Evaluation of central diaphragmatic neural function in early stages of chronic obstructive pulmonary disease

In chronic obstructive pulmonary disease (COPD), the diaphragm may contribute to respiratory decompensation. The aim of this study was to investigate the function of central neural diaphragmatic pathways in mild and moderate grades of COPD (Gold I/II) and its related factors. This study included 20 COPD patients (mean age: 52.80±3.30 years) and 20 matched healthy subjects. All were tested by applying transcranial magnetic stimulation (TMS) of the diaphragmatic motor cortex area and cervical magnetic stimulation (CMS) of the phrenic nerve roots in the neck. Diaphragmatic resting motor threshold (DRMT), cortical motor evoked potential latency (CMEPL), cortical MEP amplitude (CMEPA), peripheral motor evoked potential latency (PMEPL) and amplitude (PMEPA), were recorded from both sides. Central motor conduction time (CMCT) was estimated as follow: CMCT = CMEPL – PMEPL. Compared to controls, patients had increase in CMEPL and CMCT (P<0.0001), while DRMT was decreased (P<0.0001). Among patients, 9 (45%) had delayed CMEPL, 6 (30%) had lower CMEPA, 3 (15%) had delayed PMEPL, 5 (25%) had lower PMEPA, 9 (75%) had prolonged CMCT and 11 (55%) had reduced DRMT. Significant correlations were identified between CMEPA and FVC% (r=0.326,P<0.038), FEV1% (r=0.563,P<0.0001) and FEV1%/FVC% (r=0.710,P<0.0001); between CMEPL and FEV1% (r=-0.368,P<0.020), FEV1%/FVC% (r=-0.463,P<0.003) and between CMCT and FVC% (r=-0.316,P<0.047), FEV1% (r=-0.397,P<0.011), FVV1/FVC % (r=-0.395, P<0.012) and between DRMT and CMCT (r=-0.337,P<0.034). This study indicates that central impairment (corticospinal dysfunction) occurs early in stable COPD.

Author(s):

Sherifa Ahmad Hamed, Ahmad Hamdy Youssef, Refaat Fathy Abd-Elaal, Mahmoud Mohamad Hassan

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