Cardiovascular autonomic reflexes in heavy smokers.

In order to study the effect of smoking on cardiovascular function, 25 healthy subjects with an average smoking history of 25 +/- 9 pack-years were examined using the Valsalva manoeuvre and the deep-breathing test. For each smoker there was a healthy, non-smoking control subject of matching age, sex and body mass index. During the tests, heart rate and blood pressure were recorded continuously. Compared with the controls, the smokers had (1) a smaller increase in heart rate during the strain phase of the Valsalva manoeuvre (P = 0.04); (2) weaker rebound increases in arterial pressure after the Valsalva strain (P = 0.007 for systolic and P = 0.02 for diastolic blood pressure); (3) smaller reflex bradycardia after the Valsalva strain (P = 0.02); and (4) a longer latency between post-strain rises in pressure and bradycardia (P = 0.001). This suggests that diminished blood pressure responses occur as a consequence a chronic dysregulation of peripheral vasoconstriction, while diminished heart rate responses are due to attenuated blood pressure responses. A prolonged latency may be a sign of a dysfunction of parasympathetic baroreflex control. It is concluded that heavy smoking is accompanied by a disturbance of cardiovascular autonomic control.