Oxygen Saturation during Exercise in Cystic Fibrosis^1–3

Abstract

Cystic fibrosis (CF) is often associated with low hemoglobin oxygen saturation and with limited exercise tolerance, yet published reports do not agree on the effect of exercise on oxygenation in CF. We studied oxygen saturation (SaO2) by ear oximetry in 91 patients with CF during progressive exercise to exhaustion. Only 13 of 91 patients changed SaO2 by 5% or more; of these, 4 patients increased SaO2 by 5% or more, whereas 9 decreased by 5% or more. Small changes in SaO2 did not relate to resting pulmonary function, but large decreases in SaO2 were much more likely to be found in patients with forced expiratory volume in one second (FEV1) less than 50% of VC than in those with better pulmonary function (desaturation of 5% or greater was found in only 1 of 62 patients with FEV1 greater than 50% of VC, but in 8 of 29 patients with FEV1 less than or equal to 50% VC). However, even in severely affected patients, modest increases or no change in saturation were more common than large decreases, and 17 of 29 patients with FEV1 less than 50% VC ended exercise with SaO2 greater than 90%, including 3 patients with initial SaO2 below 90%. No single resting pulmonary function test or combination of tests could predict oxygen changes with exercise. Most patients with CF tolerate even maximal exercise without significant desaturation, but patients with FEV1 less than 50% of VC should have supervised exercise testing with ear oximetry before undertaking an exercise program.

Breathing Pattern Adopted by Children with Cystic Fibrosis with Mild to Moderate Pulmonary Impairment during Exercise

“…The ventilation-perfusion abnormalities and alveolar hypoventilation observed in patients with CF could also predispose the latter to hypoxemia [31, 32]. In our study, children with CF showed a decrease in S a O 2 during exercise (ΔS a O 2 = 4 ± 2%) (table 2).…”

“…Only the 2 patients with the lowest FEV 1 /FVC ratios and the highest RV/TLC ratios showed significant oxygen arterial hypoxemia induced by moderate exercise [13]. Indeed, Henke and Orenstein [31] found that only 1 out of 62 patients with a FEV 1 /FVC ratio >50% of the predicted value showed a drop of more than 5% in S a O 2 at maximal exercise. Versteegh et al [33] have shown that desaturation during exercise and sleep was only found in patients with FEV 1 <65% of the predicted value.…”

A model for predicting life expectancy of children with cystic fibrosis

“…Replacing FVC with FEV1 in this prognostic model consequently had no significant effect on the predictive power of the model. This close correlation between measures of lung function and exercise tolerance has not been demonstrated in CF patients with mild to moderate lung disease [12], and the authors suggest that it is a feature of patients with severe disease. This is the first study to examine the relationship between resting heart rate and survival, and this measurement was found to be a valuable predictor.…”

The effect of prelung transplant clinical status on post-transplant survival of children with cystic fibrosis

“…Pretransplant FEV1 (FEV1t) was measured by spirometry, and corrected for height, age and sex using Brompton predicted scores [10]. Pretransplant minimum oxygen saturation obtained during a 12-min walk (Sa,O 2 mint) [11] was measured by continuous pulse oximetry. Pretransplant age adjusted resting heart rate (AAHRt) was measured by an experienced member of the transplant team in a day ward environment, and expressed as a percentage of expected mean for age.…”