Assessment Of Human Diaphragm By Cervical Magnetic Stimulation

ObjectiveUsing the Cervical magnetic phrenic nerve stimulation to research thedifference of the diaphragm characteristics at different level ofmagnetic stimulation(40%、60%、80%、100%Imax) while the airway iscompletely closed or opened.To understand the strength-velocity-Imaxrelationship of the diaphragm to assess the diaphragmatic functions.Methods8normal male volunteers participated in this study. The multipairesophageal electrodes and surface electrodes were used to measure CMAPdi.Oesophageal and gastric balloon catheters were used to measure Peso, Pgas.Using the self-customed airway occlusion and trigger devices, cervicalmagnetic stimulation of the phrenic nerves were repeated three times atdifferent Imax to measure the twitch inspiratory flow, Pmou,t andPdi, t at colsed or opened airway to compare their reproducibility withIC and influence of different airway status.ResultsAt100%Imax, the within subjects coefficient of variation of Pdi,t,Pmou,t, Fin,t and the Pmou,t/Pdi,t ratio are small and similar to the5%reproducibility requirement for an acceptable recording of IC by usingthe self-customed devices.The variation does not depend on time butImax.The mean±SD values were19.16±5.68cmH2O、15.55±4.01cmH2O、2.46±0.58L/s,0.82±0.08and the mean within occation over time coefficient of variation was4.89%,4.41%,3.90%,2.40%and3.33%respectively, whilethe between subjects coefficient of variation of Pmou,t/Pdi,t ratio was8.50%. Pdi,t and Pmou,t or Fin,t were correlated as follows: r=0.96,p <0.0001; r=0.52, P <0.05. The strength-velocity-Imax relationshipshows that at100%Imax airway opened Pdi,t is samller3.82cmH2O (P=0.04),compared with the airway blocked completely, while the remaining threelevels of Imax did not show statistical differences.ConclusionsThe self-customed devices could be used in CMS. The excellentreproducibility of Pdi,t, Pmou,t, Fin,t and the Pmou,t/Pdi,t ratiosuggests that they may be the useful means of monitoring diaphragmaticcontractility.At100%Imax both of the Pdi,t were not reach the plateau,the airway opened Pdi,t is samller3.82cmH2O (P=0.04).