Selective mechanical ventilation of dependent lung regions in the anaesthetized horse in dorsal recumbency.

This research explores the impact of selectively ventilating dependent lung regions in anaesthetized horses lying on their backs. The results suggest that this technique markedly enhances oxygen saturation in the blood, making the procedure a viable option for improving arterial oxygenation in such situations.

Introduction

• Researchers investigated the effect of selective mechanical ventilation, specifically targeting dependent lung regions, in anaesthetized horses positioned on their backs, or in dorsal recumbency.
• The study seeks to determine whether selectively ventilating dependent regions of the lungs can significantly improve oxygen delivery to the body during anesthesia.
• This research is important for equine anesthesia techniques, especially in surgical procedures where horses need to be positioned supine.

Methodology

• Large horses with an average weight of 486 kg were anaesthetized and monitored in the lateral and dorsal recumbency positions during different breathing conditions.
• These conditions included spontaneous breathing, general mechanical ventilation, and a combination of spontaneous breathing and selective mechanical ventilation.
• Blood-gas readings, with particular attention to arterial oxygen tension (PaO2), were obtained and analyzed during each phase of the experiment.

Results

• When the horses were in lateral position and spontaneously breathing with a high fraction of inspired oxygen (over 92%), the average arterial oxygen tension (PaO2) stood at 32.3 kPa.
• However, when the horses were repositioned on their backs, or in dorsal recumbency, the PaO2 dropped to 10.9 kPa during spontaneous breathing and 12.6 kPa under general mechanical ventilation.
• Remarkably, when selective mechanical ventilation with an added positive end-expiratory pressure (PEEP) of 20 cm H2O was applied, the PaO2 significantly elevated to an average of 35.3 kPa, indicating improved oxygen saturation in the arterial blood of the anesthetized horses.

Conclusion

• The study’s outcomes suggest that selective intubation of dependent regions in the diaphragmatic lobes can be a viable procedure.
• It’s crucial to note that this technique significantly improves arterial oxygenation for horses under anesthesia laying on their backs.
• This finding could have vital implications in improving oxygenation methods during equine surgical procedures and possibly reducing post-anesthesia complications related to hypoxia.