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)-PET(O2) (end-tidal P(O2)) curve which was calculated by the empirical equation: VI = V0 + A/(PET(O2)-32). Hypercapnic ventilatory drive (HCVR) was measured as the parameter S denoting the shape of the VI-PET(CO2) (end-tidal P(CO2)) relation which was calculated by the empirical equation: VI = S(PET(CO2)-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 < 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 02 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 < 0.05; HT, r = 0.648, p < 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.