A 34-year-old adult was admitted in the ICU due to dyspnoea, bilateral chest pain and decreased saturation with probable clinical diagnosis of severe viral pneumonia. The patient was on mechanical pressure ventilation. On day 2nd of admission in ICU, the patient suddenly deteriorated with decreased level of saturation to 78% and on examination, the patient had extensive subcutaneous emphysema over the neck and chest regions. HRCT was done for further evaluations.
HRCT images showed extensive evidence of subcutaneous emphysema and along the fascial planes of bilateral neck as well as bilateral anterior and posterior chest wall. The large amount of air was seen within the mediastinum outlining the great vessels and pericardium. The air was dissecting superiorly to involve the neck and inferiorly to the peritoneal cavity as well as retroperitoneum. Bilateral pneumothorax was also seen (right > left). Diffuse ground glass opacities were seen within the bilateral lung fields with areas of consolidation in bilateral lower lobes. Multiple areas of tiny air lucencies were seen in the right perihilar region suggesting interstitial emphysema. Sub-pleural pocket of air was also seen in the superior segment of the right lower lobe.
Intubation and mechanical ventilation is the common aggressive procedure done in emergency, pre-operative anaesthesia and ICU settings. Indications may be to increase the oxygenation of the body through the unhealthy lung or to maintain the normal ventilation of the lung during surgical procedures. Positive pressure ventilation is a non-physiological way of maintaining the process of respiration in humans. Therefore, implementation of positive pressure ventilation in the unhealthy lung is even more risky leading to lung injury. These injuries to the lung are termed ventilator-associated lung injury (VALI) or ventilator-induced lung injury (VILI). Barotrauma is the term related to high pressure-induced injury . Barotrauma is the feared complication of mechanical ventilation which increases the patients’ morbidity and mortality. Acute respiratory distress syndrome (ARDS), aspiration pneumonia, chronic obstructive pulmonary disease (COPD) as well as pneumocystis carinii pneumonia are the independent risk factors of barotrauma. In the study done by Anzeuto et.al, incidence of barotrauma is approximately 2.9% in mechanically ventilated patients .
High pressure ventilation and global or regional overdistention of the lung is the primary cause of barotrauma . As the pressure inside the alveoli increases greater than the interstitial pressure, they rupture when it reaches the maximum. The free extra-alveolar air tracks along the pulmonary interstitium i.e. along the wall of the pulmonary vessels to reach the mediastinum. From the mediastinum, it can dissect along the fascial plane to the visceral spaces around the trachea and oesophagus of the neck and this visceral space follows inferiorly to the retroperitoneal space through the oesophageal hiatus of the diaphragm. The posterolateral portion of the retroperitoneal space has anatomic continuity with the properitoneal flank (deep to transversalis fascia) to dissect into the anterior abdominal wall .
The clinical and radiological manifestations of barotrauma can be in the form of pneumothorax, pulmonary interstitial emphysema, subcutaneous emphysema, pneumoperitoneum, pneumo-retroperitoneum, lung cysts, pneumopericardium etc. The patients present with sudden or gradual onset of dyspnoea depending upon the primary cause. Role of imaging X-ray, CT and fluoroscopy in diagnosis and management is crucial in barotrauma. Especially the CT/fluoroscopy with intra-oesophageal contrast can rule out the possibility of oesophageal perforation. In our case, oral diluted non-ionic contrast was given and oesophageal perforation was ruled out. Standard chest X-ray PA/AP and lateral view may be sufficient for the diagnosis of pneumomediastinum. However, to rule out the potential source of the extra-alveolar air that could be from the trachea, bronchi, lung, pleural space, head and neck as well as peritoneum and retroperitoneum, CT is advisable. The classic findings of extra-alveolar air are subcutaneous emphysema, thymic sail sign, pneumopericardium, ring around artery sign, continuous diaphragm sign, tubular artery sign, double bronchial artery sign, extrapleural sign and air in the pulmonary ligament .
Treatment of pulmonary barotrauma is usually supportive and conservative. Decompression of the mediastinal air or pneumothorax is done in critically ill patients. Pulmonary barotrauma is nowadays a rare complication of the ventilator support and its risk varies with the underlying disease. Lung protective strategies with proper settings of the mechanical ventilation parameters in ICU and emergency settings like tidal volume, transpulmonary pressure, positive end expiratory pressure (PEEP) can vastly minimise the complications .
 Ioannidis G, Lazaridis G, Baka S, Mpoukovinas I, Karavasilis V, Lampaki S, et al. (2015) Barotrauma and pneumothorax. Journal of Thoracic Disease 7:6. (PMID: 25774306)
 Anzueto A, Frutos–Vivar F, Esteban A, Alía I, Brochard L, Stewart T, et al. (2004) Incidence, risk factors and outcome of barotrauma in mechanically ventilated patients. Intensive Care Med 30(4):612–9 (PMID: 14991090)
 Parker JC, Hernandez LA, Peevy KJ (1993) Mechanisms of ventilator-induced lung injury. Critical care medicine 21(1):131-43 (PMID: 8420720)
 Maunder RJ (1984) Subcutaneous and mediastinal emphysema. Pathophysiology, diagnosis, and management. Archives of Internal Medicine 144(7):1447–53 (PMID: 6375617)
 Zylak CM, Standen JR, Barnes GR, Zylak CJ (2000) Pneumomediastinum Revisited. RadioGraphics 20(4):1043–57 (PMID: 10903694)