Ventilatory and circulatory O2 convection and blood acid-base changes in normoxic and hypoxic awake miniature swine.

1. Awake miniature swine were studied at rest and at neutral temperature while breathing either normoxic or hypoxic gas mixtures, PIO2 = 145 and 82 Torr, at low altitude. 2. Steady-state pulmonary ventilation (Vg) and breathing pattern (VT, fR), oxygen consumption (MO2), O2 concentrations (C) and pressures (P) in the arterial (a) and mixed venous blood (v), hematocrit (Ht) and acid-base status in arterial blood, heart frequency (fH) and systemic and pulmonary arterial pressures were measured. 3. From these data cardiac output (Vb) and stroke volume (Vs), ventilatory and circulatory requirements (Vg/MO2, Vb/MO2), extraction of O2 from inspired gas (EgO2) and blood (EbO2), capacitance coefficient of blood for oxygen (beta bO2), and the various oxygen conductances (GO2) from inspired air to mixed venous blood were calculated. 4. The miniature swine exhibited classical ventilatory and circulatory responses to hypoxia, although their ventilatory frequency was relatively low and the values of PCO2 and HCO3- concentration in the arterial were blood higher than in other mammals.