Effect of pressure support ventilation during weaning on ventilation and oxygenation indices in healthy horses recovering from general anesthesia
Article first published online: 20 APR 2013
© 2013 The Authors. Veterinary Anaesthesia and Analgesia © 2013 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia
Veterinary Anaesthesia and Analgesia
Volume 40, Issue 4, pages 339–350, July 2013
How to Cite
Ida, K. K., Fantoni, D. T., Souto, M. T., Otsuki, D. A., Zoppa, A. L., Silva, L. C. and Ambrósio, A. M. (2013), Effect of pressure support ventilation during weaning on ventilation and oxygenation indices in healthy horses recovering from general anesthesia. Veterinary Anaesthesia and Analgesia, 40: 339–350. doi: 10.1111/vaa.12041
- Issue published online: 13 JUN 2013
- Article first published online: 20 APR 2013
- Manuscript Accepted: 28 JUN 2012
- Manuscript Received: 2 MAY 2011
- mechanical ventilation;
- pressure support ventilation;
- recovery from anesthesia;
- weaning outcome
To determine if pressure support ventilation (PSV) weaning from general anesthesia affects ventilation or oxygenation in horses.
Prospective randomized clinical study.
Twenty client-owned healthy horses aged 5 ± 2 years, weighing 456 ± 90 kg.
In the control group (CG; n = 10) weaning was performed by a gradual decrease in respiratory rate (fR) and in the PSV group (PSVG; n = 10) by a gradual decrease in fR with PSV. The effect of weaning was considered suboptimal if PaCO2 > 50 mmHg, arterial pH < 7.35 plus PaCO2 > 50 mmHg or PaO2 < 60 mmHg were observed at any time after disconnection from the ventilator until 30 minutes after the horse stood. Threshold values for each index were established and the predictive power of these values was tested.
Pressure support ventilation group (PSVG) had (mean ± SD) pH 7.36 ± 0.02 and PaCO2 41 ± 3 mmHg at weaning and the average lowest PaO2 69 ± 6 mmHg was observed 15 minutes post weaning. The CG had pH 7.32 ± 0.02 and PaCO2 57 ± 6 mmHg at weaning and the average lowest PaO2 48 ± 5 mmHg at 15 minutes post weaning. No accuracy in predicting weaning effect was observed for fR (p = 0.3474), minute volume (p = 0.1153), SaO2 (p = 0.1737) and PaO2/PAO2 (p = 0.1529). A high accuracy in predicting an optimal effect of weaning was observed for VT > 10 L (p = 0.0001), fR/VT ratio ≤ 0.60 breaths minute−1 L−1 (p = 0.0001), VT/bodyweight > 18.5 mL kg−1 (p = 0.0001) and PaO2/FiO2 > 298 (p = 0.0002) at weaning. A high accuracy in predicting a suboptimal effect of weaning was observed for VT < 10 L (p = 0.0001), fR/VT ratio ≥ 0.60 breaths minute−1 L−1 (p = 0.0001) and Pe′CO2 ≥ 38 mmHg (p = 0.0001) at weaning.
Conclusions and clinical relevance
Pressure support ventilation (PSV) weaning had a better respiratory outcome. A higher VT, VT/body weight, PaO2/FiO2 ratio and a lower fR/VT ratio and Pe′CO2 were accurate in predicting the effect of weaning in healthy horses recovering from general anesthesia.