Diaphragmatic dysfunction (DD) plays a significant role in dyspnea, quality of life, and prognosis in various respiratory diseases. However, its characterization in Interstitial Lung Diseases (ILDs) remains limited. This study aimed to characterize ILD patients with probable DD using diaphragmatic electroneuromyography (dENMG) and analysis of the diaphragm's compound muscle action potential (CMAP), and to determine predictive factors of DD and its prognostic impact.

A retrospective monocentric study was conducted in our center, including all consecutive ILD patients who underwent diaphragm evaluation with ENMG between May 2018 and September 2023. Clinical data, dENMG, and other assessments were collected. Association between abnormal diaphragm’s CMAP and ILD characteristics were analyzed using logistic regression. Survival was analyzed using Kaplan-Meier curves and cox model adjusted for age and sex.

Between May 2018 and September 2023, thirty-seven ILD patients underwent an dENMG for suspected DD. Connective Tissue Disease-associated ILD (CTD-ILD) [28 (76%)] was the most common ILD-subtype. Thirteen (35%) had a DD according to dENMG. Patients with DD were predominantly older males, had a higher prevalence of coronary artery disease (CAD), and had less non-specific interstitial pneumonia (NSIP) pattern compared to patients without DD. The prognosis appeared to be worse in the DD group, with reduced survival [mean 29.3 (± 17.2) p=0.04 vs 31.3 months (± 18.3)].

In a French referral center for ILDs, suspicion of associated DD concerned only a small proportion of ILD patients, mainly with CTD-ILD. Among those, only a third had DD suspected by a dENMG and abnormal diaphragm’s CMAP. DD appears to be associated with unfavorable outcomes, although further research with larger cohorts is warranted.