TY - JOUR
AU1 - USAR, Michael Rybak, AN
AU2 - USAR, Lynn C. Huffman, MC
AU3 - USAR, Richard Nahouraii, MC
AU4 - USAR, John Loden,
AU5 - USAR, Marcos Gonzalez,
AU6 - USA, Ramey Wilson, MC
AU7 - USAR, Paul D. Danielson, MC
AB - ABSTRACT Introduction: A limitation to surgical care in an austere environment is the supply of oxygen to support mechanical ventilation and general anesthesia. Portable oxygen concentrators (OCs) offer an alternative to traditional compressed oxygen tanks. Objectives: We set out to demonstrate that a low-pressure OC system could supply the mechanical ventilation needs in an austere operating environment. Methods: An ultraportable OC (SAROS Model 3000, SeQual Technologies, Ball Ground, Georgia) was paired with an Impact 754 ventilator (Impact Instrumentation, West Caldwell, New Jersey) to evaluate the delivered fraction of inspired oxygen (FiO2) to a test lung across a range of minute ventilations and at altitudes of 1,200 and 6,500 feet above sea level. Results: The compressor-driven Impact ventilator was able to deliver FiO2 at close to 0.9 for minute ventilations equal to oxygen flow. Pairing two OCs expanded the range of minute ventilations supported. OCs were less effective at concentrating oxygen at higher altitudes. Conclusions: These results demonstrate that low-pressure, ultraportable OCs are capable of delivering high FiO2 during mechanical ventilation in austere locations at both low and high altitudes. Ultraportable OCs could therefore be sufficient to support forward area surgical procedures and positively impact logistics. INTRODUCTION The provision of surgical care under austere conditions such as encountered on the battlefield, in remote geographic regions, or at disaster sites remains a challenge. Although general anesthesia in these situations requires specialized equipment and personnel, the limiting factors for sustained operations are often logistical. Mechanical ventilation often needs a high-pressure oxygen source to deliver the necessary fraction of inspired oxygen (FiO2) concentration to a patient. Unfortunately, this may not be available or may rely upon compressed oxygen tanks which are difficult to transport, pose explosive risks, and have limited capacity. Oxygenation concentrators (OCs) offer an alternative. These electrically powered devices draw in room air and utilize a zeolite bed to absorb nitrogen thus rendering a limitless supply of concentrated oxygen. OCs are available in various sizes with differing capabilities from large, fixed machines to small, more portable versions (Table I).1–3 The successful use of nonportable OCs has been demonstrated at hospitals in Nepal although the introduction of portable OCs to a remote, high-altitude fixed hospital of the Pakistan Armed Forces decreased, but did not eliminate, the need for compressed oxygen cylinders.4,5 The French military reported the feasibility of portable OCs for a forward surgical unit in the Ivory Coast.6 TABLE I Operational Characteristics of the SeQual SAROS Model 3000, AirSep Newlife, Portable Oxygen Generation System POGS 33C   SAROS  NewLife Elite  POG 33  Weight (kg)  5.5 With Battery  24.5  Generator 120.5  Compressor 97.7  Microboost 100  Total 318.2  Dimensions (cm) W × L × D  68 × 11.1 With Battery (Length × Diameter)  40 × 72.4 × 36.8  Generator 71 × 132 × 61  Compressor 68.5 × 73.6 × 68.5  Microboost 68.5 × 73.6 × 68.5  Continuous Flow (L/min)  1–3  1–5  1–30  Pulse Dose (mL)  16–96  N/A  N/A  Outlet Pressure (psig)  4.0  8.0  50.0  Operating Environment Guidelines   Temperature (°C)  0–43  5–40  0–40   Relative Humidity (%)  10–95  10–95  10–95   Altitude        Power Consumption  ≤130 W 3L/min Continuous Flow  350 W  115 V  208–240 V  115 V  Battery Life (Minutes)   Continuous 3L/min  30 Minutes  N/A  N/A   Pulse Mode 96 mL  37 Minutes  N/A  N/A    SAROS  NewLife Elite  POG 33  Weight (kg)  5.5 With Battery  24.5  Generator 120.5  Compressor 97.7  Microboost 100  Total 318.2  Dimensions (cm) W × L × D  68 × 11.1 With Battery (Length × Diameter)  40 × 72.4 × 36.8  Generator 71 × 132 × 61  Compressor 68.5 × 73.6 × 68.5  Microboost 68.5 × 73.6 × 