to change by medical personnel is also a possible reason. We think that, with the eventual development of clinical guidelines, digital drainage systems may be used more widely. Grouping and chest tube management of the enrolled trials In the enrolled RCTs, patients were randomized by computer-generated criteria to receive either a digital drainage system or a traditional drainage system. The following variables were recorded: postoperative air leak, chest tube duration, air leak duration and length of hospital stay. The application of suction varied among the studies. If the volume of drainage reached the threshold, a chest radiograph would be performed. Chest tubes were removed if the chest radiograph showed evidence of sufficient lung expansion. The decisions about removal were made mainly by 2 surgeons in charge who were blinded to each other. In the traditional group, they removed tubes based on no detectable air in the drainage system, drainage volume for 24 h and a chest radiograph. For those on the digital system, the surgeons focused on duration of no air leak, drainage volume and evidence from the chest radiograph. Supplementary information from papers that were not included Varela et al. [10] enrolled 61 patients for pulmonary resection and randomly assigned patients to digital or traditional chest drainage systems. We did not use the study because its results were based on the variability of drainage management, not postoperative outcome. Furthermore, it contained no information about postoperative outcomes such as duration of air leak. Rodriguez et al. [31] enrolled 100 patients undergoing lung resection to conduct a prospective observational study and concluded that traditional drainage systems based on clinical variables and visual scoring of pleural air leak had a reasonably good performance in predicting the occurrence of PAL. There was no comparison group on digital systems. We thought that the limited number of patients and the selection bias in enrolling participants were reasons not to include this study in our analysis. Deng et al. [32] recently performed a systematic review and meta-analysis, focusing on the management of the chest tube after video-assisted thoracic surgery. They also analysed the effects of a digital drainage system on reducing air leaks. We noticed some limitations. First, the inclusion criteria were not correct. They included 7 RCTs to identify the effects of the digital drainage system in total; however, we found some of them were not RCTs. Second, the risk of bias of their studies was not analysed, subgroup analyses were not performed and sensitivity analysis to identify potential heterogeneity was not done. Finally, we used more parameters than they did to assess the effects of the digital drainage system, such as postoperative cost and the occurrence of PAL. In addition, our search was more current (January 2016 versus July 2017). Strengths The strengths of the present research included (i) promising results found between digital and traditional chest drainage systems regarding chest tube duration, hospital stay and air leak duration; (ii) further discussion about the differences between the 2 drainage systems and analyses for adoption by Chinese physicians; (iii) clear inclusion and exclusion criteria, careful screening of studies, independent collection of data, complete assessment of studies quality and reliable tests to identify heterogeneity. Limitations of research and risk of bias We assessed the risk of bias for each study and found some unclear risks of bias. We included 1 study that used ‘pleurectomy and lung resection’ whereas other RCTs only focused on lung resection. The differences in types of surgical procedures, types of digital and traditional drainage systems and criteria for chest tube removal among the RCTs make the data heterogeneous. The articles did not contain enough information about postoperative outcomes. For example, few studies reported detailed data concerning the risk of complications, so we were not able to make further analyses about this topic. There were not enough samples in our analysis for some data items. Our meta-analysis did not include all of the 10 studies for every outcome parameter investigated. Consequently, the number of the patients analysed for the meta-analysis varied greatly for each outcome, generally comprising only a fraction of the whole study population. To consider chest tube duration, we selected 10 studies enrolling 1268 participants, whereas only 2 studies contained information about postoperative cost. CONCLUSION In light of the results of this meta-analysis, it might be necessary to use a digital chest drainage system for patients who undergo pulmonary surgery to reduce the duration of chest tube placement, hospital stay and air leak duration. However, the difference in the effect between the 2 chest drainage systems is inconclusive with respect to occurrence of PAL and patients discharged home on a device. Further studies are needed. ACKNOWLEDGMENTS We give sincere thanks to Hong Xie from the international office of West China School of Medicine, Sichuan University, Chengdu, China, for her help with the English language editing of this manuscript. Funding This work was supported by the National Natural Science Foundation of China [No. 81172236 and No. 81372505] and the Key Science and Technology Program of Sichuan Province, China [2013SZ0005, 2014SZ0148, 2016FZ0118 to L.L.]. Conflict of interest: none declared. REFERENCES 1 Varela G, Jimenez MF, Novoa N, Aranda JL. Estimating hospital costs attributable to prolonged air leak in pulmonary lobectomy. Eur J Cardiothorac Surg  2005; 27: 329– 33. Google Scholar CrossRef Search ADS PubMed  2 Burt BM, Shrager JB. The prevention and management of air leaks following pulmonary resection. Thorac Surg Clin  2015; 25: 411– 19. Google Scholar CrossRef Search ADS PubMed  3 Stamenovic D, Bostanci K, Messerschmidt A, Jahn T, Schneider T. Fissureless fissure-last video-assisted thoracoscopic lobectomy for all lung lobes: a better alternative to decrease the incidence of prolonged air leak? Eur J Cardiothorac Surg  2016; 50: 118– 23. 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Digital chest drainage is better than traditional chest drainage following pulmonary surgery: a meta-analysis

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1010-7940
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1873-734X
D.O.I.
