Diaphragmatic Central Motor Conduction Changes In Chronic Obstructive Pulmonary Disease

Abstract

16 Background and objectives: Respiratory muscles dysfunction has been reported in 17 COPD. Transcranial magnetic stimulation (TMS) is easy non-invasive that has been 18 used for assessing the respiratory corticospinal pathways particularly of diaphragm. 19 We aimed to study the cortico-diaphragmatic motor system changes in COPD using 20 TMS and to correlate the findings with the pulmonary function.21 Methods: A case control study recruited 30 stable COPD from the out-patient 22 respiratory clinic of Main Alexandria University hospital-Egypt and 17 healthy 23 control subjects who were subjected to spirometry. Cortical conduction of the 24 diaphragm was performed by TMS to all participants followed by cervical magnetic 25 stimulation of the phrenic nerve roots. Diaphragmatic resting motor threshold 26 (DRMT), cortical motor evoked potential latency (CMEPL), CMEP amplitude 27 (CMEPA), peripheral motor evoked potential latency (PMEPL), PMEP amplitude 28 (PMEPA) and central motor conduction time (CMCT) were measured.29 Results: 66.7% of COPD patients had severe and very severe COPD with median age 30 of 59 (55-63) years. There was statistically significant bilateral decrease in DRMT, 31 CMEPA and PMEPA in COPD group versus healthy subjects and significant increase 32 in CMEPL and PMEPL (p <0.01). Left CMCT was significantly prolonged in COPD 33 group versus healthy subjects (p <0.0001) but not right CMCT. Further, there was 34 significant increase in CMEPL and CMCT of left versus right diaphragm in COPD 35 group (p= 0.003 and 0.001 respectively) that inversely correlated with FEV 1 % and 36 FVC% predicted.3 37 Conclusion: Central cortico-diaphragmatic motor system is affected in COPD 38 patients with heterogeneity of both sides that is correlated with pulmonary function. 39 Significance: Coticospinal pathway affection could be a factor for development of 40 diaphragmatic dysfunction in COPD patients accordingly its evaluation could help in 41 personalization of COPD management especially pulmonary rehabilitation programs 42 Keywords: Transcranial magnetic stimulation, corticospinal pathways, phrenic nerve, 43 pulmonary function 44 45 46 4 47 Introduction 48 Chronic obstructive pulmonary disease (COPD) is mainly presented with dyspnea and 49 exercise limitation secondary to irreversible airflow obstruction; however, nowadays 50 COPD is considered as multi-systemic inflammatory disorder rather than simple 51 respiratory disease.[1] Respiratory muscles dysfunction has been reported in COPD 52 compared to healthy elderly individuals [2] and has been implicated in the development 53 of dyspnea. 54 Respiratory muscles, particularly the diaphragm which is considered the main 55 inspiratory muscle, are affected in COPD in two main ways. Firstly, change of shape 56 and geometry of the chest wall secondary to air trapping and hyperinflation in COPD 57 leads to chronic reduction of the apposition zone of the diaphragm [3] and shorten of 58 the diaphragm fiber sarcomere.[4] Secondly, local activation of muscle proteases and 59 ...