68.5  Continuous Flow (L/min)  1–3  1–5  1–30  Pulse Dose (mL)  16–96  N/A  N/A  Outlet Pressure (psig)  4.0  8.0  50.0  Operating Environment Guidelines   Temperature (°C)  0–43  5–40  0–40   Relative Humidity (%)  10–95  10–95  10–95   Altitude        Power Consumption  ≤130 W 3L/min Continuous Flow  350 W  115 V  208–240 V  115 V  Battery Life (Minutes)   Continuous 3L/min  30 Minutes  N/A  N/A   Pulse Mode 96 mL  37 Minutes  N/A  N/A  View Large TABLE I Operational Characteristics of the SeQual SAROS Model 3000, AirSep Newlife, Portable Oxygen Generation System POGS 33C   SAROS  NewLife Elite  POG 33  Weight (kg)  5.5 With Battery  24.5  Generator 120.5  Compressor 97.7  Microboost 100  Total 318.2  Dimensions (cm) W × L × D  68 × 11.1 With Battery (Length × Diameter)  40 × 72.4 × 36.8  Generator 71 × 132 × 61  Compressor 68.5 × 73.6 × 68.5  Microboost 68.5 × 73.6 × 68.5  Continuous Flow (L/min)  1–3  1–5  1–30  Pulse Dose (mL)  16–96  N/A  N/A  Outlet Pressure (psig)  4.0  8.0  50.0  Operating Environment Guidelines   Temperature (°C)  0–43  5–40  0–40   Relative Humidity (%)  10–95  10–95  10–95   Altitude        Power Consumption  ≤130 W 3L/min Continuous Flow  350 W  115 V  208–240 V  115 V  Battery Life (Minutes)   Continuous 3L/min  30 Minutes  N/A  N/A   Pulse Mode 96 mL  37 Minutes  N/A  N/A    SAROS  NewLife Elite  POG 33  Weight (kg)  5.5 With Battery  24.5  Generator 120.5  Compressor 97.7  Microboost 100  Total 318.2  Dimensions (cm) W × L × D  68 × 11.1 With Battery (Length × Diameter)  40 × 72.4 × 36.8  Generator 71 × 132 × 61  Compressor 68.5 × 73.6 × 68.5  Microboost 68.5 × 73.6 × 68.5  Continuous Flow (L/min)  1–3  1–5  1–30  Pulse Dose (mL)  16–96  N/A  N/A  Outlet Pressure (psig)  4.0  8.0  50.0  Operating Environment Guidelines   Temperature (°C)  0–43  5–40  0–40   Relative Humidity (%)  10–95  10–95  10–95   Altitude        Power Consumption  ≤130 W 3L/min Continuous Flow  350 W  115 V  208–240 V  115 V  Battery Life (Minutes)   Continuous 3L/min  30 Minutes  N/A  N/A   Pulse Mode 96 mL  37 Minutes  N/A  N/A  View Large Over the past 15 years, the U.S. Army has employed forward surgical teams (FSTs) widely for military activity in Iraq and Afghanistan.7–9 Because of tactical imperatives and the expanded role of special operations, these teams have become increasingly mobile with fewer personnel and lighter equipment load-outs.10–12 As a result, the need to find a smaller and more easily transported oxygen source remains critical, and consequently, ultraportable OCs have been fielded with many forward area surgical elements. The U.S. Air Force has studied the capabilities of portable OCs in conjunction with mechanical ventilators in a controlled laboratory environment, but this has not been previously reported in a field environment.13 Thus, the purpose of this study was to demonstrate this proof of concept in two austere environments of different altitudes using an ultraportable OC. METHODS Conditions Elements of the U.S. Army 946th FST conducted operations at two austere locations in Afghanistan: a high-altitude location (6,500 feet above sea level) and a low-altitude location (1,200 feet above sea level). Experimental Setup An Impact 754 mechanical ventilator (Impact Instrumentation, West Caldwell, New Jersey) was used to deliver specific minute ventilations to a standard anesthesia circuit with humidity/heat/moisture exchanger and a 3-L test balloon (Portex, Smith Medical, Keene, New Hampshire). The ultraportable OC (SAROS Oxygen System Model 3000, SeQual Technologies, Ball Ground, Georgia) supplied low-pressure oxygen at either 3 L/min or at a pulsed dose mode of 96 mL per breath. A second ultraportable OC was added to achieve 6 L/min of flow. Oxygen was entrained into the system via to a 600-mL reservoir (180 cm of 22-mm-diameter Air Life Universal Portable Volume Ventilator Circuit, CareFusion, Yorba Linda, California) attached to the compressor inlet of the ventilator. This optimal reservoir size was selected on the basis of previous studies and preliminary data from this experiment.14,15 A MiniOX 3000 gas analyzer (Ohio Medical