10.1093/ejcts/ezy141
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Abstract

Abstract In this systematic review with meta-analysis, we sought to determine the current strength of evidence for or against digital and traditional chest drainage systems following pulmonary surgery with regards to hard clinical end points and cost-effectiveness. PubMed, EMBASE and Web of Science were searched from their inception to 31 July 2017. The weighted mean difference (WMD) and the risk ratio were used for continuous and dichotomous outcomes, respectively, each with 95% confidence intervals (CIs). The heterogeneity and risk of bias were also assessed. A total of 10 randomized controlled trials enrolling 1268 patients were included in this study. Overall, digital chest drainage reduced the duration of chest tube placement (WMD −0.72 days; 95% CI −1.03 to −0.40; P < 0.001), length of hospital stay (WMD −0.97 days; 95% CI −1.46 to −0.48; P < 0.001), air leak duration (WMD −0.95 days; 95% CI −1.51 to 0.39; P < 0.001), and postoperative cost (WMD −443.16 euros; 95% CI −747.60 to −138.73; P = 0.004). However, the effect differences between the 2 groups were not significant for the duration of a prolonged air leak and the percentage of patients discharged home on a device. The stability of these studies was strong. No publication bias was detected. It may be necessary to use a digital chest drainage system for patients who underwent pulmonary surgery to reduce the duration of chest tube placement, length of hospital stay and air leak duration. Chest drainage , Digital drainage , Traditional drainage , Pulmonary surgery INTRODUCTION Air leakage is one of the most common complications after pulmonary surgery, affecting both the patient’s quality of life and hospital costs [1, 2]. Despite preventive measures such as fissureless surgery [3], fibrin sealants [4] and buttressing the incision with staples [5], about 20% of pulmonary surgical patients still have postoperative air leaks [6]. Therefore, the choice of chest drainage system is important for postoperative success [7]. Currently used systems include the conventional water seal, suction [8] and a combination of the water seal and suction [9]. These are controlled by a traditional analogue system or a digital monitoring system [10]. In the past, the measurement and assessment of an air leak relied mainly on a traditional chest drainage system [11]. Since the first digital drainage system with continuous air leak monitoring was introduced in 2007 [12], several companies have manufactured new chest drainage systems [13]. However, it is unclear if it is better to use a digital or a traditional drainage system to reduce air leaks. To answer this question, we focused on postoperative results including duration of chest tube placement, hospital stay, duration of air leak, postoperative costs, occurrence of prolonged air leak (PAL) and percentage of patients discharged on a device. MATERIALS AND METHODS Information sources We used the PubMed, EMBASE and Web of Science databases (through 31 July 2017). Search strategy Two researchers independently conducted a search with the following terms: ‘pulmonary surgery’ ‘lung surgery’ ‘video-assisted thoracic surgery’ ‘lobectomy’ ‘sublobectomy’ ‘lung resection’ ‘pulmonary resection’ ‘thoracic surgery’ ‘segmentectomy’ or ‘wedge resection’ and ‘chest drain’ ‘chest tube’ ‘chest drainage’ ‘drainage system’. The language was restricted to English. Both researchers also manually found papers referenced by eligible papers to identify potential eligible studies. Eligibility criteria The inclusion criteria were (i) randomized controlled trials (RCTs); (ii) participants of the RCTs had undergone pulmonary surgery; and (iii) the studies compared postoperative outcomes. The studies were excluded if they met one of the following criteria: (i) were reviews, letters, case reports, animal experiments and conference abstracts; (ii) the patients did not undergo surgery; (iii) essential basic information was incomplete; (iv) the article was not written in English. Two independent reviewers assessed the suitability of studies based on the inclusion and exclusion criteria. Any disagreement was solved through discussion, and if necessary, by arbitration by a third party. Data items The following data items were collected from each study: the first author, publication year, country, ethnicity, enrolled year, participants’ characteristics, disease type, surgery type, number of chest tubes, tube removal criteria and postoperative data including air leak duration, duration of