Decreased ventilatory responses to hypoxia and hypercapnia have been demonstrated in a variety of disorders; however, the etiology of these decreased drives remains virtually unknown. Recent observations have suggested a familial influence on hypoxic and hypercapnic ventilatory response, but it is unclear whether this influence is the result of hereditary or environmental influences. Therefore we measured the ventilatory response to isocapnic hypoxia (HVR) and hyperoxic hypercapnia in 12 pairs of identical and 12 pairs of nonidentical twins. Significant correlation (P less than 0.01) was found for HVR within identical twin pairs but not within nonidentical twin pairs. Identical twins resembled each other more closely with respect to HVR than was the case for nonidentical twins (P less than 0.0125). This was independent of body size, blood PCO2, or pH. No such correlation could be found for ventilatory response to hyperoxic hypercapnia. It is concluded that hereditary influences affect HVR and it is speculated that such influences may play a role in clinical conditions characterized by decreased hypoxic ventilatory responses.
D D Collins, C H Scoggin, C W Zwillich, J V Weil