Respiratory physiology & neurobiology
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Cardiogenic oscillations are small waves produced by heartbeats, which are superimposed on the pressure and flow signals at the airway opening. The aim of this study was to investigate the role of the two main factors believed to generate these oscillations: (1) contact between heart and lungs and (2) pulmonary blood flow. ⋯ Cardiogenic oscillations for pressure and flow were smaller at 50% compared to 100% pulmonary blood flow (0.80+/-0.12 cmH(2)O and 1.56+/-0.34 L min(-1) vs 1.19+/-0.14 cmH(2)O and 2.38+/-0.19 L min(-1)). We conclude that the amount of pulmonary blood flow and not the contact between heart and lungs is the main factor determining the amplitude of cardiogenic oscillations.
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Respir Physiol Neurobiol · Jul 2009
Comparative StudyComparison of the metabolic and ventilatory response to hypoxia and H2S in unsedated mice and rats.
Hypoxia alters the control of breathing and metabolism by increasing ventilation through the arterial chemoreflex, an effect which, in small-sized animals, is offset by a centrally mediated reduction in metabolism and respiration. We tested the hypothesis that hydrogen sulfide (H(2)S) is involved in transducing these effects in mammals. The rationale for this hypothesis is twofold. ⋯ When mice were simultaneously exposed to H(2)S and hypoxia, the stimulatory effects of hypoxia on breathing were abolished, and a much larger respiratory and metabolic depression was observed than with H(2)S alone. H(2)S had, therefore, no stimulatory effect on the arterial chemoreflex. The ventilatory depression during hypoxia and H(2)S in small mammals appears to be dependent upon the ability to decrease metabolism.