chest tube placement, length of hospital stay, postoperative cost, occurrence of PAL and discharged on device and complications. Data collection process Two independent reviewers extracted the data. When there was disagreement regarding data, a third reviewer checked the data and made the final decision. From each study, we extracted patient characteristics, study design and outcomes. The PRISMA flow diagram of literature retrieval is shown in Fig. 1. Figure 1: View largeDownload slide The PRISMA flow diagram of literature retrieved. Figure 1: View largeDownload slide The PRISMA flow diagram of literature retrieved. Risk of bias in individual studies Included studies were assessed with the Risk of Bias Tool found in the Cochrane Handbook for Systemic Reviews of Interventions [14]. The characteristics assessed included sequence generation and concealment of allocation (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessors (detection bias), incomplete outcome data addressed (attrition bias), freedom from selective reporting (reporting bias) and other biases. This work was independently assessed by 2 reviewers (J.Z. and M.L.). When there were disagreements regarding the risk of bias, a third reviewer checked the data and made the final decision. Summary measures The main summary measures were the weighted mean difference (WMD) for duration of chest tube placement and length of hospital stay. For each summary measure, we calculated the 95% confidence interval (CI) and P-values (considered statistically significant when P < 0.05). Synthesis of results We used Cochran’s Q statistics and I2 statistics to characterize the heterogeneity of the included studies. If I2 was >50%, we would synthesize these data with the random effect model; otherwise, we used the fixed effect model. Subgroup analyses were performed to identify and explain the potential heterogeneity of the studies, including age (less than or over 60 years old), the digital drainage system types (Thopaz or Digivent or Drentech) and number of chest tubes (1 or 2). Risk of bias across studies To assess publication bias, a funnel plot was generated for each outcome and statistically assessed by Begg’s test. All statistical analyses were performed by Review Manager V.5.3 (The Cochrane Collaboration, Software Update, Oxford, UK). Sensitivity analysis We investigated the influence of a single study on the overall effect—by sequentially removing 1 study at a time—to test the robustness of the main results, allowing us to verify whether any study had an excessive influence on the overall results. RESULTS Study selection A total of 2994 articles were identified, of which 10 RCTs [15–24] were included with 1268 participants. Study characteristics A total of 1268 patients were included in 10 RCTs published between 2008 and 2017, with sample sizes ranging from 31 to 381. The ages of the participants ranged from 17 to 70 years. All recruited patients underwent pulmonary surgery for lung cancer, spontaneous pneumothorax or other lung diseases. The major types of surgical procedures were lobectomy, wedge resection and segmentectomy. Only Jablonski et al. [22] mentioned pleurectomy and lung resection. One or 2 tubes were applied in the different trials. There were 3 main brands of digital chest drainage systems: Thopaz® (Medela AG, Baar, Switzerland), Drentech® (REDAX, Mirandola, Italy) and Digivent® (Millicore AB, Danderyd, Sweden). Traditional chest drainage systems included Pleur-evac A-6002-08 (Teleflex Inc., Research Triangle Park, NC, USA) and Thora-Seal® (Covidien, Mansfield, MA, USA). The major criteria for the removal of the chest tube were no air leak detected and abnormal findings on a chest radiograph (sufficient lung expansion was shown); however, the drainage volume threshold varied among the studies. The compared outcome parameters comprised duration of chest tube placement, length of hospital stay, air leak duration, occurrence of PAL, postoperative cost, occurrence of patients discharged home on device and complications. The main characteristics of the 10 RCTs are presented in Table 1. Table 1: Main characteristics of the randomized controlled trials included in the study Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  EPR: elective pulmonary resection; NA: unavailable; NCT: number of chest tubes; SP: spontaneous pneumothorax. Table 1: Main characteristics of the randomized controlled trials included in the study Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  Study  Sample size  Ethnicity  Disease  Surgery type  Digital type  Traditional type  NCT  