title: Circulation time measurement from sleep studies in patients with obstructive sleep apnea.
abstract: BACKGROUND
  Lung to finger circulation time (LFCT) can be estimated from polysomnography (PSG) in the presence of an apneic event by using oxygen as an indicator and a finger as the site of detection. The purpose of this study was to refine the methodology of LFCT measurement and to compare LFCT in patients with obstructive sleep apnea (OSA) with and without heart failure (HF).
  
  
  METHODS
  In a retrospective manner, 10 LFCT measurements per patient were made from the PSG in 171 consecutive patients with a diagnosis of OSA who were divided into two groups: (a) those with a clinical history of underlying HF (N = 42) and (b) those without HF (N = 129). Mean values were compared between the two groups. We also examined associations of LFCT with various factors in each group and the combined group separately using multiple regression analysis.
  
  
  RESULTS
  Gender and age were significantly associated with LFCT in patients with OSA alone. Use of β-blockers was associated with LFCT in the group with OSA with HF. Among the entire cohort, HF, β-blocker, gender, and age were found to be significantly associated with LFCT. The presence of HF was the strongest predictor of a prolonged LFCT (adjusted mean LFCT: OSA only = 18.5 [95% CI: 17.2-19.7 sec] vs. OSA with HF = 26.1 [95% CI: 24.3-28.0 sec], p < 0.0001).
  
  
  CONCLUSIONS
  LFCT can be reliably measured and is prolonged in patients with OSA and underlying HF. LFCT based on PSG may be a useful marker for detection of coexisting HF in patients with OSA.
authors.affiliation: Hennepin County Medical Center, Minneapolis, MN ; University of Minnesota, Minneapolis, MN.
authors.forename: Younghoon
authors.initials: Y
authors.lastname: Kwon
authors.affiliation: Medical College of Wisconsin, Milwaukee, WI.
authors.forename: Talha
authors.initials: T
authors.lastname: Khan
authors.affiliation: Hennepin County Medical Center, Minneapolis, MN.
authors.forename: Marc
authors.initials: M
authors.lastname: Pritzker
authors.affiliation: University of Minnesota, Minneapolis, MN.
authors.forename: Conrad
authors.initials: C
authors.lastname: Iber
mesh_terms: D000328:Adult; D000367:Age Factors; D001776:Blood Circulation Time / Q000295:instrumentation / Q000379:methods; D005260:Female; D006333:Heart Failure / Q000150:complications* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods*; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications* / Q000503:physiopathology*
keywords: circulation time; heart failure; obstructive sleep apnea