Cardiovascular, respiratory, and metabolic adjustments to exercise in dogs

Abstract

Cardiovascular and metabolic parameters were studied in dogs anesthetized with pentobarbital sodium, and while awake resting or exercising for 30 min at either 6.4 km/h, 10% grade (32% .ovrhdot.VO2 max [maximum O2 uptake] or 8.0 km/h, 16% grade (50% .ovrhdot.VO2 max). The anesthetized dogs had lower cardiac outputs, stroke volumes, arterial-mixed venous O2 differences .ovrhdot.VO2, rectal temperatures, and higher diastolic and mean arterial pressures than awake resting dogs. Heart rates and arterial systolic pressures were similar in the 2 conditions. The increased .ovrhdot.VO2 during exercise were associated with approximately equal percentage increments in cardiac outputs and O2 extractions. Cardiac output increases during exercise were largely due to increases in heart rates. Arterial CO2 tension and CO2 contents as well as venous O2 and CO2 gas tensions and contents declined, and pH and rectal temperatures increased during exercise. The dogs became alkalotic during exercise. Elevated central body temperatures appeared to be the major factor controlling respiration.