Removal criteria for the digital group  Removal criteria for the traditional group  Bertolaccini et al. [15]  98  White  NA  EPR  Drentech  Conventional water seal  2  No air leak >6 h, drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Brunelli et al. [16]  159  White  Lung cancer  Lobectomy  Digivent  Pleur-evac A-6002-08  2  No air leak >6 h, drainage <400 ml/24 h  No air, drainage <400 ml/24 h  Cerfolio and Bryant [17]  100  Mixed  Lung neoplasm  EPR  Digivent  Teleflex S-11000  1  No air, drainage <450 ml/24h  No air, drainage <450 ml/24 h  Cho et al. [18]  59  Asian  Lung cancer  Wedge resection  iPRUM  Conventional water seal  1  No air leak >6 h  <20 cm fluctuation  De Waele et al. [19]  103  White  Lung cancer  EPR  Thopaz  Express  1–2  Drainage of <40 ml/min >8 h  No air, drainage <350 ml/24 h  Filosso et al. [20]  31  White  Lung cancer  Lobectomy  Drentech  Conventional water seal  2  No air leak >8 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Gilbert et al. [21]  172  White  Lung disease  Sublobectomy/ lobectomy  Thopaz  Pleur-evac A-6002-08  1–2  Drainage <250 ml/24 h  No air, drainage <250 ml/24 h  Jablonski et al. [22]  60  White  SP  Wedge resection/ pleurectomy  Thopaz  Conventional water seal  1  No air leak >6 h, drainage <200 ml/24 h  No air, drainage <200 ml/24 h  Lijkendijk et al. [23]  105  White  NA  Lobectomy  Thopaz  Thora-Seal  1  Air leak ≤20 ml/min for 6 h  No detectable air  Pompili et al. [24]  381  White  Lung disease  Lobectomy/ segmentectomy  Thopaz  Conventional water seal  1  Air leak ≤30 ml/min for 8 h  No detectable air  EPR: elective pulmonary resection; NA: unavailable; NCT: number of chest tubes; SP: spontaneous pneumothorax. Risk of bias across studies Two independent investigators assessed the risk of bias of the included studies. Seven of the 10 articles contained a low risk of bias in every aspect assessed. Cho et al. [18] had an unclear risk of bias for sequence generation. Filosso et al. [20] had an unclear risk of bias for sequence generation and concealment of allocation. Jablonski et al. [22] had an unclear risk of bias for sequence generation, concealment of allocation and incomplete outcome data addressed. The results of analyses of the risk of bias of the included studies are shown in Table 2 and Fig. 2. Table 2: Assessment of risk of bias Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Table 2: Assessment of risk of bias Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Study  Sequence generation  Concealment of allocation  Blinding of participants and personnel  Blinding of outcome assessors  Incomplete outcome data addressed  Free of selective reporting  Other bias  Bertolaccini et al. [15]  Low  Low  Low  Low  Low  Low  Low  Brunelli et al. [16]  Low  Low  Low  Low  Low  Low  Low  Cerfolio and Bryant [17]  Low  Low  Low  Low  Low  Low  Low  Cho et al. [18]  Unclear  Low  Low  Low  Low  Low  Low  De Waele et al. [19]  Low  Low  Low  Low  Low  Low  Low  Filosso et al. [20]  Unclear  Unclear  Low  Low  Low  Low  Low  Gilbert et al. [21]  Low  Low  Low  Low  Low  Low  Low  Jablonski et al. [22]  Unclear  Unclear  Low  Low  Unclear  Low  Low  Lijkendijk et al. [23]  Low  Low  Low  Low  Low  Low  Low  Pompili et al. [24]  Low  Low  Low  Low  Low  Low  Low  Figure 2: View largeDownload slide Assessment of risk of bias. (A) Graph of the risk of bias for the included studies; (B) graph of the risk of bias summary for the included studies. Figure 2: View largeDownload slide Assessment of risk of bias. (A) Graph of the risk of bias for the included studies; (B) graph of the risk of bias summary for the included studies. Synthesis of results Duration of chest tube placement Ten studies measured the duration of chest tube placement (chest tube duration) with 642 individuals having digital chest drainage systems whereas 626 were connected to traditional chest drainage systems. Patients with digital chest drainage systems had significantly shorter chest tube durations (WMD −0.72 days; 95% CI −1.03 to −0.40; P < 0.001) (Fig. 3). Figure 3: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on duration of chest tube placement (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Figure 3: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on duration of chest tube placement (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Length of hospital stay Nine studies measured the length of hospital stay, with 612 patients on digital chest drainage systems and 597 on traditional chest drainage systems. Patients who were on a digital chest drainage system had