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Objective: To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in anesthetized pigs and to describe a new mode of ventilation for anesthetized veterinary species. Study design: Randomized, crossover design without washout. Animals: Twelve healthy, female white Landrace pigs. Methods: Following ketamine-midazolam premedication and anesthetic induction with propofol, the trachea was intubated, and each pig was positioned in dorsal recumbency. Anesthesia was maintained with propofol and sufentanil infusions. Pigs were instrumented and their lungs were sequentially ventilated with each mode, in random order, for 1 h according to predefined criteria [fraction of inspired oxygen (FiO2) = 0.21, 10mL kg-1 tidal volume (VT), and arterial carbon dioxide tension (PaCO2) within 40-45 mmHg]. Cardiopulmonary data were collected at baseline, 30 and 60min. In 8 pigs, thoracic computed tomography (CT) was performed following the 60min time point for each mode of ventilation and images were analyzed to quantify lung aeration. The effects of ventilation mode, time, and order were analyzed using repeated measures ANOVA. Paired t-tests were used to compare lung aeration between modes. Significance was defined as p < 0.05. Results: Data from12 pigs were analyzed. A significant effect of mode was found for heart rate, mean arterial pressure (MAP), pulmonary artery occlusion pressure, cardiac index (CI), stroke volume index, systemic vascular resistance, pulmonary vascular resistance, oxygen delivery index (DO2I), oxygen extraction ratio (O2ER), VT, arterial oxygen tension, arterial hemoglobin saturation, PaCO2, end-tidal carbon dioxide tension, alveolar dead space (VDalv/VTalv), venous admixture (Qs/Qt), mean airway pressure, and dynamic compliance index (CRSI). Order effects were also observed for some cardiovascular and respiratory variables. For the eight pigs that underwent thoracic CT, AAV resulted in significantly larger proportions of normally and hyperaerated lung while CMV resulted in larger proportions of hypoaerated and atelectatic lung. Conclusions: In dorsally recumbent anesthetized pigs, ventilated with FiO2 = 0.21, both modes of ventilation supported adequate oxygenation while AAV resulted in higher CRSI, and lower VDalv/VTalv and Qs/Qt, compared with CMV. AAV was also associated with lower MAP, CI, and DO2I and higher O2ER compared with CMV. Further investigation of AAV in anesthetized animals is warranted. [ABSTRACT FROM AUTHOR]

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 alveolararterial 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. [ABSTRACT FROM AUTHOR]

To compare the cardiopulmonary effects of apneustic anesthesia ventilation (AAV) and conventional mechanical ventilation (CMV) in dorsally recumbent anesthetized horses. Randomized, crossover design. A total of 10 healthy adult horses from a university-owned herd. Following xylazine, midazolam and ketamine administration, horses were orotracheally intubated and positioned in dorsal recumbency. Anesthesia was maintained with isoflurane in oxygen [inspired oxygen fraction (F i O 2) = 0.3 initially, with subsequent titration to maintain PaO 2 ≥ 85 mmHg (11.3 kPa)]. Horses were instrumented and ventilated with AAV or CMV for 1 hour according to predefined criteria [10 mL kg–1 tidal volume (V T), PaCO 2 of 40–45 mmHg (5.3–6.0 kPa) during CMV and <60 mmHg (8.0 kPa) during AAV]. Dobutamine was administered to maintain mean arterial pressure (MAP) >65 mmHg. Cardiopulmonary data were collected at baseline, 30 and 60 minutes. The effects of ventilation mode and time were analyzed using repeated-measures anova with significance defined as p < 0.05. Data from nine horses were analyzed. A significant effect of mode at one or more time points was found for respiratory rate, arterial and end-tidal CO 2 tensions, arterial pH, mean airway pressure (P aw), respiratory system dynamic compliance index (C rs I), venous admixture (Q ˙ s / Q ˙ t), mean pulmonary artery pressure and systemic vascular resistance. No significant differences between modes were found for V T , F i O 2 , PaO 2 , arterial hemoglobin saturation, alveolar dead space, heart rate, MAP, cardiac index, stroke volume index, oxygen delivery index, oxygen extraction ratio and dobutamine administration. In dorsally recumbent anesthetized horses, both ventilation modes supported adequate oxygenation with minimal supplemental oxygen. Compared with CMV, AAV resulted in higher C rs I and lower Q ˙ s / Q ˙ t. Despite higher mean P aw with AAV, the cardiovascular effects of each mode were not different. Further trials of AAV in anesthetized horses are warranted. [ABSTRACT FROM AUTHOR]

To compare PaO 2 and PaCO 2 in horses recovering from general anesthesia maintained with either apneustic anesthesia ventilation (AAV) or conventional mechanical ventilation (CMV). Randomized, crossover design. A total of 10 healthy adult horses from a university-owned herd. Dorsally recumbent horses were anesthetized with isoflurane in oxygen [inspired oxygen fraction = 0.3 initially, with subsequent titration to maintain PaO 2 ≥ 85 mmHg (11.3 kPa)] and ventilated with AAV or CMV according to predefined criteria [10 mL kg–1 tidal volume, PaCO 2 40–45 mmHg (5.3–6.0 kPa) during CMV and < 60 mmHg (8.0 kPa) during AAV]. Horses were weaned from ventilation using a predefined protocol and transferred to a stall for unassisted recovery. Arterial blood samples were collected and analyzed at predefined time points. Tracheal oxygen insufflation at 15 L minute–1 was provided if PaO 2 < 60 mmHg (8.0 kPa) on any analysis. Time to oxygen insufflation, first movement, sternal recumbency and standing were recorded. Data were analyzed using repeated measures anova , paired t tests and Fisher's exact test with significance defined as p < 0.05. Data from 10 horses were analyzed. Between modes, PaO 2 was significantly higher immediately after weaning from ventilation and lower at sternal recumbency for AAV than for CMV. No PaCO 2 differences were noted between ventilation modes. All horses ventilated with CMV required supplemental oxygen, whereas three horses ventilated with AAV did not. Time to first movement was shorter with AAV. Time to oxygen insufflation was not different between ventilation modes. Although horses ventilated with AAV entered the recovery period with higher PaO 2 , this advantage was not sustained during recovery. Whereas fewer horses required supplemental oxygen after AAV, the use of AAV does not preclude the need for routine supplemental oxygen administration in horses recovering from general anesthesia. [ABSTRACT FROM AUTHOR]