The influence of patent foramen ovale on oxygen desaturation in obstructive sleep apnoea

¹ Sahlgrenska University Hospital/Östra
² Sahlgrenska University Hospital/Sahlgrenska, Göteborg
³ Dept Community Medicine, Lund University, Malmö
⁴ Dept Community Medicine, Lund University, Malmö; and Skaraborg Institute, Skövde, Sweden

^* To whom correspondence should be addressed. E-mail: Magnus.C.Johansson{at}vgregion.se.

	Abstract

Obstructive sleep apnoea (OSA) is associated with oxygen desaturation to a varying degree. Patent foramen ovale (PFO) may allow interatrial right-to-left shunting. The hypothesis of the study is that oxygen desaturation will occur more often, proportionally to the frequency of respiratory disturbances, in OSA subjects with PFO than in those without.

In a group of 209 subjects diagnosed with OSA, the proportion of desaturation to respiratory events was calculated as the ratio of "oxygen desaturation index /apnoea-hypopnoea index" (ODI/AHI). Fifteen cases with high proportional desaturation (ODI/AHI0.66) were individually matched with 15 controls with low proportional desaturation (ODI/AHI0.33), all without pulmonary disease. PFO was assessed with contrast transoesophageal echo and considered large when at least 20 bubbles passed over to the left atrium after a single injection.

The prevalence of large PFO was 9 out of 15 (60%) in the high-proportional desaturation group, versus 2 out of 15 (13%) in the low-proportional desaturation group (p=0.02). The median number of passing bubbles was positively correlated to minimum oxygen saturation among those with PFO (r=0.62, p=0.02).

Oxygen desaturation occurs more often proportionally to the frequency of respiratory disturbances in OSA subjects with PFO than in those without.

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