Management of Occult Pneumothoraces in Mechanically Ventilated Patients

Prospective Randomized Trial of the Management of Occult Pneumothoraces in Mechanically Ventilated Patients

Collapsed lungs are common injuries after traumatic injury that regularly cause needless deaths despite being treatable with chest tubes. Properly used these tubes can be life-saving. Unfortunately, improperly used they can cause pain, bleeding, and other fatal complications themselves. Over the last few decades with increased use of CT scanning it is apparent that many small collapsed lungs are not seen on chest X-rays, and there is little guidance for the treating Doctors as to how to treat these patients. There is almost no good data that tells us whether these smaller pneumothoraces require treatment with chest tubes or whether they can simply be closely watched. This proposal is to carry out a simple trial of randomly assigning patients who do not appear to have any symptoms or problems from their occult pneumothorax to either having a standard chest tube or to being watched. Our careful review of the medical literature indicates that the investigators cannot honestly tell patients and their families which treatment is best or required. Our audit of current practice also indicates that Doctors in Calgary and across Canada, regularly prescribe both treatments regularly but in a hap-hazard. The patients in this study will be very closely watched in the intensive care unit and if they develop any breathing problems and do not have a chest tube in, then one will be inserted. The main results that the investigators are trying to determine with this pilot study, though, is whether the investigators are able to detect appropriate patients, to recruit them into such a study, and whether the guidelines the investigators have created to manage these patients in this study will be acceptable to all the patient's care givers. This data will help us to design a future large multi-centre trial that will hopefully provide information as how best to manage this type of injured patient.

The term "Occult Pneumothorax" (OPTX), describes a pneumothorax (PTX) that while not suspected on the basis of either clinical examination or plain radiograph, is ultimately detected with thoraco-abdominal computed tomograms (CT). This situation is increasingly common in contemporary trauma care with the increased use of CT. The incidence appears to approximately 5% in injured populations presenting to hospital, with CT revealing at least twice as many PTXs as suspected on plain radiographs. While PTXs are a common and treatable (through chest drainage) cause of mortality and morbidity, there is clinical equipoise and significant disagreement regarding the appropriate treatment of the OPTX. Based on level III evidence, some authors have recommended observation without chest drainage for all but the largest OPTXs, recommendations that contravene the standard dictum for ventilated patients as recommended by the Advanced Trauma Life Support Course of the American College of Surgeons. The controversy is the greatest in the critical care unit population who require positive pressure ventilation. This is also the group for whom the highest rates of chest tube complications have been reported. Complication rates related to chest tubes in general, have been claimed in up to 21% of cases.

No previous studies have focused specifically on the population of mechanically ventilated patients. There have been only 45 reported ventilated trauma patients ever randomized to treatment or observation. Enderson found that 8 (53%) of 15 patients had PTX progression with 3 tension pneumothoraces. Brasel found that of 9 observed OPTXs, 2 progressed. Brasel concluded observation was safe, while Enderson felt chest tubes were mandatory. The investigators thus propose to carry out a prospective randomized trial to examine the need for chest drainage in small to moderate sized OPTX's, as well as the practicalities of carrying out such a study.

The experience and knowledge gained from this pilot will be intended to provide additional support to a future submission to the Canadian Institute for Health Research in order to carry out a multi-centre prospective trial involving the member institutions of the Canadian Trauma Trials Collaborative (CTTC). The investigators believe they have invested more time and effort into developing this line of investigation than any other group in the World. The investigators first reviewed the pertinent literature and subsequently retrospectively reviewed the outcomes of this entity at both this institution and with collaborators at other CTTC sites. The investigators have examined the anatomic and practical reasons as to why OPTXs are occult, as well as novel investigation methods to detect them during the initial evaluation for trauma, and documented the morbidity that may occur with their treatment.

Inclusion Criteria:

1. age >= 18 years old
2. small to moderate sized occult pneumothorax identified on chest or abdominal CT scan
3. no chest drain in-situ
4. no hemothorax which warrants drainage in the judgment of attending clinician
5. no respiratory compromise in the judgment of the attending clinician

Exclusion Criteria:

1. not expected to survive
2. large occult pneumothorax
3. pneumothorax obvious on plain CXR (not occult)
4. respiratory distress in the judgment of the attending clinician
5. pre-existing chest drain in-situ