Phrenic nerve stimulation in normal subjects and in patients with diaphragmatic weakness.

Abstract

Phrenic nerve stimulation is often considered to be difficult and unreliable. The time taken for the phrenic nerves to be located and adequately stimulated was measured in 110 subjects, aged 21-89 years, 26 of whom had diaphragmatic weakness; and phrenic nerve conduction time was recorded in 76 of these individuals. Each phrenic nerve was stimulated transcutaneously in the neck with square wave impulses 0 I ms in duration at 1 Hz and 80-160 volts while diaphragmatic muscle action potentials were recorded with surface electrodes. The time taken to locate either phrenic nerve ranged from two seconds to 22 minutes (median 10 s). Both nerves were located in 83 of the 84 control subjects (99%) and in 21 of the 26 patients with diaphragmatic weakness (81%). Mean (SD) phrenic nerve conduction time in the control subjects was 6-94 (0-77) ms on the right and 6-61 (0 77) ms on the left. A weak relationship was found between conduction time and the subjects' age and height. Four out of 24 patients with diaphragmatic weakness had a prolonged phrenic nerve conduction time. Transcutaneous stimulation of the phrenic nerves was not a time consuming procedure, and it was well tolerated, reproducible, and successful in 95% of subjects.Assessment of phrenic nerve function is necessary in candidates for permanent diaphragm pacing' and may be required in the investigation of patients with diaphragmatic weakness. Phrenic nerve conduction time provides a sensitive indicator of phrenic nerve function when the nerves are affected either by local lesions or by generalised ieuropathies. Prolonged conduction time has been fo'upd in phrenic neuritis,2 in mediastinal tumour, after surgical trauma,3 and in peripheral neuropathies.4Although percutaneous phrenic nerve stimulation was described in 19515 as a means of providing ventilatory support and again in 19674 as a method of investigation, phrenic nerve studies have not gained wide acceptance. Failure to locate the nerves,6 7 and discomfort have been considered to be important problems. The purpose of this study was to establish how often, how quickly, and how reproducibly each phrenic nerve could be located by means of twitch stimulations, to see whether this investigation could be applied routinely. Studies were performed in control subjects to determine the normal range of phrenic nerve conduction time and in patients with

Assessment of diaphragm paralysis with oesophageal electromyography and unilateral magnetic phrenic nerve stimulation

“…However, it can be difficult to perform. The time taken to locate the phrenic nerve with ES can be up to 20 min [9]. MIER et al [9] found that the phrenic nerve could not be located with ES in some subjects, especially patients with diaphragm weakness.…”

“…The time taken to locate the phrenic nerve with ES can be up to 20 min [9]. MIER et al [9] found that the phrenic nerve could not be located with ES in some subjects, especially patients with diaphragm weakness. Repeated stimulation for 30 min has been required to establish a diagnosis of diaphragm paralysis with reasonable confidence in the absence of a CMAP response to ES [9].…”

“…MIER et al [9] found that the phrenic nerve could not be located with ES in some subjects, especially patients with diaphragm weakness. Repeated stimulation for 30 min has been required to establish a diagnosis of diaphragm paralysis with reasonable confidence in the absence of a CMAP response to ES [9]. Once the phrenic nerve is located, it can be difficult; with ES, to sustain maximal stimulation because the position and direction of the stimulating electrode is critical, whatever the stimulus intensity.…”

Phrenic nerve conduction studies: normative data and technical aspects

“…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 .…”

“…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 .…”