Oxygen desaturation during a 6-minute walk test as a predictor of maximal exercise-induced gas exchange abnormalities in sarcoidosis

Abstract

Background: Common tests for evaluating gas exchange impairment have different strengths and weaknesses. Alveolar-to-arterial oxygen pressure difference (AaDO 2 ) at peak exercise is a sensitive indicator but it cannot be measured repeatedly. Diffusing capacity of the lung for carbon monoxide (DLco) is measured at rest and may be too insensitive to predict the effects of exercise on gas exchange impairment.Oxygen desaturation during a 6-minute walk test (∆SpO 2 -6MWT) can be measured repeatedly, but its value in sarcoidosis is unknown. Here, we evaluated the ability of ∆SpO 2 -6MWT and DLco to predict gas exchange impairment during exercise in sarcoidosis.Methods: This retrospective study of 130 subjects with sarcoidosis investigated the relationship between DLco, ∆SpO 2 -6MWT, and peak AaDO 2 using correlation tests, inter-test reliability analyses, and predictive values. For the analyses of inter-test reliability and predictive values, DLco, peak AaDO 2 , and ∆SpO 2 -6MWT were considered as binary variables (normal/abnormal) according to previously defined thresholds.Results: Correlation coefficients between DLco, ∆SpO 2 -6MWT, and peak AaDO 2 were intermediate (0.53-0.67, P<0.0003) and Kappa coefficients were low (0.21-0.42, P=0.0003-0.02). DLco predicted (I) increased peak AaDO 2 with a positive predictive value (PPV) of 66% and a negative predictive value (NPV) of 78% and (II) increased ∆SpO 2 -6MWT with a PPV at 36% and an NPV at 88%. Normal DLco was a good predictor of the absence of severe desaturation during the 6MWT (94% NPV) and at peak exercise during cardiopulmonary exercise test (CPET) (100% NPV). ∆SpO 2 -6MWT predicted peak AaDO 2 increase with a PPV of 74% and an NPV of 60%. Conclusions:In a large population of sarcoidosis patients, neither ∆SpO 2 -6MWT nor DLco was a good predictor of increased peak AaDO 2 . In contrast, normal DLco was a good predictor of the absence of severe desaturation during the 6MWT and at peak exercise during CPET.

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

“…Resting DLco is a specific but insensitive predictor of abnormal gas exchange during exercise, as assessed by the 6MWT (SpO 2 nadir) or cardiopulmonary exercise tests (peak alveolar-arterial oxygen difference). 5 , 6 , 28 Gas exchange impairment is associated with exertional dyspnea, 29 , 30 exercise limitation, 30 , 31 and altered quality of life. 31 In IPF patients, desaturation during a 6MWT is an independent predictor of mortality.…”

Clinical characteristics and organ system involvement in sarcoidosis: comparison of the University of Minnesota Cohort with other cohorts

“…Similar results were also seen for FEV1, and obstructive changes were common with an FEV1/FVC ratio of < 70% in more than [27,28]. Lung volumes or formal cardiopulmonary exercise testing (CPET) is not routinely used nor is a standard of care in sarcoidosis clinical practice or research as it is more invasive, expensive and normal in many [29]. Patient-reported outcome measures and the six-minute walk test have been recommended in disease assessment [30].…”

The impact of alveolar hemorrhage on lung function tests

“…Although gas exchange measurements in interstitial lung disease, including lung pathology associated with AH, usually are done by measuring the DLCOc, it is unclear whether estimates of gas exchange might be improved by measuring oxygen desaturation during 6MWT. A study of 130 patients diagnosed with sarcoidosis found that DLCOc is a good predictor of the absence of severe gas exchange impairment 26 , the same being valid in the case of AH syndrome. Also, a normal DLCOc value was a good predictor of the absence of severe desaturation during the 6MWT in sarcoidosis 26 .…”

“…A study of 130 patients diagnosed with sarcoidosis found that DLCOc is a good predictor of the absence of severe gas exchange impairment 26 , the same being valid in the case of AH syndrome. Also, a normal DLCOc value was a good predictor of the absence of severe desaturation during the 6MWT in sarcoidosis 26 . In our study, the degree of desaturation did not correlate with the degree of severity of AH.…”