932: A SIMPLIFIED EQUATION TO ESTIMATE TIDAL VOLUME FOR LUNG-PROTECTIVE VENTILATION

Abstract

Introduction: Low tidal volume ventilation (LTVV) has been associated with improved patient-centered outcomes in the emergency department (ED) and intensive care unit (ICU). However, disparities exist in the application of LTVV. Shorter, female, and obese patients are less likely to receive appropriate tidal volumes (Vt). Misestimation of patient size, “preset” tidal volumes, and the perceived complexity of calculating an IBW-based Vt may contribute to this disparity. The current approach to calculating an IBW-based Vt may not always be practical. We hypothesized that a single-step height-based formula could successfully predict LTVV. Methods: We first conducted a retrospective observational cohort study of patients who received mechanical ventilation (MV) at 2 EDs from January 2016 to June 2019. An automatic query abstracted patient demographics, MV, and outcome data. Patients < 18 years old, < 60 inches in height (lower limit of the Devine formula), and with implausible or incomplete MV or demographic data were excluded. LTVV was defined as ≤ 8mL/kg IBW as calculated by the Divine formula. We then created a formula that predicted a 6-8 mL/kg IBW Vt. Next, we applied this formula to a population of ICU patients in the same healthcare system who received MV from January 2017 to December 2019 using the same exclusion criteria. The primary outcome was whether the proposed equation predicted a Vt of 6-8 mL/kg IBW. Results: We included a total of 982 ED patients; 753 (76.7%) had an initial Vt < 8 mL/kg IBW. Initial Vt was set at 450, 500, or 550 mL in 82.8% of patients. The following equation for VtL was derived: VtL = 20 x (Htin-60) + 300. A total of 3720 ICU patients were included; 2511 (64.9%) had an initial Vt < 8mL/kg IBW. The VtL equation successfully predicted a Vt of 6-8 mL/kg IBW in 3720 (100%) patients. Conclusions: A simplified, single-step height-based equation successfully predicted tidal volumes for LTVV in a cohort of ICU patients ≥ 60 inches independent of sex.