Effect of end-inspiratory pause on airway and physiological dead space in anesthetized horses |
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| Institution: | 1. Department of Comparative, Diagnostic, and Population Medicine, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA;2. Department of Veterinary Sciences, University of Pisa, Pisa, Italy;3. Department of Clinical Sciences, College of Veterinary Medicine, Ithaca, NY, USA;4. Department of Anesthesiology and Pain Management, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Buenos Aires, Argentina;5. Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA;6. Department of Anaesthesiology and Perioperative Intensive Care Medicine, University of Veterinary Medicine Vienna, Vienna, Austria;1. Royal (Dick) School of Veterinary Studies, Easter Bush Campus, Roslin, UK;2. Queen’s Veterinary School Hospital, Cambridge, UK;1. Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Veterinarias, MEVET, Tandil, BA, Argentina;2. CIVETAN, UNCPBA-CONICET, Tandil, BA, Argentina;3. Facultad de Ciencias Agropecuarias, IRNASUS CONICET – Universidad Católica de Córdoba, CB, Argentina;4. Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada;5. Universidad Nacional del Centro de la Provincia de Buenos Aires, Facultad de Ciencias Veterinarias, FISFARVET, Tandil, BA, Argentina;1. Dick White Referrals, Station Farm, Six Mile Bottom, Cambridgeshire, UK;2. Hospital Veterinari Glòries, Barcelona, Spain;3. Department of Comparative, Diagnostic and Population Medicine, College of Veterinary Medicine, University of Florida, FL, USA |
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| Abstract: | ObjectiveTo 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 designProspective research study.AnimalsA group of eight healthy research horses undergoing laparotomy.MethodsAnesthetized 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.ResultsThe 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 relevanceThe 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. |
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| Keywords: | airway dead space Bohr equation end-inspiratory pause physiological dead space volumetric capnography |
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