Ultrasonographic and electromyographic assessment of the diaphragm in
IPF: Is it associated with functional parameters and fibrosis?
Abstract
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.