LATE-BREAKING ABSTRACT: Validation of anindirect calorimetry method among healthy volunteers with non-invasive ventilation at different oxygen concentrations: An agreement study

Abstract

Background: The assessment of resting energy expenditure (REE) through indirect calorimetry (IC) in patients that require oxygen or non-invasive ventilation (NIV) may provide erroneous values due to gas mixture instability of the supplementary oxygen and NIV gas leakage.

Purpose and Objectives: To validate a new REE measurement method using an indirect calorimeter in healthy subjects undergoing NIV at a FiO₂ of 0.21 and 0.3 (new method) comparing their REE values with those breathing spontaneously (SB) at a FiO₂ of 0.21 (reference method).

Methods: Prospective, observational, agreement study.

We measured REE of healthy volunteers in three different settings: a) SB-FiO₂ 0.21, b) NIV-FiO₂0.21 and c) NIV-FiO₂ 0.30.

Results: We analyzed 56 volunteers: 29 women (52%), mean age 31 years old, mean body mass index of 24.2kg/m².

We found an adequate agreement among REE measurement with NIV-FiO₂ 0.21, NIV FiO₂ 0.3 and SB-FiO₂ 0.21.

The average difference between NIV-FiO₂ 0.21 and NIV FiO₂ 0.3 was 60kcal (IC 95% 15.9 to 104); between NIV-FiO₂ 0.21 and SB-FiO₂ 0.21, 117kcal (IC 95% 79to 155); and between NIV FiO₂ 0.3 and SB-FiO₂ 0.21, 57kcal (0.8 to 113).

Measurement errors were similar among different ranges of REE. We found a slight tendency towards over-estimation of REE without clinical significance.

Conclusions: REE measurement with IC using NIV at different Fi0₂ concentrations proved an adequate agreement with REE measurements in SB subjects.

These new method will allow the use of IC to measure REE in patients with supplementary oxygen and/or NIV needs.