Air-test for assessing gas exchange and the potential benefit of alveolar recruitment manoeuvre in anaesthetized dogs

Abstract

This retrospective cohort study investigated the use of the Air-Test in ventilated, anaesthetized dogs to evaluate oxygen uptake and its utility in guiding alveolar recruitment manoeuvres (ARM). Records of 25 client-owned dogs were analysed; inclusion required controlled ventilation, SpO₂ ≥ 99% at FiO₂ 0.5, and a completed Air-Test, which involved reducing FiO₂ to 0.21 for 4 minutes. A positive Air-Test was defined as SpO₂ < 96%, followed by an ARM with positive end-expiratory pressure adjustments. Haemodynamic variables, gas exchange, static compliance (Cst), and PaO₂/FiO₂ were evaluated. Ten dogs (40%) had positive Air-Tests, with significantly lower baseline PaO₂/FiO₂ ratios (364 ± 39.6 mmHg) compared to negative cases (510 ± 65 mmHg; p < 0.001). In Air-Test-positive dogs, ARM significantly increased Cst and PaO₂/FiO₂, while no other variables changed. Findings suggest the Air-Test is a useful, noninvasive tool to identify impaired oxygenation and monitor improvements after ARM in anaesthetized, mechanically ventilated dogs.