Is a Lung Protective Tidal Volume Routinely Used for Pediatric and Adult Patients in the ICU?

Abstract

Background: Tidal volume (V_T) selection for patients undergoing mechanical ventilation continues to be a controversial issue. While ideal body weight (IBW) has been recommended to calculate the V_T in adults, actual body weight (ABW) is often used for both children and adults. The purpose of this study was to determine if the V_T selection (based on IBW or ABW) was consistent with a lung protective strategy (<8 mL/kg). Methods: Retrospective chart review using EMRs of pediatric and adult patients admitted to a medical and pediatric ICU. Patients less than 1 year of age, patients undergoing non-conventional modes of ventilation (airway pressure release ventilation [APRV], high frequency oscillatory ventilation [HFOV], high frequency jet ventilation [HFJV]) or extracorporeal membrane oxygenation (ECMO) were excluded from the study. Demographic information, vital signs, arterial blood gases, and ventilator parameters upon admission to ICU (FIO₂, V_T, PEEP) were collected. A V_T of 8 mL/kg was defined as protective for comparison and analysis. Instituional IRB approved the study. Results: Data was collected from 141 patients (30 children; 111 adults) admitted to the ICU between January of 2016 and March of 2018. Mean pediatric age was 7.3 (± 5.8) years and for adults was 46.6 (± 25.7) years, 44% were female (n = 62) and 56% were male (n = 79). Mean PaO₂/FIO₂ (PF) ratio in adults was 213, while mean pediatric PF ratio was 278. The ABW was used as IBW in the pediatric group. Mean adult ABW was 56.4 (± 46.2) kg, while mean pediatric actual weight was 29.1 (± 23.9; IQR 25-75: 11.0-49.3) kg. Mean V_T was 8.36 (± 3.64) and 7.64 (± 2.55) mL/kg when ABW was used for adult and pediatric patients, respectively (P = .15). Mean adult IBW was 64.0 (± 12.52; IQR 25-75: 52.27-75.45) kg, while mean pediatric ABW was 29.14 (± 23.93; IQR 25-75: 5.3-8.2) kg. When using IBW, the mean V_T set for adult patients was 7.19 (± 1.51; range 6.16-10.68; IQR 6.18-8.11) mL/kg and was not significantly different from V_T set in pediatric patients (P = .10). However, ten pediatric patients (33.3%) and 42 adults (37.8%) were set on a V_T > 8 mL/kg. Conclusions: This retrospective chart review demonstrates that while the mean V_T selected for these patients was less than 8 mL/kg, a large number of patients received a V_T considered outside the range considered as lung protective. Published scientific data suggests evidence that using V_T outside the range considered as lung protective is unsafe.