Respiratory Electroneurophysiologic Studies In Acute Exacerbation Of Chronic Obstructive Pulmonary Disease

Objective:To investigate the characteristics of phrenic nerve conduction (PNC) and motor evoked potentials of diaphragm elicited through magnetic stimulation (dMEP) in critical patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and COPD patients with different mechanical ventilation duration (MVD).Methods:20 patients who experienced acute respiratory failure enough to require mechanical ventilation and 20 healthy control subjects were included. A MagPro Compact magnetic stimulator and a Keypoint 4 electromyogram machine were utilized to perform PNC and dMEP tests. Arterial blood gas was analyzed with a Rapidlab 860 blood gas analyzer. Further more,10 COPD patients with regular mechanical ventilation (Group A, the duration of mechanical ventilation<7d),10 COPD patients with prolonged mechanical ventilation (Group B, the duration of mechanical ventilation>7d) and 10 healthy control subjects were chosen. All tests were carried out within 24 hours of mechanical ventilation and re-examined after weaning within 24 hours in COPD patients.Results:1. The latency of PNC in COPD group was delayed, the common logarithm of the amplitude of PNC was decreased in AECOPD group compared with the control group before and after weaning (P<0.01 for all). There were no statistical differences between before weaning and after weaning in AECOPD group in PNC parameters.2. The latencies of dMEP were delayed, the common logarithm of the amplitude of cervical dMEP was decreased in AECOPD group compared with the control group before and after weaning (P<0.01 for all).3. CMCT was prolonged in AECOPD group compared with control group (P<0.01), it was shorter than the baseline in AECOPD group (P<0.01). It showed no statistical differences between AECOPD group after weaning and control group.4. PaO2 and pH value were decreased, PaCO2 and HCO3- were increased in AECOPD group before weaning compared with control group; PaO2 was decreased; PaCO2 and HCO3- were increased in AECOPD group after weaning compared with control group. PaO2 and pH value were higher, PaCO2 and HCO3- were lower than the baseline in AECOPD group (P<0.01 for all).5. We found a significant positive correlation between the latency of PNC and MVD (P<0.01), a significant negtive correlation between the common logarithm of the amplitudes of PNC and MVD (P<0.05), a significant negtive correlation between the latency of cortical dMEP, CMCT and PaO2 (P<0.01).6. There were significant differences.in the latency and the common logarithm of the amplitude of PNC, cervical dMEP and cortical dMEP in three groups before and after weaning (P<0.01 or P<0.05). The latencies of PNC and dMEP were delayed, the common logarithm of the amplitudes of PNC and dMEP were decreased in group A and group B compared with the control group before and after weaning (P<0.01 or P<0.05). The latency of PNC were delayed; the common logarithm of the amplitude of cervical dMEP was decreased in group B compared with group A before weaning (P<0.05). The latencies of PNC and cortical dMEP were delayed; the common logarithm of the amplitudes of PNC and cervical dMEP were decreased in group B compared with group A after weaning (P<0.05 or P<0.01).7. There were significant differences in CMCT in three groups before and after weaning (P<0.01). CMCT was delayed in group A and group B compared with the control group before weaning (P<0.01). CMCT was delayed in group B compared with the control group and group A after weaning (P<0.01).Conclusion:The central and peripheral respiratory pathway may be involved and central respiratory pathway function is improved after weaning in AECOPD patients with respiratory failure. There are dysfunctions of the cortico-diaphragmatic pathway in COPD patients with mechanical ventilation at different levels and prolonged mechanical ventilation group are worse. The combined use of PNC and dMEP may help evaluate the function of phrenic nerve, diaphragm and respiratory central motor conduction, and may help define the cause of respiratory dysfunction in COPD patients with mechanical ventilation.