Corporation, Gurnee, Illinois) just proximal to the humidity/heat/moisture exchanger provided continuous FiO2 measurements (Fig. 1). This setup was constructed to best replicate a previously reported laboratory study.13 FIGURE 1 View largeDownload slide Experimental setup. FIGURE 1 View largeDownload slide Experimental setup. The ventilator was set to assist control mode with an inspiration:expiration ratio of 1:2. The ventilator's oxygen blender was set to “21%” to ensure that all gas fed into the compressor came from the room air intake valve to which was attached the reservoir.16 Tidal volumes were held at 500 mL and the respiratory rate was used to vary the minute ventilation (Table II). Five separate FiO2 measurements were recorded at the end of the inspiratory phase for each minute ventilation selected and a 5-minute stabilization period was used between ventilator changes. The ventilator volume and pressure alarms demonstrated no circuit leaks during the experiments. The temperature and humidity were the same at both testing locations; however, the atmospheric pressure differed as a result of the altitude. TABLE II Ventilator and Oxygen Concentrator Parameter Combinations Tested Ventilator Settings  POC Oxygen Flow (L/min)  I/E Ratio  Tidal Volume (mL)  Respiratory Rate (Breaths/min)  PEEP (cmH2O)  Assist Control  3  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  6  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  96 mL/Breath  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Ventilator Settings  POC Oxygen Flow (L/min)  I/E Ratio  Tidal Volume (mL)  Respiratory Rate (Breaths/min)  PEEP (cmH2O)  Assist Control  3  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  6  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  96 mL/Breath  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  POC, portable oxygen concentrator; I/E, inspiratory/expiratory; PEEP, positive end-expiratory pressure. View Large TABLE II Ventilator and Oxygen Concentrator Parameter Combinations Tested Ventilator Settings  POC Oxygen Flow (L/min)  I/E Ratio  Tidal Volume (mL)  Respiratory Rate (Breaths/min)  PEEP (cmH2O)  Assist Control  3  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  6  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  96 mL/Breath  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Ventilator Settings  POC Oxygen Flow (L/min)  I/E Ratio  Tidal Volume (mL)  Respiratory Rate (Breaths/min)  PEEP (cmH2O)  Assist Control  3  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  6  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  Assist Control  96 mL/Breath  1/2  500  4, 6, 8, 10, 12, 14, 16, 18, 20  0  POC, portable oxygen concentrator; I/E, inspiratory/expiratory; PEEP, positive end-expiratory pressure. View Large RESULTS The ultraportable OC system delivering low-pressure oxygen to a compressor-driven ventilator circuit was able to increase the FiO2 delivered to a test balloon at both the high- and low-altitude testing locations. At high altitude, the continuous mode of 3 L/min was able to achieve an FiO2 of 0.9 at minute ventilations of 3 L/min and still kept the FiO2 greater than 0.5 up to minute ventilations of 6 L/min. The introduction of the second ultraportable OC to the system increased the flow of oxygen to the reservoir to 6 L/min, and this resulted in a ventilator delivered FiO2 of 0.9 up to a minute ventilation of 6 L/min and an FiO2 of >0.6 up to a minute ventilation of 10 L/min. The pulse mode of oxygen delivery from the ultraportable OC was less effective in maintaining an increased FiO2 (Table III). The oxygen concentration measured in the reservoir at the end of all testing and while the ventilator was in standby mode measured 0.91 regardless of the OC's output mode or flow rate. TABLE III Mean Delivered FiO2 for Various Minute Ventilations and Oxygen Concentrator Modes Oxygen Source  Minute Ventilation (L/min)  3  4  5  6  7  8  9  10  High Altitude   3 L/min Continuous  0.89  0.71  0.59  0.52  0.49  0.45  0.43  0.42   6 L/min Continuous  0.90  0.89  0.90  0.89  0.81  0.73  0.68  0.63   96-mL Pulse  0.56  0.57  0.48  0.47  0.45  