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Vet Anaesth Analg. 2009 May;36(3):209-19. doi: 10.1111/j.1467-2995.2009.00449.x.

In vitro validation of a Pitot-based flow meter for the measurement of respiratory volume and flow in large animal anaesthesia.

Author information

1
Clinic of Anaesthesiology and Perioperative Intensive Care, University of Veterinary Medicine, Vienna, Austria. yves.moens@vu-wien.ac.at

Abstract

OBJECTIVE:

To remodel and validate commercially available monitors and their Pitot tube-based flow sensors for use in large animals, using in vitro techniques.

STUDY DESIGN:

Prospective, in vitro experiment.

METHODS:

Both the original and the remodelled sensor were studied with a reference flow generator. Measurements were taken of the static flow-pressure relationship and linearity of the flow signal. Sensor airway resistance was calculated. Following recalibration of the host monitor, volumes ranging from 1 to 7 L were generated by a calibration syringe, and bias and precision of spirometric volume was determined. Where manual recalibration was not available, a conversion factor for volume measurement was determined. The influence of gas composition mixture and peak flow on the conversion factor was studied.

RESULTS:

Both the original and the remodelled sensor showed similar static flow-pressure relationships and linearity of the flow signal. Mean bias (%) of displayed values compared with the reference volume of 3, 5 and 7 L varied between -0.4% and +2.4%, and this was significantly smaller than that for 1 L (4.8% to +5.0%). Conversion factors for 3, 5 and 7 L were very similar (mean 6.00 +/- 0.2, range 5.91-6.06) and were not significantly influenced by the gas mixture used. Increasing peak flow caused a small decrease in the conversion factor. Volume measurement error and conversion factors for inspiration and expiration were close to identity.

CONCLUSION:

The combination of the host monitor with the remodelled flow sensor allowed accurate in vitro measurement of flows and volumes in a range expected during large animal anaesthesia.

CLINICAL RELEVANCE:

This combination has potential as a reliable spirometric monitor for use during large animal anaesthesia.

[Indexed for MEDLINE]

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