Predictors of subclinical interstitial lung disease in patients with obstructive sleep apnea

Rationale
The association between interstitial lung disease (ILD) and obstructive sleep apnea (OSA) is commonly encountered in clinical practice. ILD diagnosis can be easily missed in those patients.


Objective
To investigate for predictors of ILD in patients with OSA.


Methods
This is a prospective observational study. 309 patients presented to polysomnography unit in Assiut University Hospital, diagnosed with OSA [Respiratory Disturbance Index (RDI) more than 5] were reviewed. High resolution computed tomography (HRCT) chest was done for all included patients to screen for ILD. Spirometry was done to evaluate the severity of the restriction. Echocardiography was performed by a cardiologist to screen for pulmonary hypertension.


Results
In all 228 (73.8%) patients had normal HRCT. Eighty-one (26.2%) cases were found to have features of ILD in HRCT chest. Patients with subclinical ILD 73 (90.1%) cases had significantly higher RDI when compared with known cases of ILD 8 (9.9%) cases. Their level of PO2 and forced vital capacity (FVC) were significantly reduced (P=0.003, and <0.001, respectively). There was significant negative correlation between RDI and Desaturation Index (DI) (r= –0.476, P<0.001), PO2 (r=–0.598, P<0.001), and FVC (r=– 0.576, P<0.001). Younger age at admission, higher RDI, lower FVC, and prolonged forced expiratory volume in one second/FVC are significant predictors for subclinical ILD among patients with OSA.


Conclusions
ILD is a notable association in patients with OSA. The younger age at diagnosis, higher RDI, lower FVC, and higher ratio of forced expiratory volume in one second/FVC are significant predictors for subclinical or undiagnosed ILD among patients with OSA.
Clinical trial.gov: NCT06058052