Diaphragmatic ultrasonography in patients with IPF: Is diaphragmatic structure and mobility related to fibrosis severity and pulmonary functional changes?

Introduction: There is evidence to suggest that dyspnea and impaired exercise capacity are associated with respiratory muscle dysfunction in idiopathic pulmonary fibrosis (IPF) patients. We aimed to evaluate the functions of the diaphragm with ultrasonography (US) and to determine the correlation of the data obtained with the pulmonary function parameters of the patients, exercise capacity, and the extent of fibrosis radiologically. Materials and Methods: Diaphragmatic mobility, thickness, and thickening fraction (TF) were measured by ultrasonography in IPF patients and the control group. The correlation between these measurements, pulmonary function tests (PFT), six-minute walking test (6MWT), mMRC score, and total fibrosis score (TFS) was evaluated. Result: Forty-one IPF patients and twenty-one healthy volunteers were included in the study. No difference was found between the patient and control groups in diaphragmatic mobility during quiet breathing (QB) on ultrasound (2.35 cm and 2.56 cm; p= 0.29). Diaphragmatic mobility during deep breathing (DB) was found to be lower in the patient group when compared to the control group (5.02 cm and 7.66 cm; p<0.0001). Diaphragmatic thickness was found to be higher during QB and DB in IPF patients (0.33 cm and 0.31 cm, p= 0.043; 0.24 cm and 0.22 cm, p= 0.045). No difference was found between the two groups in terms of thickening fraction (39.37%, 44.16%; p= 0.49). No significant correlation was found between US measurements and PFT, 6MWT, mMRC score, and TFS in IPF patients (p> 0.05). Conclusions: The functions of the diaphragm do not appear to be affected in patients with mild-to-moderate restrictive IPF. This study showed that there was no relationship between diaphragmatic functions and respiratory function parameters and the extent of fibrosis. Further studies, including advanced stages of the disease, are needed to understand the changes in diaphragmatic functions in IPF and to determine whether this change is associated with respiratory function parameters and the extent of fibrosis.