Capillary pressure, pulse pressure amplitude, and pressure waveform in healthy volunteers.

The influence of gender, local temperature, and systemic blood pressure on human capillary pressure is unknown. Finger nail fold capillary pressure was therefore directly measured in 74 healthy supine volunteers (40 female) at midaxillary level. Capillary pressure was lower in women than in men (15.9 +/- 3.0 vs. 18.2 +/- 2.3 mmHg; P = 0.001), particularly in premenopausal women, but was not related to systolic, diastolic, or mean blood pressure. Capillary pulse pressure amplitude was related to skin temperature, an effect more marked in women (P = 0.003). There was a significant association between skin temperature and the time taken for the systolic pressure rise to reach the capillary, in women only (r = -0.69, P < 0.001). Increasing age reduced the high-frequency waves in the pressure waveform [2nd harmonic percentage of fundamental: r = -0.52 and P = 0.002 (women), r = -0.52 and P = 0.004 (men)]. Thus mean capillary pressure and the pressure waveform may be influenced by gender, age, and skin temperature, illustrating the necessity to adequately match control groups during assessments of capillary pressure pathophysiology.