[Exertional hypoxemia evaluated by pulse oximetry in patients with interstitial lung diseases]

The pattern of change in arterial oxyhemoglobin saturation (SpO2) measured by pulse oximetry (PO) during exercise, including daily activities, was studied in 23 patients with interstitial lung disease (ILD), 19 of whom had idiopathic pulmonary fibrosis, 3 collagen vascular disease, and 1 BOOP. Hypoxemia, as detected by PO appeared without dyspnea at the beginning of exertion or at a mild workload. Exercise usually induced significant changes in the same fashion first in heart rate, then in SpO2, and then in dyspnea, but stair climbing had a different pattern. Workload at the lactate threshold (LT) and symptom-limited maximal exercise (SL) in a bicyclergometer incremental exercise test correlated well with distance walked in a 10-minute walking test (10-eMD) (p < 0.01). Similarly, the degree in desaturation in each exercise test was closely correlated (p < 0.01). Exertional hypoxemia was more prominent in patients with ILD than in those with chronic pulmonary emphysema. Nevertheless, dyspne changed less per change in SpO2 in ILD patients. We conclude that prolonged monitoring of SpO2 by PO will disclose the presence of exertional desaturation in ILD patients.