Effect of exercise on acid-base status and ventilatory kinetics

The normal respiratory responses and changes in acid base status in twenty normal height, weight and age matched subjects were studied; using Auto Spiro AS 300 spirometer for ventilatory parameters and NOVA stat profile 3 analyser for gas analysis. Each subject performed a progressive incremental treadmill exercise by Bruce protocol to their symptom limited maximum. Minute ventilation (VE), tidal volume (VT) and frequency of respiration (f) increased significantly (P<0.001). Acidosis occured following exercise as pH of arterialized venous blood declined significantly (P<0.05). Gas analysis of arterialized venous blood showed a rise in pO2 (P<0.001) and a fall in pCO2 (P<0.001). Recovery of acid base status as well as gaseous pressure in blood did not occur after 10 min. Expired gas pCO2 declined significantly (P<0.05) and pO2 increase significantly (P<0.05). These pressures returned to resting levels 10 min after exercise. Thus in normal young adults heavy exercise caused an increment in ventilatory kinetics producing hyperpnoea which recovers after a rest of 10 min. Acidosis stimulates the respiratory centre to cause hyperventilation which tries to meet the added metabolic demands of strenuous exercise.