Provider Bias Impacts Tidal Volume Selection and Ventilator Days in Trauma Patients

The ARDSnet (Acute Respiratory Distress Syndrome Clinical Network) study demonstrated that low tidal volume (Vt) reduces mortality from ARDS. It is unknown whether low Vt is beneficial in at-risk trauma patients. We hypothesized that Vt selection would be low in accordance with ARDSnet criteria and that subsequent outcomes would be improved.

A 1-year retrospective observational study was conducted on all trauma patients aged 15 years and older and on mechanical ventilation for 48 hours or longer, excluding those with cardiopulmonary disease. Using maximum Vt, we identified low and high Vt groups (≤8 mL/predicted body weight (PBW) and >8 mL/PBW). Data collected included demographic characteristics, lengths of stay, ventilator and ICU days, ARDS, and other complications.

A total of 364 patients were identified and organized into low Vt (n = 181) and high Vt (n = 183) groups. There was no difference between groups in age, Injury Severity Score, Glasgow Coma Scale, or mechanism of injury. The rate of ARDS was the same in each group. Patients with a high Vt had lower PBW (63.1 ± 8.8 vs 71.7 ± 6.9; p < 0.001), higher BMI(29.7 ± 6.9 kg/m(2) vs 26.6 ± 6.5 kg/m(2); p < 0.001), and were more likely to be female. Height was inversely correlated with Vt (r(2) = -0.579; p < 0.001). The high Vt group experienced longer ICU stays (9.9 ± 8.8 days vs 8.1 ± 7.9 days; p = 0.045) and more ventilator days (8.55 ± 10.5 days vs 6.14 ± 7.4 days; p = 0.015).

Trauma patients receiving high Vt were shorter, had higher BMI, and were more likely to be female. The consequences included longer ICU stays and more ventilator days. Formal calculation of PBW and subsequent Vt is advocated.