Apneustic anesthesia ventilation improves pulmonary function in anesthetized bottlenose dolphins (Tursiops truncatus) - PubMed (original) (raw)

Apneustic anesthesia ventilation improves pulmonary function in anesthetized bottlenose dolphins (Tursiops truncatus)

Carolina R Le-Bert et al. Front Vet Sci. 2024.

Abstract

Introduction: Use of mechanical ventilation during general anesthesia is a necessary practice in the anesthetization of small cetaceans as spontaneous ventilation fails to provide adequate gas exchange. Currently available methods of ventilation do not account for the intermittent breathing strategy of representative species within this infraorder of fully aquatic mammals and may have a significant effect on cardiac and respiratory physiology.

Methods: To understand the impact of mechanical ventilation on cardiopulmonary function in one small species of cetacean, the bottlenose dolphin (Tursiops truncatus), we compared controlled mechanical ventilation (CMV) to a novel ventilation method known as apneustic anesthesia ventilation (AAV). AAV simulates the normal inspiratory breath-hold pattern of dolphins. Ten anesthetic procedures (dental procedure, n = 9; bronchoscopy, n = 2) were performed on nine dolphins (age range: 10-42 years; mean = 32 years; median = 37 years; female = 3, 40%; male = 6, 60%). In a cross-over study design, dolphins were instrumented and randomly assigned to AAV or CMV as the initial mode of ventilation, then switched to the alternate mode. Baseline cardiopulmonary data were collected and again after 30 min on each mode of ventilation. Cardiac index, stroke volume index, systemic vascular resistance, alveolar dead space, alveolar-arterial oxygen tension gradient, arterial oxygen content, oxygen delivery index, and dynamic respiratory system compliance index were calculated at each of the four time points.

Results: During AAV, dolphins had higher arterial oxygen tension, higher mean airway pressure, reduced alveolar dead space ventilation and lower alveolar-arterial oxygen difference. Cardiovascular performance was not statistically different between the two modes.

Discussion: Our study suggests AAV, which more closely resembles the conscious intermittent respiratory pattern phenotype of dolphins, improves ventilation and pulmonary function in the anesthetized dolphin. Future studies should evaluate the cardiopulmonary effects of neutral buoyancy and cardiopulmonary sparing drug protocols to reduce the need for hemodynamic support of current protocols.

Keywords: anesthesia; apneustic anesthesia ventilation; bottlenose dolphin; mechanical ventilation; physical status classification; pulmonary physiology.

Copyright © 2024 Le-Bert, Bukoski, Downs, Hodgson, Thombs, Ridgway and Bailey.

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Conflict of interest statement

JB is the owner of Innovative Veterinary Medicine, Inc. (IVM). IVM manufactured the DolVent System through funding provided by the Office of Naval Research, contract number N68335-16-C-0020. JD was an employee of IVM during research execution and is the inventor of both airway pressure release ventilation (APRV; U.S. patent 4773411) and apneustic anesthesia ventilation (AAV; U.S. patent 6123072). The remaining 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.

Figures

Figure 1

Figure 1

Schematic illustration of the pressure, flow, and volume vs. time waveforms for controlled mechanical ventilation (CMV) and apneustic anesthesia ventilation (AAV). Gray background indicates periods of tidal ventilation corresponding to inspiratory time during CMV and the time (TLOW) at PLOW during AAV. White background indicates expiratory time during CMV and the time (THIGH) of PHIGH during AAV. For AAV waveforms, the first release, illustrates proper limitation of release time whereas the second release illustrates a long release time with flow stagnation (arrow). Reproduced with permission from Innovative Veterinary Medicine, Inc.

Figure 2

Figure 2

Cross-over study design to compare two ventilation modes in bottlenose dolphins. Order of ventilation mode was randomly determined. Times in each phase are approximate. Figure created using

Biorender.com

.

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