Effects of positive end-expiratory pressure after recruitment maneuvers on respiratory mechanics and gas exchange during laparoscopy in obese patients

Objective To investigate the effects of positive end-expiratory pressure (PEEP) after recruitment maneuvers (RM) on respiratory mechanics and gas exchange during laparoscopy in obese patients.Methods Sixty-three ASA physical status Ⅱ or Ⅲ patients,aged 42-64 yr,with body mass index 30-40kg/m2,were randomly allocated into 3 groups (n=21 each):PEEP0 group,PEEP5 group and PEEP10 group.PEEP was not given after RM in PEEP0 group.In PEEP5 and PEEP10 groups,a recruiting maneuver was followed by PEEP 5 and 10 cm H2 O,respectively,until the end of pneumoperitoneum.The intraabdominal pressure was set at 12mmHg in the three groups.Parameters of respiratory mechanics including peak airway pressure (Ppeak),airway plateau pressure (Peat),chest wall plateau pressure (PplatCW),airway resistance (Raw),elastance of respiratory system (ERS),elastanc of chest wall (ECW) and elastance of lung (EL) and parameters of gas exchange including oxygenation index (PaO2/FiO2),arterial to end-tidal difference in carbon dioxide (Da-ETCO2),alveolar-arterial oxygen tension difference (DA-aO2),and dead space/tidal volume ratio (VD/VT) were measured before pneumoperitoneum (T0),at 20 min of pneumoperitoneum (T1),at 10 min after the end of recruitment (T2),and at the end of pneumoperitoneum (T3).Results Da-ETCO2,ERS and Raw were decreased at T2,ECW and EL were decreased at T3 in PEEP5 group,and Da-ETCO2,VD/VT,DA-aO2,Pplatcw Raw and EL were decreased at T2.3,and PaO2/FiO2 was increased at T2,ECW was decreased at T3 in group PEEP10 as compared with that in group PEEP0 (P ＜ 0.05).Da-ETCO2 and VD/VT were decreased and PaO2/FiO2 was increased at T2,3,Raw was increased and EL was decreased at T2 in group PEEP10 as compared with that in group PEEP5 (P ＜ 0.01).Conclusion PEEP after RM can improve respiratory mechanics and gas exchange during laparoscopy in obese patients and PEEP maintained at 10 cm H2O after RM provides better efficacy than PEEP at 5 cm H2 O. Key words: Positive-pressure respiration;  Respiratory mechanics;  Pulmonary gas exchange ;  Obesity ;  Laparoscopy