Reliability of Desaturation-Distance Ratio in Interstitial Lung Disease: A cross-sectional Study
DOI:
https://doi.org/10.64149/J.Ver.7.2.69-76Keywords:
Interstitial Lung Disease, Six-Minute Walk Test, Desaturation-Distance Ratio, Pulmonary Function, Reliability.Abstract
Background: Interstitial lung diseases (ILDs) impair gas exchange, necessitating reliable functional assessment tools. The desaturation-distance ratio (DDR), combining oxygen desaturation area and walked distance during the six-minute walk test (6MWT), has emerged as a promising composite index.
Objective: To evaluate the test-retest reliability of DDR and its correlation with pulmonary function parameters in ILD patients.
Methods: Thirty-three ILD patients (mean age 45.2 ± 14.5 years) performed two 6MWTs 30 minutes apart. DDR was calculated as the ratio of desaturation area (DAO₂) to distance walked, using fingertip pulse oximetry (Nonin GO2). Pulmonary function tests (PFTs) included DLCo%, FEV1%, and TLC%. Paired t-tests assessed DDR reliability; Pearson’s correlation evaluated associations.
Results: DDR1 (3.14 ± 0.86) and DDR2 (2.91 ± 0.78) showed high reliability (mean difference 0.22, t(32) = 5.27, p < 0.001). DDR1 significantly correlated with FEV1% (r = 0.451, p = 0.008) but not DLCo% (r = -0.206, p = 0.276) or TLC% (r = -0.105, p = 0.582). Distance walked correlated negatively with FEV1% (r = -0.374, p = 0.032).
Conclusion: DDR demonstrates excellent test-retest reliability and superior correlation with airflow limitation (FEV1%) compared to diffusion capacity in mild-moderate ILD. It offers a cost-effective alternative to holter oximetry for functional evaluation
