Predictability of oxygen desaturation during sleep in patients with cysticfibrosis - Clinical, spirometric, and exercise parameters

Background: The purpose of this study was to determine how common sleep-rel ated desaturation with preserved awake resting pulse oximetric saturation ( SpO(2)) was in a large cohort of adult cystic fibrosis (CF) patients with v ariable degrees of pulmonary disease. We then determined whether nocturnal desaturation could reliably be predicted from standard clinical and exercis e parameters. Methods: Seventy CF patients participated in the study (mean [SD] age, 27.3 [8.7] years; women, 54%; percent predicted FEV1 [%predFEV(1)], 55.7% [23.9 %]). Nocturnal, resting, and exercise SpO(2) were measured. Nocturnal oxime try was measured in the patient's home. Maximal oxygen capacity ((V) over d ot O(2)max) was determined from a graded exercise test on a stationary bicy cle ergometer. The Shwachman-Kulczycki (S-K) illness severity score was cal culated incorporating categories of functional capacity, physical examinati on, nutrition, and chest radiograph. Results: Multivariate analysis reported significant differences (p < 0.0001 ) between pulmonary disease severity and overall distribution of nocturnal SpO(2), with the main difference being for patients with severe pulmonary d isease (%predFEV(1), of < 50%) compared to patients with mild or moderate d isease in the SpO(2) intervals of 100 to 96% (p < 0.0001) and 90 to 86% (p = 0.0001). Pulmonary function, S-K clinical scores, (V) over dot O(2)max, a nd resting and maximal SpO(2) correlated significantly (p < 0.03) with noct urnal SpO(2) levels. Stepwise discriminant analysis identified %predFEV(1) (or S-K scores) and resting SpO(2) as the parameters that could best discri minate patients not likely to experience nocturnal desaturation. Specifical ly, our equation could predict 91% of cases less likely to nocturnally desa turate, but could only modestly predict those more likely to desaturate (ie , 26% of cases). Conclusions: Spirometric parameters and measurements of awake resting oxyge nation are of limited utility in predicting nocturnal desaturation. Nocturn al oximetry should be considered in patients with moderate to severe lung d isease even with preserved awake resting SpO(2).