EP229 Initial Measurement of Ideal Body Weight in Ventilated Patients to Guide Tidal Volumes

Published Date: 13th August 2019

Publication Authors: Edwards M, Tridente A

Introduction

Lung hyperinflation is a known contributing factor to ventilator-induced lung injury. Tidal volume (Vt) strategies utilising 6 ml/kg targets have shown decreased mortality and fewer days of ventilation when compared to more traditional Vt approaches1,2. Early measurement of Ideal Body Weight (IBW) on admission to critical care is essential to allow accurate tidal volume ventilation which will subsequently improve patient outcomes.

Objectives

To identify ventilated patients who were managed with a lung protective strategy upon arrival to critical care based on their recorded ideal body weight (IBW), comparing accuracy of ventilation against patients where IBW was not calculated on admission.

Methods

Retrospective note analysis of all patients admitted to critical care over a 2-month period (25/8/17–25/10/17). The patient’s actual Vt was compared to their ideal Vt (6 ml/kg) as calculated from their IBW. IBW was calculated using the Devine formula. Patient height was calculated using the British Association for Parenteral and Enteral Nutrition (BAPEN) method that utilises measurement of ulna length.

Results

52 patients requiring invasive ventilation were identified. 16 (30.7%) of patients had their IBW recorded on arrival with 36 (69.2%) having their IBW recorded during their stay. The mean difference between IBW and actual body weight (ABW) was 8.5 kg (11.1% of ABW). The average discrepancy between ideal tidal volume and actual tidal volume was 58.7 ml/min; if IBW was recorded on admission this was 49.1 ml/min but increased to 70.4 ml/min in those whose IBW was not recorded at all. Logistic regression analysis of mortality with adjustment for APACHE-II score, gender and age however identified no significant difference in patient outcome.

Conclusions

Patients who have their IBW recorded on admission are more likely to be ventilated nearer to the ideal 6 ml/kg Vt. Whilst our study was likely underpowered due to insufficient patient numbers, it is important to maximise the number of patients whose IBW is recorded upon arrival at critical care.

Edwards, M and Tridente, A. (2019). EP229 Initial Measurement of Ideal Body Weight in Ventilated Patients to Guide Tidal Volumes . Journal of the Intensive Care Society. 20 (Suppl 2), 174-5

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