CT-lung volume estimates in trauma patients undergoing stabilizing surgery for flail chest.

AIM: To estimate and compare lung volumes from pre- and post-operative computed tomography (CT) images and correlate findings with post-operative lung function tests in trauma patients with flail chest undergoing stabilizing surgery.

PATIENTS AND METHODS: Pre- and post-operative CT images of the thorax were used to estimate lung volumes in 37 patients who had undergone rib plate fixation at least 6 months before inclusion for flail chest due to blunt thoracic trauma. Computed tomography lung volumes were estimated from airway distal to each lung hilum by outlining air-filled lung tissue either manually in images of 5 mm slice thickness or automatically in images of 0.6 mm slice thickness. Demographics, pain, range of motion in the thorax, breathing movements and Forced Vital Capacity (FVC) were assessed. Total Lung Capacity (TLC) measurements were also made in a subgroup of patients (n = 17) who had not been intubated at time of the initial CT. Post-operative CT lung volumes were correlated to FVC and TLC.

RESULTS: Patients with a median age of 62 (19-90) years, a median Injury Severity Score (ISS) of 20 (9-54), and a median New Injury Severity Score (NISS) of 27 (17-66) were enrolled in the study. Median follow-up time was 3.9 (0.5-5.6) years. Two patients complained of pain at rest and when breathing. Pre-operative CT lung volumes were significantly different (p < 0.0001) from post-operative CT lung volumes, 3.51 l (1.50-6.05) vs. 5.59 l (2.18-7.78), respectively. At follow-up, median FVC was 3.76 l (1.48-5.84) and median TLC was 6.93 l (4.21-8.42). Post-operative CT lung volumes correlated highly with both FVC [rs  = 0.75 (95% CI 0.57‒0.87, p < 0.0001)] and TLC [rs  = 0.90 (95% CI 0.73‒0.96, p < 0.0001)]. The operated thoracic side showed decreased breathing movements. Range of motion in the lower thorax showed a low correlation with FVC [rs  = 0.48 (95% CI 0.19‒0.70, p = 0.002)] and a high correlation with TLC [rs  = 0.80 (95% CI 0.51‒0.92, p < 0.0001)].

CONCLUSIONS: Post-operative CT-lung volume estimates improve compared to pre-operative values in trauma patients undergoing stabilizing surgery for flail chest, and can be used as a marker for lung function when deciding which patient with chest wall injuries can benefit from surgery.