Factors affecting respiratory system compliance in anaesthetised mechanically ventilated healthy dogs: a retrospective study

Abstract

Objectives: To determine the influence of several factors on respiratory system compliance in volume-controlled mechanically ventilated healthy anaesthetised dogs. Materials and Methods: Review of 100 dogs anaesthetised for elective surgeries between 2015 and 2016. Dogs were mechanically ventilated with a respiratory rate adjusted to maintain normocapnia and a fraction of inspired oxygen of 50%. Body weight, body condition score, age, thoracic shape, time in spontaneous ventilation before volume-controlled ventilation, time with a fraction of inspired oxygen of 100% until starting mechanical ventilation, type of surgery and patient position were recorded. Respiratory system compliance, expressed per kg of bodyweight, was recorded every 15 minutes following initiation of volume-controlled ventilation. Results: Baseline respiratory system compliance was 1.3 ± 0.3 mL/cmH2O/kg and was reduced by high body condition score and barrel-shaped thorax but not by age, type of surgery or patient position, time in spontaneous ventilation nor time with a fraction of inspired oxygen of 100%. Clinical Significance: Respiratory system compliance is lower in overweight and barrel-chested dogs and should be taken into account during monitoring of lung function and ventilation management under general anaesthesia.