significantly shorter hospital stays (WMD −0.97 days; 95% CI −1.46 to −0.48; P < 0.001) (Fig. 4). In subgroup analyses, we found that digital devices reduced the length of hospital stay of patients who underwent lung resection (WMD −0.87 days; 95% CI −1.37 to 0.36; P < 0.001). Figure 4: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on length of hospital stay (weighted mean difference). Figure 4: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on length of hospital stay (weighted mean difference). Air leak duration Three studies measured the duration air leaks, with 316 patients on digital chest drainage systems and 309 patients on traditional chest drainage systems. Digital chest drainage systems were associated with shorter durations of air leaks (WMD −0.95 days; 95% CI −1.51 to −0.39; P < 0.001) (Fig. 5). No significant differences were observed in the subgroup analyses. Figure 5: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on air leak duration (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Figure 5: View largeDownload slide Meta-analysis of the effect of digital or traditional chest drainage on air leak duration (weighted mean difference). CI: confidence interval; df: degree of freedom; SD: standard deviation. Occurrence of prolonged air leak Three studies assessed the effect of the digital drainage system on the occurrence of a PAL, which was defined as a persistent air leak for more than 5 days. The difference between the effects of the digital and the traditional drainage systems on the occurrence of PAL is inconclusive (risk ratio 0.36; 95% CI 0.04–3.17; P = 0.36), and no meaningful discoveries were observed in the subgroup analyses. Postoperative cost Two studies comprising 219 patients measured postoperative costs. Digital chest drainage may significantly lower postoperative cost (WMD −443.16 euro; 95% CI −747.60 to −138.73; P = 0.004). Patients discharged home on a device Three studies measured the number of patients discharged home on a device: a total of 147 individuals were on digital drainage systems whereas 143 individuals were on traditional drainage systems. Results indicated that the difference between the 2 groups was not significant (risk ratio 0.67; 95% CI 0.25–1.79; P = 0.43; I2 0%). Other: percent air leak on postoperative days 1, 2 and 3 To identify any other factors that may affect the prognosis, we looked at the percentage of the occurrence of an air leak on postoperative days 1, 2 and 3. However, we found no significant difference among them. All of the main results of our analysis are shown in Table 3. Table 3: Main results of our analysis Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  CI: confidence interval; P-value: P-value of overall effect; P.H: P-value of heterogeneity; PAL: prolonged air leak; RR: risk ratio; WMD: weighted mean difference. Table 3: Main results of our analysis Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  Outcomes  Number of studies  Number of participants  Results   Heterogeneity         WMD/RR  95% CI  P-value  I2 (%)  P.H  Model  Duration of chest tube placement  10  1268  WMD −0.72  −1.03  −0.40  <0.001  70  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.58  −0.88  −0.29  <0.001  60  0.02  Random    <60  2  119  WMD −1.22  −1.87  −0.57  0.0002  51  0.15  Random   Digital type                      Drentech  2  129  WMD −0.75  −1.11  −0.39  <0.001  28  0.24  Fixed    Digivent  2  259  WMD −0.83  −1.45  −0.21  0.009  0  0.89  Fixed    Thopaz  5  821  WMD −0.67  −1.19  −0.14  0.010  82  <0.001  Random   Number of chest tubes                      1  5  705  WMD −0.90  −1.34  −0.47  <0.001  61  0.04  Random    2  3  288  WMD −0.77  −1.11  −0.42  <0.001  0  0.49  Fixed   Drainage threshold for removal                    200 ml/24 h  2  91  WMD −1.21  −1.81  −0.60  <0.001  55  0.13  Random    250 ml/24 h  2  270  WMD −0.46  −0.92  −0.01  0.05  0  0.82  Fixed  Length of hospital stay  9  1209  WMD −0.97  −1.46  −0.48  <0.001  90  <0.001  Random   Age (years)                      >60  8  1149  WMD −0.87  −1.37  −0.36  <0.001  91  <0.001  Random   Digital type                      Drentech  2  129  WMD −1.68  −3.82  0.47  0.13  98  <0.001  Random    Digivent  2  259  WMD −0.79  −1.32  −0.26  0.004  0  0.71  Fixed    Thopaz  5  821  WMD −0.75  −1.42  −0.07  0.03  85  <0.001  Random   Number of chest tubes                      1  4  646  WMD −1.09  −1.44  −0.74  <0.001  39  0.18  Fixed    2  3  288  WMD −1.42  −2.84  0.00  0.05  96  <0.001  Random   Drainage threshold for removal    200 ml/24 h  2  91  WMD −2.37  −3.27  −1.47  <0.001  