NORMAL VARIATION IN CUTANEOUS BLOOD CONTENT AND RED-BLOOD-CELL VELOCITY IN HUMANS

This study was designed to determine normal variations in cutaneous bl ood content, red blood cell content and skin thickness in healthy huma n volunteers. The blood content (BC) of human skin and the velocity of red blood cells (REV) has been comprehensively mapped over 30 anatomi cal sites in 28 volunteers between the age of 7 and 77 years using ref lectance spectrophotometry (RFS) and laser Doppler (LD) techniques res pectively. Total skin thickness, which may have a relationship with bl ood content. has been mapped at the same anatomical sites in six of th e volunteers using two-dimensional array, 12 MHz ultrasound equipment. The major determinant of BC and REV was found to be anatomical site. Regardless of age, gender or prior sun exposure, anatomical sites abov e the waist produced higher readings than below. BC and REV were found to be dependent on age and gender at most sites with higher readings being observed in males and younger volunteers. The largest difference was seen in males under 55 years whose RFS readings above the waist w ere significantly higher than in older males or females of any age. He avy prior sun exposure and skin thickness could not be demonstrated to impact on either RFS or LD readings independently of the effects of a natomical site, gender or age. In general, RFS and LD readings paralle led one another and correlated linearly at most anatomical sites. Whil e RFS readings tended to decrease in the cranio-caudal direction, LD r eadings were relatively uniform across the body except for the head an d groin where they were higher, and the abdomen where they were lower. The site-to-site variations in RFS readings observed in this study co rrespond well to capillary density variations noted in previous studie s.