Characteristics of skin blood flow over the trochanter under constant, prolonged pressure

Although laboratory studies have documented that externally applied pressure disrupts circulation, in clinical practice little is known about the characteristics of blood flow over bony prominences as a function of time. The purpose of this study was to describe the pattern of blood flow over the trochanter when subjected to a constant interface pressure for a prolonged period of time. A quasi-experimental design was used to measure skin blood flow over the left trochanter in a sample of 19 healthy adults. With the use of laser doppler flowmetry, the pattern of blood flow was monitored continuously while subjects lay on a supportive air mattress. Measurement of blood flow was described for three periods: preload with subjects supine, loading with subjects in the left lateral position and hyperemia after subjects returned to the supine position. Rate of blood flow under loading showed a gradual increase from preload. There was a marked initial increase in flow during hyperemia that gradually tapered off, but failed to reach preload levels within 30 min. Individual blood flow tracings revealed an inconsistent pattern of response to loading, suggesting the presence of a range of physiological response to compressive surface pressure. Given the individual variation in response to a common external pressure, further research is recommended to evaluate the pattern of blood flow over bony prominences subjected to known interface pressure.