Abstract
Objective
To evaluate the impact of a 30% end-inspiratory pause (EIP) on alveolar tidal volume
(VTalv), airway (VDaw) and physiological (VDphys) dead spaces in mechanically ventilated horses using volumetric capnography, and
to evaluate the effect of EIP on carbon dioxide (CO2) elimination per breath (Vco2br–1), PaCO2, and the ratio of PaO2-to-fractional inspired oxygen (PaO2:FiO2).
Study design
Prospective research study.
Animals
A group of eight healthy research horses undergoing laparotomy.
Methods
Anesthetized horses were mechanically ventilated as follows: 6 breaths minute–1, tidal volume (VT) 13 mL kg–1, inspiratory-to-expiratory time ratio 1:2, positive end-expiratory pressure 5 cmH2O and EIP 0%. Vco2br–1 and expired tidal volume (VTE) of 10 consecutive breaths were recorded 30 minutes after induction, after adding
30% EIP and upon EIP removal to construct volumetric capnograms. A stabilization period
of 15 minutes was allowed between phases. Data were analyzed using a mixed-effect
linear model. Significance was set at p < 0.05.
Results
The EIP decreased VDaw from 6.6 (6.1–6.7) to 5.5 (5.3–6.1) mL kg–1 (p < 0.001) and increased VTalv from 7.7 ± 0.7 to 8.6 ± 0.6 mL kg–1 (p = 0.002) without changing the VTE. The VDphys to VTE ratio decreased from 51.0% to 45.5% (p < 0.001) with EIP. The EIP also increased PaO2:FiO2 from 393.3 ± 160.7 to 450.5 ± 182.5 mmHg (52.5 ± 21.4 to 60.0 ± 24.3 kPa; p < 0.001) and Vco2br–1 from 0.49 (0.45–0.50) to 0.59 (0.45–0.61) mL kg–1 (p = 0.008) without reducing PaCO2.
Conclusions and clinical relevance
The EIP improved oxygenation and reduced VDaw and VDphys, without reductions in PaCO2. Future studies should evaluate the impact of different EIP in healthy and pathological
equine populations under anesthesia.
Keywords
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Article info
Publication history
Published online: March 21, 2023
Accepted:
March 16,
2023
Received in revised form:
March 15,
2023
Received:
November 23,
2022
Publication stage
In Press Journal Pre-ProofIdentification
Copyright
© 2023 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.
