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Simultaneous bilateral spontaneous pneumothorax is a rare but serious cause of respiratory distress. A possible link with cannabis use highlights the importance of eliciting a full drug history.
A man aged 23 came to accident and emergency in severe respiratory distress. After two weeks of cough he had become short of breath with pleuritic chest pain. There was no medical history of note and he was not on any regular medication. Later he told us he had smoked cannabis since the age of 13 and now smoked it daily. Previously he had mixed the cannabis with tobacco but increasingly he had been using it unmixed.
On examination of the chest there was decreased air entry bilaterally and the trachea was central. Oxygen saturations on 10 L/min via a reservoir bag were 60%, respiratory rate 30. Arterial blood pO2 was 5.78 kPa, pCO2 9.09 kPa, pH 7.13. Mobile chest radiography showed bilateral pneumothoraces, with complete collapse of the left lung (Figure 1). After needle decompression, chest drains were inserted bilaterally, with relief of symptoms.
A subsequent high-resolution CT scan showed entirely normal lung parenchyma, mediastinum and airways. On respiratory function testing, transfer factor was normal but spirometry suggested a mild restrictive pattern (forced expiratory volume 3.0 L [63%], forced vital capacity 3.9 L [69%]) but the technician felt the tests were hampered by patient discomfort from the chest drains. There were no clinical findings suggestive of Marfan's syndrome or ankylosing spondylitis. Because of the high risk of further pneumothoraces he was transferred to a specialist centre for pleurodesis, from which he discharged himself without having the operation.
Though cannabis (marijuana) is an illegal drug in the UK, it is widely used in the 18–25-year age group. In those who smoke it there are increasing reports of detrimental effects on the respiratory tract.1 An association between spontaneous pneumothorax and pneumomediastinum with marijuana has previously been described.2,3 A suggested mechanism is coughing while breath-holding in inspiration, for example, after taking a draw on a 'joint'.3 Perhaps this was the explanation in the present case.
Cannabis apart, the risk of pneumothorax seems to be increased by tobacco smoke,4 and the two may be synergistic.3 Our patient was unusual in not regularly mixing them. The separate influence of cannabis is hard to investigate; moreover, patients may be reluctant to disclose information about use of other illicit drugs. For example, bilateral pneumothorax has been reported after cocaine smoking.5