title: Respiratory and non respiratory oscillations of the skin blood flow: a window to the function of the sympathetic fibers to the skin blood vessels.
abstract: OBJECTIVE
  The skin blood flow (SBF) has been known to oscillate in frequency and amplitude. The nature and type of these oscillations have remained obscure. We studied the oscillations of the SBF in frequency and amplitude with non invasive techniques during normal breathing at rest and compared it to the oscillations during rhythmic paced breathing at 6 cycles per minute.
  
  
  METHODS
  Thirty healthy subjects were studied under normothermic conditions. The following variables were recorded: 1) EKG signal; 2) SBF signal given by an infrared photoplethysmograph; 3) respiratory movements (RM). A correlation of the frequency of the respiration, the SBF and the EKG was made. The variability of the amplitudes of the SBF, RR intervals and pulse intervals was analyzed in the time domain and with spectral analysis using Fourier analysis.
  
  
  RESULTS
  We found no clear respiratory modulation of the amplitude of the SBF during natural breathing at rest. With default breathing there was a low frequency oscillations (LF 0.04 to 0.15 Hz) modulation of the amplitude of the SBF that was non respiratory in nature. During rhythmic breathing at 0.1 Hz there was a strong modulation at LF of the SBF with a typical waxing and waning appearance, decreasing in amplitude during the tachycardia period and increasing in amplitude during the bradycardia period.
  
  
  CONCLUSIONS
  Under normothermic conditions there is a consistent variability of the frequency and amplitude of the SBF with normal and rhythmic breathing. While breathing at rest the modulation of SBF amplitude was clearly seen at LF and non respiratory related. With rhythmic breathing there is a strong modulation of amplitude and frequency at the respiratory frequency.
authors.affiliation: Department of Neurology and Psychiatry, Instituto Nacional de Ciencias Médicas y Nutrición, Salvador Zubirán, Mexico City. brunoest@hotmail.com
authors.forename: Bruno
authors.initials: B
authors.lastname: Estañol
authors.forename: Horacio
authors.initials: H
authors.lastname: Sentíes-Madrid
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Elías
authors.forename: Plácido
authors.initials: P
authors.lastname: Coyac
authors.forename: Raúl
authors.initials: R
authors.lastname: Martínez-Memije
authors.forename: Oscar
authors.initials: O
authors.lastname: Infante
authors.forename: José Francisco
authors.initials: JF
authors.lastname: Tellez-Zenteno
authors.forename: Guillermo
authors.initials: G
authors.lastname: García-Ramos