The Effect Of Inverse Ratio Ventilation With Positive End-expiratiry Pressure On Pulmonary Function In Patients Undergoing Gynecologic Laparoscopic Surgery

Objective:To evaluate the effect of inverse ratio ventilation（IRV）with positive end-expiratory pressure（PEEP）on pulmonary function in patients undergoing gynecologic laparoscopic surgery.Methods:One hundred ASA physical status I orⅡpatients,aged18-64 yr,with body mass index of 19-30 kg/m²,scheduled for elective gynecologic laparoscopic surgery,were divided into 4 groups（n=25each）using a random number table method:conventional ventilation group（Group A）;IRV+PEEP group（group B）;IRV group（group C）and PEEP group（group D）.The patients were tracheally intubated after anesthesia induction and mechanically ventilated in volume-controlled mode,with tidal volume 6-8 ml/kg,inspiratory/expiratory ratio 1:2,respiratory rate 12 breaths/min,fraction of inspired oxygen 75%,the end-tidal pressure of carbon dioxide at 30-50 mm Hg and pneumoperitoneum pressure maintained at 13-15 mm Hg.I:E ratio and PEEP were adjusted at the onset of pneumoperitoneum.Before pneumoperitoneum,at 20,60 min after onset of CO₂insufflation and 5 min after pneumoperitoneum,blood samples from the radical artery were obtained for blood gas analysis,a irway peak pressure（Ppeak）,mean airway pressure（Pmean）,pulmonary dynamic compliance（Cdyn）,partial pressure of arterial carbon dioxide（P_aCO₂）,oxygenation index（P_aO₂/F_iO₂）,alveolar arterial oxygen pressure difference(P_A-aO₂),mean arterial pressure（MAP）,heart rate（HR）and respiration rate（RR）were recorded.Simultaneously,venous blood samples were obtained at before induction of anesthesia,5 min afer pneumoperitoneum and 24 h after the surgery to measure the serum concentrations of surfacetant protein-A（SP-A）and interleukin-6（IL-6）by enzyme-linked immunosorbent assay.The occurrence of several complications was recorded within 72 h after operation,including:body temperature>38°C,cough,expectoration,nausea and vomiting,abdominal distension and postoperative shoulder pain.Results:1 Comparison of respiratory mechanics parameters at different time points in four groups:Compared with T₁,Ppeak and Pmean were increased,but Cdyn was decreased at T₂,T₃in all groups（P<0.05）.Compared with group A,there was no significant difference in Ppeak in group B（P>0.05）,but Ppeak was decreased in group C at T₂,T₃;Pmean and Cdyn were significantly increased at T₂,T₃in groups B and C,while Ppeak and Pmean were increased at T₂,T₃in group D（P<0.05）.Compared with group B,Ppeak and Pmean were increased at T₂,T₃in group C;Ppeak was increased at T₂,Pmean and Cdyn were significantly decreased at T₂,T₃in group D（P<0.05）.Compared with group C,Ppeak and Pmean were increased at T₂,T₃in group D（P<0.05）.2 Comparison of respiratory oxygenation parameters at different time points in four groups:Compared with T₁,P_aCO₂was increased in four groups at T_2-4（P<0.05）.There were no significant difference in P_A-aO₂,P_aO₂/F_iO₂,P_aCO₂in all groups（P>0.05）.3 Comparison of hemodynamics at different time points in four groups:Compared with T₁,MAP was increased at T₂,T₃,and RR was elevated at T₃,T₄in all groups;HR was similarly increased at T₂,T₃in groups B,C,D（P<0.05）.There was no significant difference in hemodynamics at each time point among the four groups（P>0.05）.4 Comparison of serum IL-6 and SP-A concentrations at times T₀,T₄,and T₅in four groups:Compared with T₀,the serum concentrations of SP-A and IL-6 were significantly increased at T₄in all groups（P<0.05）.Compared with group A,the serum concentrations of SP-A and IL-6 were decreased at T₄,T₅in group B,while they were also decreased at T₄in group C（P<0.05）.5 There were no significant difference in the incidence of complications within 72 hours after operation among the four groups（P>0.05）.Conclusion:IRV with PEEP not only increases Pmean、improves Cdyn,but also reduces systemic inflammatory responses in the patients undergoing minor gynecologic laparoscopic surgery without elevating Ppeak.It exterts better efficacy than either alone.