Diaphragmatic muscle ultrasound in COPD patients

Background/Purpose. COPD is a multisystemic disorder that mainly affects beside the lungs, the muscle mass. The force generated by the respiratory muscles decreases resulting in a negative impact on the possible alteration of the ventilator and exercise capacity. In this study we aimed to quantify the diaphragm muscle dysfunction (the most important inspiratory muscle) by ultrasound measurement and correlation of this method with the maximal inspiratory pressure (MIP). Methods. 38 patients with stable COPD B, C and D and 17 healthy subjects entered the study. All the subjects presented similar anthropometric data. Diaphragmatic ultrasound was performed using a fixed transducer on the midclavicular axillary line in the ninth right intercostal space. All subjects performed spirometry, MIP and the 6 minutes walking test (6MWT). Results. Patients advanced stages of COPD showed a significant decrease in diaphragmatic muscle thickness (mm) compared with the healthy subject (7.81 control group vs. 7.35 COPD A, 6.21 C and 3.37 D p=0.314). Diaphragm muscle thickness correlated with MIP value and 6MWD especially for patients in group D (r=0.571). Conclusions. Our understanding of the muscle dysfunction in COPD is evolving. Although MIP remains a “gold standard” in the assessment of the respiratory muscle dysfunction such data should be associated with other methods. Diaphragmatic ultrasound represents an accessible and reliable technique in the overall assessment together with MIP and 6MWD. Limitations and future directions. Our study was limited on a reduced sample of patients. In future we want to determine the cut-points of the diaphragmatic muscle thickness when the respiratory muscle dysfunction starts to develop.