0.44  0.38  0.33  Low Altitude   3 L/min Continuous  0.90  0.72  0.63  0.58  0.56  0.52  0.50  0.48   96-mL Pulse  0.69  0.57  0.55  0.55  0.54  0.50  0.42  0.40  Oxygen Source  Minute Ventilation (L/min)  3  4  5  6  7  8  9  10  High Altitude   3 L/min Continuous  0.89  0.71  0.59  0.52  0.49  0.45  0.43  0.42   6 L/min Continuous  0.90  0.89  0.90  0.89  0.81  0.73  0.68  0.63   96-mL Pulse  0.56  0.57  0.48  0.47  0.45  0.44  0.38  0.33  Low Altitude   3 L/min Continuous  0.90  0.72  0.63  0.58  0.56  0.52  0.50  0.48   96-mL Pulse  0.69  0.57  0.55  0.55  0.54  0.50  0.42  0.40  View Large TABLE III Mean Delivered FiO2 for Various Minute Ventilations and Oxygen Concentrator Modes Oxygen Source  Minute Ventilation (L/min)  3  4  5  6  7  8  9  10  High Altitude   3 L/min Continuous  0.89  0.71  0.59  0.52  0.49  0.45  0.43  0.42   6 L/min Continuous  0.90  0.89  0.90  0.89  0.81  0.73  0.68  0.63   96-mL Pulse  0.56  0.57  0.48  0.47  0.45  0.44  0.38  0.33  Low Altitude   3 L/min Continuous  0.90  0.72  0.63  0.58  0.56  0.52  0.50  0.48   96-mL Pulse  0.69  0.57  0.55  0.55  0.54  0.50  0.42  0.40  Oxygen Source  Minute Ventilation (L/min)  3  4  5  6  7  8  9  10  High Altitude   3 L/min Continuous  0.89  0.71  0.59  0.52  0.49  0.45  0.43  0.42   6 L/min Continuous  0.90  0.89  0.90  0.89  0.81  0.73  0.68  0.63   96-mL Pulse  0.56  0.57  0.48  0.47  0.45  0.44  0.38  0.33  Low Altitude   3 L/min Continuous  0.90  0.72  0.63  0.58  0.56  0.52  0.50  0.48   96-mL Pulse  0.69  0.57  0.55  0.55  0.54  0.50  0.42  0.40  View Large Experiments conducted at low altitude showed a similar pattern (Table III). Overall, mean FiO2 delivery was significantly higher at lower altitude for both the 3 L/min mode and 96-mL pulse mode with a reservoir oxygen concentration at the end of all testing measuring 0.94. Trials in which the reservoir was doubled in size showed no increase in delivered FiO2. Also, to better reflect pediatric clinical ventilator settings, the lower minute ventilation trials were repeated with smaller tidal volumes and higher respiratory rates and yielded similar FiO2 measurements when the OC was in continuous mode (These data are not shown to conserve space.). DISCUSSION The results indicate that low-pressure ultraportable OCs can be used in conjunction with compressor-driven ventilators to provide mechanical ventilation support in remote areas and at high altitudes. The optimal characteristics of an oxygen source for use by an expeditionary surgical team would include light weight, ease of transport, low electricity demand, and an internal battery. Although many OCs are considered portable, those with weights exceeding 10 kg have limited usefulness for many military resuscitative surgical teams. The ultraportable model used in this study (5.5 kg) meets all the necessary requirements at a fraction of the weight, size, and power requirements of other OCs (Table I). The ultraportable OC can deliver a continuous oxygen flow of 3 L/min or a pulse dose of 96 mL per breath. Although the latter mode consumes 15% less power, it did not achieve as high an FiO2 as the continuous mode.1 Concern about a decrease in the oxygen concentration during continuous output over time was not observed in these experiments which spanned several hours, a period much longer than any anticipated forward area resuscitative surgical procedure. It is known that fixed and portable OCs are less effective in concentrating oxygen at higher altitudes as a result of the decrease in atmospheric pressure. We demonstrated that this also occurred with ultraportable OCs. However, the device was still able to achieve concentration of at least 0.9 oxygen to the circuit reservoir and maintain high FiO2 delivery despite the OC's performance and the lower oxygen concentration of any room air drawn into the reservoir. This was not a human study so no data were collected regarding alveolar oxygen concentration as related to atmospheric pressure and altitude. However, the clinically important point is that adequate oxygen delivery to a patient can be achieved, even at high minute ventilations. A previous