The ventilatory and metabolic response to hypercapnia in newborn mammalian species |
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| Affiliation: | 1. Department of Physiology, McGill University, 3655 Drummond Street, Montreal, Quebec, H3G 1Y6, Canada;2. Société Zoologique de Granby, Granby, Québec, Canada;1. Department of Orthodontics, The Affiliated Stomatological Hospital of Xi’an Jiaotong University, Xi’an, Shaanxi 710004, China;2. Institute of Neurobiology, Xi’an Jiaotong University Health Science Center, Xi’an, Shaanxi 710061, China;1. Institute of Physiology, University of Regensburg, D-93053, Regensburg, Germany;2. University Hospital of Mannheim, Department of Internal Medicine V, Theodor-Kutzer-Ufer 1-3,D-68167 Mannheim, Germany;3. University Children’s Hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland;4. Laboratories of Excellence, Ion channel Science and Therapeutics, Nice, France;5. Institute of Anesthesiology, University of Ulm, D-89081 Ulm, Germany;6. University Hospital of Erlangen, Department of Internal Medicine 1, Ulmenweg 18, D-91054 Erlangen, Germany;7. Institute of Forensic Medicine, University of Zurich, Switzerland;1. Medizinische Klinik, University hospital Mannheim, University of Heidelberg, Theodor-Kutzer-Ufer 1-3, D-68167 Mannheim, Germany;2. Institute of Physiology, University of Regensburg, D-93053 Regensburg, Germany;3. Department of Anaesthesiology, University of Ulm, D-89075 Ulm, Germany;4. University children''s hospital, Steinwiesstr. 75, CH-8032 Zürich, Switzerland;1. Department of Orthodontics, Medical Faculty, University of Bonn, Welschnonnenstr.17, D-53111 Bonn, Germany;2. Endowed Professorship for Oral Medical Technology, University of Bonn, Welschnonnenstr. 17, D-53111 Bonn, Germany;3. Institute of Molecular Psychiatry, Medical Faculty, University of Bonn, Sigmund-Freud-Str. 25, D-53127 Bonn, Germany;4. Orthodontic private practice, Richard-Wagner-Straße 9-11, 50674 Cologne, Germany |
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| Abstract: | Conscious newborns of 12 species from 4 mammalian orders, ranging in body mass (M) from 1 g (mouse) to 5 kg (deer), were studied during air and during 5% CO2 breathing. The interspecies relationship between oxygen consumption (V̇O2) and M was the same in air and hypercapnia, in both cases V̇O2 ∝ M0.90; on average, hypercapnic V̇O2 was 101% of the air value. In 5% CO2, ventilation (V̇e) increased in all newborns, mostly because of the increase in tidal volume (178%), whereas breathing rates averaged 98% of the air values. The hyperpnea during CO2 was slightly greater in the larger newborns. Body temperature was not altered by CO2 breathing. We conclude that the average respiratory response of the newborn to moderate hypercapnia is a hyperventilation different from that of the neonatal mammal in acute hypoxia (Mortola et al., Respir. Physiol. 78: 31–43, 1989). In fact, hypercapnic hyperventilation resulted only from the hyperpnea, with no hypometabolic contribution, and the hyperpnea reflected the increase in tidal volume, with no change in rate. It is also concluded that the neonatal hypometabolic response is specific to hypoxia, and not an undifferentiated response to chemoreceptors stimulation. |
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