Abstract 386: Prehospital Capnography in Non-Intubated Traumatic Brain Injury Patients: Association Between End-Tidal CO2 and Level of Consciousness

Abstract

Background: The EMS traumatic brain injury (TBI) guidelines encourage limiting prehospital intubation (ETI) to patients with profoundly depressed level of consciousness (LOC) and who cannot protect their airway or adequately ventilate without ETI. Thus, EMS providers may manage many TBI patients without intubating even when they have significant alterations in LOC. Monitoring End-Tidal CO2 by placing sensors in the nares (NC-CO2) of non-intubated patients may give providers valuable information about ventilatory status and trends. Study Objective: To evaluate the association between LOC and NC-CO2 in non-intubated TBI patients. Methods: Non-intubated cases from 6 EMS agencies reporting continuous monitor data (Philips MRx™) in the EPIC Study (NIH 1R01NS071049) were evaluated (4/13-3/17). Glasgow Coma Scale (GCS) was available from the EMS record in call cases. Comparisons in patient-level mean, median, lowest and highest NC-CO2 levels were made across GCS categories using clinically meaningful thresholds: <15, <12, <9, and 3. Statistics: Wilcoxon rank-sum test. Results: Included were 106 cases [median age: 47 (range: 9-91), 66% male]. The Table shows the NC-CO2 patterns and comparisons across the GCS categories. In no case was there a significant difference in NC-CO2 between the better vs. worse mental status cohort. Conclusion: We believe this is the first evaluation of the association between NC-CO2 and mental status in TBI. Patients that had significant (and even profound) decreases in LOC, but whom paramedics chose not to intubate, had remarkably similar NC-CO2 patterns compared to those with normal or near-normal mental status. This may support the overall approach of limiting ETI to those with airway/ventilatory compromise or impending hypoxia as there was no evidence of increasing NC-CO2, indicative of hypercapnia, in the non-intubated patients even when they had very depressed LOC.