Patients With Traumatic Injury Transported By Critical Care Air Transport Teams: The Influence of Altitude and...

During previous military conflicts, the U.S. Air Force Critical Care Air Transport Teams (CCATTs) transported critical patients out of theater to Landstuhl Regional Medical Center (LRMC) with cabin pressures equivalent to an altitude of 5,000 to 8,000 feet. In order to avoid risks associated with hypobaria, in-theater medical providers are tasked with determining if cabin altitude restrictions (CAR) to 4,000-6,000 feet should be prescribed for individual patients. The purpose of this study was to describe and compare CCATT trauma patients transported with CAR and without CAR to evaluate the impact of CAR on clinical outcomes for trauma populations other than TBI.

We conducted a retrospective cohort study to compare patients with traumatic injury who were prescribed and flew with CAR to those who did not fly with CAR (nonCAR). Patients with moderate to severe injury severity scores (ISSs > 12) transported between January 2007 and December 2020 were included. We analyzed data for 837 patients evacuated by CCATT to a Role 4 treatment facility with non-TBI traumatic injuries. We classified patients into the CAR and nonCAR groups based on the CAR prescription (a yes/no checkbox) and the maximum cabin altitude (<5,000 feet indicated a CAR) listed on their CCATT record.

One hundred fourteen patients (14%) were included in the CAR group and 723 (86%) were in the nonCAR group. Patients in the CAR group were more likely to have a penetrating injury than the nonCAR group (32.5% vs. 23.4%, P = .0364). The CAR group had higher rates of chest tube management than the nonCAR group (43.9% vs. 26.1%, P < .0001). There were no other significant differences in rates of in-flight interventions or in medications administered. In the nonCAR group, we observed an increase in the proportion of patients with hypoxemia (10.0% pre-flight to 18.1% in-flight, P < .0001). The overall mortality rate was 2.4% (n = 18 patients). The median time spent on a ventilator was 5 days (IQR 3-8 days), time in the ICU was 8 days (IQR 6-14 days), and hospital length of stay was 25 days (IQR 7-48 days). The CAR and nonCAR groups did not significantly differ in any of these outcome measures. Subgroup analyses revealed that in the nonCAR group, patients with in-flight hypoxemia spent more time on the ventilator (median 6 days [IQR 3-11 days] vs. 5 days [IQR 2-8 days], P = .0011) and in the ICU (median 11 days [IQR 7-20 days] vs. 8 days [IQR 6-12 days], P = .0004) than those without in-flight hypoxemia. There were no differences in any outcome measures for the CAR group.

Hypoxemia occurred more frequently in CCAT patients flown without cabin altitude restrictions but no overall differences in patient outcomes were observed. The prescription of CAR may serve as a mediator in the presence of hypoxemia, therefore in theater medical providers should consider the potential benefits of CAR in select patients.