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_stRS) and the ratio of partial pressure of end-tidal to arterial carbon dioxide (Pe'CO₂/PaCO₂), in healthy dogs using two approaches for tidal volume (V_T) 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_T selection strategy, randomized to a constant V_T of 15 mL kg^-1 of actual body mass (V_TBW) or ΔPaw-guided V_T (V_TΔP) of 7-8 cmH₂O. Both strategies used an inspiratory time of 1 second, 20% end-inspiratory pause, 4 cmH₂O positive end-expiratory pressure and fraction of inspired oxygen of 0.4. Respiratory frequency was adjusted to maintain Pe'CO₂ between 35 and 40 mmHg. Respiratory mechanics, arterial blood gases and Pe'CO₂/PaCO₂ 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_T was significantly higher in dogs ventilated with V_TΔP than with V_TBW strategy (17.20 ± 4.04 versus 15.03 ± 0.60 mL kg^-1, p = 0.036). C_stRS was significantly higher with V_TΔP than with V_TBW strategy [2.47 (1.86-2.86) versus 2.25 (1.79-2.58) mL cmH₂O^-1 kg^-1, p = 0.011]. There were no differences in Pe'CO₂/PaCO₂ between V_TΔP and V_TBW 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'CO₂/PaCO₂ between the V_T selection strategies employed, C_stRS significantly increased during the V_TΔP approach. A future trial should explore if V_TΔP improves perioperative gas exchange and prevents lung damage.