Background: The purpose of this study was to determine
how common sleep-related desaturation with preserved awake
resting pulse oximetric saturation
(Spo2) was in a large cohort of adult cystic
fibrosis (CF) patients with variable degrees of pulmonary disease. We
then determined whether nocturnal desaturation could reliably be
predicted from standard clinical and exercise parameters.
Methods: Seventy CF patients participated in the study
(mean [SD] age, 27.3 [8.7] years; women, 54%; percent predicted
FEV1 [%predFEV1], 55.7% [23.9%]).
Nocturnal, resting, and exercise Spo2 were
measured. Nocturnal oximetry was measured in the patient’s home.
Maximal oxygen capacity (V̇o2max)
was determined from a graded exercise test on a stationary bicycle
ergometer. The Shwachman-Kulczycki (S-K) illness severity score was
calculated incorporating categories of functional capacity, physical
examination, nutrition, and chest radiograph.
Multivariate analysis reported significant differences (p < 0.0001)
between pulmonary disease severity and overall distribution of
nocturnal Spo2, with the main difference being
for patients with severe pulmonary disease (%predFEV1 of< 50%) compared to patients with mild or moderate disease in the
Spo2 intervals of 100 to 96% (p < 0.0001)
and 90 to 86% (p = 0.0001). Pulmonary function, S-K clinical
scores, V̇o2max, and resting and maximal
Spo2 correlated significantly (p < 0.05)
with nocturnal Spo2 levels. Stepwise
discriminant analysis identified %predFEV1 (or S-K scores)
and resting Spo2 as the parameters that could
best discriminate patients not likely to experience nocturnal
desaturation. Specifically, our equation could predict 91% of cases
less likely to nocturnally desaturate, but could only modestly predict
those more likely to desaturate (ie, 26% of
Conclusions: Spirometric parameters and
measurements of awake resting oxygenation are of limited utility in
predicting nocturnal desaturation. Nocturnal oximetry should be
considered in patients with moderate to severe lung disease even with
preserved awake resting Spo2.