Valsalva constrictor and heart rate reflexes in subjects with essential hypertension and with normal blood pressure

1. The haemodynamic and heart rate responses to graded expiratory pressures were studied during Valsalva manoeuvres of standard 30 s duration in two groups of normotensives in the upper (n= 10) and lower (n= 9) halves of the ‘normal’ blood pressure range, and in a group of essential hypertensive subjects with minimal complications (n= 10). Haemodynamic variables were arterial, atrial and peripheral vein pressures, cardiac output and total peripheral resistance. 2. Reflex and mechanical effects of the manoeuvre were assessed in each subject from changes in the relationship between the expiratory pressure and circulatory responses before autonomic blockade, after cardiac effector block and after ‘total’ blockade. 3. The relationships between expiratory pressure and central and peripheral vein pressures were not changed by autonomic blockade, indicating that they depended on mechanical factors. In hypertensives the rise in venous pressures per unit expiratory pressure was significantly smaller than in normotensive subjects. 4. The expiratory pressure‐related rise in total peripheral resistance was reflex and was similar in magnitude in all groups before autonomic blockade. However, after cardiac effector blockade the rise was greatest in the hypertensive subjects. The sensitivity of the constrictor response was related to the subjects’ resting total peripheral resistance index when measurements from all subjects were included. 5. The reflex heart rate responses of the hypertensives showed: (i) accentuation of the bradycardia at the start of forced expiration; (ii) an increased threshold for eliciting tachycardia during the latter part of the manoeuvre; and (iii) attenuation of the ‘overshoot’ bradycardia following release of expiratory pressure. 6. The differences between the responses of hypertensives and normotensives were relatively small and probably depended at least partly on differences in venous filling, structural differences of resistance vessels and different afferent inputs through arterial and cardiopulmonary baroreceptors.