Mechanisms of O 2 transport in andean dogs

Abstract

Using previously inserted catheters. 11 dogs native to high altitude (7.5 23 kg b.wt.) were studied standing and unsedated in Cerro de Pasco. Peru at 4350 meters. Hemoglobin (Hb). hemalocrit (Hct). O 2 and CO 2 contents, p O 2 , p CO 2 and pH were measured in simultaneously obtained arterial and mixed venous blood samples. Blood pressures were measured in the pulmonary artery and the left ventricle and cardiac output (0) was determined by dye dilution. Moderately higher values for Hb and Hct were found in these dogs. Hb O 2 affinity was no different than that found in sea level dogs: the P in the Andean dogs was 31.6 mm Hg at 38 C and pH of 7.4. Because of the low barometric pressure at 4350 m (458 mm Hg) the partial pressures of oxygen in inspired and in alveolar air were lower than at sea level: 84.3 and 56.4 mm Hg, respectively. Pa, and Pv, were 55.5 and 32.9 mm Hg while the Sao. and Svo. were 79.5 and 50.7, respectively. Marked hyperventilation was observed (Pace, 25.6 mm Hg). however. pH was normal. Cardiac output was normal (average 162 + 39 ml/min/kg). Moderate pulmonary arterial hypertension was observed in the presence of normal left ventricular end diastolic pressure suggesting increased pulmonary vascular resistance.