Exercise-induced hypoxia predicts hypobaric hypoxia during flight in patients after Fontan operation

Hypobaric hypoxia (HH) during flight might be more detrimental to pulmonary circulation in Fontan patients compared healthy individuals. This study was designed to clarify whether exercise-induced hypoxia could predict HH during flight in Fontan patients.

Percutaneous oxygen saturation (SpO₂) was analyzed during flight in 11 Fontan patients and eight volunteers. SpO₂ was measured before taking off (S1), at the initial (S2), the end of stabilization (S3), and after landing (S4). The SpO₂-dynamics were compared with SpO₂-dynamics during cardiopulmonary exercise testing (CPX), pulmonary function, and hemodynamics in the Fontan patients. At all measurements, SpO₂ was lower in the Fontan patients than the volunteers during flight. The total SpO₂ decline from S1 to S3 was greater in the Fontan patients than the volunteers. While SpO₂ change from S2 to S3 was negative in the Fontan patients, it was stable in the volunteers. In the Fontan patients, the median value of exercise-induced SpO₂ decline (Ex-dSpO₂), SpO₂ at rest, and SpO₂ at peak was -6%, 93%, and 88%, respectively. In addition to exercise capacity and pulmonary function, the Ex-dSpO₂ was correlated strongly with SpO₂ at all phases during flight (r = 0.75-0.98, p < 0.01 for all). Flight-associated adverse events occurred in two patients with SpO₂ < 80% at S3.

Both the Fontan patients and the volunteers demonstrated similar SpO₂-dynamics during flight with a greater HH in the Fontan patients. CPX with SpO₂ monitoring is useful in predicting SpO₂-dynamics and adverse events during flight in these patients.