69  0.07  Random    250 ml/24 h  2  270  WMD −0.42  −0.96  0.12  0.13  56  0.13  Random  Air leak duration  3  625  WMD −0.95  −1.51  −0.39  <0.001  10  0.33  Fixed  Occurrence of PAL  3  643  RR 0.36  0.04  3.17  0.36  81  0.005  Random  Postoperative cost  2  219  WMD −443.16  −747.60  −138.73  0.004  0  0.89  Fixed  Number of patients discharged home on device  3  290  RR 0.67  0.25  1.79  0.43  0  0.68  Fixed  Other parameters   Postoperative air leak (Day 1)  2  198  RR 1.17  0.86  1.58  0.32  0  0.69  Fixed   Postoperative air leak (Day 2)  2  198  RR 1.15  0.68  1.95  0.61  0  0.87  Fixed   Postoperative air leak (Day 3)  2  198  RR 1.20  0.54  2.65  0.65  0  1.00  Fixed  CI: confidence interval; P-value: P-value of overall effect; P.H: P-value of heterogeneity; PAL: prolonged air leak; RR: risk ratio; WMD: weighted mean difference. Sensitivity analysis and publication bias From derived forest plots, we did not notice any outcomes out of the estimated range, and no significant results were identified in sensitivity analyses. Furthermore, we found no significant publication bias by visual inspection of the funnel plot and Begg’s test. DISCUSSION Summary of evidence Our meta-analysis showed that, compared to the use of analogue drainage systems, the use of digital drainage systems following pulmonary surgery is associated with a shorter duration of chest tube placement, air leak duration and hospital stay and lower postoperative costs. However, there was no significant difference regarding occurrence of pronged air leak, air leak on postoperative day 1, 2 or 3 or percentage of patients discharged with a device. Reasons for using a digital chest drainage system Digital drainage systems have several benefits over traditional systems. First, they allow continuous recording of air leaks [25, 26]. An abundance of well-recorded data enhances medical research in this field [27, 28]. Second, digital devices decrease the variability caused by physician judgments regarding when a chest tube should be removed [10]. Third, digital chest drains provide precise, stable negative pressure without the influence of position changes or obstruction of tubes. Fourth, digital devices maintain a stable intrathoracic pressure more effectively. Fifth, digital drainage systems, especially the Thopaz (Medela AG), are portable and quiet. Patients with a non-complicated pneumothorax can be discharged earlier if they are placed on this system (compared to traditional systems) [29, 30]. Adoption of the digital chest drainage system: perspectives from China Physicians have been slow to adopt the digital drainage systems. There are several possible reasons. The first is the large number of choices and the lack of clear guidelines for when to use each system. Price is another factor. Resistance to change by medical personnel is also a possible reason. We think that, with the eventual development of clinical guidelines, digital drainage systems may be used more widely. Grouping and chest tube management of the enrolled trials In the enrolled RCTs, patients were randomized by computer-generated criteria to receive either a digital drainage system or a traditional drainage system. The following variables were recorded: postoperative air leak, chest tube duration, air leak duration and length of hospital stay. The application of suction varied among the studies. If the volume of drainage reached the threshold, a chest radiograph would be performed. Chest tubes were removed if the chest radiograph showed evidence of sufficient lung expansion. The decisions about removal were made mainly by 2 surgeons in charge who were blinded to each other. In the traditional group, they removed tubes based on no detectable air in the drainage system, drainage volume for 24 h and a chest radiograph. For those on the digital system, the surgeons focused on duration of no air leak, drainage volume and evidence from the chest radiograph. Supplementary information from papers that were not included Varela et al. [10] enrolled 61 patients for pulmonary resection and randomly assigned patients to digital or traditional chest drainage systems. We did not use the study because its results were based on the variability of drainage management, not postoperative outcome. Furthermore, it contained no information about postoperative outcomes such as duration of air leak. Rodriguez et al. [31] enrolled 100 patients undergoing lung resection to conduct a prospective observational study and concluded that traditional drainage systems based on clinical variables and visual scoring of