A novel flow partition device for spirometry during large animal anaesthesia

Abstract

Objective: We describe and test a novel device for large animal anaesthesia monitoring that uses standard human medicine spirometry sensors.

Study design: In-vitro study.

Methods: The device consists of two adapters that enable the flow to be split evenly into four tubes in parallel, each tube containing a D-lite sensor. The performance of this flow partitioning device (FPD) over a range of flows from 100 to 700 L minute⁻¹ was determined and the pressure versus flow relation, resistance and dead space was compared with a Horse-lite (Moens 2010).

Results: Equipped with four D-lite sensors, and a flow of 700 L minute⁻¹ the pressure drop of the FPD was 13.5 cm H₂O, resistance 1.17 cm H₂O second L⁻¹ and volume (potential dead space) 182 mL, compared to 2.8 cm H₂O, 0.24 cm H₂O second L⁻¹ and 54 mL respectively for the Horse-lite. The predicted value of the flow partition of ¼ could be confirmed. Limits of agreement were found to be 4.2% in inspiratory direction and 7.1% in expiratory direction.

Conclusions and clinical relevance: The FPD is an affordable device that extends the specification of any commercially available human spirometry sensors to large animal applications. However, an increase in total resistance and dead space has to be taken into account. Therefore, the new device could be useful during equine anaesthesia.

Keywords: large animal anaesthesia; monitoring; spirometry.