Effects of positive end-expiratory pressure alone or an open-lung approach on recruited lung volumes and respiratory mechanics of mechanically ventilated horses.

This study investigates the impact of positive end-expiratory pressure (PEEP) both alone and preluded by a lung recruitment manoeuvre (LRM) on lung volumes and mechanics of horses under general anaesthesia. The results demonstrate that pairing PEEP with LRM effectively increases lung volumes, enhances lung compliance, and reduces driving pressure in anaesthetized horses.

Study Methodology

• The study was a controlled, clinical study that was prospectively conducted on 15 horses undergoing arthroscopy.
• Post anaesthetic induction, the initial ventilatory settings were set with specific parameters. These included a tidal volume of 15 mL kg, an inspiratory:expiratory ratio of 1:2, and a respiratory rate designed to maintain end-tidal CO levels between 5.3-6.6 kPa (40-50 mmHg).
• The researchers applied different ventilatory strategies sequentially: zero PEEP (ZEEP), PEEP of 10 cmHO (PEEP), and LRM (50 cmHO for 20 seconds) followed by 10 cmHO of PEEP (LRM + PEEP).
• Various assessments for static compliance (C), driving pressure, delta end-expiratory volumes (ΔEELV), and recruited lung volumes (RLV) were executed 30 minutes after each ventilatory strategy’s initiation.
• Data extracted was analyzed using paired t test or analysis of variance, followed by further analysis with Tukey’s post hoc test. Any p-value less than 0.05 was considered significant.

Study Results

• Application of PEEP resulted in a ΔEELV of 6.68 ± 3.36 mL kg. However, this volume was significantly increased to 14.28 ± 5.59 mL kg (p < 0.0001) in the case of LRM + PEEP.
• RLV was found to be greater during the LRM + PEEP phase (12.30 ± 5.85 mL kg) than during PEEP (4.47 ± 3.97 mL kg; p < 0.0001).
• The C was unaffected from ZEEP to PEEP but increased when applying LRM + PEEP.
• Driving pressure was recorded to be lesser during the LRM + PEEP phase than during PEEP and ZEEP.

Study Conclusion

• The study concluded that PEEP, when executed alone, did not enhance RLV or C or reduce driving pressure in horses under anaesthesia.
• However, PEEP administered following LRM significantly increased RLV and C while reducing driving pressure in anaesthetized horses.