The influence of age on reactive hyperaemia in the human calf: a study with strain gauge plethysmography.

Postischaemic reactive hyperaemia in the calf was investigated by strain gauge plethysmography in four groups of ten subjects. The mean age of the different groups was 6, 13, 24 and 57 years respectively. Basal calf flow, repayment and recovery time in the 6-year-old children were greater than in the other groups, which may be related to a higher metabolic rate in young children. Maximal flow in the four groups was not significantly different, which indicates that the arteriolar response to circulatory arrest is not altered by increasing age. The cause of delay in maximal flow in the group of 6-year-olds is not clearly understood. Basal and postischaemic lowest peripheral resistance increased with age, which is probably caused by changes of the arterioles due to ageing and possibly inactivity. The fall in peripheral resistance induced by 3 min of ischaemia was positively correlated with mean blood pressure. This may be due to a greater net reduction in blood pressure during ischaemia, which brobably elicits a stronger myogenic response of the vessel wall. It is concluded that in clinical use of the reactive hyperaemia test in the calf, the influence of age is of minor importance, whereas postischaemic peripheral resistance is a more accurate measure of vasocilation for comparison of subjects with different blood pressure.