Arterial H+ as a determinant for interindividual variability of respiratory chemosensitivity to hypoxia in man

Ventilatory response to normocapnic progressive hypoxia (A/BSA) was measured in 76 healthy males to examine how arterial blood gases and acid base status are involved in interindividual variability of hypoxic chemosensitivity. A/BSA and HCO3- were significantly higher in Group 1 (26 subjects, mean age = 15.8 +/- S.D. 0.9 years) than those in Group III (26 subjects, mean age = 46 +/- 7.1 years). A/BSA and HCO3- in Group II (24 subjects, mean age = 29.8 +/- 6 years) were in the middle of Groups I and III. Arterial blood gases and H+ were similar among the 3 groups. Arterial H+ correlated inversely with A/BSA (subjects with lower arterial H+ on air had higher hypoxic response) in Group I, while the correlation was positive (subjects with higher H+ on air had higher hypoxic response) in Group III. The correlation was not seen in Group II. PaCO2 and H+ correlated positively in the 3 groups. Intrasubject stability was equivalent among H+, PaCO2, and HCO3- (mean coefficients of variation = 1.81, 1.83, and 1.65, respectively), but smaller than that in PaO2 (3.28%). These results indicate that interindividual variability in hypoxic ventilatory response is related to arterial H+ in adolescent and middle age groups but the relation is opposite between the 2 groups.