pleural air leak had a reasonably good performance in predicting the occurrence of PAL. There was no comparison group on digital systems. We thought that the limited number of patients and the selection bias in enrolling participants were reasons not to include this study in our analysis. Deng et al. [32] recently performed a systematic review and meta-analysis, focusing on the management of the chest tube after video-assisted thoracic surgery. They also analysed the effects of a digital drainage system on reducing air leaks. We noticed some limitations. First, the inclusion criteria were not correct. They included 7 RCTs to identify the effects of the digital drainage system in total; however, we found some of them were not RCTs. Second, the risk of bias of their studies was not analysed, subgroup analyses were not performed and sensitivity analysis to identify potential heterogeneity was not done. Finally, we used more parameters than they did to assess the effects of the digital drainage system, such as postoperative cost and the occurrence of PAL. In addition, our search was more current (January 2016 versus July 2017). Strengths The strengths of the present research included (i) promising results found between digital and traditional chest drainage systems regarding chest tube duration, hospital stay and air leak duration; (ii) further discussion about the differences between the 2 drainage systems and analyses for adoption by Chinese physicians; (iii) clear inclusion and exclusion criteria, careful screening of studies, independent collection of data, complete assessment of studies quality and reliable tests to identify heterogeneity. Limitations of research and risk of bias We assessed the risk of bias for each study and found some unclear risks of bias. We included 1 study that used ‘pleurectomy and lung resection’ whereas other RCTs only focused on lung resection. The differences in types of surgical procedures, types of digital and traditional drainage systems and criteria for chest tube removal among the RCTs make the data heterogeneous. The articles did not contain enough information about postoperative outcomes. For example, few studies reported detailed data concerning the risk of complications, so we were not able to make further analyses about this topic. There were not enough samples in our analysis for some data items. Our meta-analysis did not include all of the 10 studies for every outcome parameter investigated. Consequently, the number of the patients analysed for the meta-analysis varied greatly for each outcome, generally comprising only a fraction of the whole study population. To consider chest tube duration, we selected 10 studies enrolling 1268 participants, whereas only 2 studies contained information about postoperative cost. CONCLUSION In light of the results of this meta-analysis, it might be necessary to use a digital chest drainage system for patients who undergo pulmonary surgery to reduce the duration of chest tube placement, hospital stay and air leak duration. However, the difference in the effect between the 2 chest drainage systems is inconclusive with respect to occurrence of PAL and patients discharged home on a device. Further studies are needed. ACKNOWLEDGMENTS We give sincere thanks to Hong Xie from the international office of West China School of Medicine, Sichuan University, Chengdu, China, for her help with the English language editing of this manuscript. Funding This work was supported by the National Natural Science Foundation of China [No. 81172236 and No. 81372505] and the Key Science and Technology Program of Sichuan Province, China [2013SZ0005, 2014SZ0148, 2016FZ0118 to L.L.]. Conflict of interest: none declared. REFERENCES 1 Varela G, Jimenez MF, Novoa N, Aranda JL. Estimating hospital costs attributable to prolonged air leak in pulmonary lobectomy. Eur J Cardiothorac Surg  2005; 27: 329– 33. Google Scholar CrossRef Search ADS PubMed  2 Burt BM, Shrager JB. The prevention and management of air leaks following pulmonary resection. Thorac Surg Clin  2015; 25: 411– 19. Google Scholar CrossRef Search ADS PubMed  3 Stamenovic D, Bostanci K, Messerschmidt A, Jahn T, Schneider T. Fissureless fissure-last video-assisted thoracoscopic lobectomy for all lung lobes: a better alternative to decrease the incidence of prolonged air leak? Eur J Cardiothorac Surg  2016; 50: 118– 23. 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Journal

European Journal of Cardio-Thoracic SurgeryOxford University Press

Published: Apr 6, 2018

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