Occult Pneumothoraces in Acute Trauma Patients

Abstract

IntroductionMany traumatic pneumothoraces (PTX) are not seen on initial chest radiograph (CR) (occult PTX) but are detected only on computed tomography (CT). Although CR remains the first tool for detecting PTX, most trauma patients with significant thoracoabdominal injuries will receive both CT and CR. The primary objective of this study was to retrospectively determine the effectiveness of CR for detecting PTX in trauma patients. Our hypotheses were that CR is a sensitive indicator of PTX on CT, that chest pain and shortness of breath are good predictors of PTX on CR, and that we could determine other predictors of PTX on CR.MethodsAll trauma patients presenting to our Level I trauma center with a CT-diagnosed PTX over a 2-year period who had both a CR and a chest CT were included. The CT reading was considered the gold standard for PTX diagnosis. Electronic medical records were searched using key words for diagnoses, symptoms, demographics, and radiologic results. We recorded the official radiologist readings for both CR and CT (positive or negative) and the size of the PTX on CT (large, moderate, small, or tiny). The outcome variable was dichotomized based on presence or absence of PTX detected on CR. Descriptive statistics and χ2 tests were used for univariate analysis. A regression analysis was performed to determine characteristics predictive of a PTX on CR, and 1 variable was added to the model for every 10 positive CRs. With equal-size groups, this study has the power of 80% to detect a 10% absolute difference in single predictors of PTX on CR with 45 subjects in each group.ResultsThere were 134 CT-documented PTXs included in the study. Mean age was 42, and 74% were men. For 66 (49%) patients, PTX was detected on CR (sensitivity = 50%). The CR detected 30% of small PTX, 35% of moderate PTX, and 33% of large PTX. Comparing patients with and without PTX on CR, there were no significant differences in shortness of breath or chest pain. There no relationships between PTX detected on CR and age, gender, penetrating versus blunt injury, bilaterality of the PTX, or presence of lung contusion or hemothorax on CT. After adjusting for all significant variables, predictor of a PTX detected on CR was air in the tissue on CR (adjusted odds ratio [OR] = 3.8) and PTX size (compared to a tiny PTX, adjusted OR = 2.0 for a small PTX, 7.5 for a moderate PTX, and 51 for a large PTX). Chest tubes were used in 89% of patients with PTX on CR and 44% of patients with PTX only on CT (difference 45%; 95% confidence interval 30, 58).Conclusion Factors associated with PTX on CR included air in the soft tissue on CR and size of the PTX. Even when PTX is not apparent on CR, 44% of these PTXs received placement of a chest tube.

Prevalence of large and occult pneumothoraces in patients with severe blunt trauma upon hospital admission: experience of 526 cases in a French level 1 trauma center

“…Lee et al [10] reported a higher rate, 22% (8/36) in a center where thoracic CT scans were performed at clinician discretion and in a trauma population of variable severity. This drainage rate even reached 44% (30/68) in another series, but chest tube indications were left at the discretion of the physician [9]. Thus, a large range of prevalence is observed in the literature, mainly due to selection biases with studied populations, strategies of nonsystematic thoracic CT scan, the nondistinguishing of mechanical ventilation, or wide difference between the indications of drainage.…”

“…This is probably due to continuing improvements in imaging techniques these last years and to our policy of systematic whole-body CT scans of patients with severe trauma [24,25]. Although OPTXs are not visible on chest x-ray, some require an emergent drainage or a change of the initial management strategy [8,9]; Guerrero-López et al [8] had thus found that 18% of patients (19/104) admitted to a trauma intensive care unit who had a CT scan had an OPTX requiring chest tube insertion during their management. Lee et al [10] reported a higher rate, 22% (8/36) in a center where thoracic CT scans were performed at clinician discretion and in a trauma population of variable severity.…”

“…Furthermore, these injuries occur frequently; their likelihood of occurrence increases with the severity of the trauma [3][4][5][6][7][8][9]19], in up to 26% of patients in several series of severely injured patients [7]. Occult PTXs represented almost half of the overall number of PTXs in the literature [3,[7][8][9]. In our series, a higher prevalence was observed: OPTXs were diagnosed in 37% of patients (Table 1) and accounted for twothirds of the total number of PTXs.…”

“…These OPTXs were found in onequarter of patients in some studies [5,6]. Although chest x-ray does not provide the diagnosis, some OPTXs were reported in several studies to require emergency management or chest drainage [7][8][9]. Occult PTXs may therefore be a real diagnostic and therapeutic challenge on admission of patients with trauma, until the initial computed tomographic (CT) scan is performed.…”

The Selective Conservative Management of Small Traumatic Pneumothorax Following Stab Injuries of the Chest in Emergency Department Patients

“…Although there is sufficient evidence to advocate a conservative approach in these patients [19], the underlying pathophysiology is likely to differ from traumatic Pneumothorax [20]. Occult pneumothorax, on the otherhand, specifically describes the entity where chest x-ray is considered normal, but CT scan of the chest reveals evidence of a pneumothorax [21]. Several studies on the management of traumatic pneumothorax often include patients with occult pneumothorax as part of their cohort and, this substantially weakens their generalizability [22] [23].…”