Abstract 252: End-Tidal CO2 and Glasgow Coma Scale in Non-Intubated Traumatic Brain Injury Patients: Evaluation of Prehospital Nasal Capnography and Level of Consciousness

Abstract

Background: The EMS traumatic brain injury (TBI) guidelines recommend limiting intubation (ETI) to patients with profoundly-depressed level of consciousness (LOC) and who cannot protect their airway or adequately ventilate with basic maneuvers. Thus, many major TBIs are managed without ETI in the field. Monitoring ETCO2 via nasal sensors (NC-CO2) in non-ETI patients may provide valuable information about ventilatory status and trends. However, EMS NC-CO2 remains unstudied. Objective: To evaluate the association between LOC and NC-CO2 in non-intubated TBI. Methods: Cases from 7 EMS agencies reporting continuous monitor data (Philips MRx™) in the EPIC TBI Study (NIH 1R01NS071049) were evaluated (4/13-4/18). Comparisons in patient-level mean, median, lowest and highest NC-CO2 levels were made across GCS categories using clinically meaningful thresholds: <15, <12, <9, 3. Results: Included: 177 cases [median age: 52 (range: 9-94), 66% male]. Overall, while not statistically significant, NC-CO2 tended to be lower in patients with lower GCS (Table). In addition, minimum NC-CO2 was significantly lower (p=0.01) in patients with compromised LOC (Table). O2 management (Hi-flow/Lo-flow/No O2) was documented in 176 patients (99.4%). Among the 107 patients with all GCS = 15, 44 (41%) had Hi-flow administered compared to 47/69 (68%) with any GCS <15 (p=0.0008). Conclusion: The utility of prehospital capnography in non-intubated patients is unknown. In this study, NC-CO2 tended to be lower in TBI patients with lower GCS. Whether this reflects physiological/respiratory differences with changes in LOC, or variations in methods of managing oxygenation is unclear. These intriguing new findings require future study to determine if NC-CO2 is directly reflective of LOC-related ventilatory patterns. Furthermore, studies are needed to evaluate whether NC-CO2 monitoring has clinical utility as a non-invasive adjunct to care in spontaneously-breathing, non-ETI patients.