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Low tidal volume ventilation in healthy dogs

Oura, Trisha, Rozanski, Elizabeth A., Buckley, Gareth, Bedenice, Daniela
Journal of veterinary emergency and critical care 2012 v.22 no.3 pp. 368-371
Beagle, acidosis, analysis of variance, blood gases, distress, dogs, lung function, mechanics, pH, tidal volume
OBJECTIVE: To determine if low tidal volume (VT) ventilation is associated with the development of respiratory acidosis and changes in lung function in healthy dogs. DESIGN: Randomized prospective experimental cross‐over study. SETTING: Pulmonary function laboratory at a university teaching hospital. ANIMALS: Five healthy Beagle dogs. INTERVENTIONS: Dogs were anesthetized and randomly mechanically ventilated with VT of 6, 8, 10, 12, and 15 mL/kg while maintaining a constant minute volume. MEASUREMENTS AND MAIN RESULTS: Arterial blood gases and pulmonary mechanics were collected after 15 minutes of equilibration at each VT. Repeated measures ANOVA was used to determine the effect of VT with a P‐value of <0.05 considered significant, and a Pearson product moment was used to determine correlation between VT and pH and PaCO₂. VT had a significant effect on PaCO₂ (P < 0.001) and on pH (P < 0.001) with lower VT being associated with higher PaCO₂ and lower pH. There was a strong correlation between VT and PaCO₂ (r = –0.87) and VT and pH (r = 0.83). Increased airway pressures and pulmonary compliance were associated with increasing VT. CONCLUSIONS: There is a predictable decrease in the pH, decrease in airway pressure, decrease in compliance, and increase in the PaCO₂ associated with lower VT. Low VT ventilation is well tolerated in healthy dogs; the role of low VT ventilation in dogs with acute lung injury/acute respiratory distress syndrome as well as the influence of positive end expiratory pressure requires further evaluation.