Flow-controlled expiration improves respiratory mechanics, ventilation, and gas exchange in anesthetized horses.

This research article explores the effects of flow-controlled expiration (FLEX) on lung compliance and gas exchange in anesthetized horses, compared to traditional volume-controlled ventilation. The study found that FLEX led to significantly higher oxygen levels and better dynamic lung compliance, improving the horse’s overall respiratory system without compromising its cardiovascular function.

Objective of the Study

The researchers aim to investigate the impact of FLEX—a method of ventilation where the rate of lung emptying is actively managed for linear gas flow—on the respiratory and cardiovascular systems of anesthetized horses in dorsal recumbency (lying on their back). The primary focus of the study was to measure any changes to lung compliance (the ease with which lungs can expand) and gas exchange (how effectively oxygen and carbon dioxide are exchanged) in these horses.

Methodology

• The study involved eight healthy horses, each anesthetized twice to allow for direct comparison of traditional volume-controlled ventilation and FLEX ventilation.
• The order of the ventilation methods was randomized to avoid bias, and each method was applied for 1.5 hours during a total anesthesia time of 3 hours.
• The researchers measured several parameters during anesthesia, including heart rate, mean arterial blood pressures, central venous pressure, and pulmonary arterial pressure.
• They also recorded peak, plateau, and mean airway pressures and dynamic lung compliance (Cdyn).
• Arterial blood gases were analyzed every 15 minutes for a comprehensive overview of gas exchange in the horses’ respiratory systems.
• The results were then statistically analyzed using ANOVA (Analysis of Variance).

Key Findings

• Results showed that FLEX ventilation led to notably higher arterial oxygen partial pressures (measures of oxygen in the blood) and increased Cdyn.
• While the peak and plateau airway pressure were lower, the mean airway pressure was remarkably higher among FLEX ventilated horses.
• Importantly, there were no detected differences in cardiovascular parameters, indicating that FLEX had no negative impact on heart function.

Conclusions

In conclusion, the use of FLEX ventilation in anesthetized horses resulted in significant improvement to both oxygen levels and dynamic lung compliance, without compromising their cardiovascular system. The findings suggest that FLEX could be a more effective ventilation method than traditional volume-controlled ventilation during anesthesia for horses.