title: The pulse transit time arousal index in obstructive sleep apnea before and after CPAP.
abstract: OBJECTIVE
  Pulse transit time (PTT) is a non-invasive index which reflects changes in peripheral vascular resistance and intrathoracic pressure. PTT arousal index (PTT Ar/I) is defined as the frequency (number/hour) of a defined decrease in PTT which may serve as a marker for respiratory events, and associated arousals which occur in patients with obstructive sleep apnea (OSA). This study was designed to evaluate the PTT Ar/I before and after patients with OSA were treated with continuous positive airway pressure (CPAP).
  
  
  METHODS
  Individuals referred for evaluation of possible OSA underwent split-night polysomnography (PSG). The findings from 144 consecutive patients with a respiratory disturbance index (RDI)>/=20, who demonstrated at least a 50% drop in RDI with CPAP, provide the basis for this analysis. The PTT Ar/I measured before and after CPAP were compared to other measures of severity for OSA, including RDI and arousal index.
  
  
  RESULTS
  The PTT Ar/I correlates with the RDI (r=0.43, P</=0.0001) and with the arousal index (r=0.43, P<0.0001). Moreover, the decrease in RDI and arousal index that occurs with CPAP treatment correlates with a similar decrease in the PTT Ar/I (r=0.54, P<0.0001).
  
  
  CONCLUSIONS
  The PTT Ar/I correlates well with other standard measures of severity in patients with OSA and is potentially a non-invasive marker with which to measure the frequency of disruptive events that occur during sleep.
authors.affiliation: The Tampa Sleep Center, University Community Hospital, 3100 East Fletcher Avenue, Tampa, Florida 33613, USA. thetampasleepcenter@att.net
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Schwartz
mesh_terms: D001143:Arousal / Q000502:physiology*; D015992:Body Mass Index; D001921:Brain / Q000502:physiology; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000209:etiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods; D012372:ROC Curve; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000175:diagnosis / Q000628:therapy*; D012892:Sleep Deprivation / Q000175:diagnosis / Q000209:etiology; D013997:Time Factors