Ambulatory oxygen therapy assessment: a comparative study of incremental shuttle and 6-minute walking tests

BackgroundWalking tests, such as the incremental shuttle walk test (ISWT) and the 6-minute walk test (6MWT), are recommended in the assessment of ambulatory oxygen for patients with chronic obstructive pulmonary disease (COPD). However, there is no evidence that these tests can be used interchangeably.ObjectivesTo compare the ISWT and the 6MWT in COPD patients in terms of indication for ambulatory oxygen therapy.DesignCrossover design.SettingPatients attended as outpatients.ParticipantsFifty patients with stable COPD (31 males; age 67 years, range 43 to 83 years); mean forced expiratory volume in 1 second 1.2 l [standard deviation (SD) 0.6 l] and 48.6% predicted (SD 23.4%).InterventionPatients performed both the ISWT and the 6MWT whilst breathing air. Breathlessness (Borg scale), percutaneous arterial oxygen saturation (SpO2) and heart rate were measured before and after both tests.Main outcome measuresPost-test SpO2 and change from baseline.ResultsThe mean change in saturation was −4.6% (SD 6.2%) and −2.8% (SD 5.3%) after the ISWT and the 6WMT, respectively. Using Bland and Altman plots, the limits of agreement for difference in change in SpO2 (%) between the two tests were wide (−8.1 to 11.6) and clinically relevant. Sixteen patients (32%) and 13 patients (26%) met the criteria for ambulatory oxygen with the ISWT and the 6MWT, respectively (P = 0.32).ConclusionsThis study found a wide variation between differences in exercise oxygen desaturation after the ISWT compared with the 6MWT, supporting the premise that these tests should not be used interchangeably in the assessment of ambulatory oxygen for COPD patients.