Guidelines for conducting the 6-minute walk test (6MWT) indicate that oxyhaemoglobin saturation (SpO 2) should not be monitored constantly during the test. The aim of this study was to determine whether the nadir SpO 2 differs from the end-6MWT SpO 2 in patients with chronic respiratory disease. A total of 86 subjects underwent the 6MWT according to a standardized protocol with continuous monitoring of SpO 2 by pulse oximeter. Comparison of nadir SpO 2 and end SpO 2 was made and the proportion of subjects with important desaturation according to each measure was determined. The effect of resting during the 6MWT on the likelihood of a significant difference between nadir and end SpO 2 was evaluated. A total of 29 subjects with chronic obstructive pulmonary disease (COPD; mean [SD] forced expiratory volume in 1 second [FEV1] 51 % predicted) and 57 with interstitial lung disease (ILD; TLCO 49 % predicted) were studied. Nadir SpO 2 was slightly lower than end-test SpO 2 (median 87% vs. 88%, p < 0.001) with differences ranging from 1% to 10%. Those who rested during the test (n = 14) were more likely to have a significant difference between nadir SpO 2 and end SpO 2 (p = 0.04). End SpO 2 did not accurately identify desaturation in 21% of subjects. No differences between COPD and ILD were observed. For most patients with chronic respiratory disease, the end SpO 2 and the nadir SpO 2 are similar during the 6MWT. However, the end SpO 2 does not give an accurate estimate of nadir SpO 2 in patients who rest. Consideration should be given to the constant monitoring of SpO 2 during the 6MWT.
- Exercise test
- Pulmonary disease chronic obstructive
- Pulmonary fibrosis