RESUMO
OBJECTIVE: To compare the effects of pressure controlled ventilation (PCV) with volume-controlled ventilation (VCV) on lung compliance, gas exchange, and hemodynamics in isoflurane-anesthetized dogs. DESIGN: Prospective randomized study. SETTING: Veterinary teaching hospital. ANIMALS: Forty client-owned bitches undergoing elective ovariohysterectomy. INTERVENTIONS: Dogs were randomly assigned to be ventilated with 100% oxygen using PCV (n = 20) or VCV (n = 20). The respiratory rate was 20/min and positive end-expiratory pressure (PEEP) was 5 cm H2 O, with a tidal volume of 10 mL/kg. Cardiac output (CO) was measured using thermodilution. Cardiopulmonary and blood gas data were obtained during spontaneous ventilation and after 30 (T30) and 60 minutes (T60) of controlled ventilation. MEASUREMENTS AND MAIN RESULTS: In dogs ventilated with PCV, at T30 and T60, PIP was lower (11.4 ± 1.9 and 11.1 ± 1.5 cm H2 O, respectively) and static compliance (CST ) was higher (51 ± 7 and 56 ± 6 mL/cm H2 O, respectively) than in VCV group (PIP of 14.3 ± 1.3 and 15.5 ± 1.4 cm H2 O; CST of 34 ± 8 and 33 ± 9 mL/cm H2 O, P < 0.0001). Compared with spontaneous ventilation, both groups had decreased alveolar-arterial oxygen difference at T30 and T60 (PCV: 128 ± 32 mm Hg vs 108 ± 20 and 104 ± 16 mm Hg, respectively; VCV: 131 ± 38 mm Hg vs 109 ± 19 and 107 ± 14 mm Hg, respectively; P < 0.01), while CO was maintained at all time points. CONCLUSIONS: Compared to spontaneous ventilation, both ventilatory modes effectively improved gas exchange without hemodynamic impairment. PCV resulted in higher lung CST and lower PIP compared to VCV.
