The 1-minute sit-to-stand test to detect exercise-induced oxygen desaturation in patients with interstitial lung disease

Abstract

Background: Although the 6-min walk test (6MWT) is the gold standard for assessing exercise-induced impairment of gas exchange, it cannot easily be performed in a clinical office environment. The aim of this study was to compare the 1-min sit-to-stand test (1STST) with the 6MWT for the ability to assess exercise-induced oxygen desaturation in patients with interstitial lung diseases (ILDs).

Methods: A total of 107 patients were enrolled and classified into three groups: sarcoidosis, fibrotic idiopathic interstitial pneumonia (f-IIP), and other forms of ILD. The 6MWT and 1STST were performed on the same day, and pulmonary function tests, pulse oxygen saturation (SpO₂), and dyspnea and fatigue (modified Borg scale) were assessed. SpO₂ desaturation was evaluated by intraclass correlation coefficient (ICC), Bland-Altman analysis, and kappa (κ) coefficient in the whole population and the patient subgroups.

Results: The SpO₂ nadir during the 1STST and 6MWT showed good consistency [mean ± standard deviation: 92.5% ± 5% and 90% ± 7%, respectively; ICC 0.77, 95% confidence interval (CI) 0.71-0.83] and correlated strongly ( r = 0.9, p < 0.0001). The frequency of patients with oxygen desaturation ⩾4% was also consistent for the two exercise tests ( κ = 0.68, 95% CI 0.54-0.82). The number of repetitions in the 1STST correlated with the 6MWT distance ( r = 0.5, p < 0.0001), but the dyspnea scores were higher during the 1STST than the 6MWT ( p < 0.0001). These findings did not differ for the three patient subgroups.

Conclusion: The 1STST can measure exercise-induced desaturation in ILD patients and could be used as an alternative test to the 6MWT in office practice.

Keywords: 1-min sit-to-stand test; 6-min walk test; exercise; functional tests; interstitial lung disease.

Figure 1.

Correlation between aspects of the 6MWT and 1STST. Left: SpO₂ nadir values during the 6MWT and 1STST. Right: Distance walked in the 6MWT and number of repetitions in the 1STST. 1STST, 1-min sit-to-stand test; 6MWT, 6-min walk test; SpO₂, oxygen saturation.

Figure 2.

Bland–Altman plot of the difference in SpO₂ nadir between the 6MWT and 1STST as a function of the mean SpO₂ nadir in both tests. Solid black line represents the mean difference and the dotted lines define the limits of the 95% confidence interval. 1STST, 1-min sit-to-stand test; 6MWT, 6-min walk test; SpO2, oxygen saturation.