Apneustic Anesthesia Ventilation Compared to Controlled Mechanical Ventilation in Anesthetized Bottlenose Dolphins (Tursiops truncatus) and California Sea Lions (Zalophus californianus)
Abstract
Use of mechanical ventilation during general anesthesia is common practice for humans and other mammals when spontaneous ventilation fails to provide adequate gas exchange. Many ventilation approaches for terrestrial species are well studied and understood; however, few studies exist on mechanical ventilation approaches for aquatic and semi-aquatic species.1,2 Commonly employed approaches do not account for the apneustic breathing pattern of some conscious aquatic mammals.3 To understand the impact of mechanical ventilation on cardiopulmonary function in anesthetized aquatic mammals, we applied a novel ventilation strategy, apneustic anesthesia ventilation (AAV), to bottlenose dolphins (Tursiops truncatus) and California sea lions (Zalophus californianus).3-5 We compared indices of cardiopulmonary function to the commonly used controlled mechanical ventilation (CMV) strategy. In a cross-over design study, ten dolphins and ten sea lions were instrumented and randomly assigned to AAV or CMV, then switched to the alternate mode. Cardiopulmonary data were collected at baseline and after 30 minutes of each mode. Cardiac output, pulmonary compliance, and arterial and mixed venous (sea lions only) oxygen tensions were measured. Systemic vascular resistance, alveolar dead space, and venous admixture (sea lions only) were calculated. During AAV, both dolphins and sea lions showed less ventilation-perfusion mismatch and higher pulmonary compliance. Markers of cardiovascular performance were not statistically significant between the two modes. Our studies suggest AAV, which closely resembles the normal, conscious respiratory pattern of aquatic mammals, may provide clinicians with the ability to optimize ventilation. Future studies should evaluate the cardiopulmonary effects of low inspired oxygen and alternative drug protocols.
*Presenting author
+Student presenter
Literature Cited
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