Controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in laterally or dorsally recumbent horses.

The research investigated the effects of controlled mechanical ventilation with constant positive end-expiratory pressure and alveolar recruitment manoeuvres during anaesthesia in horses lying on their sides or back. The study found this method improves oxygenation during anaesthesia and early recovery in dorsally recumbent horses but not laterally recumbent horses.

Methods

• The study involved 48 Warmblood horses undergoing elective surgery, half lying on their sides (lateral recumbency) and half lying on their backs (dorsal recumbency).
• Within each recumbency group, half were ventilated using controlled mechanical ventilation (CMV) alone, while the other half were ventilated with a combination of CMV, constant positive end-expiratory pressure (PEEP) and intermittent recruitment manoeuvres (RMs) to maintain adequate oxygen levels.
• All the horses underwent the same premedication, induction, and maintenance of anaesthesia procedure.
• RMs were controlled to keep partial pressure of arterial oxygen (PaO) at > 400 mmHg (> 53.3 kPa), and Dobutamine was administered to maintain mean arterial blood pressure at > 60 mmHg.
• Physiological parameters were recorded every 10 minutes, and arterial blood gases were measured intra- and postoperatively. Statistical analyses were conducted using analyses of variance (anova), t tests and the Mann-Whitney U-test.

Results

• Horses in dorsal recumbency that had been ventilated with CMV, constant PEEP and interposed RM displayed better oxygenation during anaesthesia and into the early recovery period than horses ventilated with CMV alone.
• No significant differences were seen in the laterally recumbent horses, whether they were ventilated with or without PEEP/RM.
• No significant differences were noted in other measured parameters across the groups.

Conclusions

• The study concluded that using controlled mechanical ventilation with constant PEEP and interposed RM techniques improves arterial oxygenation during anaesthesia and early recovery in horses lying on their backs.
• However, these techniques offered no observable benefits in horses lying on their sides.
• This mode of ventilation could be a clinically applicable method for enhancing oxygenation in anaesthetised horses, particularly those in dorsal recumbency.