Monograph: Electrodiagnostic and ultrasound evaluation of respiratory weakness-Article

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Phrenic nerve conduction studies (NCSs), needle electromyography (EMG), and diagnostic ultrasound can be used to evaluate respiratory weakness. These techniques can provide important information on the underlying causes of symptoms such as shortness of breath or failure to wean from a ventilator. However, they can be technically challenging and lack sensitivity and specificity. Diagnostic ultrasound is a non-invasive and readily available tool that can increase the overall sensitivity and specificity of the neurophysiologic evaluation of respiratory symptoms. Ultrasound can identify atrophy, evaluate contractility, and localize a safe zone for needle EMG. It can also assess the excursion and motion of the diaphragm, improving the reliability of phrenic NCSs. By combining ultrasound, phrenic NCSs, and EMG of the diaphragm, neuropathic, myopathic, and central respiratory disorders can be differentiated, aiding in prognosis and treatment decisions. Techniques for performing phrenic NCSs, needle EMG of the diaphragm, and ultrasound of the diaphragm are reviewed, including technical pitfalls and clinical indications. The use of ultrasound-guided EMG and the evaluation of patients as candidates for phrenic nerve pacemaker implantation are also discussed. Overall, these techniques provide valuable diagnostic information in patients with respiratory weakness and can help guide appropriate clinical management.

Keywords

Phrenic nerve conduction studies

Needle electromyography

Diagnostic ultrasound

Respiratory weakness evaluation

Shortness of breath

Ventilator weaning

Diaphragm assessment

Neurophysiologic evaluation

Ultrasound-guided EMG

Phrenic nerve pacemaker implantation