A study to assess the reproducibility of limb blood flow measurements by venous occlusion plethysmography using mercury-in-Silastic strain gauges was performed in six normal volunteers under standardized conditions. Using this technique forearm and calf blood flow were measured at rest and between 2 and 3 min after submaximal exercise on six separate occasions over a 1 month period. The mean coefficient of variation for resting forearm blood flow was 10.5% (range 7.8-15.6%). The mean coefficient of variation for resting calf blood flow was 11.5% (range 7.4-14.2%). The mean coefficient of variation for post-exercise calf blood flow was 13% (range 11.5-16.4%). The results suggest that limb blood flow measurement by this technique may be useful in studies where serial measurements are required.
1 To compare the haemodynamic effects of secondary characteristics of beta‐adrenoceptor blockers with an angiotensin converting enzyme inhibitor forty patients with previously untreated mild to moderate hypertension were prescribed either atenolol 50‐100 mg day‐1, labetalol 200‐800 mg day‐1, pindolol 10‐30 mg day‐1 or captopril 25‐100 mg day‐1 and observed for 6 months. 2 Over this period: (a) All four drugs produced similar reductions in blood pressure at rest (P less than or equal to 0.01) and after exercise (P less than or equal to 0.01). (b) All four drugs significantly decreased resting forearm (P less than or equal to 0.01) and calf blood flow (P less than or equal to 0.01). They all also caused a significant reduction in the increased calf blood flow following exercise (P less than or equal to 0.01). (c) No drug produced a change in resting forearm vascular resistance, while resting calf vascular resistance was decreased by captopril and pindolol, unaltered by labetalol and increased by atenolol. Post‐exercise calf vascular resistance was increased by atenolol, labetalol and pindolol but unaltered by captopril. (d) Although all four drugs produced a fall in resting heart rate this was significantly greater for atenolol and labetalol (P less than or equal to 0.01). All four treatments however significantly reduced the increase in heart rate following exercise (P less than or equal to 0.01). (e) No drug produced any significant change in resting and post‐exercise stroke volume/ejection fraction. 3 It is concluded that despite differing modes of action all four drugs reduce limb blood flow. This primarily appears to be a consequence of reduced perfusion pressure associated with limited autoregulation of skeletal muscle circulation. The reduction in arterial vascular resistance produced by captopril and pindolol is inconsistent and does not appear of major benefit in preserving limb blood flow. The reduction in perfusion with the agents studied may in part be related to a fall in cardiac output associated with decreased heart rate. This suggests that captopril may exert antisympathetic activity when used as an antihypertensive agent.
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