Arterial H+ as a Determinant for Interindividual Variability of Respiratory Chemosensitivity to Hypoxia in Man

Abstract

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.