High-resolution Computed Tomography Findings and Serum Biomarker of Subclinical Interstitial Lung Disease in Moderate-to-severe Obstructive Sleep Apnea Patients

ABSTRACT

Background: Obstructive sleep apnea (OSA) has association with many comorbidities. Based on the postulated hypothesis from few studies, the primary objective of this study was to assess the occurrence of subclinical interstitial lung disease in moderate-to-severe OSA patients. Materials and methods: It was a prospective observational study, conducted at a tertiary care chest institute of India, 43 moderate-to-severe OSA patients diagnosed by level-I polysomnography were enrolled. All the patients underwent detailed clinical examination with high-resolution computed tomography (HRCT) chest, pulmonary function test (PFT), and serum markers MMP-1,7, SP-A, and Krebs von den Lungen-6 (KL-6). Subclinical interstitial lung disease (ILD) was identified based on the two validated measures: high-attenuation areas (HAA), defined as the percentage of imaged lung volume having computed tomography (CT) attenuation between ?600 and ?250 HU and interstitial lung abnormalities (ILA), defined as the presence of ground-glass, reticular abnormality, diffuse centrilobular nodularity, honeycombing, traction bronchiectasis, nonemphysematous cysts, or architectural distortion in at least 5% of nondependent portions of the lung in HRCT chest without respiratory symptoms with preserved lung function. Results: The mean age was 54.33 � 11.5 years with 22 (51%) males. The mean apnea?hypopnea index (AHI) was 42.38 � 27.6 with BMI >30 kg/m2 in 18 (42%) patients. The subclinical ILD was diagnosed in 12 patients. The HRCT finding of ILA was seen in 12 and high-attenuation areas (HAA) in 5 patients. The serum markers were higher in subclinical ILD compared with non-ILD OSA patients, however, only the level of MMP-7 was significantly higher in subclinical ILD patients. Conclusion: It was concluded that subclinical ILD is quite common among OSA patients with HRCT findings seen in nearly 30% of cases. This supports the hypothesis that OSA may be considered as a risk factor of subclinical ILD.