Ventilatory responses in patients with essential hypertension.

We investigated the ventilatory responses to hypoxia and hypercapnia in patients with essential hypertension (HT) as compared with healthy subjects (NV). Further, to evaluate the contribution of the peripheral chemoreceptors to ventilatory response, we used a withdrawal test. Hypoxic ventilatory drive (HVR) was measured as the parameter A denoting the shape of VI (inspiratory minute ventilation)-PETO2 (end-tidal PO2) curve which was calculated by the empirical equation: VI = V0 + A/(PETO2-32). Hypercapnic ventilatory drive (HCVR) was measured as the parameter S denoting the shape of the VI-PETCO2 (end-tidal PCO2) relation which was calculated by the empirical equation: VI = S(PETCO2-B). There were no significant differences in the parameters of HVR and HCVR between NV and HT. A positive correlation between A/BSA and S/BSA was found to be significant in NV (r = 0.873, p less than 0.05). Conversely, there was no significant correlation between A/BSA and S/BSA (r = 0.547) in HT. On the other hand, the withdrawal responses (delta VI/BSA and % delta VI:delta VI/VI x 100%) were obtained from the magnitude of depression in ventilation caused by two breaths of O2 in hypoxic hypercapnia. In the withdrawal responses, delta VI/BSA and % delta VI in HT were significantly higher than those in NV. A/BSA significantly correlated with delta VI/BSA (NV, r = 0.684, p less than 0.05; HT, r = 0.648, p less than 0.05) in both NV and HT. However, delta VI/BSA in HT tended to be higher than that in NV, under the same value of A/BSA. These results suggested that the peripheral chemoreceptor activity was augmented in HT.