study demonstrated higher FiO2 delivery and lower power usage when a portable OC's pulse dose mode was utilized; however, those experiments were performed in a laboratory setting, with a more complex ventilator circuit and a modified OC.13 Although future developments with microprocessor control of a paired ventilator/OC system may yield additional advantages to a pulse dose mode, our methods were selected on the basis of simplicity and current ease of application in the field. The setup as tested in this study is well suited to forward area surgical care. The ventilator and ultraportable OC together can be easily powered by a 5-kW electrical generator and both have 30 minutes of battery life in the event that power is interrupted. The use of standard ventilator tubing as a reservoir provides a simple setup constructed from supplies already carried. Lastly, besides the weight restriction of the equipment brought forward, resuscitative surgical teams also have limited personnel. The ability to oxygenate and ventilate a patient mechanically frees a team member for other duties. This study did not involve any human subjects and therefore exists only as a proof of concept. One concern is that there may be situations in which patients would require a high flow of >0.9 oxygen concentration, e.g., during the preoxygenation phase of anesthesia induction or during rapid sequence intubation. Or, there may be critically ill patients who require an FiO2 approaching 1.0 just to maintain adequate tissue oxygenation. Therefore, it may still be necessary to have compressed oxygen tanks available for these situations. Although by relying heavily on OCs for all other oxygen needs, the demand for compressed oxygen tanks could be minimized.5 It is important to remember that three ultraportable OCs feeding a reservoir could provide an effective flow of 9 L/min of >0.9 oxygen, and thus it may be possible to eliminate compressed oxygen tanks completely. A limitation of this study is that we did not examine different ventilator modes or simulate spontaneous breathing and triggered ventilator breathes. Moreover, only one ventilator type (compressor driven) was tested, although it is likely that similar outcomes could be achieved with a turbine-driven ventilator as well.6,17 The success of ultraportable OCs in this study has important implications for military planners. When developed by the U.S. Army in the 1990's, the FST, which consists of 20 personnel, represented the smallest, self-contained unit able to perform resuscitative surgery and was considered highly mobile by traveling in six Humvees with trailers.8,9 The wars in Iraq and Afghanistan saw these units deployed in many nondoctrinal ways, including split FST detachments in which 10 personnel would be deployed to a remote location to perform damage control surgery.7,10,11 The Special Forces require an even more nimble capability which has given rise to Golden Hour Off-set Surgical Treatment (GHOST) teams. These units can be as small as four personnel (surgeon, anesthetist, operating room technician, and medic) and can deploy by either fixed wing, rotary wing, or even parachute.12 Medical evacuation (MEDEVAC) assets are limited to a “ring of coverage” defined by the time/distance required to travel to the point of injury and return. The purpose of a GHOST mission is to temporarily expand “golden hour” surgical capability by deploying a resuscitative surgery team beyond the traditional MEDEVAC ring.12 As the size of these resuscitative surgery teams have gotten smaller, so too is their capacity for carriage of equipment. This is where the ultraportable OC's can have a positive impact on logistics. Just one 5.5-kg device can meet mission requirements although there is the flexibility of adding additional ultraportable OCs on the basis of anticipated needs. CONCLUSIONS Overall, this study demonstrates that low-pressure ultraportable OCs are capable of delivering high FiO2 during mechanical ventilation in austere locations at both low and high altitudes. The clinical implication is that ultraportable OCs could be sufficient to support forward area surgical procedures that require general anesthesia. The size of these ultraportable OCs is advantageous for expeditionary surgery teams who have space and weight limitations when it comes to equipment. REFERENCES 1. SeQual Technologies, Inc. SAROS Oxygen System Model 3000 Technical Manual . Ball Ground, GA, 2014. Available at http://www.chartindustries.com/Respiratory-Healthcare/Military/SAROS; accessed April 1, 2016. 