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

To compare static compliance of the respiratory system (CstRS) 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 (VT) selection during volume-controlled ventilation: body mass based and driving pressure (ΔPaw) guided. Randomized, nonblinded, crossover, clinical trial. A total of 19 client-owned dogs anesthetized for castration and ovariohysterectomy. After a stable 10 minute baseline, each dog was mechanically ventilated with a VT selection strategy, randomized to a constant VT of 15 mL kg–1 of actual body mass (VTBW) or ΔPaw-guided VT (VTΔP) 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. The VT was significantly higher in dogs ventilated with VTΔP than with VTBW strategy (17.20 ± 4.04 versus 15.03 ± 0.60 mL kg–1, p = 0.036). CstRS was significantly higher with VTΔP than with VTBW 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 VTΔP and VTBW strategies (0.94 ± 0.06 versus 0.92 ± 0.06, p = 0.094). No discernible difference in ΔPaw was noted between the strategies. While no apparent difference was observed in the Pe′CO2/PaCO2 between the VT selection strategies employed, CstRS significantly increased during the VTΔP approach. A future trial should explore if VTΔP improves perioperative gas exchange and prevents lung damage.