Occult pneumothorax in the blunt trauma patient: tube thoracostomy or observation?

BACKGROUND: The term occult pneumothorax (OP) describes a pneumothorax that is not suspected on the basis of either clinical examination or initial chest radiography, but is subsequently detected on computed tomography (CT) scan. The optimal management of OP in the blunt trauma setting remains controversial. Some physicians favour placement of a thoracostomy tube for patients with OP, particularly those undergoing positive pressure ventilation (PPV), while others favour close observation without chest drainage. This study was conducted both to determine the incidence of OP and to describe its current treatment status in the blunt trauma population at a Canadian tertiary trauma centre. Of interest were the rates of tube thoracostomy vs. observation without chest drainage and their respective outcomes.
METHODS: A retrospective review was conducted of the Nova Scotia Trauma Registry. The data on all consecutive blunt trauma patients between October 1994 and March 2003 was reviewed. Outcome measures evaluated include length of stay, discharge status-dead vs. alive, intervention and time to intervention (tube thoracostomy and its relation to institution of PPV). Direct comparison was made between the OP with tube thoracostomy group and OP without tube thoracostomy group (observation or control group). They were compared in terms of their baseline characteristics and outcome measures.
RESULTS: In 1881 consecutive blunt trauma patients over a 102-month period there were 307 pneumothoraces of which 68 were occult. Thirty five patients with OP underwent tube thoracostomy, 33 did not. Twenty nine (82.8%) with tube thoracostomy received positive pressure ventilation (PPV), as did 16 (48.4%) in the observation group. Mean injury severity score (ISS) for tube thoracostomy and observation groups were similar (25.80 and 22.39, p=0.101) whereas length of stay (LOS) was different (17.4 and 10.0 days, p=0.026). Mortality was similar (11.4% and 9.1%). There were no tension pneumothoraces.
CONCLUSION: The natural history of OP in blunt trauma patients at our institution appears to be one of uneventful resolution irrespective of ISS, need for PPV, or placement of tube thoracostomy. This study suggests an interesting hypothesis that observation of the blunt trauma patient with OP, without tube thoracostomy, may be safe and contribute to a shorter hospital stay. These are observations that would benefit from further study in a large, prospective randomised controlled trial.