Abstract Body: Background: The EMS TBI Guidelines support carefully controlling ventilation in the EMS management of intubated TBI patients [preventing hyperventilation (to enhance cerebral blood flow) and over-ventilation (to provide lung-protective volumes). However, it is difficult to achieve guideline-compliant ventilation when manually ventilating intubated patients in the field. While mechanical ventilators (Mech) have been used for decades in air medical transport, little is known about the impact of their use in ground-based EMS systems.

Methods:
We analyzed the EPIC Study data (NIH-1R01NS071049; DOD-W81XWH-19-C-0058) to compare hospital mortality in intubated major TBI patients transported by ground-based EMS who received Manual vs. Mech. Context: The pre- and post-implementation cohorts of EPIC (intervention: aggressive prevention/treatment of hypoxia, hypotension, and hyperventilation). Chi-squared was used for unadjusted comparisons. Adjusted analysis used logistic regression, controlling for pre-determined confounders.

Results: Included were 2083 intubated subjects [74.4% male; median age 36 years (IQR 22-54); Manual: n=1913; 1341 deaths (70.1% mortality); Mech: n=170; 51 deaths (30.0%; p<0.0001). The unadjusted OR for death in the Manual cohort vs Mech was 5.5 (95%CI: 3.9, 7.7) and the adjusted OR was 2.5 (1.3, 4.8; p=0.005). The Figure portrays the unadjusted and adjusted mortality comparisons in the pre- vs post-implementation periods. The association between ventilation method and mortality was marginally stronger in the post-implementation period (p=0.07).

Conclusions: In this observational study of intubated, severe TBI patients cared for by ground-based EMS, prehospital Mech was associated with significantly lower mortality than Manual (both unadjusted and adjusted). Furthermore, in the setting of implementing the EMS TBI Guidelines, these associations were even stronger in the post-implementation period. This implies that, in the setting of ground EMS, the combination of mechanically-controlled ventilation and training that focuses on reducing hyper- and over-ventilation (by carefully managing End-Tidal CO2) may be associated with better outcome. We do not believe this finding has been previously reported. The magnitude of the associated improvement seen in this preliminary study clearly sets the stage for a large, multisystem clinical trial. These findings may also have implications for EMS resuscitative care in other critically ill patients.