ARDS after pulmonary contusion: accurate measurement of contusion volume identifies high-risk patients

The pathophysiology of pulmonary contusion (PC) is poorly understood, and only minimal advances have been made in management of this entity over the past 20 years. Improvement in understanding of PC has been hindered by the fact that there has been no accurate way to quantitate the amount of pulmonary injury. With this project, we examine a method of accurately measuring degree of PC by quantifying contusion volume relative to pulmonary function and outcome.

Patients with PC from isolated chest trauma who had admission chest computed tomographic scan were identified from the registry of a Level I trauma center over a 1.5-year period. Subsequently, prospective data on all patients admitted to the intensive care unit with PC during a 5-month period were collected and added to the retrospective database. Using computer-generated three-dimensional reconstruction from admission chest computed tomographic scan, contusion volume was measured and expressed as a percentage of total lung volume. Admission pulmonary function variables (Pao2/FiO2, static compliance), injury descriptors (chest Abbreviated Injury Score, Injury Severity Score, injury distribution), and indicators of degree of shock (admission systolic blood pressure, admission base deficit) were documented. Outcomes included maximum positive end-expiratory pressure, ventilator days, pneumonia, and acute respiratory distress syndrome (ARDS).

Forty-nine patients with PC (35 bilateral) were identified. The average severity of contusion was 18% (range, 5-55%). Patients were classified using contusion volume as severe PC (> or =20%, n = 17) and moderate PC (< 20%, n = 32). Injury Severity Score was similar in the severe and moderate groups (23.3 vs. 26.5, p = 0.33), as were admission Glasgow Coma Scale score (12 vs. 13, p = 0.30), admission blood pressure (131 vs. 129 mm Hg, p = 0.90), and admission Pao2/Fio2 (197 vs. 255, p = 0.14). However, there was a much higher rate of ARDS in the severe group as compared with the moderate group (82% vs. 22%, p < 0.001). There was a trend toward higher pneumonia rate in the severe group, with 50% of patients in the severe group developing pneumonia as compared with 28% in the moderate group (p = 0.20).

Extent of contusion volumes measured using three-dimensional reconstruction allows identification of patients at high risk of pulmonary dysfunction as characterized by development of ARDS. This method of measurement may provide a useful tool for the further study of PC as well as for the identification of patients at high risk of complications at whom future advances in therapy may be directed.