Impact of Nocturnal Oxygen Saturation on Sleep Quality and Exercise Performance in Adult Fontan Patients

Introduction A decreased peripheral oxygen saturation (SpO 2 ) is common in Fontan patients. We aimed to determine whether these patients experience increased nocturnal desaturation (ΔSpO 2 ), and to which extent this may impact sleep quality and exercise performance, compared to healthy controls. Methods 16 adult Fontan patients and 16 healthy, individually matched controls completed questionnaires on quality of life, sleep quality, and daytime sleepiness, performed measurements of lung function and diffusion capacity (DLCO), and cycled in a cardiopulmonary exercise test to volitional exhaustion. Sleep quality was assessed with a wrist-worn actigraph and ΔSpO 2 was measured with a pulse oximeter during six nights. Results Fontan patients experienced a larger ΔSpO 2 (-3.4±0.8%-points, n=14) compared to their controls (-2.5±0.6%-points, n=14; p=0.001). In patients, ΔSpO 2 correlated with baseline SpO 2 , DLCO, and exercise performance. Fontan patients had a longer sleep onset latency (22.8±9.6 vs. 10.8±6.0 min, p<0.001) and lower self-perceived physical functioning (91±7 vs. 100±0 points; p < 0.001), but similar subjective sleep quality (4.2±1.5 vs. 3.4±1.4 points, p=0.121) and daytime sleepiness (6.1±4.3 vs. 6.3±2.8 points, p=0.884) compared to controls. In patients, daytime sleepiness correlated with the total number of ΔSpO 2 events (r=0.74, p=0.003). Conclusion Indices of nocturnal desaturation were related to daytime sleepiness and reduced exercise performance and may therefore be a contributing factor to exercise limitation in adult Fontan patients. Alleviation of nocturnal desaturation may thus be a promising target to improve daytime performance in adult Fontan patients.