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Effects of Hypoxia and Acidity on the Initiation of Breathing in the Fetal Lamb at Term

Effects of Hypoxia and Acidity on the Initiation of Breathing in the Fetal Lamb at Term Abstract DESPITE their immense importance, the factors initiating respiration at birth are incompletely understood. The classic theory has been that respiration is initiated as a result of sensory stimulation of the baby as it passes through the birth canal and encounters the cooler, external environment. If this fails to elicit respiration, then asphyxic stimulation, acting through peripheral chemoreceptors, may be activated as an emergency mechanism to restore the depressed infant by induction of gasps. Since all infants undergo a degree of asphyxiation at birth, it was believed that a study of the effects of fall in fetal Po2 and pH and rise in fetal Pco2 on the initiation of respiration, under conditions where the fetus was not subjected to other stimulation, might indicate whether asphyxic stimulation is an emergency mechanism or actually a physiologic part of the initiation of breathing. Gas mixtures were administered to term ewes, References 1. Harned, H.S., Jr., et al: Relationship of PO2, Pco2, and pH to Onset of Breathing of the Term Lamb as Studied by a Flow-Through Cuvette Electrode Assembly , Pediatrics 33:672, 1964. 2. Harned, H.S., Jr., et al: Hemodynamic Observations During Birth of the Lamb: Studies of the Unanesthetized Full-Term Animal , Amer J Dis Child 102:180,1961.Crossref 3. Dawes, G.: "Changes in the Circulation at Birth and the Effects of Asphyxia," in Gairdner, D. (ed.): Recent Advances in Paediatrics , ed 2, Boston: Little, Brown & Company, 1958, pp 5-6. 4. Hornbein, T.F.; Griffo, Z.J.; and Roos, A.: Quantitation of Chemoreceptor Activity: Interrelation of Hypoxia and Hypercapnia , J Neurophysiol 24:561, 1961. 5. Eyzaguirre, C., and Lewin, J.: Chemoreceptor Activity of the Carotid Body of the Cat , J Physiol 159:222, 1961. 6. Apgar, V.: A Proposal for a New Method of Evaluation of the Newborn Infant , Anesth Analg 32:260, 1953.Crossref 7. Rudolph, A.M.; Heymann, M.; and Hait, G.: Distribution of the Circulation in the Fetus in Utero , Circulation 32 (suppl II): ( (Oct) ) 1965. 8. Cestan, R.; Sendrail, M.; and LaSalle, H.: Les Modifications de l'equilibre acide-base du Liquide Cephalorachidien dans les Acidosis Experimentales , Compt Rend Soc Biol 93:475, 1925. 9. Lambertsen, G.J.: Carbon Dioxide and Respiration in Acid-Base Homeostasis , Anesthesiology 21: 642, 1960.Crossref 10. Sevringhaus, J.W., et al: Respiratory Control At High Altitude Suggesting Active Transport Regulation of Cerebrospinal Fluid pH , J Appl Physiol 18:1155, 1964. 11. Avery, M.E.; Chernick, V.; and Young, M.: Fetal Respiratory Movements in Response to Rapid Changes of CO2 in Carotid Artery , J Appl Physiol 20: 225, 1965. 12. Windle, W.F.; Monnier, M.; and Steele, A.G.: Fetal Respiratory Movements in the Cat , Phys Zool 11:425,1938. 13. Schaffer, A.J.: The Pathogenesis of Intrauterine Pneumonia: I. A Critical Review of the Evidence Concerning Intrauterine Respiratory-Like Movements , Pediatrics 17:747, 1956. 14. Barcroft, J.: Researches on Pre-Natal Life , Springfield, Ill: Charles C Thomas, Publishers, 1947, vol 1, p 268. 15. Dawes, G.: "Changes in the Circulation at Birth and the Effects of Asphyxia," in Gairdner, D. (ed.): Recent Advances in Paediatrics , ed 2, Boston: Little, Brown & Company, 1958, p 9. 16. Schmidt, C.: "Reflex Regulation of Respiration," in Bard, P. (ed.): Medical Physiology , ed 10, St. Louis: C. V. Mosby Co., 1956. 17. Reynolds, S.R.M.: Nature of Fetal Adaptation to the Uterine Environment: A Problem of Sensory Deprivation , Amer J Obstet Gynec 83:800, 1962. 18. Burns, B.D.: The Central Control of Respiratory Movements , Brit Med Bull 19:7, 1963. 19. Avery, M.E.: Some Effects of Altered Environments: Relationships Between Space Medicine and Adaptations at Birth , Pediatrics 35:345, 1965. 20. Cross, K.W., and Malcolm, J.L.: Evidence of Carotid Body and Sinus Activity in Newborn and Foetal Animals , J Physiol 118:10P, 1952. 21. Cross, K.W.: Respiration in the Newborn Baby , Brit Med Bull 17:160, 1961. 22. Mitchell, R.A., et al: Regions of Respiratory Chemosensitivity on the Surface of the Medulla , Ann NY Acad Sci 109:661, 1963.Crossref 23. Winterstein, H.: Chemical Control of Pulmonary Ventilation: III. The Reaction Theory of Respiratory Control , New Eng J Med 255:331, 1956.Crossref 24. James, L.S.: Acidosis of Newborn and Its Relation to Birth Asphyxia , Acta Paediat 49 ( (suppl 122) ):17-28, 1960.Crossref 25. James, L.S., and Adamsons, K., Jr.: Respiratory Physiology of the Fetus and Newborn , New Eng J Med 271:1352, 1964Crossref 26. 271:1403, 1964. 27. Castro, F., de: Sur la Structure de la Synapse dans les Chemorecepteurs: Leur Mecanisme d'Excitation et Role dans la Circulation Sanquine Locale , Acta Physiol Scand 22:14, 1951.Crossref 28. Joels, M., and Neil, E.: The Excitation Mechanism of the Carotid Body , Brit Med Bull 19:21, 1963. 29. Downing, S.D.; Remensnyder, J.P.; and Mitchell, J.H.: Cardiovascular Responses to Hypoxic Stimulation of the Carotid Bodies , Circ Res 10:676, 1962.Crossref 30. Daly, M. de B., and Haggledine, J.L.: The Effects of Artificially Induced Hyperventilation on the Primary Cardiac Reflex Response to Stimulation of the Carotid Bodies in the Dog , J Physiol 168:872, 1963. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png American Journal of Diseases of Children American Medical Association

