Authors: Yasmeen Elsawaf; Linda Papa, MD (Orlando, FL)

Introduction: Capnography is a fast, non-invasive technique that is easily administered and accurately measures exhaled ETCO 2 concentration. ETCO 2 levels respond to changes in ventilation, perfusion, and metabolic state,alteration of which is well documented following a traumatic brain injury. This study examined the relationship between ETCO 2 levels and severity of TBI as measured by injury severity indicators including Glasgow Coma Scale (GCS) score, Computerized Tomography (CT) findings, and requirement of neurosurgical intervention. Methods: This prospective cohort study enrolled adult patients presenting to a Level 1 trauma center following a MMTBI defined by blunt head trauma followed by loss of consciousness, amnesia, or disorientation and a GCS 9-15. ETCO 2 measurements were recorded from the prehospital and emergency department records and compared to indicators of TBI severity. Results: Of the 46 patients enrolled, 21 (46%) had a normal ETCO 2 level and 25 (54%) had an abnormal ETCO 2 level. The mean age of enrolled patients was 40 (range 19-70) and 32 (70%) were male. Mechanisms of injury included motor vehicle collision in 19 (41%), motor cycle collision in 9 (20%), fall in 8 (17%), bicycle/pedestrian struck in 8 (17%) and other in 2 (4%). Eight (17%) patients had a GCS 9-12 and 38 (83%) had a GCS 13-15. Of the 11 (24%) patients with intracranial lesions on CT, 10 (91%) had an abnormal ETCO 2 level (p=0.006). Of the 5 (11%) patients who required a neurosurgical intervention 100% had an abnormal ETCO 2 level (p=0.05). Conclusion: Abnormal levels of ETCO 2 were significantly associated with clinical measures of brain injury severity, in particular, the need for neurosurgical intervention. Future applications ofETCO 2 levels include integration of noninvasive vital signs to predict the extent of injury. Further research with a larger sample of TBI patients will be required to better understand and validate these findings.