title: Wavelet analysis of skin blood oscillations in persons with spinal cord injury and able-bodied subjects.
abstract: OBJECTIVE
  To assess the blood oscillations in the skin over the ischial tuberosity (high-risk area for pressure ulcer) using spectral analysis of laser Doppler flowmetry signals based on wavelet transform.
  
  
  METHODS
  Wavelet analysis of skin blood oscillations in persons with spinal cord injury (SCI) and able-bodied subjects.
  
  
  METHODS
  Seating and body support interface laboratory.
  
  
  METHODS
  Ten men were recruited for this study, of whom 5 were able-bodied subjects (age, 31.2+/-3.3 y) and 5 were persons with SCI (age, 37.2+/-7.3 y).
  
  
  METHODS
  External pressure of 16.0 kPa (120 mmHg) was applied to the ischial tuberosity via 1 specifically designed pneumatic indentor. The loading duration was 30 minutes.
  
  
  METHODS
  Skin blood flow was monitored for 10 minutes prior to loading and 20 minutes after the prescribed loading period. With spectral analysis based on wavelet transform, 5 frequency intervals were identified (.01-.02, .02-.06, .06-.15, .15-.40, .40-2.0 Hz) corresponding to endothelial related metabolic, neurogenic, myogenic, respiratory, and cardiac activities, respectively.
  
  
  RESULTS
  The relative amplitude of the metabolic component for persons with SCI was significantly lower (F=5.26, P=.032) during the resting conditions as compared with able-bodied subjects. During the postloading period, the response of oscillatory activities was evidently lower in the skin over the ischial tuberosity for persons with SCI when compared with able-bodied subjects. In addition, the relative amplitude of the neurogenic component (.02-.06 Hz) during postloading was significantly lower for persons with SCI (F=5.44, P=.029).
  
  
  CONCLUSIONS
  These findings suggest that the contributions of endothelial related metabolic and neurogenic activities to the blood perfusion regulation become relatively less for persons with SCI during the resting and postloading periods, respectively.
authors.affiliation: Department of Health Technology and Informatics, Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China.
authors.forename: Zengyong
authors.initials: Z
authors.lastname: Li
authors.forename: Jonathan Y
authors.initials: JY
authors.lastname: Leung
authors.forename: Eric W
authors.initials: EW
authors.lastname: Tam
authors.forename: Arthur F
authors.initials: AF
authors.lastname: Mak
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D006801:Humans; D008297:Male; D003668:Pressure Ulcer / Q000209:etiology; D012212:Rheology; D012867:Skin / Q000098:blood supply* / Q000378:metabolism; D013119:Spinal Cord Injuries / Q000503:physiopathology*