Hypoxic ventilatory response in subjects with normal and high oxygen affinity hemoglobins.

Abstract

A C T It has still not been shown unequivo- cally whether a decrement of arterial oxygen content or tension governs the ventilatory response to hypoxia. In an attempt to discriminate between the two pos- sibilities, we have measured the ventilatory response to isocapnic progressive hypoxia in two healthy children with a high oxygen affinity hemoglobin (Hb Andrew- Minneapolis) and in their age-and sex-matched normal siblings. Hypoxic ventilatory response was identical in all subjects, there being no difference in minute ven- tilation at PAO2 = 40 mm Hg or in k (decrement of Po2 required to increase ventilation by a factor of 2.718). In contrast, at PAO2 = 40 mm Hg, hemoglobin oxygen saturation decreased markedly in controls but only slightly in high affinity subjects. Furthermore, the in- crease in heart rate at PAO2 = 40 mm Hg was signifi- cantly less in high affinity subjects, suggesting a con- comitant difference in oxygen delivery. Thus, with identical decrements in PAO2 but widely divergent changes in arterial oxygen content and oxygen delivery, controls and high affinity subjects showed virtually identical ventilatory response to hypoxia. We conclude