Respiratory resistance and compliance in the anaesthetized horse.

The research is about the measurement of total compliance and lower respiratory resistance during passive expiration in anaesthetized horses lying on their sides. It was found that the drop in pressure across the lower respiratory resistance could be satisfactorily related to the expiratory flow by a specific equation, except in the case of an emphysematous horse.

Objective and Methodology

• The main focus of the study was to measure the total compliance and lower respiratory resistance in anaesthetized horses during passive expiration. This was accomplished by examining the animals in a fully relaxed state, lying on their sides post-anesthesia.
• The subjects of the study included nine horses and one mule. The researchers ensured that the animals were completely intubated prior to the start of the study.

Findings and Analysis

• The research observed the volumes expired after the endotracheal inflation of the lungs, which were used to determine compliance for each animal. For the horses, the mean compliance was found to be 0.246 litre/cm H2O or 0.573 (ml/cm H2O)/kg body mass.
• Resistance was calculated during passive expiration through an endotracheal tube. The results underlined that the reduction of expiratory flow deviated significantly from an exponential, with the reasons discussed within the study.
• Apart from one horse, which had been confirmed to be suffering from emphysema, the pressure drop across the lower respiratory resistance was directly related to the expiratory flow. The researchers derived an equation (P = k1V̇ + k2V̇2) with the mean values of k1 and k2 stated in the study to express this relationship.