A review of non-obstetric spontaneous pneumomediastinum and subcutaneous emphysema.

A man in his early twenties was admitted from the streets. He was hallucinating and incoherent. His vital signs were normal and there was no sign of injury. There was subcutaneous emphy-sema over the neck and anterior chest. The breath sounds were good and the heart sounds were audible. Chest X-ray showed extensive subcutaneous emphysema extending into the neck, but no pneumomediastinum or pneumothorax. A Hexabrix swallow demonstrated no leak. A computed tomography (CT) scan showed extensive surgical emphysema but no underlying pathology. Over the following 48 hours he was treated with a 40% oxygen mask. He remained stable and the surgical emphysema settled completely. Urine testing for cannabis and cocaine were negative. He was certified and admitted to a closed psychiatric ward. No further surgical problems occurred during the following month. Review Louis Hamman originally reported the syndrome that bears his name in 1939, 1 describing it in women in labour ('postpartum pneumomediastinum'). More recently, the syndrome has been loosely applied to all cases of spontaneous pneumomediastinum and subcutaneous emphysema. This review includes an overview of 561 cases, nearly 10 times more than in any other study. Spontaneous pneumomediastinum (SPM) is an uncommon and usually benign entity, characterised by the presence of free air in the mediastinum, in the absence of traumatic or iatrogenic causes or preceding pulmonary pathology such as emphysema, chronic bronchitis or lung cancer. 2 Macklin 3 elucidated the patho-physiology of this condition based on animal laboratory studies in 1944; this was revised by Maunder et al. 4 SPM produces a dramatic increase of endopulmonary pressure 5 that results in rupture of alveolar septa, which causes interstitial air to extend along peribronchial and perivascular spaces into the mediastinum. 3,4 Frequently, air extends to the neck along the cervical fascia, developing into subcutaneous emphysema. 6 Valsalva manoeuvres have been implicated as the cause of SPM. If prolonged, they result in acute, intermittent lower airway obstruction and increased intra-alveolar pressure resulting in rupture of alveoli. 10 'Hamman's crunch' (Hamman's sign) is a precordial crunching sound, heard best when the patient is in the left lateral decubitus position. 1 It is, however, not pathognomonic, and can occur with bullous emphysema, pneumothorax and dilatation of the distal oesophagus. 8 Pneumomediastinum is seen on chest X-ray. On P-A projections there are radiolucent streaks in the mediastinum that can surround the pericardium and reveal the thin dense line of the anterior mediastinal …