Predictors of Oxygen Desaturation During Submaximal Exercise in 8,000 Patients

Study objectives

To determine predictors of oxygendesaturation during submaximal exercise in patients with various lungdiseases.

Design and setting

This retrospective caseseries used pulmonary function laboratory results from all patientsreferred to a major tertiary-care center.

Patients andmeasurements

All patients ≥ 35 years old who underwentspirometry, diffusing capacity of the lung for carbon monoxide(Dlco), lung volumes, and pulse oximetry during 3-minsubmaximal step-test exercise during 1996 were included (4,545 men and3,472 women). Logistic regression models, correcting for gender, age, and weight, determined the odds ratios (ORs) for oxygen desaturation of≥4% during exercise for each category of lung function abnormality(compared to those with entirely normal lung function).

Results

Approximately 74% of the patients had airwaysobstruction, while only 5.6% had restriction of lung volumes. Onethird of those with obstruction had a low Dlco, compared to56% with restriction, while 2.7% had a low Dlco withoutobstruction or restriction. The risk of oxygen desaturation duringsubmaximal exercise was very high (OR, 34) in patients with restrictionand low Dlco (as in interstitial lung disease) and inpatients with obstruction and low Dlco (as in COPD; OR,18), intermediate (OR, 9) in patients with only a low Dlco, and lowest in those with a normal Dlco (OR, 4 ifrestricted; OR, 2 if obstructed). A cut point of Dlco< 62% predicted resulted in 75% sensitivity and specificity forexercise desaturation. No untoward cardiac events occurred in anypatients during or following the submaximal exercise tests.

Conclusions

The risk of oxygen desaturation duringsubmaximal exercise is very high in patients with a low Dlco. Submaximal exercise tests are safe, even in elderlypatients with heart and lung diseases.