HbO2 dissociation in man during prolonged work in chronic hypoxia.
In healthy human sojourners to 3,100 m we studied exercise-induced shifts in HbO2 dissociation: their regulation in femoral venous blood and their net effect on estimated capillary PO2 (PC-O2) in working skeletal muscle. Prolonged heavy work effected an increase of 10.3 plus or minus 0.9 mmHg in in vivo P50 (7.30 PH-v, 41 degrees C-v, and 45 Pv-CO2); due entirely to the additive effects of increased venous temperature and [H+]. The rightward curve shift during work at 3,000 m, compared to that at 250 m, produced a similar increase in in vivo P50 but a reduced net effect on PC-O2, because Cv-02 at 3,100 m was reduced similar to 2 ml/100 ml to the lower converging portions of the curve. The lower Cv-O2 (and Pv-O2) at 3,100 M was attributable to a small decrease in total systemic blood flow. The net effect of the rightward curve shift during exercise on mean to end-capillary PO2 was positive in most cases (+1 to +8 mmHg PCO2). However, it was shown that the levels of mean to end-capillary PO2 (28-13 mmHg), which would have been obtained during exercise in the absence of any rightward curve shift, were more than adequate to sustain a steady state of aerobic energy production in working skeletal muscle. These data do not support the concept of a significant contribution to oxygen delivery to working skeletal muscle from in vivo shifts in HbO2 dissociation, during either acclimatization to high altitude or during prolonged muscular work.
D000064:Acclimatization; D000136:Acid-Base Equilibrium; D000328:Adult; D000531:Altitude; D001783:Blood Flow Velocity; D001831:Body Temperature; D002196:Capillaries; D002302:Cardiac Output; D005268:Femoral Vein; D006339:Heart Rate; D006454:Hemoglobins; D006801:Humans; D000860:Hypoxia; D008297:Male; D009132:Muscles / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D005082:Physical Exertion; D013990:Tidal Volume; D013997:Time Factors
D006454:Hemoglobins; D010100:Oxygen