A Pneumomediastinum with Diffuse Subcutaneous Emphysema

Abstract

A 65-year-old man presented to the Emergency Department with facial angioedema. It occurred just after an intramuscular morphine injection in the shoulder for a minor chest trauma from falling off a chair. On physical examination, he had right chest pain, a pulse of 90 beats/min, blood pressure of 140/80 mm Hg, respiratory rate of 35 breaths/min, and room air oxygen saturation of 88%. Diffuse wheezes were detectable in both lungs. He was provided with supplemental oxygen, salbutamol aerosol, and corticosteroid treatment. After initial stabilization, subcutaneous emphysema developed suddenly over his chest. Chest radiography revealed a right lucency, some mediastinal radiolucent streaks, and subcutaneous emphysema (Figure 1). Chest computed tomography scan with intravenous contrast confirmed the right pneumothorax and the pneumomediastinum (Figure 2, Figure 3), and revealed a rib fracture (Figure 4). A chest drain was inserted and the patient’s condition improved.Figure 2Chest computed tomography scan (tissue window). Right pneumothorax (arrow) and pneumomediastinum (arrow) are visible.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Chest computed tomography scan (tissue window) reveals right and left pneumothoraces and pneumomediastinum with dissection of bronchovascular sheaths (arrows).View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4Chest computed tomography scan (bone window) shows a rib fracture (arrow).Used with permission of Emilie Dehours, MD, Department of Emergency Medicine, Purpan, Toulouse, France.View Large Image Figure ViewerDownload Hi-res image Download (PPT) The term pneumothorax was first coined in 1803 by Itard, and its clinical features were described by Laennec in 1819. More than half of pneumothoraces are traumatic (accidental or iatrogenic); the others occur without any preceding trauma and are labeled spontaneous (1Schramel F.M.N.H. Postmus P.E. Vanderschueren R.G.J.R.A. Current aspects of spontaneous pneumothorax.Eur Respir J. 1997; 10: 1372-1379Crossref PubMed Scopus (257) Google Scholar). Traumatic pneumothoraces result from penetrating or nonpenetrating chest injuries (2Gupta D. Hansell A. Nichols T. et al.Epidemiology of pneumothorax in England.Thorax. 2000; 55: 666-671Crossref PubMed Scopus (259) Google Scholar). It is noteworthy that, in the literature, there is a strong association between rib fractures and pneumothoraces (3Bridges K.G. Welch G. Silver M. et al.CT detection of occult pneumothorax in multiple trauma patients.J Emerg Med. 1993; 11: 179-186Abstract Full Text PDF PubMed Scopus (90) Google Scholar). On the other hand, pneumomediastinum, reported in 1939 by Hamman, is an uncommon clinical entity (4Chalumeau M. Clainche L. Sayeg N. et al.Spontaneous pneumomediastinum in children.Pediatr Pulmunol. 2001; 31: 67-75Crossref PubMed Scopus (147) Google Scholar). The first described pneumomediastinum by Laennec in 1819 was a consequence of traumatic injury. The most widely accepted explanation for the development of pneumomediastium is a sudden rupture of distended alveoli under high-pressure gradient between the alveoli and the surrounding interstitial space. The free air then dissects from the ruptured alveoli along the bronchovascular sheaths toward the mediastinum. This sequence of events is known as the “Macklin Effect” (5Macklin M.T. Macklin C.C. Malignant interstitial emphysema of the lungs and mediastinum as an important occult complication in many respiratory diseases and other conditions.Medicine. 1994; 23: 281-352Crossref Scopus (604) Google Scholar). Gas can also escape retroperitoneally through periaortic and periesophageal planes (6Zylak C.M. Standen J.R. Barnes G.R. et al.Pneumomediastinum revisited.Radiographics. 2000; 20: 1043-1057Crossref PubMed Scopus (164) Google Scholar). As a result, the air within the mediastinum can further dissect through these planes, causing pneumopericardium, pneumoretroperitoneum, and pneumoperitoneum. As a consequence of our finding, early incorporation of a routine chest computed tomography scan in all patients with rib fractures might be required to successfully diagnose pneumothoraces and pneumomediastinum.