Is a practice incremental shuttle walk test needed for patients with chronic obstructive pulmonary disease admitted to hospital for an acute exacerbation?

Background: The incremental shuttle walk test (ISWT) assesses exercise capacity in chronic obstructive pulmonary disease (COPD) patients. Guidelines suggest that 2 ISWTs should be performed. However, in inpatients with an acute exacerbation, it is unknown if 2 ISWTs are required.

Objective: To investigate if a practice ISWT is needed for inpatients with an acute COPD exacerbation.

Methods: Patients admitted to hospital with an acute exacerbation completed 2 ISWTs prior to discharge. Patients provided informed consent and were included if they used the same oxygen and mobility aid (if any) between tests.

Results: Thirty-nine inpatients with COPD were included with a mean (SD) forced expiratory volume in 1 s (FEV1) of 1.1 litres (0.5) [42.5% predicted (13.2)] and a median (interquartile range) Medical Research Council dyspnoea grade of 4 (3-5). Participants achieved 88.2 m (96.7) on ISWT1, and there was a statistically significant increase of 14.1 m (28.4) for ISWT2 (p < 0.05). Multiple regression explained 98.8% of the variance (F(8-22) p < 0.001, R2 = 0.988) between ISWTs using age, FEV1/forced vital capacity (FVC)%, FVC, resting oxygen saturation, resting heart rate (HR), ISWT1 distance, ISWT1 post-HR and post-Rated Perceived Exertion (p < 0.05). Using this equation to calculate predicted ISWT2, there was good agreement and no significant difference between this and actual ISWT2 (0.01 m, p > 0.05).

Conclusions: There was a small but statistically significant increase between ISWTs, which was below the minimal clinically important difference but would have had consequences for exercise prescription. This exploratory work has shown that we may be able to predict the difference between ISWTs using a multiple regression equation which could substitute the need for a second ISWT; this needs to be confirmed prospectively.