Comparison of Effects of an Endotracheal Tube or Facemask on Breathing Pattern and Distribution of Ventilation in Anesthetized Horses.
Authors: Moreno-Martinez Fernando, Byrne David, Raisis Anthea, Waldmann Andreas D, Hosgood Giselle, Mosing Martina
Journal: Frontiers in veterinary science
Summary
# Editorial Summary The presence of an endotracheal tube during equine general anaesthesia appears to fundamentally alter how horses breathe and distribute air to their lungs compared with facemask ventilation. Researchers compared these two airway management approaches in six healthy horses undergoing total intravenous anaesthesia with spontaneous breathing, using sophisticated monitoring including electrical impedance tomography to map ventilation distribution, spirometry, and oesophageal pressure measurements across two separate anaesthetic episodes. Horses breathing through an endotracheal tube exhibited significantly more atypical breathing patterns (including sighing and crown-like breaths), shifted ventilation preferentially towards the non-dependent (upper) lung, demonstrated reduced inspiratory-to-expiratory ratios and respiratory effort, but paradoxically showed larger physiologic dead space. These findings suggest that the mechanical resistance and sensory irritation of an endotracheal tube triggers compensatory breathing changes that may compromise ventilation efficiency and gas exchange uniformity in spontaneously breathing anaesthetised horses. For practitioners managing anaesthetised horses, these results warrant consideration when selecting between airway devices—facemask ventilation may better preserve normal breathing mechanics in cases where spontaneous respiration is preferred, though the clinical significance of these shifts in healthy horses requires further investigation.
Read the full abstract on PubMed
Practical Takeaways
- •Consider facemask ventilation for short procedures requiring spontaneous breathing in horses, as ETT alters normal breathing mechanics and causes ventilation maldistribution toward non-dependent lung
- •Be aware that endotracheal intubation increases physiologic dead space and requires higher breathing effort (larger pressure swings) to maintain adequate ventilation in anesthetized horses
- •ETT-induced changes in breathing pattern and ventilation distribution may affect oxygenation and recovery from anesthesia—weigh benefits against respiratory physiology impacts for your case
Key Findings
- •Endotracheal tube placement increases alternate breathing patterns (sighs and crown-like breaths) compared to facemask in anesthetized horses (p = 0.012)
- •ETT causes rightward shift in ventilation distribution toward non-dependent lung with reduced center of ventilation right-to-left ratio (p = 0.025)
- •ETT reduces inspiratory:expiratory ratio (p = 0.017) and esophageal pressure difference (p < 0.001) while increasing physiologic dead space (p = 0.034)
- •Facemask allows more normal breathing pattern and more homogeneous ventilation distribution compared to endotracheal intubation