Twitch Transdiaphragmatic Pressure Morphology Can Distinguish Diaphragm Paralysis from a Diaphragm Defect

Images in Pulmonary, Critical Care, Sleep Medicine and the Sciences Twitch Transdiaphragmatic Pressure Morphology Can Distinguish Diaphragm Paralysis from a Diaphragm Defect Zaid Zoumot1, Simon Jordan1, Nicholas S. Hopkinson1, and Michael I. Polkey1 1

NIHR Respiratory Biomedical Research Unit at Royal Brompton and Harefield NHS Foundation Trust and National Heart & Lung Institute, Imperial College London, London, United Kingdom

Figure 1. (A) Coronal slice of computed tomography scan preoperatively; like the chest radiograph (B), this confirmed left hemidiaphragm elevation, but the diaphragmatic defect was not visualized. (C) Chest radiograph after repair of the hemidiaphragm defect, showing lowering of the hemidiaphragm.

Figure 2. Left diaphragm defect. The anterior margin of the split in the diaphragm is visible through the intact parietal pleura (marked with arrows/dots).

Figure 3. Esophageal (Pes), gastric (Pga), and transdiaphragmatic (Pdi) pressures in response to bilateral magnetic stimulation of the phrenic nerves (top panel) before (a) and after (b) repair of the large left diaphragmatic defect. Note the reversal of polarity of twitch Pga back to the usual physiological state (green arrows). Each tick mark on the xaxes represents 200 ms.

Am J Respir Crit Care Med Vol 188, Iss. 2, p e3, Jul 15, 2013 Copyright ª 2013 by the American Thoracic Society DOI: 10.1164/rccm.201207-1185IM Internet address: www.atsjournals.org

Surgical treatment of an elevated hemidiaphragm (plication) differs from repair of a defect, which entails a wider approach; however, imaging cannot distinguish the two. The negative intrathoracic pressure elicited by phrenic nerve stimulation should be transmitted to the abdomen through a defect. We report a 21-year-old man with an elevated hemidiaphragm 6 years after a high-speed car accident. Computed tomography scanning failed to demonstrate a diaphragmatic defect (Figure 1). Bilateral magnetic phrenic nerve stimulation was performed before and after repair of the defect (Figure 2). Preoperatively, both negative gastric (Pga) and esophageal (Pes) pressures were elicited (Figure 3); after repair, a positive twitch Pga was observed. Transdiaphragmatic pressures (Pdi) in response to stimulation increased from 4 to 15 cm H2O (normal range . 18 cm H2O). Phrenic nerve stimulation predicted the physiologic presence of a defect. The effect of surgical repair of a diaphragm defect on transdiaphragmatic pressure morphology has not been previously described. Author disclosures are available with the text of this article at www.atsjournals.org.