Infrared imaging of trauma patients for detection of acute compartment syndrome of the leg* Laurence M. Katz, MD; Varidhi Nauriyal, MD; Shruti Nagaraj; Alex Finch; Kevin Pearlstein; Adam Szymanowski; Charles Sproule; Preston B. Rich, MD; B. D. Guenther, PhD; Robert D. Pearlstein, PhD C ompartment syndrome can be difficult to diagnose, espe- cially in patients with altered mental status or multiple trauma (1). The diagnosis of compart- ment syndrome is usually a clinical diag- nosis, although direct measurements of compartment pressures can support the diagnosis. There are disagreements on what pressure readings are diagnostic of compartment syndrome (2). In addition, abnormal compartment pressures may occur in patients who do not develop compartment syndrome, further reduc- ing the reliability of pressure measure- ments (3). Trauma with swelling of muscles within confined compartments, such as the legs, can produce elevated pressures and leg ischemia (4, 5). The precise time from leg ischemia to muscle and nerve necrosis is unknown, but this may occur as early as 3 hrs after the onset of injury (6, 7). Better methods are needed for the early diagnosis of compartment syn- drome, since delays in the diagnosis that occur with the current procedures are common and can result in permanent disability or death (8 –10). The purpose of this study was to explore the potential of infrared imag- ing for detecting differences in surface temperatures in the legs of trauma pa- tients who develop compartment syn- drome. Infrared imaging is a noninva- sive method for measuring surface temperatures, and a correlation exists between skin temperatures and limb blood flow (5, 11–15). Advances in the development of an uncooled camera, image resolution, and software, now available at relatively low cost, make infrared imaging practical for medical applications (16). Since compartment syndrome causes a decrease in leg blood flow, we hypothesize that development of compartment syndrome is associated with a reduction in surface temperature in the involved leg. *See also p. 1962. From the University of North Carolina at Chapel Hill, Department of Emergency Medicine (LMK, VN, SN, AF, KP, AS, CS) and Department of Surgery (PBR); Duke University Fitzpatrick Center (BDG), Duke Univer- sity Medical Center, Free Electron Laser Laboratory (RDP), and Department of Surgery (RDP). Supported, in part, by the Air Force Office of Scientific Research (principal investigator Laurence M. Katz). The authors have not disclosed any potential con- flicts of interest. Address requests for reprints to: Laurence Katz, Department of Emergency Medicine, University of North Carolina School of Medicine, Neurosciences Hospital Ground Floor, 101 Manning Drive, Chapel Hill, North Carolina 27599. E-mail: lkatz@med.unc.edu Copyright © 2008 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins DOI: 10.1097/CCM.0b013e318174d800 Objective: Early compartment syndrome is difficult to diag- nose, and a delay in the diagnosis can result in amputation or death. Our objective was to explore the potential of infrared imaging, a portable and noninvasive technology, for detecting compartment syndrome in the legs of patients with multiple trauma. We hypothesized that development of compartment syn- drome is associated with a reduction in surface temperature in the involved leg and that the temperature reduction can be detected by infrared imaging. Design: Observational clinical study. Setting: Level I trauma center between July 2006 and July 2007. Patients: Trauma patients presenting to the emergency depart- ment. Interventions: Average temperature of the anterior surface of the proximal and distal region of each leg was measured in the emergency department with a radiometrically calibrated, 320  240, uncooled microbolometer infrared camera. Measurements and Main Results: The difference in surface temperature between the thigh and foot regions (thigh-foot index) of the legs in trauma patients was determined by investigators blinded to injury pattern using thermographic image analysis software. The diagnosis of compartment syndrome was made intraoperatively. Thermographic images from 164 patients were analyzed. Eleven patients developed compartment syndrome, and four of those patients had bilateral compartment syndrome. Legs that developed compartment syndrome had a greater difference in proximal vs. distal surface temperature (8.80  2.05°C) vs. legs without compartment syndrome (1.22  0.88°C) (analysis of variance p < .01). Patients who developed unilateral compart- ment syndrome had a greater proximal vs. distal temperature difference in the leg with (8.57  2.37°C) vs. the contralateral leg without (1.80  1.60°C) development of compartment syndrome (analysis of variance p < .01). Conclusions: Infrared imaging detected a difference in surface temperature between the proximal and distal leg of patients who developed compartment syndrome. This technology holds promise as a supportive tool for the early detection of acute compartment syndrome in trauma patients. (Crit Care Med 2008; 36:1756–1761) KEY WORDS: infrared imaging; thermography; compartment syn- drome; trauma; crush injury; ischemia 1756 Crit Care Med 2008 Vol. 36, No. 6