Increased sensitivity of the arterial chemoreceptor drive in young men with mild hypertension

Ventilatory, airway occlusion pressure, arterial blood pressure and heart rate responses to isocapnic progressive hypoxia and to hypercapnia in high oxygen, both induced by a rebreathing method, were measured in 20 hypertensive male subjects aged 20 to 21 years with a diastolic blood pressure of 13.1 KPa +/- 0.34 SD (98 mmHg +/- 2.6 SD) and in 20 age-matched normotensive male subjects. Ventilatory, airway occlusion pressure and blood pressure response to hypoxia was significantly greater in the hypertensive subjects. Hypoxic ventilatory drive measured as the parameter A denoting the shape of the V1-O2 curve was 28.8 +/- 2.7 SEM (range 7.0 to 44.2) in the normotensive group and 116.1 +/- 10.5 SEM (range: 71.6 to 234.77) in the hypertensive group, the difference being highly significant (P less than 0.001). The magnitude of respiratory sinus arrhythmia (RSA) recorded during progressive hypoxia and plotted against either PA. O2 or VI values was significantly greater in the hypertensive group. The difference in ventilatory and circulatory responses to hyperoxic hypercapnia between the two groups of subjects was not significant. There was a significant correlation between the responses to hypoxia and hypercapnia in the normotensive subjects (r = 0.56, t = 2.861, P less than 0.01) but no correlation in the hypertensive subjects (r = 0.07). It is concluded that dissociation of the responsiveness of the peripheral and central chemosensitivity, the former being significantly increased and predominant, occurs in early, mild hypertension.