Abstract
Background and objectivesRespiratory muscles dysfunction has been reported in COPD. Transcranial magnetic stimulation (TMS) has been used for assessing the respiratory corticospinal pathways particularly of diaphragm. We aimed to study the cortico-diaphragmatic motor system changes in COPD using TMS and to correlate the findings with the pulmonary function.MethodsA case control study recruited 30 stable COPD from the out-patient respiratory clinic of Main Alexandria University hospital- Egypt and 17 healthy control subjects who were subjected to spirometry. Cortical conduction of the diaphragm was performed by TMS to all participants followed by cervical magnetic stimulation of the phrenic nerve roots. Diaphragmatic resting motor threshold (DRMT), cortical motor evoked potential latency (CMEPL), CMEP amplitude (CMEPA), peripheral motor evoked potential latency (PMEPL), PMEP amplitude (PMEPA) and central motor conduction time (CMCT) were measured.Results66.7% of COPD patients had severe and very severe COPD with median age of 59 (55–63) years. There was statistically significant bilateral decrease in DRMT, CMEPA and PMEPA in COPD group versus healthy subjects and significant increase in CMEPL and PMEPL (p <0.01). Left CMCT was significantly prolonged in COPD group versus healthy subjects (p <0.0001) but not right CMCT. Further, there was significant increase in CMEPL and CMCT of left versus right diaphragm in COPD group (p = 0.003 and 0.001 respectively) that inversely correlated with FEV1% and FVC% predicted. Right and left DRMT were insignificantly different in COPD group (p >0.05) but positively correlated with FEV1/FVC, FEV1% and FVC% predicted.ConclusionCentral cortico-diaphragmatic motor system is affected in COPD patients with heterogeneity of both sides that is correlated with pulmonary function.SignificanceCoticospinal pathway affection could be a factor for development of diaphragmatic dysfunction in COPD patients accordingly its evaluation could help in personalization of COPD management especially pulmonary rehabilitation programs.
Highlights
Chronic obstructive pulmonary disease (COPD) is mainly presented with dyspnea and exercise limitation secondary to irreversible airflow obstruction; nowadays COPD is considered as multi-systemic inflammatory disorder rather than simple respiratory disease. [1] Respiratory muscles dysfunction, including the diaphragm which is considered the main inspiratory muscle, has been reported in COPD compared to healthy elderly individuals [2] and has been implicated in the development of dyspnea
[9] Transcranial magnetic stimulation (TMS) pulse applied over the primary motor cortex, using the stimulation coil placed tangentially on the head, induces action potentials in cortical axons that spreads transsynaptically to neurons along the corticospinal tract and peripheral motor nerve. [10,11] These excitation signals elicit responses in those muscles that receive corticomotor input from the stimulated motor cortical area which are recorded as motor evoked potentials (MEPs). [10] TMS has been used as an investigation tool for assessing the respiratory corticospinal pathways and studying of diaphragmatic MEPs. [7,12,13]
Baseline FVC%, FEV1% and FEV1/FVC were significantly lower in COPD group (p < 0.0001) where 2 COPD patient (6.7%) had mild airway obstruction, 8 patients (26.7%) had moderate airway obstruction, 12 patients (40%) had severe airway obstruction and 8 patients (26.7%) had very severe airway obstruction according to GOLD classification
Summary
Chronic obstructive pulmonary disease (COPD) is mainly presented with dyspnea and exercise limitation secondary to irreversible airflow obstruction; nowadays COPD is considered as multi-systemic inflammatory disorder rather than simple respiratory disease. [1] Respiratory muscles dysfunction, including the diaphragm which is considered the main inspiratory muscle, has been reported in COPD compared to healthy elderly individuals [2] and has been implicated in the development of dyspnea. [10] TMS has been used as an investigation tool for assessing the respiratory corticospinal pathways and studying of diaphragmatic MEPs. [14] Recently, other studies found dysfunction of the corticospinal motor pathway assessed by TMS during acute exacerbation of COPD patients with or without respiratory failure. We aimed to study the cortico-diaphragmatic motor system changes in COPD patients using TMS compared to healthy subjects as primary outcome. We aimed to correlate between the MEPs changes and the pulmonary function; and to detect possible cut-off value for corticospinal diaphragmatic pathway affection that could be a reference in this group of patients as secondary outcomes. We aimed to study the cortico-diaphragmatic motor system changes in COPD using TMS and to correlate the findings with the pulmonary function.
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