204 Mechanical Ventilation of Burn Patients Who Do Not Have the Acute Respiratory Distress Syndrome (ARDS)

Abstract

Lung protective (LP) mechanical ventilation (MV) protocols are well-defined, recommended, and frequently translated to burn patients with ARDS. Less is known about application and suitability of these protocols in burn patients who do not develop ARDS but who nevertheless require MV. The purpose of this study was to examine the use of LPMV strategies in burn patients without ARDS. Retrospective review of all patients requiring MV admitted to an adult regional ABA-verified burn center between 14/11/15 and 23/4/17. Our MV protocol was a low tidal volume (Vt), plateau pressure (Pplat) limited, positive end-expiratory pressure (PEEP) directed strategy defined by the ARDS Network (ARDSNet). Values are shown as the mean ± SD or median (1st, 3rd quartiles) as appropriate. We screened 92 patients who required MV and excluded the following: admission > 24h post burn (n=8), < 48h of MV (n=29), use of comfort measures < 24 h (n=6), ARDS (n=9), non-burn diagnosis (n=18), and burn < 1% TBSA without an inhalation injury (INH), (n=20), leaving a study population of 20 subjects. Characteristics were age 51 ± 15 yr, 20% female, %TBSA burn 35 ± 23, % BSA full thickness burn 7 (0,29), and 45% with INH. Duration of MV was 16 ± 9 days. Mortality was 25%. Volume controlled ventilation (VCV), pressure controlled ventilation (PCV), and pressure support ventilation (PSV) were used for a median of 28%, 1%, and 61% of all MV time, respectively. On VCV, Vt and Pplat were 6.5 ± 0.8 ml/kg and 22.3 ± 4.2 cm H2O, respectively. On PCV, Vt was 6.7 ± 0.9 ml/kg while on PSV it was 8.3 ± 2 ml/kg. Across all modes of MV, PaCO2 and pH were 42 ± 5 and 7.4 (7.35,7.41), respectively. FiO2 was 0.4 (0.4, 0.5), and PEEP was set at 8.5 ± 2.4 cm H2O, which was 1.7 (0.6, 2.6) cmH2O higher than ARDSNet recommended (p=0.3). No patients required “rescue” with unconventional MV. No significant differences in mode of MV, minute ventilation (min vent), Vt, Pplat, FiO2, or PEEP were identified between those with INH (n=9) and without INH (No INH, n=11) over the entire course of MV. In the 1st 96 hours of MV, VCV was used for 70% and 73% of all ventilation hours in INH and No INH, respectively while INH spent a greater proportion of ventilation time on PCV (17%) than No INH (4%). Subjects with INH tended to have a higher min vent [11 ± 2 L/min vs 10 ± 2 L/min, p=0.43], a higher PEEP setting [10 ± 4 cm H2O vs 8 ± 3 cm H2O, p=0.13] and a lower PaO2/FiO2 [205 ± 65 vs 273 ± 79, p=0.05] during the 1st 96 h of MV. Although a small number of patients were studied, the ARDSNet protocol was applied and targets were met even when there was an inhalation injury. A larger prospective observational study would be required to confirm these observations. This study may help to guide use of MV in burn patients.