Effects of Hypoxia and Acidity on the Initiation of Breathing in the Fetal Lamb at Term

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Publisher
American Medical Association
Copyright
Copyright © 1966 American Medical Association. All Rights Reserved.
ISSN
0002-922X
DOI
10.1001/archpedi.1966.02090130108010
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Abstract

Abstract DESPITE their immense importance, the factors initiating respiration at birth are incompletely understood. The classic theory has been that respiration is initiated as a result of sensory stimulation of the baby as it passes through the birth canal and encounters the cooler, external environment. If this fails to elicit respiration, then asphyxic stimulation, acting through peripheral chemoreceptors, may be activated as an emergency mechanism to restore the depressed infant by induction of gasps. Since all infants undergo a degree of asphyxiation at birth, it was believed that a study of the effects of fall in fetal Po2 and pH and rise in fetal Pco2 on the initiation of respiration, under conditions where the fetus was not subjected to other stimulation, might indicate whether asphyxic stimulation is an emergency mechanism or actually a physiologic part of the initiation of breathing. Gas mixtures were administered to term ewes, References 1. Harned, H.S., Jr., et al: Relationship of PO2, Pco2, and pH to Onset of Breathing of the Term Lamb as Studied by a Flow-Through Cuvette Electrode Assembly , Pediatrics 33:672, 1964. 2. Harned, H.S., Jr., et al: Hemodynamic Observations During Birth of the Lamb: Studies of the Unanesthetized Full-Term Animal , Amer J Dis Child 102:180,1961.Crossref 3. Dawes, G.: "Changes in the Circulation at Birth and the Effects of Asphyxia," in Gairdner, D. (ed.): Recent Advances in Paediatrics , ed 2, Boston: Little, Brown & Company, 1958, pp 5-6. 4. Hornbein, T.F.; Griffo, Z.J.; and Roos, A.: Quantitation of Chemoreceptor Activity: Interrelation of Hypoxia and Hypercapnia , J Neurophysiol 24:561, 1961. 5. Eyzaguirre, C., and Lewin, J.: Chemoreceptor Activity of the Carotid Body of the Cat , J Physiol 159:222, 1961. 6. Apgar, V.: A Proposal for a New Method of Evaluation of the Newborn Infant , Anesth Analg 32:260, 1953.Crossref 7. Rudolph, A.M.; Heymann, M.; and Hait, G.: Distribution of the Circulation in the Fetus in Utero , Circulation 32 (suppl II): ( (Oct) ) 1965. 8. Cestan, R.; Sendrail, M.; and LaSalle, H.: Les Modifications de l'equilibre acide-base du Liquide Cephalorachidien dans les Acidosis Experimentales , Compt Rend Soc Biol 93:475, 1925. 9. Lambertsen, G.J.: Carbon Dioxide and Respiration in Acid-Base Homeostasis , Anesthesiology 21: 642, 1960.Crossref 10. Sevringhaus, J.W., et al: Respiratory Control At High Altitude Suggesting Active Transport Regulation of Cerebrospinal Fluid pH , J Appl Physiol 18:1155, 1964. 