Electromyographic tools to assess hemidiaphragm paralysis

Non-invasive measurements of the phrenic nerve conduction time (CT) and diaphragmatic electromyographic response to voluntary inspiratory efforts may help to document an abnormal diaphragmatic function in the presence of hemidiaphragm elevation on chest radiographs. Twenty-one patients were addressed for the diagnosis of abnormal placement and motion of the right (13) or left (8) cupola on chest radiographs. CT was measured by recording the diaphragmatic M-wave evoked by electrical transcutaneous phrenic nerve stimulation. The integrated diaphragmatic surface electromyogram (Edi) was recorded during sniff and Müller manoeuvres. Four patients were followed up during the next 8-16 months. Among the twenty-one patients, five (24%) had a lengthened or absent CT. A right-to-left peak Edi asymmetry was measured in fourteen (67%), including those having abnormal CT. Agreement between side-related radiographic abnormalities and Edi asymmetry was high in the cases of an elevation of the right cupola (12/13, 92%) but poor when the left cupola was suspected (1/8, 13%). Long-term follow-up of Edi asymmetry showed a partial or total recovery. Thus, the combination of measurements of phrenic nerve CT and Edi recordings during voluntary inspiratory efforts confirmed 67% of the radiographic suspicion of diaphragmatic dysfunction.