Gas Exchange in Two Male Age Groups in Relation to Inspiratory Oxygen Fraction, Physical Exercise and Body Posture

Abstract

Two groups of male subjects, mean age 25 and 50 years, were studied at rest supine during air breathing, 15–11 and 100% O₂ breathing, sitting at rest and during exercise up to maximal work load, and supine during a constant submaximal work load combined with D_LCO measurements. At rest supine, the mean and range of P_aO2 was 90.2 (79–97) in the young and 78.2 (68–88) mmHg in the middle-aged. P_{A - aO2} was 4.3 (−1–14) and 23.4 (15–33) mmHg, respectively. Corresponding S_aO2 values were 97.3 (95.7–99.0) and 94.5 (91.7–98.6) per cent. During hypoxia, the P_aO2 and P_{A - aO2} values were lower in the young than the middle-aged. During hyperoxia the P_aO2 and P_{A - aO2} were 611 (574–644) and 48(31–60) in the young and 573 (492–612) and 93 (60–108) mmHg in the middle-aged, respectively. V_D and V_D/V_T were constantly higher in the middle-aged. At max. work load, no great difference in P_aO2 (87.5 and 85.8 mmHg) or S_aO2 (95.8 and 94.2 %) was found. The mean D_LCO values were 39.2 (young) and 36.8 (middle-aged) ml/mmHg min, as measured at _O2 1 490 and 1 656 ml/min, and at _E 35.9 and 43.6 1/min, respectively.