Desaturation-distance ratio during field exercise test in lymphangioleiomyomatosis: a cross-sectional study

Abstract

Background: Desaturation-distance ratio (DDR) evaluates the oxygen desaturation during field walking tests, it is considered a reliable and simple tool, and has been used to assess functional capacity in subjects with respiratory diseases. Lymphangioleiomyomatosis (LAM) is a rare (1/million) neoplastic disease associated with exercise impairment; however, DDR has not been tested in LAM patients.

Objectives: to assess DDR during maximal and submaximal exercise test and its association with lung function parameters.

Methods: This study included a cohort of women with LAM. The 6-minute (6MWT) and the incremental shuttle walking (ISWT) tests were performed, and DDR was assessed in both tests. Lung function was assessed at rest by spirometry and body plethysmography. Pearson’s correlation following multiple regression analysis was used to evaluate the association between DDR during 6MWT and ISWT and lung function parameters. Predictive models were constructed considering the best independent coefficient (R2).

Results: Forty patients were included (46±10 y/o). The distance walked was 517±65m and 443±127m for the 6MWT and ISWT, respectively. Obstructive airway pattern, reduced carbon monoxide diffusing capacity, and air trapping were found in 60%, 57%, and 15% of patients. DDR value was greater in the ISWT than in 6MWT (6.6 vs 8.3, respectively). Those variables were the independently predicted DDR during submaximal (DDR6MWT) and maximal exercise (DDRISWT).

Conclusion: DDR is a useful tool for functional evaluation during maximal and submaximal exercises in patients with LAM and can be predicted by airway obstruction, reduced carbon monoxide diffusing capacity, and air trapping.