Effect Of Different Ventilation Modes On Intraoperative Respiratory Parameters In Elderly Patients Undergoing Laparoscopic Colorectal Surgery

Objective:In the past few decades,laparoscopic surgery has become more and more common,more widely used,and the age span of patients undergoing laparoscopic surgery is also growing.The impact of laparoscopic surgery for a long time of artificial pneumoperitoneum and special position on the patient’s circulation,respiratory and other physiological functions more and more aroused everyone’s attention.We compared the effects of two different ventilation modes,volume controlled ventilation（VCV）combined with positive end expiratory pressure（PEEP）and pressure controlled ventilation（PCV）combined with PEEP,on patient hemodynamics and respiratory system to find out more suitable for elderly patients with laparoscopic colorectal resection of the ventilation mode.Methods:Sixty patients with laparoscopic rectum and sigmoid colon resection undergoing general anesthesia at the First Affiliated Hospital of China Medical University from August 2016 to May 2017 were enrolled in this study.Patients age 60 or higher,sex unlimited,ASA I-II,body mass index（BMI）18 kg/m²³0 kg/m²,and all patients with heart and lung function within the normal range.Sixty patients were randomly divided into two groups:VCV+PEEP（VP group,n=30）and PCV+PEEP（PP group,n=30）.After the patient entered the operating room,the left upper limb venous access and routine electrocardiographic monitoring were performed in the supine position.Tracheal intubation was performed under the visual laryngoscope after induction of anesthesia（Enhanced Tracheal Catheter:Male ID=7.5 mm;Female ID=7.0 mm）.Then the VCV was performed at the tidal volume（Vt）of 8 ml/kg,respiratory rate（RR）of 12,I:E=1:2,fresh gas flow 2 L/min,inhaled oxygen concentration（FiO₂）60%,and the patient was placed in Trendelenburg after establishment of the artificial pneumoperitoneum.Before the artificial pneumoperitoneum was established,the VP group was adjusted to Vt=6 ml/kg with PEEP of 5cmH₂O for mechanical ventilation,and intraoperative P_ETCO₂ was maintained at 30⁴0 mmHg by adjusting the RR;the PP group first adjusted Vt of 6 ml/kg,stable after switch to PCV with PEEP of 5cm H₂O,and intraoperative P_ETCO₂ was maintained at 30⁴0 mm Hg by adjusting the preset airway pressure and RR,other parameters default ventilator system settings parameters.When the patient resumes supine position after the artificial pneumoperitoneum is stopped,the I:E,fresh gas flow and inspired oxygen concentration remain unchanged throughout the anesthesia period.The systolic blood pressure（SBP）,diastolic blood pressure（DBP）,heart rate（HR）and pulse oxygen saturation（SpO₂）were recorded at 5 minutes after the patient entered the operating room（T0）,5 minutes after endotracheal intubation in VCV（T1）,5 minutes after establish artificial pneumoperitoneum（T2）,35 minutes after establish artificial pneumoperitoneum（T3）,65 minutes after establish artificial pneumoperitoneum（T4）,5 minutes after secondary pneumoperitoneum（T5）,leaving the operating room（T6）,PACU wake up before tracheal extubation（T7）,returning to the ward（T8）.Tidal volume（Vt）,End-tidal carbon dioxide pressure(P_ETCO₂),Airway Peak Pressure（Ppeak）,Airway Pressure Platform（Pplat）,Dynamic Lung Cdyniance（Cdyn）,were recorded at T1^T7.Radial artery blood samples were collected for blood gas analysis at T1,T3,T4 and T8 respectively to monitored Arterial oxygen partial pressure（PaO₂）and Partial pressure of carbon dioxide in arterial blood（PaCO₂）.Oxygenation Index（OI）,Respiratory Index（RI）,Alveolar-Arterial Oxygen Partial Pressure（PA-aDO₂）and intrapulmonary shunt volume（Qs/Qt）were calculated according to the results of blood gas analysis.Postoperative follow-up recorded patients with or without intraoperativeawarenessofanesthesia-relatedcomplicationsandpulmonary complications within 5 days after surgery.Results:1.Two groups of patients characteristics and operative data no significant difference（p>0.05）.2.Compared with T1,SBP of both groups decreased at T3^T7（p<0.05）,DBP increased at T2,T5 while T6,T7 decreased（p<0.05）;T2^T7 HR decreased（p<0.05）,SBP,DBP and HR returned to T1 level at T8.There was no significant difference in hemodynamics between the two groups（p>0.05）.3.After establishment of artificial pneumoperitoneum,the Vt and Cdyn in both groups decreased（p<0.05）,and returned to the level of before pneumoperitoneum at T6.Compared with VP group,Vt increased at T3 and T4（p<0.05）,while T6 and T7 Cdyn increased（p<0.05）.4.After establishment of artificial pneumoperitoneum,the Ppeak and Pplat of both groups increased（p<0.05）,and the PP group returned to the level of before pneumoperitoneum at T6;compared with the VP group,both Ppeak and Pplat of T2^T7is decreased（p<0.05）.5.Compared with T1,PaO₂ in both groups decreased at T8（p<0.05）,PaO₂ significantly increased at T4 in PP group（p<0.05）compared with VP group;PaCO₂ were increased at T3,T4 and T8（p<0.05）,no significant difference between groups.6.Compared with T1,the PA-aDO₂ and QS/QT of VP group decreased and the OI of PP group decreased at T8（p<0.05）;RI,PA-aDO₂ and QS/QT were decreased and OI is increased at T4 compared with VP group（p<0.05）.7.The incidence of postoperative pulmonary complications was no significant difference between the two groups（p>0.05）.Conclusion:The mechanical ventilation mode of PCV with PEEP used in elderly patients with laparoscopic colorectal surgery with the advantages in restricting Ppeak and Pplat,increasing Vt and Cdyn compared with small tidal volume of VCV with PEEP,meanwhile,PCV with PEEP significantly improved lung oxygenation function at 65min after artificial pneumoperitoneum.Therefore,Intraoperative mechanical ventilation of elderly patients with laparoscopic colorectal surgery should give priority to the use of PCV with PEEP.