Desaturations During 6-Minute Walk Test and Predicting Nocturnal Desaturations in Adult Subjects With Cystic Fibrosis

Nocturnal desaturation in cystic fibrosis (CF) may have prognostic implications because a significant and maintained nocturnal desaturation can contribute to the development and progression of pulmonary hypertension with cor pulmonale. Its relation with the desaturation in exercise has not been sufficiently studied. We aimed to determine whether desaturation during 6MWT can be an indicator of nocturnal desaturation in adult subjects with CF.

57 subjects were included: 50.9% male, 27.5 ± 7.7 y old, mean FEV₁ = 2.37 ± 0.74 L, and %FEV₁ 67 ± 18.1%. Desaturation during 6MWT was defined as oxygen saturation (S_pO ) ≤ 90% or a decline of > 4 points in S_pO from baseline, and nocturnal desaturation as a desaturation index > 4 or > 5% of sleep time with S_pO ≤ 90%.

Desaturation observed during 6MWT in adult subjects with CF did not correlate with nocturnal desaturation (P = .27). Subjects with %FEV₁ ≤ 55% and diffusion capacity of carbon monoxide (D_LCO) ≤ 50 mmol/min/mm Hg were at higher risk of 6MWT desaturation. Nocturnal desaturation was more frequent in males, with P_aO ≤ 71 mm Hg in blood gas analysis.

Desaturation observed in 6MWT cannot predict desaturation at night in adults with CF. Other parameters were identified as predictors of desaturation.