Oxygen desaturation and adverse events during 6-min walk testing in patients with COPD

The 6-min walk test (6MWT) is a simple test assessing functional capacity, but concerns about risks of substantial oxygen desaturation in pulmonary patients have led to non-adherence to the standardised American Thoracic Society guideline. We evaluated the safety of the 6MWT in stable COPD patients and compared the incidence of adverse events in patients with and without substantial exertional hypoxaemia.

6MWT data were obtained for 1136 patients with moderate to very severe COPD. Demographics, adverse events, oxygen saturation (SpO2), 6-min walk distance, lung function and quality of life measures were compared between patients with substantial exertional hypoxaemia (nadir SpO2 < 85%) and those without (SpO2 ≥ 85%). Comparisons were made using Mann-Whitney U-test for continuous variables and Fisher's exact test for categorical variables.

Twenty-five patients (2.2%) had adverse events, the most common being dizziness, chest tightness, chest pain and palpitations. Substantial exertional hypoxaemia did not increase the incidence of adverse events. No significant morbidity or mortality was recorded. Patients with adverse events had lower baseline SpO2, worse quality of life scores, and higher depression and anxiety scores. However, no significant differences were seen in anthropometric data, spirometric values or SpO2 during and after the 6MWT.

Asymptomatic exertional hypoxaemia is not associated with an increased incidence of adverse events during 6MWT in COPD patients. Our data support the ATS guideline that the 6MWT should be continued in the absence of symptoms and that intermittent oximetry monitoring does not assist in preventing adverse events.