PMID: 591470Nov 1, 1977

Effects of acute prolonged hypoxia on cardiovascular dynamics in dogs

Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology
J F Borgia, S M Horvath


Intact anesthetized dogs were exposed for 75 min to either 5.75, 9.0, or 12.0% oxygen in nitrogen. Although pulmonary artery pressures were significantly elevated in all hypoxic exposures, systemic hypertension occurred only at the onset of severe hypoxia(5.75% O2). Coronary blood flow increased from an average of 130 during normoxia to a peak of 400 ml/100 g per min during inhalation of 5.75% O2, and coronary sinus oxygen tensions of 8 Torr and oxygen contents of 1.1 ml/100 ml were sustained for 75 min without biochemical, functional, or electrophysiological evidence of myocardial ischemia. Cardiac index (CI) increased significantly only during severe hypoxia (5.75% O2) with the greatest elevation after 30 min. Subsequently, CI decreased concomitantly with a 27% elevation in arterial hemoglobin concentration and oxygen-carrying capacity. It is concluded that the hypoxic threshold for significant elevations of cardiac output is between 6.0 and 9.0% O2.


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Feb 1, 1993·International Journal of Biometeorology·M TakeokaY Zhang
Mar 20, 2009·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Michael K SticklandJerome A Dempsey

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