title: Prevalence of patent foramen ovale and its impact on oxygen desaturation in obstructive sleep apnea.
abstract: BACKGROUND
  A possible association between patent foramen ovale (PFO) and obstructive sleep apnea has been suggested (OSA), whereby right-to-left shunting may exacerbate the severity of nocturnal oxygen desaturation. However, the interaction between these two conditions has not been well characterised.
  
  
  METHODS
  A case-control study was conducted to evaluate the epidemiological association between PFO and OSA. Subjects were recruited prospectively from a sleep laboratory population, and 102 OSA subjects (mean age 51.5 ± 13 years) were compared to 50 controls without OSA (mean age 49.9 ± 12.4). The presence and size of right-to-left shunting were determined by contrast transcranial Doppler ultrasonography with Valsalva provocation. Using the 21,749 obstructive breathing events recorded at polysomnography from the OSA group, a mixed-effects linear regression model was developed to evaluate the impact of right-to-left shunting on nocturnal oxygen desaturation (ΔSpO2).
  
  
  RESULTS
  A higher prevalence of PFO was present in the OSA group compared to the control group (47.1% vs. 26.0%, OR 2.53, CI 1.20 to 5.31, p=0.014). From the regression model, right-to-left shunt size did not exert a significant influence on the severity of ΔSpO2 (coefficient 0.85, CI -0.62 to 2.32, p=0.254); whereas sleep state, event type, body position, event duration, awake oxygen saturation, apnea-hypopnea index and body mass index were all independent predictors of ΔSpO2.
  
  
  CONCLUSIONS
  A higher prevalence of PFO is found in OSA subjects. However, the degree of right-to-left shunting, characterised by Valsalva provocation, is not associated with an increased severity of nocturnal oxygen desaturation.
authors.affiliation: Department of Respiratory and Sleep Medicine, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.
authors.forename: Edmund M T
authors.initials: EM
authors.lastname: Lau
authors.forename: Shareen K
authors.initials: SK
authors.lastname: Jaijee
authors.forename: Kerri L
authors.initials: KL
authors.lastname: Melehan
authors.forename: Keith K
authors.initials: KK
authors.lastname: Wong
authors.forename: Brendon J
authors.initials: BJ
authors.lastname: Yee
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Grunstein
authors.forename: David S
authors.initials: DS
authors.lastname: Celermajer
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D054092:Foramen Ovale, Patent / Q000175:diagnosis / Q000453:epidemiology* / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000378:metabolism*; D017286:Polysomnography / Q000379:methods; D015995:Prevalence; D011446:Prospective Studies; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis / Q000453:epidemiology* / Q000378:metabolism*; D014636:Valsalva Maneuver / Q000502:physiology
chemical_list: D010100:Oxygen