Introduction:There is increasing evidence that dyspnea and impaired exercise capacity are partially associated with respiratory muscle dysfunction,particularly diaphragmatic dysfunction,in patients with IPF.We aimed to assess the functions of the diaphragm, which is the main respiratory muscle,using both US and sEMG in patients with IPF,and to establish the correlation of these data with pulmonary function parameters,exercise capacity and radiological extent of fibrosis. Methods:We measured diaphragmatic mobility,diaphragmatic thickness and TF by US and the strength of diaphragmatic contraction on sEMG in IPF patients and compared with healthy individuals.We further assessed the correlation of these measurements with each other and with FVC,DLCO,6MWT,spO2 changes,mMRC score and TFS in patients with IPF. Results:41 IPF patients and 21 healthy individuals were included in the study.There was no difference in diaphragmatic mobility on US during quiet breathing between the patient and control groups(2.35 cm vs. 2.56 cm;p=0.29).Diaphragmatic mobility during deep breathing was lower in the patient group compared to the control group(5.02 cm vs. 7.66 cm;p<0.0001).IPF patients had greater diaphragmatic thickness during quiet and deep breathing than the control group(0.24 cm vs. 0.22 cm, 0.33 cm vs. 0.31 cm,respectively;p=0.045;p=0.043).There was no difference in TF between the two groups(39.37% vs. 44.16%;p=0.49).The strength of diaphragmatic contraction measured on sEMG was higher in IPF patients compared to healthy individuals(0.61 mV vs. 0.51 mV;p=0.03).In IPF patients,US and sEMG measurements had no significant relationship with FVC,DLCO,6MWT,spO2 change levels,mMRC scores and TFS(p>0.05).When the relationship between US and sEMG findings in IPF patients was evaluated,a positive correlation was found between the diaphragmatic thickness during quiet breathing and the strength of contraction(r=0.32;p=0.04). Conclusion:The functions of the diaphragm do not appear to be affected in IPF patients with mild-to-moderate restriction.However,the functions of the diaphragm may deteriorate as a result of inadequate compensatory response to the load on respiratory muscles in the later stages of the disease.