Utility of cervical spinal and abdominal computed tomography in diagnosing occult pneumothorax in patients with blunt trauma: Computed tomographic imaging protocol matters

Occult pneumothoraces – red flag or red herring?

Pneumothorax is a relatively common complication following blunt chest trauma; however, the investigation and management of these injuries remains a contentious issue. Occult pneumothoraces are those not diagnosed by conventional radiographic imaging, but by subsequent computed tomography. This review examines the current evidence base behind the investigation and management of this condition. An anteroposterior chest x-ray should not be underestimated in its ability to provide sufficient radiological information to instigate an initial management plan in the trauma setting. Ultrasound has a high diagnostic rate for pneumothoraces; however, it is subjected to influence from other injuries, whilst failing to address other important injuries in trauma patients requiring computed tomography imaging. It is therefore best used in situations where computed tomography is unavailable or contraindicated. In the management of occult pneumothoraces, there is little difference in patient outcome between those managed conservatively or with a prophylactic chest drain. Clinicians must be wary of recommendations which in this area are often based on inadequate study size and they should continue to provide the best individual care on a case-by-case basis. Observation alone in patients that are haemodynamically stable can be considered, with a view to drainage of the pneumothorax should the clinical status of the patient deteriorate.

[Results of conservative treatment in patients with occult pneumothorax]

INTRODUCTION

An occult pneumothorax is found in 2-15% trauma patients. Observation (without tube thoracostomy) in these patients presents still some controversies in the clinical practice. The objective of the study is to evaluate the efficacy and the adverse effects when observation is performed.

METHODS

A retrospective observational study was undertaken in our center (university hospital level II). Data was obtained from a database with prospective registration. A total of 1087 trauma patients admitted in the intensive care unit from 2006 to 2013 were included.

RESULTS

In this period, 126 patients with occult pneumothorax were identified, 73 patients (58%) underwent immediate tube thoracostomy and 53 patients (42%) were observed. Nine patients (12%) failed observation and required tube thoracostomy for pneumothorax progression or hemothorax. No patient developed a tension pneumothorax or experienced another adverse event related to the absence of tube thoracostomy. Of the observed patients 16 were under positive pressure ventilation, in this group 3 patients (19%) failed observation. There were no differences in mortality, hospital length of stay or intensive care length of stay between the observed and non-observed group.

CONCLUSION

Observation is a safe treatment in occult pneumothorax, even in pressure positive ventilated patients.

Occult pneumothoraces in children with blunt torso trauma

OBJECTIVES

Plain chest x-ray (CXR) is often the initial screening test to identify pneumothoraces in trauma patients. Computed tomography (CT) scans can identify pneumothoraces not seen on CXR ("occult pneumothoraces"), but the clinical importance of these radiographically occult pneumothoraces in children is not well understood. The objectives of this study were to determine the proportion of occult pneumothoraces in injured children and the rate of treatment with tube thoracostomy among these children.

METHODS

This was a planned substudy from a large prospective multicenter observational cohort study of children younger than 18 years old evaluated in emergency departments (EDs) in the Pediatric Emergency Care Applied Research Network (PECARN) for blunt torso trauma from May 2007 to January 2010. Children with CXRs as part of their trauma evaluations were included for analysis. The faculty radiologist interpretations of the CXRs and any subsequent imaging studies, including CT scans, were reviewed for the absence or presence of pneumothoraces. An "occult pneumothorax" was defined as a pneumothorax that was not identified on CXR, but was subsequently demonstrated on cervical, chest, or abdominal CT scan. Rates of pneumothoraces and placement of tube thoracostomies and rate differences with 95% confidence intervals (CIs) were calculated.

RESULTS

Of 12,044 enrolled in the parent study, 8,020 (67%) children (median age=11.3 years, interquartile range [IQR]=5.3 to 15.2 years) underwent CXRs in the ED, and these children make up the study population. Among these children, 4,276 had abdominal CT scans performed within 24 hours. A total of 372 of 8,020 children (4.6%; 95% CI=4.2% to 5.1%) had pneumothoraces identified by CXR and/or CT. The CXRs visualized pneumothoraces in 148 patients (1.8%; 95% CI=1.6% to 2.2%), including one false-positive pneumothorax, which was identified on CXR, but was not demonstrated on CT. Occult pneumothoraces were present in 224 of 372 (60.2%; 95% CI=55.0% to 65.2%) children with pneumothoraces. Tube thoracostomies were performed in 85 of 148 (57.4%; 95% CI=49.0% to 65.5%) children with pneumothoraces on CXR and in 35 of 224 (15.6%; 95% CI=11.1% to 21.1%) children with occult pneumothoraces (rate difference=-41.8%; 95% CI=-50.8 to -32.3%).

CONCLUSIONS

In pediatric patients with blunt torso trauma, pneumothoraces are uncommon, and most are not identified on the ED CXR. Nearly half of pneumothoraces, and most occult pneumothoraces, are managed without tube thoracostomy. Observation, including in children requiring endotracheal intubation, should be strongly considered during the initial management of children with occult pneumothoraces.

Occult pneumothoraces in critical care: a prospective multicenter randomized controlled trial of pleural drainage for mechanically ventilated trauma patients with occult pneumothoraces

BACKGROUND

Patients with an occult pneumothoraces (OPTXs) may be at risk of tension pneumothoraces (TPTXs) without drainage or pleural drainage complications if treated.

METHODS

Adults with traumatic OPTXs and requiring positive-pressure ventilation (PPV) were randomized to pleural drainage or observation (one side only enrolled if bilateral). All subsequent care and method of pleural drainage was per attending physician discretion. The primary outcome was a composite of respiratory distress (RD) (need for urgent pleural drainage, acute/sustained increases in O2 requirements, ventilator dysynchrony, and/or charted respiratory events).

RESULTS

Ninety severely injured patients (mean [SD], Injury Severity Score [ISS], 33 [11]) were studied at four centers: Calgary (55), Toronto (27), Quebec (6), and Sherbrooke (3). Forty were randomized to tube thoracostomy, and 50 were randomized to observation. The risk of RD was similar between the observation and tube thoracostomy groups (relative risk, 0.71; 95% confidence interval, 0.40-1.27). There was no difference in mortality or intensive care unit (ICU), ventilator, or hospital days between groups. In those observed, 20% required subsequent pleural drainage (40% PTX progression, 60% pleural fluid, and 20% other). One observed patient (2%) undergoing PPV at enrollment had a TPTX, which was treated with urgent tube thoracostomy without sequelae. Drainage complications occurred in 15% of those randomized to drainage, while suboptimal tube thoracostomy position occurred in an additional 15%. There were three times (24% vs. 8%) more failures and more RDs (p = 0.01) among those observed with OPTXs requiring sustained PPV versus just for an operation, which increases threefold after a week in the ICU (p = 0.07).

CONCLUSION

Our results suggest that OPTXs may be safely observed in hemodynamically stable patients undergoing PPV just for an operation, although one third of those requiring a week or more of ICU care received drainage, and TPTXs still occur. Complications of pleural drainage remain unacceptably high, and future work should attempt to delineate specific factors among those observed that warrant prophylactic drainage.

LEVEL OF EVIDENCE

Therapeutic study, level III.