Effects of dopamine and domperidone on ventilatory sensitivity to hypoxia after 8 h of isocapnic hypoxia.

Acclimatization to altitude involves an increase in the acute hypoxic ventilatory response (AHVR). Because low-dose dopamine decreases AHVR and domperidone increases AHVR, the increase in AHVR at altitude may be generated by a decrease in peripheral dopaminergic activity. The AHVR of nine subjects was determined with and without a prior period of 8 h of isocapnic hypoxia under each of three pharmacological conditions: 1) control, with no drug administered; 2) dopamine (3 microg. min-1. kg-1); and 3) domperidone (Motilin, 40 mg). AHVR increased after hypoxia (P </= 0. 001). Dopamine decreased (P </= 0.01), and domperidone increased (P </= 0.005) AHVR. The effect of both drugs on AHVR appeared larger after hypoxia, an observation supported by a significant interaction between prior hypoxia and drug in the analysis of variance (P </= 0. 05). Although the increased effect of domperidone after hypoxia of 0. 40 l. min-1. %saturation-1 [95% confidence interval (CI) -0.11 to 0. 92 l. min-1. %-1] did not reach significance, the lower limit for this confidence interval suggests that little of the increase in AHVR after sustained hypoxia was brought about by a decrease in peripheral dopaminergic inhibition.