Optimal PEEP for volume-controlled ventilation in patients undergoing surgery with general anesthesia: pulmonary electrical impedance tomography monitoring

Abstract

Objective To determine the optimal positive end-expiratory pressure (PEEP) for volume-controlled ventilation using pulmonary electrical impedance tomography in the patients undergoing surgery with general anesthesia. Methods Fifty patients of both sexes, aged 18-64 yr, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, with body mass index of 18.5-28.0 kg/m2, scheduled for surgery for ureteral calculi under general anesthesia, were enrolled in this study.The patients were tracheally intubated after anesthesia induction and mechanically ventilated in volume-controlled mode, with tidal volume 6 ml/kg, mean arterial pressure was recorded at 3 min of ventilation and served as the baseline value, and then PEEP was increased with an increment of 3 cmH2O every 3 min until PEEP reached 15 cmH2O.The percentage of dorsal pulmonary ventilation and peak airway pressure were recorded at 3 min of ventilation with different PEEPs.When the decrease in mean arterial pressure was more than 20% of the baseline value during ventilation, deoxyepinephrine 0.1 mg was injected intravenously, and the consumption of deoxyepinephrine was recorded within 3 min of ventilation with different PEEPs. Results Peak airway pressure was gradually increased with the increase of PEEP(P<0.05), the percentage of dorsal pulmonary ventilation was gradually increased when PEEP was 6 cmH2O (P<0.05), and the consumption of deoxyepinephrine was gradually increased when PEEP was 15 cmH2O (P<0.05). Conclusion The optimal PEEP is 12 cmH2O during volume-controlled ventilation with tidal volume of 6 ml/kg in the patients undergoing surgery with general anesthesia. Key words: Anesthesia, general; Respiration, artificial; Positive-pressure respiration; Pulmonary impedance tomography