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Monograph: Electrodiagnostic and ultrasound evaluation of respiratory weakness
Monograph: Electrodiagnostic and ultrasound evaluation of respiratory weakness
Phrenic nerve conduction studies (NCSs) and needle electromyography (EMG) can provide important information on the underlying pathophysiology in patients presenting with unexplained shortness of breath, failure to wean from the ventilator, or consideration of phrenic nerve pacemaker implantation. However, these techniques are often technically challenging, require experience, can lack sensitivity and specificity,
and, in the case of diaphragm EMG, involve some degree of risk. Diagnostic highresolution ultrasound has been introduced in recent years as an adjuvant technique readily available at the bedside that can increase the overall sensitivity and specificity of the neurophysiologic evaluation of respiratory symptoms. Two-dimensional ultrasound in the zone of apposition can identify atrophy and evaluate contractility of the diaphragm, in addition to localizing a safe zone for needle EMG. M-mode ultrasound can identify decreased excursion or paradoxical motion of the diaphragm and can increase the reliability of phrenic NCSs. When used in combination, ultrasound, phrenic NCSs and EMG of the diaphragm can differentiate neuropathic, myopathic, and central disorders, and can offer aid in prognosis that is difficult to arrive at solely from clinical examination. This article will review techniques to successfully perform phrenic NCSs, needle EMG of the diaphragm, and ultrasound of the diaphragm. The discussion will include technical pitfalls and clinical pearls as well as future directions and clinical indications.

Objectives: The objectives of this activity are to: 1) Be able to perform or supervise phrenic nerve conduction studies; 2) Be able to perform and/or interpret ultrasound studies of the diaphragm; 3) Understand and be able to implement proper techniques for needle electromyography of the diaphragm.

The AANEM is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians.

None of the authors has any conflict of interest to disclose. 

The AANEM designates this enduring material for a maximum of 1.0 AMA PRA Category 1 Credits TM. Physicians should claim only the credit commensurate with the extent of their participation in the activity. Credit expires 11/15/2026.
Andrea Boon MD; William J. Litchy MD
Availability: On-Demand
Expires on Nov 15, 2026
Cost: Member: $0.00
Non-Member: $15.00
Credit Offered:
1 CME Credit
1 CEU Credit
2621 Superior Drive NW Rochester, MN 55901
Phone: 507.288.0100
Fax: 507.288.1225
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