Objective:The aim of the present study was to define normative data of phrenic nerve conduction parameters of a healthy population. Methods: Phrenic nerve conduction studies were performed in 27 healthy volunteers. Results: The normative limits for expiratory phrenic nerve compound muscle action potential were: amplitude (0.47 mv -0.83 mv), latency (5.74 ms -7.10 ms), area (6.20 ms/mv -7.20 ms/mv) and duration (18.30 ms -20.96 ms). Inspiratory normative limits were: amplitude (0.67 mv -1.11 mv), latency (5.90 ms -6.34 ms), area (5.62 ms/mv -6.72 ms/mv) and duration (13.77 ms -15.37 ms). Conclusion: The best point of phrenic nerve stimulus in the neck varies among individuals between the medial and lateral border of the clavicular head of the sternocleidomastoid muscle and stimulation of both sites, then choosing the best phrenic nerve response, seems to be the appropriate procedure.Keywords: electrodiagnosis; reference values; phrenic nerve; spirometry; neural conduction. RESUMOObjetivo: O objetivo do presente estudo foi definir os dados normativos de condução do nervo frênico de uma população saudável. Métodos: Foram realizados estudos de condução do nervo frênico em 27 voluntários saudáveis. Resultados: Os limites normais do potencial de ação muscular composto do nervo frênico durante a expiração foram: amplitude (0.47 mv -0.83 mv), latência (5.74 ms -7.10 ms), área (6.20 ms/mv -7.20 ms/mv) e duração (18.30 ms -20.96 ms). E durante a inspiração os limites normais foram: amplitude (0.67 mv -1.11 mv), latência (5.90 ms -6.34 ms), área (5.62 ms/mv -6.72 ms/mv) e duração (13.77 ms -15.37 ms). Conclusão: O melhor ponto de estímulo do nervo frênico no pescoço varia entre a borda medial e lateral da cabeça clavicular do músculo esternocleidomastóideo. Estimular ambos os locais e escolher a melhor resposta do nervo frênico parece ser o procedimento mais adequado.Palavras-chave: eletrodiagnóstico; valores de referência; nervo frênico; espirometria; condução nervosa.Phrenic nerve conduction has found increasing application in the diagnosis of respiratory dysfunction associated with surgical, neuromuscular, and pulmonary disorders 1,2,3,4,5,6 , which are important causes of respiratory failure and frequently contribute to difficulties in weaning patients off the ventilator in the critical care unit 7 . To determine a neuromuscular cause of hypercapnic respiratory failure, respiratory electrodiagnostic studies are often used 8 . Recently, many authors have correlated phrenic nerve conduction abnormalities with chronic obstructive pulmonary disease. These studies demonstrated abnormal phrenic compound motor action potential (CMAP) amplitudes and latencies in chronic obstructive pulmonary disease patients 9,10,11,12 .Innervated by the phrenic nerve, the diaphragm is the principal respiratory muscle in humans. The diaphragmatic CMAPs are recorded with chest surface electrodes following phrenic nerve stimulation in the neck. Amplitude, latency, and area are measures used to evaluate phrenic nerve integrity 1,2,3,4,5,...

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Quantitative electromyography is an important tool to evaluate myopathies, and some difficult-to-treat asthmatic patients may have a subclinical corticosteroid myopathic process, using only inhaled corticosteroid, according to some studies. In this report, diaphragm quantitative electromyography was used to evaluate asthmatic difficult-to-treat patients, comparing them with a control group. Significant differences were obtained in amplitude, duration and size index of motor unit action potentials, with lower parameters in the asthmatic patients, which may indicate a myopathic process.

Objective The aim of this study was to obtain data on phrenic neuroconduction and electromyography of the diaphragm muscle in difficult-to-treat asthmatic patients and compare the results to those obtained in controls. Methods The study consisted of 20 difficult-to-treat asthmatic patients compared with 27 controls. Spirometry, maximal inspiratory and expiratory pressure, chest X-ray, phrenic neuroconduction and diaphragm electromyography data were obtained. Results The phrenic compound motor action potential area was reduced, compared with controls, and all the patients had normal diaphragm electromyography. Conclusion It is possible that a reduced phrenic compound motor action potential area, without electromyography abnormalities, could be related to diaphragm muscle fiber abnormalities due to overload activity.