title: Identification of prolonged phrenic nerve conduction time in the ICU: magnetic versus electrical stimulation.
abstract: OBJECTIVE
  Retrospective study of prospectively collected data to assess the reliability of cervical magnetic stimulation (CMS) to detect prolonged phrenic nerve (PN) conduction time at the bedside. Because PN injuries may cause diaphragm dysfunction, their diagnosis is relevant in intensive care units (ICU). This is achieved by studying latency and amplitude of diaphragm response to PN stimulation. Electrical stimulation (ES) is the gold standard, but it is difficult to perform in the ICU. CMS is an easy noninvasive tool to assess PN integrity, but co-activates muscles that could contaminate surface chest electromyographic recordings.
  
  
  METHODS
  In a first set of 56 ICU patients with suspected PN injury, presence and latency of compound motor action potentials elicited by CMS and ES were compared. With ES as the reference method, CMS was evaluated as a test designed to indicate presence or absence of PN injury. In eight additional patients, intramuscular diaphragm recordings were compared with surface diaphragm recordings and with the electromyograms of possible contamination sources.
  
  
  RESULTS
  The sensitivity of CMS to diagnose abnormal PN conduction was 0.91, and specificity was 0.84, whereas positive and negative predictive values were 0.81 and 0.92, respectively. Passing-Bablok regression analysis suggested no differences between the two measures. The correlation between PN latency in response to CMS and ES was significant. The "diaphragm surface" and "needle" latencies were close, and were significantly different from those of possibly contaminating muscles. One hemidiaphragm showed likely signal contamination.
  
  
  CONCLUSIONS
  CMS provides an easy reliable tool to detect prolonged PN conduction time in the ICU.
authors: Service de Pneumologie et Réanimation Médicale, Groupe Hospitalier Pitié-Salpêtrière, Assistance Publique - Hôpitaux de Paris, 47-83, Bd de l'Hôpital, 75651, Paris Cedex 13, France. alexandre.demoule@psl.aphp.fr
authors: Alexandre
authors: A
authors: Demoule
authors: Capucine
authors: C
authors: Morelot-Panzini
authors: Hélène
authors: H
authors: Prodanovic
authors: Christophe
authors: C
authors: Cracco
authors: Julien
authors: J
authors: Mayaux
authors: Alexandre
authors: A
authors: Duguet
authors: Thomas
authors: T
authors: Similowski
mesh_terms: D000328:Adult; D000368:Aged; D003964:Diaphragm / Q000294:innervation; D004599:Electric Stimulation Therapy; D005260:Female; D005602:France; D006801:Humans; D007362:Intensive Care Units; D055909:Magnetic Field Therapy; D008297:Male; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D058765:Neurofeedback; D010523:Peripheral Nervous System Diseases; D010791:Phrenic Nerve / Q000503:physiopathology*; D019095:Point-of-Care Systems; D011446:Prospective Studies; D012189:Retrospective Studies; D055815:Young Adult