2. On Site Gas Systems, Inc. Portable Oxygen Generation System 33 L/MIN – POGS 33C Service Manual . Newington, CT, 2009. Available at http://www.onsitegas.com/portable-oxygen-generator.html; accessed April 1, 2016. 3. AirSep Corp. NewLife Elite Patient Manual . Buffalo, NY, 2002. Available at http://www.airsep.com; accessed April 1, 2016. 4. Shrestha BM, Singh BB, Gautam MP, Chand MB The oxygen concentrator is a suitable alternative to oxygen cylinders in Nepal. Can J Anesth  2002; 49: 8– 12. Google Scholar CrossRef Search ADS PubMed  5. Masroor R, Iqbal A, Buland K, Kazi WA Use of a portable oxygen concentrator and its effect on the overall functionality of a remote field medical unit at 3650 meters elevation. Anesth Pain Intens Care  2013; 17: 45– 50. 6. Bordes J, d'Aranda E, Savoie P-H, Montcriol A, Goutorbe P, Kaier E FiO2 delivered by a turbine portable ventilator with an oxygen concentrator in an austere environment. J Emer Med  2014; 47: 306– 12. Google Scholar CrossRef Search ADS   7. Eastridge BJ, Stansbury LG, Stinger H, Blackbourne L, Holcomb JB Forward surgical teams provide comparable outcomes to combat support hospitals during support and stabilization operations on the battlefield. J Trauma  2009; 66: S48– 50. Google Scholar CrossRef Search ADS PubMed  8. Patel TH, Wenner KA, Price SA, Weber MA, Leveridge A, McAtee SJ A U.S. Army forward surgical team's experience in Operation Iraqi Freedom. J Trauma  2004; 57: 201– 7. Google Scholar CrossRef Search ADS PubMed  9. Beekley AC, Watts DM Combat trauma experience with the US Army 102nd forward surgical team in Afghanistan. Am J Surg  2004; 187: 652– 4. Google Scholar CrossRef Search ADS PubMed  10. Nessen SC, Cronk DR, Edens J, Eastridge BJ, Blackbourne LH US Army split forward surgical team management of mass casualty events in Afghanistan: surgeon performed triage results in excellent outcomes. Am J Disaster Med  2009; 4: 321– 9. Google Scholar PubMed  11. Counihan TC, Danielson PD The 912th forward surgical team in Operation New Dawn: employment of the forward surgical team during troop withdrawal under combat conditions. Mil Med  2012; 177( 11): 1267– 71. Google Scholar CrossRef Search ADS PubMed  12. Remick KN The surgical resuscitation team: surgical trauma support for U.S. Army special operations forces. J Spec Op Med  2009; 9: 20– 5. 13. Rodriquez DR, Blakeman TC, Dorlac W, Johannigman JA, Branson RD Maximizing oxygen delivery during mechanical ventilation with a portable oxygen concentrator. J Trauma  2010; 69: S87– 93. Google Scholar CrossRef Search ADS PubMed  14. Eales M, Rowe P, Tully R Improving the efficiency of the drawover anaesthetic breathing system. Anesth  2007; 62: 1171– 4. Google Scholar CrossRef Search ADS   15. Meekins A, Lange E, Levine E, Austin P Comparison of oxygen reservoir tube length and imposed work of breathing with the universal portable anesthesia complete. Mil Med  2005; 170: 291– 4. Google Scholar CrossRef Search ADS PubMed  16. Impact Instrumentation, Inc. Operation and Service Manual: UNI-VENT Eagle 700 Series Model 754M . West Caldwell, NJ, 1998. Available at http://www.med.navy.mil/sites/nmotc/nemti/Documents/Tech%20Online/ICU%20WARD%20AND%20TRAUMA%20BAY/Impact%20Ventilator.pdf; accessed April 1, 2016. 17. 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TI - Ultraportable Oxygen Concentrator Use in U.S. Army Special Operations Forward Area Surgery: A Proof of Concept in Multiple Environments
JF - Military Medicine
DO - 10.7205/MILMED-D-16-00100
DA - 2017-01-01
UR - https://www.deepdyve.com/lp/oxford-university-press/ultraportable-oxygen-concentrator-use-in-u-s-army-special-operations-Ust7cKCG7B
SP - e1649
EP - e1652
VL - 182
IS - 1
DP - DeepDyve
ER -