Effect of Cdyn-guided PEEP titration on pulmonary function of elderly patients undergoing robotic-assisted radical prostatectomy

Abstract

Objective To evaluate the effect of dynamic lung compliance (Cdyn)-guided positive end-expiratory pressure (PEEP) titration on the pulmonary function of elderly patients undergoing robotic-assisted radical prostatectomy. Methods Forty patients, aged 65-80 yr, with body mass index of 19-28 kg/m2, of American Society of Anesthesiologists physical status Ⅱ or Ⅲ, scheduled for elective robotic-assisted laparoscopic radical prostatectomy, were divided into 2 groups (n=20 each) using a random number table method: control group (group C) and PEEP group (group P). After anesthesia induction and endotracheal intubation, all the patients were mechanically ventilated in pressure-controlled ventilation-volume guaranteed mode, with tidal volume 6-8 ml/kg, respiratory rate 12 breaths/min, fraction of inspired oxygen 50%, and inspiratory/expiratory ratio 1∶2.Respiratory rate was adjusted after onset of pneumoperitoneum to maintain the end-tidal pressure of carbon dioxide at 30-45 mmHg.Immediately after intubation and immediately after establishing pneumoperitoneum-Trendelenburg position, patients received PEEP titration from the lowest PEEP available in the anesthesia machine, with an increment of 2 cmH2O every 4 min until the maximal Cdyn was achieved in group P. Patients in group C received no PEEP during procedure.At 4 min after completion of the first PEEP titration, 4 min and 1 and 2 h after completion of the second PEEP titration, and 1 min after closure of abdominal cavity in group P and at 4 min after the end of intubation, 4 min and 1 and 2 h after establishing pneumoperitoneum-Trendelenburg position in group C, blood samples from the radical artery were obtained for blood gas analysis, peak airway pressure was recorded, and oxygenation index, driving pressure, alveolar-arterial oxygen difference, and ratio of physical dead space to tidal volume were calculated. Results Compared with group C, the oxygenation index and partial pressure of arterial oxygen were significantly increased, and driving pressure and alveolar-arterial oxygen difference were decreased at each time point (P 0.05). Conclusion Cdyn-guided PEEP titration can improve pulmonary function of elderly patients undergoing robotic-assisted radical prostatectomy. Key words: Lung compliance; Positive-pressure respiration; Prostatic neoplasms; Respiratory function tests