Effect of an increase in systemic blood pressure on nailfold capillary pressure in humans.
Moderate autoregulation of capillary pressure occurs during changes in arterial and/or venous pressure in animals. Whether an increase in systemic blood pressure is transmitted to capillaries in humans is unknown. Eight healthy volunteers performed isometric handgrip exercise (30% of maximum) while nailfold capillary pressure (CP) and digital arterial blood pressure (DBP) were measured in the contralateral hand. CP was measured for 40 s before exercise and 40-100 s during exercise. Only experiments with no change in pipette position and no artifactual changes in flow were accepted. Basal DBP was stable [91.5 +/- 12.7 mmHg (-40 to -20 s basal) and 91.3 +/- 11.8 mmHg (-20 to 0 s basal)], and isometric exercise increased DBP [100.4 +/- 13.9 mmHg (0-20 s exercise) and 103.1 +/- 15.3 mmHg (20-40 s exercise); P < 0.05]. CP was unchanged during the first 40 s of exercise [18.9 +/- 4.9 mmHg (-40 to 20 s basal), 18.9 +/- 5.2 mmHg (-20 to 0 s basal), 18.4 +/- 4.7 mmHg (0-20 s exercise), and 18.3 +/- 5.3 mmHg (20-40 s exercise)] and remained unchanged for up to 100 s (n = 5), despite a continued elevation of DBP. These data suggest that protective mechanisms minimize the transmission of increases in systemic blood pressure to the capillary bed in humans.
Shore
A C
AC
Clinical Microvascular Unit, Postgraduate Medical School, University of Exeter, United Kingdom.
Sandeman
D D
DD
Tooke
J E
JE
D000328:Adult; D001794:Blood Pressure / Q000502:physiology*; D002196:Capillaries / Q000502:physiology; D005260:Female; D005385:Fingers / Q000098:blood supply; D006801:Humans; D008297:Male; D008875:Middle Aged; D009262:Nails / Q000098:blood supply*; D011674:Pulse; D015203:Reproducibility of Results