Effect Of Low Tidal Volume Ventilation On Pulmonary Gas Exchange Under General Anesthesia

Objective By collecting the blood gas analysis under low tidal volume(LTV)ventilation and the normal tidal volume ventilation,and caculating the Pa-v O2,alveolar-arterial oxygen tension difference(PA-a O2)and the shunt rate QS/QT,to observe the effects of Pa-v O2,pulmonary gas exchange in patients under general anesthesia and mechanical ventilation.Methods Eighty patients for selective operation were enrolled from March 2015 to September 2016,including 42 surgeries in supine position,and 38 surgeries in prone position,all the test subjects were called the Total Subject,the supine position surgeries were called the Supine Group,the prone position surgeries were called the Prone Group.they were ASA I grade and II grade.After the patients were induced and intubated,the patients were ventilated mechanically in an volume control model.The tidal volume was set to 8 ml/kg(the name was called as T8,S8 ? P8 in different group)and the respiration rate was set to 10 times per minute.After thirty minutes,extracting dynamic venous blood for blood gas analysis,and at the same time,set the tidal volume was6ml/kg(the name was called as T6,S6?P6 in different group)and the respiration rate was 13 times per minute,extracting dynamic venous blood for blood gas analysis after thirty minutes.Pa-v O2,PA-a O2 and QS/QT were calculated respectively. Data are presented as mean with standard deviation for parametric data,and are expressed by x±s,the comparison among multiple groups(?2)mean using one-way ANOVA.With P<0.05 for the difference was statistically significant.Results Use the mechanical ventilation in general anesthesia,(1)In all surgeries,when set the VT at 8ml/kg,the Pa-v O2 was(402.10±103.55 mm Hg),while as the VT set at 6ml/kg,the Pa-v O2was(419.70±73.13 mm Hg),there was no statistically difference between them(P=0.222>0.05);when set the VT at 8ml/kg,the PA-a O2 was(206.3±100.01 mm Hg),while as the VT set at 6ml/kg,the PA-a O2 was(177.45±175.62 mm Hg),there was no statistically difference between them(P=0.069>0.05);when set the VT at 8ml/kg,the QS/QTwas(11.10±4.66%),while as the VT set at 6ml/kg,the QS/QT was(9.76±3.83%),there was no statistically difference between them(P=0.062>0.05).(2)In supine position surgeries,when set the VT at8ml/kg,the Pa-v O2was(388.85±95.16 mm Hg),while as the VT set at 6ml/kg,the Pa-v O2was(404.00±74.52 mm Hg),there was no statistically difference between them(P=0.269>0.05);when set the VT at 8ml/kg,the PA-a O2 was(221.27±92.73 mm Hg),while as the VT set at 6ml/kg,the PA-a O2 was(199.17±92.73 mm Hg),there was no statistically difference between them(P=0.167>0.05);when set the VT at 8ml/kg,the QS/QT was(11.86±4.28%),while as the VT set at 6ml/kg,the QS/QT was(10.87±3.43%),there was no statistically difference between them(P=0.161>0.05).(3)In the prone position surgeries,when set the VT at 8ml/kg,the Pa-v O2 was(426.71±121.48 mm Hg),while as the VT set at 6ml/kg,the Pa-v O2 was(448.86±65.62 mm Hg),there was no statistically difference between them(P=0.32>0.05);when set the VT at 8ml/kg,the PA-a O2 was(178.85±114.39 mm Hg),while as the VT set at 6ml/kg,the PA-a O2 was(137.11±74.20 mm Hg),there was no statistically difference between them(P=0.,268>0.05);when set the VT at 8ml/kg,the QS/QTwas(9.67±5.33%),while as the VT set at 6ml/kg,the QS/QT was(7.69±3.92%),there was no statistically difference between them(P=0.248>0.05).(4)In all surgeries,when set the VT as 8ml/kg,the Pa-v O2 in the supine position was(388.85±95.16 mm Hg),and in the prone position was(426.71±121.48 mm Hg),there was no statistically difference between them(P=0.450>0.05);when set the VT as 8ml/kg,the PA-a O2 in the supine position was (221.27±92.73 mm Hg),and in the prone position was(178.85±114.39 mm Hg),there was no statistically difference between them(P=0.414>0.05);when set the VT as 8ml/kg,the QS/QT in the supine position was(11.86±4.28%),and in the prone position was(9.67±5.33%),there was no statistically difference between them(P=0.329>0.05).(5)In all surgeries,when set the VT as 6ml/kg,the Pa-v O2 in the supine position was(404.00±74.52 mm Hg),and in the prone position was(448.86±65.62 mm Hg),there was no statistically difference between them(P=0.199>0.05);when set the VT as 6ml/kg,the PA-a O2 in the supine position was(199.17±92.73 mm Hg),and in the prone position was(137.11±74.20 mm Hg),there was no statistically difference between them(P=0.079>0.05);when set the VT as 6ml/kg,the QS/QT in the supine position was(10.87±3.43%),and in the prone position was(7.69±3.92%),there was no statistically difference between them(P=0.075>0.05).Conclusion Considered of the pulmonary gas exchange function,whether in supine position or prone position,there were no difference between low tidal volume ventilation and conventional tidal volume ventilation,so in conclusion,Low tidal volume mechanical ventilation can be used in general anesthesia safely.