In vitro and in vivo evaluation of a new large animal spirometry device using mainstream CO2 flow sensors.
Authors: Ambrisko T D, Lammer V, Schramel J P, Moens Y P S
Journal: Equine veterinary journal
Summary
# Editorial Summary: Large Animal Spirometry with Mainstream CO₂ Sensors Accurate respiratory monitoring during equine anaesthesia has been hampered by the lack of suitable mainstream spirometry devices designed for horses, prompting Ambrisko and colleagues to develop and validate a novel flow partitioning device (FPD) equipped with four human CO₂ flow sensors. Their in vitro and in vivo evaluation involved measuring pressure differentials across the device at clinically realistic flow rates (90–720 l/min) and comparing tidal volume measurements against established reference methods in five anaesthetised horses using Bland-Altman analysis. The device demonstrated acceptable agreement with reference standards within ±10% for clinically relevant volumes, though the FPD exhibited greater airway resistance than the horse-lite sensor (0.3–1.5 cmH₂O s/l, increasing with flow rate), and occasionally produced erroneous readings below 4 litres tidal volume. For equine anaesthetists and those involved in perioperative respiratory assessment, this validated device offers a practical mainstream monitoring option for adult Warmblood horses that is sufficiently accurate for clinical decision-making, though users should apply the determined correction factor (3.97) and exercise caution when interpreting measurements from smaller-volume breaths.
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Practical Takeaways
- •This new spirometry device provides a clinically acceptable alternative for monitoring respiratory parameters in anaesthetised adult horses, filling a gap in large animal anaesthetic monitoring equipment
- •Users should be aware that accuracy is best in the clinically relevant tidal volume range (>4 litres); extra caution may be warranted when monitoring smaller horses or shallow breathing patterns
- •The device demonstrates reliable flow partitioning across sensors and acceptable agreement with reference methods, making it suitable for routine anaesthetic monitoring in equine practice
Key Findings
- •A new flow partitioning device with mainstream CO2 sensors showed device resistance of 0.3-1.5 cmH2O s/l, increasing with flow rates up to 720 l/min
- •In vitro volume measurements had limits of agreement within -1 and 2%, with a correction factor of 3.97±0.03
- •In vivo tidal volume measurements in 5 anaesthetised horses showed limits of agreement of -12 to 0%, with 138 of 147 measurements (94%) within ±10% acceptance limits
- •The device is suitable for measuring tidal volumes in adult Warmblood horses during anaesthesia, with particular reliability for volumes above 4 litres