Tidal volume selection in volume-controlled ventilation guided by driving pressure versus actual body weight in healthy anesthetized and mechanically ventilated dogs: A randomized crossover trial.

Objective: To compare static compliance of the respiratory system (C) and the ratio of partial pressure of end-tidal to arterial carbon dioxide (Pe'CO/PaCO), in healthy dogs using two approaches for tidal volume (V) selection during volume-controlled ventilation: body mass based and driving pressure (ΔPaw) guided.

Study Design: Randomized, nonblinded, crossover, clinical trial.

Animals: A total of 19 client-owned dogs anesthetized for castration and ovariohysterectomy.

Methods: After a stable 10 minute baseline, each dog was mechanically ventilated with a V selection strategy, randomized to a constant V of 15 mL kg of actual body mass (V) or ΔPaw-guided V (V) of 7-8 cmHO. Both strategies used an inspiratory time of 1 second, 20% end-inspiratory pause, 4 cmHO positive end-expiratory pressure and fraction of inspired oxygen of 0.4. Respiratory frequency was adjusted to maintain Pe'CO between 35 and 40 mmHg. Respiratory mechanics, arterial blood gases and Pe'CO/PaCO were assessed. Continuous variables are presented as mean ± SD or median (interquartile range; quartiles 1-3), depending on distribution, and compared with Wilcoxon signed-rank tests.

Results: The V was significantly higher in dogs ventilated with V than with V strategy (17.20 ± 4.04 versus 15.03 ± 0.60 mL kg, p = 0.036). C was significantly higher with V than with V strategy [2.47 (1.86-2.86) versus 2.25 (1.79-2.58) mL cmHO kg, p = 0.011]. There were no differences in Pe'CO/PaCO between V and V strategies (0.94 ± 0.06 versus 0.92 ± 0.06, p = 0.094). No discernible difference in ΔPaw was noted between the strategies.

Conclusions And Clinical Relevance: While no apparent difference was observed in the Pe'CO/PaCO between the V selection strategies employed, C significantly increased during the V approach. A future trial should explore if V improves perioperative gas exchange and prevents lung damage.