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Frontiers in veterinary science2023; 10; 1135452; doi: 10.3389/fvets.2023.1135452

Flow-controlled expiration reduces positive end-expiratory pressure requirement in dorsally recumbent, anesthetized horses.

Abstract: Equine peri-anesthetic mortality is higher than that for other commonly anesthetized veterinary species. Unique equine pulmonary pathophysiologic aspects are believed to contribute to this mortality due to impairment of gas exchange and subsequent hypoxemia. No consistently reliable solution for the treatment of peri-anesthetic gas exchange impairment is available. Flow-controlled expiration (FLEX) is a ventilatory mode that linearizes gas flow throughout the expiratory phase, reducing the rate of lung emptying and alveolar collapse. FLEX has been shown to improve gas exchange and pulmonary mechanics in anesthetized horses. This study further evaluated FLEX ventilation in anesthetized horses positioned in dorsal recumbency, hypothesizing that after alveolar recruitment, horses ventilated using FLEX would require a lower positive end-expiratory pressure (PEEP) to prevent alveolar closure than horses conventionally ventilated. Unassigned: Twelve adult horses were used in this prospective, randomized study. Horses were assigned either to conventional volume-controlled ventilation (VCV) or to FLEX. Following induction of general anesthesia, horses were placed in dorsal recumbency mechanically ventilated for a total of approximately 6.5 hours. Thirty-minutes after starting ventilation with VCV or FLEX, a PEEP-titration alveolar recruitment maneuver was performed at the end of which the PEEP was reduced in decrements of 3 cmH2O until the alveolar closure pressure was determined. The PEEP was then increased to the previous level and maintained for additional three hours. During this time, the mean arterial blood pressure, pulmonary arterial pressure, central venous blood pressure, cardiac output (CO), dynamic respiratory system compliance and arterial blood gas values were measured. Unassigned: The alveolar closure pressure was significantly lower (6.5 ± 1.2 vs 11.0 ± 1.5 cmH2O) and significantly less PEEP was required to prevent alveolar closure (9.5 ± 1.2 vs 14.0 ± 1.5 cmH2O) for horses ventilated using FLEX compared with VCV. The CO was significantly higher in the horses ventilated with FLEX (37.5 ± 4 vs 30 ± 6 l/min). Unassigned: We concluded that FLEX ventilation was associated with a lower PEEP requirement due to a more homogenous distribution of ventilation in the lungs during expiration. This lower PEEP requirement led to more stable and improved cardiovascular conditions in horses ventilated with FLEX.
Copyright © 2023 Brandly, Midon, Douglas and Hopster.
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Publication Date: 2023-04-14 PubMed ID: 37124564PubMed Central: PMC10140341DOI: 10.3389/fvets.2023.1135452Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research investigated the effects of a ventilation method, called Flow-controlled Expiration (FLEX), on anesthetized horses placed in a dorsal position. It found that FLEX improved gas exchange and pulmonary mechanics, thus requiring less positive-end expiratory pressure (PEEP) to prevent alveolar closure and proved more favourable for the horses’ cardiovascular conditions when compared to traditional volume-controlled ventilation (VCV).

Methodology

  • The researchers conducted a prospective, randomized study that involved twelve adult horses.
  • Each horse was assigned randomly to either conventional volume-controlled ventilation (VCV) or FLEX.
  • Upon administering general anesthesia, the horses were positioned dorsally and mechanically ventilated for a total duration of approximately 6.5 hours.
  • Thirty minutes into the ventilation with either VCV or FLEX, a PEEP-titration alveolar recruitment maneuver was performed. After this maneuver, the PEEP was reduced in decrements of 3 cmHO until the alveolar closure pressure was determined.
  • The PEEP was then raised back to the previous level and maintained for an additional three hours. During this period, various measurements were taken, including mean arterial blood pressure, pulmonary arterial pressure, central venous blood pressure, cardiac output (CO), dynamic respiratory system compliance and arterial blood gas values.

Findings

  • The study found that the alveolar closure pressure was notably lower for horses ventilated using FLEX when compared to horses ventilated with VCV.
  • Additionally, less PEEP was required to prevent alveolar closure in horses ventilated using FLEX as compared to VCV.
  • The cardiac output (the quantity of blood being pumped by the heart per minute) was also significantly higher in the horses ventilated using the FLEX modality. This indicates a more robust cardiovascular condition in the horses ventilated with FLEX.

Conclusion

  • Based on the results, the researchers concluded that FLEX ventilation provides a lower PEEP requirement due to a more homogenous distribution of ventilation in the lungs during expiration.
  • The lower PEEP requirement implies better lung function and gas exchange in anesthetized horses under FLEX ventilation.
  • The improvement in cardiac output also suggested that the FLEX method has added benefits of maintaining a better cardiovascular condition in the horses.

Cite This Article

APA
Brandly JE, Midon M, Douglas HF, Hopster K. (2023). Flow-controlled expiration reduces positive end-expiratory pressure requirement in dorsally recumbent, anesthetized horses. Front Vet Sci, 10, 1135452. https://doi.org/10.3389/fvets.2023.1135452

Publication

Frontiers in veterinary science
ISSN: 2297-1769
NlmUniqueID: 101666658
Country: Switzerland
Language: English
Volume: 10
Pages: 1135452

Researcher Affiliations

Brandly, Jerrianne E
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, United States.
Midon, Monica
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, United States.
Douglas, Hope F
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, United States.
Hopster, Klaus
  • Department of Clinical Studies, New Bolton Center, University of Pennsylvania School of Veterinary Medicine, Kennett Square, PA, United States.

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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