Prevalence of patent foramen ovale and its impact on oxygen desaturation in obstructive sleep apnea

BackgroundA 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.MethodsA 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).ResultsA 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.ConclusionA 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.