title: Wavelet-based spectrum analysis of sacral skin blood flow response to alternating pressure.
abstract: OBJECTIVE
  To provide insight into the physiologic mechanisms associated with alternating pressure, using wavelet analysis of skin blood flow (SBF) oscillations, and to determine whether the application of alternating pressure induces myogenic responses, thereby enhancing SBF as compared with constant loading.
  
  
  METHODS
  Repeated-measures design.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Healthy, young adults (N=10; 5 men, 5 women; mean age +/- standard deviation, 30.0+/-3.1 y).
  
  
  METHODS
  Alternating pressure for 20 minutes (four 5-min cycles with either 60 mmHg or 3 mmHg) and constant loading for 20 minutes at 30 mmHg on the skin over the sacrum.
  
  
  METHODS
  A laser Doppler flowmeter was used to measure sacral SBF response to both alternating pressure and constant loading. Wavelet-based spectrum analysis of SBF oscillations was used to assess underlying physiologic mechanisms including endothelium-related metabolic (.008-.02 Hz), neurogenic (.02-.05 Hz), and myogenic (.05-.15 Hz) controls.
  
  
  RESULTS
  Alternating pressure stimulated an increase in sacral SBF of compressed soft tissues as compared with constant loading (P<.01). SBF during the high-pressure phase of 4 alternating pressure cycles showed an increasing trend. An increase in power in metabolic frequency range and a decrease in power in the myogenic frequency range during alternating pressure were observed compared with SBF prior to loading. Power increased in the myogenic frequency range during the low-pressure phase of alternating pressure and decreased during the high-pressure phase.
  
  
  CONCLUSIONS
  SBF control mechanisms, as assessed by the characteristic frequencies embedded in SBF oscillations, show different responses to 2 loading pressures with the same average pressure but different patterns. Our study suggests that optimization of operating parameters and configurations of alternating pressure support surfaces to compensate for impaired SBF control mechanisms in pathologic populations may be possible using wavelet analysis of blood flow oscillations.
authors.affiliation: Department of Rehabilitation Science and Technology, University of Pittsburgh, Pittsburgh, PA 15203, USA. yij2@pitt.edu
authors.forename: Yih-Kuen
authors.initials: YK
authors.lastname: Jan
authors.forename: David M
authors.initials: DM
authors.lastname: Brienza
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Geyer
authors.forename: Patricia
authors.initials: P
authors.lastname: Karg
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D003668:Pressure Ulcer / Q000503:physiopathology* / Q000517:prevention & control; D012039:Regional Blood Flow; D015427:Reperfusion Injury / Q000503:physiopathology; D012447:Sacrum; D012867:Skin / Q000098:blood supply*; D013057:Spectrum Analysis; D014664:Vasodilation / Q000502:physiology