Predictors of oxygen desaturation during submaximal exercise in 8,000 patients

Study objectives: To determine predictors of oxygen desaturation during sub maximal exercise in patients with various lung diseases. Design and setting: This retrospective case series used pulmonary function laboratory results from all patients referred to a major tertiary-care cent er. Patients and measurements: All patients greater than or equal to 35 years o ld who underwent spirometry, diffusing capacity of the lung for carbon mono xide (DLCO), lung volumes, and pulse oximetry during 3-min submaximal step- test exercise during 1996 were included (4,545 men and 3,472 women). Logist ic regression models, correcting for gender, age, and weight, determined th e odds ratios (ORs) for oxygen desaturation of greater than or equal to 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 airways obstruction, while o nly 5.6% had restriction of lung volumes. One third of those with obstructi on had a low DLCO, compared to 50% with restriction, while 2.7% had a low D LCO without obstruction or restriction. The risk of oxygen desaturation dur ing submaximal exercise was very high (OR, 34) in patients with restriction and low DLCO las in interstitial lung disease) and in patients with obstru ction and low DLCO was in COPD; OR, 18), intermediate (OR, 9) in patients w ith only a low DLCO, and lowest in those with a normal DLCO (OR, 4 if restr icted; OR, 2 if obstructed). A cut point of DLCO < 62% predicted resulted i n 75% sensitivity and specificity for exercise desaturation, No untoward ca rdiac events occurred in any patients during or following the submaximal ex ercise tests. Conclusions: The risk of oxygen desaturation during submaximal exercise is very high ill patients with a low DLCO, Submaximal exercise tests are safe, even in elderly patients H with heart and lung diseases.