The Application Of Different Ventilation Modes In Elderly Patients Undergoing Laparoscopic Rectal Cancer Surgery

Objectives:To compare the effects of traditional volume controlled ventilation（VCV）, pressure controlled ventilation（PCV） and small tidal volume with low level positive end expiratory pressure（PEEP） ventilation mode on respiratory mechanics and lung oxygenation function in the elderly undergoing laparoscopic rectal cancer surgery, looking for a more suitable ventilation management mode.Methods:The study included 60 patients aged 65 or higher, sex unlimited, ASA class I-II, who were undergoing laparoscopic rectal cancer surgery（estimated pneumoperitoneum time over 90 mins） in Bethune First Hospital of Jilin University from June 2015 to January 2014. Using the random number method divided the patients into volume controlled ventilation group（Group V, n = 20）, low tidal volume + PEEP ventilation group（Group L, n = 20） and pressure controlled of ventilation group（Group P, n = 20）. In the operating room, standard monitoring was established. A radial artery catheter was inserted before induction of anesthesia. All the patients started volume controlled ventilation after endotracheal intubation. The ventilator settings were oxygen flow rate 1 L/min, air flow rate 1 L/min, tidal volume（Vt） 8 m L/kg, I/E 1:2, respiratory rate was adjusted to maintain PETCO2 35-45 mm Hg. After CO2 pneumoperitoneum was set up（intraoperative pneumoperitoneum pressure fluctuated within 10-12 mm Hg）, Group V kept Vt = 8 m L/kg; In Group P, set inspiratory pressure（Pinsp） to make Vt of 8 ml/kg, and made sure that the Pinsp was lower than 28 cm H2O; In Group L, the settings were Vt=6 m L/kg with PEEP of 8 cm H2 O. RR was adjusted to maintain PETCO2 35-45 mm Hg in all groups. After pneumoperitoneum, setting the respiratory parameters to Vt= 8 m L/kg in every group. The mean artery pressure（MAP） and heart rate（HR） were recorded at 5 minutes after endotracheal intubation（T1）, 45 minutes after pneumoperitoneum（T2）, 90 minutes after pneumoperitoneum（T3）,15 minutes after the end of pneumoperitoneum（T4） and 45 minutes after removal the endotracheal intubation（T5）; Peak airway pressure（Ppeak）、Plateau airway pressure（Pplat）、end-tidal carbon dioxide partial pressure（PETCO2） and Dynamic lung cdyniance（Cdyn） were recorded at T1-T4; Arterial blood samples were took for blood gas analysis, and monitored Pa O2 and Pa CO2 at T1,T3,T4 and T5, and calculated the oxygenation index（OI）, respiratory index（RI）, alveolar-arterial oxygen partial pressure difference（PA-a DO2）. Observed and recorded the postoperative pulmonary complications in seven days.Results:1. There were no differences among the three groups in patient characteristics and operative data;2. In all groups, MAP increased at T2 and T3 compared with T1, and then backed to T1 level at T4 and T5.There were no significant difference among groups;3. Ppeak and Pplat increased at T2 and T3, Group P rose the least. Cdyn decreased obviously in all patients after pneumoperitoneum, Group V was the most significant one, and had not yet recovered to T1 level at T4, there was no difference in the Group L and Group P;4. Compared with T1, PaCO₂ increased at T2 and T3, especially Group L at T3, and backed to T1 level at T5; Pa O2 decreased at T3 in all groups, especially Group V, and then backed to normal level at T5. Group V was lower compared with Group P and Group L;5. Compared with T1, OI decreased obviously in all groups, Group V made the most decline; PA-a DO₂ and RI decreased in Group V at T3;6. The morbidity of postoperative pulmonary complications in Group V was higher than P and Group L significantly.Conclusions:1. Compared with traditional VCV ventilation mode, PCV ventilation mode and protective lung ventilation mode can improve arterial oxygenation, prevent the occurrence of lung injury in laparoscopic rectal cancer surgery in elderly men, the difference in PCV ventilation mode and protective lung ventilation mode is not significant.2. Compared with protective lung ventilation mode, PCV mode is the most suitable for the operation for its superiority in airway pressure control and maintenance of PaCO₂.