The 1-min sit-to-stand test as a screening tool to assess exercise-induced oxygen desaturation in normoxemic people with interstitial lung disease

Background

In patients with interstitial lung disease (ILD), exercise-induced desaturation during the 6-min walk test (6MWT), specifically nadir oxygen saturation (nSpO2) of ≤88 % is a negative prognostic marker. As the 6MWT is often impractical for ILD patients, the aim of this study is to compare the 1-min sit-to-stand test (1minSTS) with the 6MWT to detect exercise-induced desaturation.

Methods

Participants were recruited from a tertiary referral clinic with both tests performed on the same day. Utilising Bland-Altman analysis, the relationship between nSpO2 on 1minSTS and 6MWT was determined. An area under the receiver operating characteristic curve (AUC) determined the ability of nSpO2 on 1minSTS test to predict SpO2 ≤88 % on 6MWT.

Results

Fifty participants completed the study (idiopathic pulmonary fibrosis n = 24, 48 %; connective tissue disease associated ILD n = 20, 40 %; other ILD n = 6, 12 %). Mean (SD) FVC%pred was 73 ± 16 %, mean DLCO%pred 57 ± 16 % and resting SpO2 99 ± 1 %. The 1minSTS resulted in less exercise-induced oxygen desaturation, with a median IQR nSpO2 of 95 % (89–98) and 93 % (85–96) respectively (p < 0.001). Moderate agreement was determined between the nSpO2 on both tests, with a mean difference of 3.2 % [-14 to +3.0 %]. The 1minSTS test accurately identified participants with nSpO2 ≤88 % on 6MWT (AUC 0.96). Oxygen desaturation ≤94 % during the 1minSTS test provided 100 % sensitivity and 87 % specificity for oxygen desaturation ≤88 % at 6MWT.

Conclusion

This study demonstrates that exercise-induced oxygen desaturation during the 1minSTS test correlates with oxygen desaturation on 6MWT. The 1minSTS may be a practical screening tool for ILD patients who would benefit from further exercise testing.