The Role of Ultrasound and Air Leak Measurement in Assessing Lung Expansion after Thoracic Surgery

Objective: To determine if lung ultrasound semiology is applicable to the post-surgical hemithorax, and its value in the evaluation of lung expansion in the postoperative period when paired with the use of digital chest drain systems. Methods: Prospective observational study including all patients undergoing thoracic surgery from June 2012 to March 2013. Patients undergoing pleurodesis or hemodynamically unstable were not considered candidates. Final inclusion in the study was based on the availability of digital chest drain system. A transthoracic lung ultrasound evaluation of the anterior and anterolateral windows was performed 20 minutes after chest drain placement. Presence or not of lung sliding and air leak values taken from the digital chest drain system were recorded. Data were submitted to a binomial classification test for analysis. Results: Forty-nine patients were included, yielding a total of 64 hemithoraces. Lung sliding was seen in 53 cases (82.8%), and an air leak value of 20 ml/min or less in 56 cases (87.5%). Sensitivity was 92.8% (95% CI: 82.6% to 97.9%) and specificity 87.5% (95% CI: 47.3% to 97.9%). Positive predictive value was 98.1%, and negative predictive value was 63.6%. Conclusions: Transthoracic lung ultrasound is a useful technique that can complement the use of digital chest drain systems in the evaluation of post-surgical lung expansion. The incorporation of lung ultrasound can greatly reduce the need for chest radiographs in thoracic surgery departments.