11. Avery, M.E.; Chernick, V.; and Young, M.: Fetal Respiratory Movements in Response to Rapid Changes of CO2 in Carotid Artery , J Appl Physiol 20: 225, 1965. 12. Windle, W.F.; Monnier, M.; and Steele, A.G.: Fetal Respiratory Movements in the Cat , Phys Zool 11:425,1938. 13. Schaffer, A.J.: The Pathogenesis of Intrauterine Pneumonia: I. A Critical Review of the Evidence Concerning Intrauterine Respiratory-Like Movements , Pediatrics 17:747, 1956. 14. Barcroft, J.: Researches on Pre-Natal Life , Springfield, Ill: Charles C Thomas, Publishers, 1947, vol 1, p 268. 15. Dawes, G.: "Changes in the Circulation at Birth and the Effects of Asphyxia," in Gairdner, D. (ed.): Recent Advances in Paediatrics , ed 2, Boston: Little, Brown & Company, 1958, p 9. 16. Schmidt, C.: "Reflex Regulation of Respiration," in Bard, P. (ed.): Medical Physiology , ed 10, St. Louis: C. V. Mosby Co., 1956. 17. Reynolds, S.R.M.: Nature of Fetal Adaptation to the Uterine Environment: A Problem of Sensory Deprivation , Amer J Obstet Gynec 83:800, 1962. 18. Burns, B.D.: The Central Control of Respiratory Movements , Brit Med Bull 19:7, 1963. 19. Avery, M.E.: Some Effects of Altered Environments: Relationships Between Space Medicine and Adaptations at Birth , Pediatrics 35:345, 1965. 20. Cross, K.W., and Malcolm, J.L.: Evidence of Carotid Body and Sinus Activity in Newborn and Foetal Animals , J Physiol 118:10P, 1952. 21. Cross, K.W.: Respiration in the Newborn Baby , Brit Med Bull 17:160, 1961. 22. Mitchell, R.A., et al: Regions of Respiratory Chemosensitivity on the Surface of the Medulla , Ann NY Acad Sci 109:661, 1963.Crossref 23. Winterstein, H.: Chemical Control of Pulmonary Ventilation: III. The Reaction Theory of Respiratory Control , New Eng J Med 255:331, 1956.Crossref 24. James, L.S.: Acidosis of Newborn and Its Relation to Birth Asphyxia , Acta Paediat 49 ( (suppl 122) ):17-28, 1960.Crossref 25. James, L.S., and Adamsons, K., Jr.: Respiratory Physiology of the Fetus and Newborn , New Eng J Med 271:1352, 1964Crossref 26. 271:1403, 1964. 27. Castro, F., de: Sur la Structure de la Synapse dans les Chemorecepteurs: Leur Mecanisme d'Excitation et Role dans la Circulation Sanquine Locale , Acta Physiol Scand 22:14, 1951.Crossref 28. Joels, M., and Neil, E.: The Excitation Mechanism of the Carotid Body , Brit Med Bull 19:21, 1963. 29. Downing, S.D.; Remensnyder, J.P.; and Mitchell, J.H.: Cardiovascular Responses to Hypoxic Stimulation of the Carotid Bodies , Circ Res 10:676, 1962.Crossref 30. Daly, M. de B., and Haggledine, J.L.: The Effects of Artificially Induced Hyperventilation on the Primary Cardiac Reflex Response to Stimulation of the Carotid Bodies in the Dog , J Physiol 168:872, 1963.

Journal

American Journal of Diseases of ChildrenAmerican Medical Association

Published: Oct 1, 1966

References