Should the 6-Minute Walk Test Be Stopped If Oxyhemoglobin Saturation Falls Below 80%?

Objective: To examine the occurrence of adverse events in patients undergoing assessment for pulmonary rehabilitation when a 6-minute walk test (6MWT) continues despite desaturation below 80%.

Design: Retrospective audit following REporting of studies Conducted using Observational Routinely-collected health Data (RECORD) Statement.

Setting: Large teaching hospital.

Participants: All patients (N=549) (55% men, mean age 69±11y) assessed for pulmonary rehabilitation (September 2005 to January 2016).

Interventions: The standardized tests were conducted by experienced cardiorespiratory physiotherapists. Oxyhemoglobin saturation was monitored continuously using a pulse oximeter (lowest value used for analysis). Medical records were reviewed, and adverse events defined as tachycardia, bradycardia, chest pain, or other sign/symptom necessitating cessation.

Main outcome measure: 6MWT.

Results: Data from 672 walk tests were included with mean distance 369 (124) meters. The main diagnoses were chronic obstructive pulmonary disease (70%), interstitial lung disease (14%), and bronchiectasis (8%). Sixty individuals (11%) recorded desaturation below 80% without adverse events. Two adverse events were recorded during tests without desaturation; in 1 instance, chest pain with no evidence of cardiorespiratory compromise and in another, the patient stopped due to concern regarding blood sugar levels (11.5 mmol/L when tested). Independent predictors of desaturation to less than 80% were resting oxyhemoglobin saturation <95% (odds ratio [OR] 3.82, 95% confidence interval [CI] 2.06-7.08) and a diagnosis of interstitial lung disease or pulmonary arterial hypertension (OR 5.24, 95% CI 2.59-10.58).

Conclusions: This study found that desaturation to less than 80% during a 6MWT was not associated with adverse events in a large cohort of patients referred to pulmonary rehabilitation and assessed by experienced physiotherapists, suggesting that test cessation due to desaturation in stable patients may be unwarranted.