Effects of lateral recumbency on regional lung function in anesthetized horses.

This study investigates the effects of different body positions on lung function in anesthetized horses, using a radioactive gas to measure ventilation and perfusion. It found consistent variations in these measurements based on body position, without observed effects of time.

Study Design and Procedure

• The experiment involved six horses that were put under anesthesia.
• Each horse was positioned on one side (lateral recumbency) for one hour, and then turned to the opposite side for an additional hour.
• Ventilation and perfusion of the horses’ lungs were evaluated by using an 81mKr radioactive gas. This gas is short-lived and allowed researchers to accurately track the relative spatial distribution of ventilation (V) and perfusion (Q).

Results

• A consistent V/Q gradient was discovered at all times during the experiment. The top, or non-dependent part of the lung field, had the highest V/Q values, while the bottom, dependent portion had the lowest.
• This V/Q gradient was present within each lung and also between the two lungs of each horse.
• Interestingly, no effects of time on the V/Q distribution were noted.
• Differences in gradients were also observed between horses starting in different positions – those that started in right lateral recumbency had larger V/Q gradients compared to horses that began on the left.
• Following the rotation from one side to another, the V/Q gradient decreased in both groups, but it remained larger in the right lung than in the left.

Conclusion

• The research indicates a correlation between body position (specifically lateral recumbency, or lying on the side) and lung function in horses, as determined by ventilation and perfusion measurements.
• This has implications for animal care practices, particularly when anesthetizing horses for procedures or surgeries that require them to be in lateral recumbency for extended periods.
• The study also provides a foundation for further research in this area, with potential relevance for human medical practices as well (e.g., patient positioning in critical care).