Comparative circulatory responses to systemic hypoxia in man and in unanesthetized dog.

Studies on the regulation of myocardial blood flow in man II. Effects of acute arterial hypoxia

“…5). Increase in heart rate and cardiac output as well as alterations of arterial and pulmonary artery pressures are in accordance with findings reported in the literature (10,12,21,37,42,45,48,49,68). Undulating variations in arterial blood pressure were seen during the hypoxic tolerance test and the period of adaptation to hypoxia prior to the beginning of flow measurements.…”

Effects of prolonged anoxia on electrical activity of the heart in Crucian carp (Carassius carassius)

“…When anoxia develops, the homeostatic response to oxygen shortage involves a strong bradycardic reflex and remarkable lengthening of ventricular AP duration. Anoxic bradycardia probably delivers energy savings via AP arrest, while the ultra-long ventricular AP keeps blood flowing even with heart beat intervals of 15-20 s. These responses contrast with those of hypoxia-sensitive endotherms, where _ Q is maintained by tachycardia and energy savings in hypoxic myocytes are achieved by shortening of AP duration (Kontos et al, 1967;Vogel and Harris, 1967;Noma, 1983). These remarkable adaptations of the crucian carp heart are probably necessary for the exceptional anoxia tolerance of the species, driven by selection pressure in shallow lakes, which may freeze down to the bottom during the long northern winters (Nikolsky, 1963;DeVries, 1971;Holopainen and Oikari, 1992).…”

“…In contrast to fishes, adult mammals usually respond to hypoxia with tachycardia (Kontos et al, 1967). In this case, cardiac protection is provided by the shortening of ventricular AP, due to the opening of ATP-sensitive K + channels (Noma, 1983).…”

Quick Increase of Pulmonary Blood Flow in Response to an Acute Alveolar Hypdxia in Human Subjects

“…KONTOS et al(1967)compared the changes in heart rate,cardiac output and stroke volume in human subjects and dogs in response to hypoxia.The increase of these variable were stronger in human subjects than in dogs. MALIK and KIDD(1973) observed a gradual but clear increase in cardiac output in anesthetized dogs.…”

“…One of the fundamental adjustments may be an increment in pulmonary blood flow, by which a sufficient amount of oxygen would be taken up from the hypoxic alveolar gas. Cardiac output (i .e., pulmonary blood flow) increases in human subjects when they breathe mild hypoxic gas mixtures (KONTOS et al, 1967;MOCHIZUKI et al, 1975;RICHARDSON et al, 1966;WESTCOTT et al, 1951). However, the time course of the increase in response to hypoxia is still unknown, probably because no method applicable to the measurement of quick changes of cardiac output in human subjects has been available.…”