The 35-mm rule to guide pneumothorax management: Increases appropriate observation and decreases unnecessary chest tubes.

Introduction: Axial imaging has allowed for more precise measurement and, in-turn, more objective guidelines related to the management of traumatic pneumothoraces (PTXs). In 2017, our trauma center used a guideline to observe any PTX ≤35 mm in stable patients. We hypothesize that this guideline would decrease unnecessary chest tubes without affecting failure rates.

Methods: This is a single-center retrospective review of all adult trauma patients who had a PTX diagnosed on computed tomography before (2015-2016) and after (2018-2019) guideline implementation. We excluded patients with chest tubes inserted before computed tomography, concurrent hemothoraces, mechanical ventilation, or mortality in the first 24 hours. Descriptive statistical analyses, χ2 test, and Mann-Whitney U test were performed as appropriate.

Results: A total of 266 patients met our inclusion criteria. Ninety-nine (37.2%) and 167 patients (62.7%) were admitted before and after 2017, respectively. Overall, there were no differences in demographics or severity of injuries between both groups. After guideline implementation, there was a significant increase in observation rates and compliance rate. Tube thoracostomies decreased from 28.3% to 18% (p = 0.04). There were no statistically significant changes in observation failure rates, hospital or intensive care unit length of stay, complications, or mortality.

Conclusion: The implementation of the 35 mm guideline is an effective tool to decrease unnecessary tube thoracostomy in hemodynamically normal patients without evidence of hemothorax.

Level Of Evidence: Therapeutic/care management, level III.