Horses Auto-Recruit Their Lungs by Inspiratory Breath Holding Following Recovery from General Anaesthesia.
Authors: Mosing Martina, Waldmann Andreas D, MacFarlane Paul, Iff Samuel, Auer Ulrike, Bohm Stephan H, Bettschart-Wolfensberger Regula, Bardell David
Journal: PloS one
Summary
# Editorial Summary Prolonged dorsal recumbency during general anaesthesia causes gravitational atelectasis (lung collapse) in dependent regions, yet the mechanisms by which horses recover normal ventilation remain poorly characterised. Using electrical impedance tomography (EIT)—a non-invasive imaging technique that maps regional ventilation distribution—researchers monitored six horses at baseline and at hourly intervals up to 6 hours post-recovery, analysing spontaneous breathing patterns and regional lung filling dynamics across seven dorso-ventral zones. All horses exhibited inspiratory breath holding (a pause during inhalation lasting up to 50% of breath duration) persisting for approximately 5 hours post-standing, during which ventilation progressively redistributed from ventral (dependent) to dorsal regions; filling times accelerated ventrally whilst dorsal regions inflated more slowly, indicating active recruitment of collapsed lung tissue without requiring external intervention. The degree of breath holding correlated significantly with arterial CO₂ levels (PaCO₂), suggesting this is a physiologically regulated response rather than an incidental finding. For practitioners managing post-anaesthetic recovery, these findings validate the protective value of allowing horses natural movement and spontaneous breathing in the hours following general anaesthesia, as this auto-recruitment mechanism appears to be the primary means of re-expanding atelectatic lung tissue and restoring normal gas exchange—advocating against forced exercise or aggressive handling during the critical early recovery window.
Read the full abstract on PubMed
Practical Takeaways
- •Post-anaesthetic horses naturally perform inspiratory breath holding for several hours after standing, which represents a physiologic auto-recruitment mechanism to re-expand collapsed lung tissue—monitor respiratory patterns closely during recovery but recognise this as beneficial
- •Extended recovery periods (5+ hours) should be expected before normal ventilation distribution returns; plan post-op management with adequate time for pulmonary self-correction
- •The correlation between breath holding and CO2 levels suggests monitoring arterial blood gases may help assess adequacy of post-anaesthetic lung recruitment in cases with prolonged or absent breath holding
Key Findings
- •All 6 horses demonstrated inspiratory breath holding persisting up to 5 hours post-anaesthesia recovery
- •Breath holding was significantly correlated with PaCO2 levels (p<0.05)
- •Gas redistributed from ventral to dorsal lung regions during breath holding, indicating auto-recruitment of previously atelectatic tissue
- •Ventral lung regions showed faster filling and shorter inflation periods post-recovery compared to baseline, while dorsal regions showed slower filling and longer inflation periods