The hyperaemic response of forearm skin to prolonged ischaemia, heating and pharmacological vasodilatation has been extensively studied and impaired endothelium dependent vasodilator function has been associated with disease such as diabetes (Caballero et al. 1999) and hypertension (Panza et al. 1995). Such tests are largely impractical for research into acutely changing conditions such as sepsis. We have therefore developed a modification of the technique using brief arterial occlusion to provoke a small hyperaemic response which is predominantly of myogenic rather than ischaemic origin. It is non-invasive and repeatable. We have previously shown this technique to be sensitive to changes in vascular tone (Webster et al. 2002) and to inhibition of prostaglandin synthesis (Moppett et al. 2003). In this study we investigated whether there was a significant difference in the transient hyperaemic response between young and old human subjects.

Following ethics committee approval and written informed consent, 33 young subjects (21-35 years) and 33 older subjects (65-85 years) were studied. All subjects were healthy and with blood pressure < 140/90, non-smoking and not taking any cardiovascular medication Forearm skin blood flow-flux was measured using two laser Doppler probes attached to the volar aspect of the outstretched forearm. Following a period of acclimatisation the axillary artery was compressed digitally for 20 seconds and then released. This was then repeated twice more. The transient hyperaemic response (THR) was recorded using custom designed software (Moor, Axminster, UK) and analysed offline. Values for net baseline flux and the THR ratio (peak hyperaemic flux divided by baseline flow flux) were recorded for each THR test and the mean of the three tests used for analysis. Data were analysed using Student’s unpaired t test, taking P < 0.05 overall as significant.

Baseline flow-flux was reduced in the older group compared to the younger (10.6 (0.98) vs. 15.2 (1.2) but THRR was not significantly different (3.51 (0.24) vs. 2.96 (0.11) (mean (S.E.M.)).The reduction in baseline flux is consistent with previous work.

Our data suggest that the healthy elderly have a preserved vasodilator response compared to young adults when using a myogenic stimulus. This is in contradistinction to their reduced response to prolonged ischaemia or pharmacological vasodilatation (Celermajer et al. 1994).

This work was supported by a grant from the Special Trustees of Nottingham Hospitals