| ObjectivesFor both of surgeon and anesthesiologist,the focus of attention is always the lung.We took it for granted that the acute lung injury?ALI?was due to the operation during surgery in the past.However,after the pulmonary lobectomy,the imaging density of the dependent lung was significantly higher than the opposite lung.This showed that the damage of the dependent side lung was higher than that of the independent side lung.Now the main cause of the death after thoracic surgery is the pulmonary complications.The occurrence of the ALI is not only related to the preoperative pulmonary condition,operation and intraoperative blood transfusion,but also related to the mode of one lung ventilation.So the ventilation strategies in thoracic surgery are to maintain sufficient gas exchange and improve oxygenation through the use of protective ventilation strategies without lung injury.Low tidal volume?TV?and Positive end expiratory pressure?PEEP?are the core of the protective lung ventilation?PLV?.But how to apply the appropriate PEEP value during one lung ventilation?OLV?has become the focus of the problem.The so-called‘appropriate PEEP'means that under ideal oxygenation state,alveoli opening and closing produce the minimum shear force?the maximal compliance of lung?,the lowest pulmonary shunt and the smallest hemodynamic side reaction.So 70 patients who received thoracoscopic surgery were divided randomly to 5groups?PEEP value:0,4,6,8,10cmH2O?.Then we observed the effect of different PEEP on lung compliance?C?,lung dead space?D?,cardiac output?CO?and oxygen.We try to find a suitable PEEP between4-10cmH2O,which provides a basis for the selection of OLV and appropriate PEEP in clinical anesthesia.Methods70 patients undergoing selective thoracoscopic surgery in the Affiliated Hospital of Southwest Medical University from October 2016 to May 2017were included.The mode of volume controlled ventilation?VCV?was used when the two lungs were ventilated according to the weight of the patient?the tidal volume was set to 10 ml/kg with the inspiratory-to-expiratory ratio of 1:2?,and respiratory rate was regulated to maintain end-tidal partial pressure of carbon dioxide(PETCO2)35-45mmHg.One lung ventilation was also controlled by VCV according to the weight of the patients?the tidal volume was 6 ml/kg with the inspiratory-to-expiratory ratio was 1:1.5?,and respiratory rate was regulated to maintain PETCO2 35-45mmHg.According to the different PEEP values during one lung ventilation,the patients were randomly divided into five groups?14 cases in each group?.The tidal volume?TV?,peak airway pressure?Ppeak?,PETCO2,noninvasive cardiac output?CO?and arterial partial pressure of oxygen?PaO2?were observed at 6 time points after anesthesia induction:two-lung ventilation at supine position?T1?,two-lung ventilation at lateral decubitus position for 15 min?T2?,one-lung ventilation for 30 min?T3?,one-lung ventilation for 60 min?T4?,one-lung ventilation for 90 min?T5?,one-lung ventilation for 120 min?T6?.According to the above indicators,the respiratorysystemcompliance[C=VT/?Ppeak-PEEP?]anddeadspace fraction[D=(PaCO2-PETCO2/PaCO2]at each time point were calculated.Finally,the M value was calculated based on C,D and CO?M=C/D*CO?.The larger the M value,the better ventilation,in other word,there are less damage to the lung and less inhibition to the cardiovascular system.The maximum M value calculated by ventilation under the corresponding PEEP value is the best PEEP value.ResultsLung compliance of 63 patients at T1 was significantly higher than that at T2?P<0.05?.The lung compliance of zero PEEP group at T3 was significantly lower than that at T2?P<0.05?.There was no significant difference in dead space fraction among T3,T4,T5and T6 in every group?P>0.05?.And there was no significant difference in cardiac output among T3,T4,T5 and T6 in every group?P>0.05?.M values of 63 patients at T1 were significantly higher than that at T2?P<0.05?.The M values of the zero PEEP group at T2 was significantly higher than that at T3?P<0.05?.At T3,the M values of group without PEEP was lower than that of group with PEEP 4,6,8,10cmH2O?P<0.05?,but there was no significant difference between groups with PEEP 4,6,8,10 cmH2O?P>0.05?.There was no significant difference in M values between every group at T3,T4,T5 and T6?P>0.05?.The PaO2 of every group at T3 was significantly lower than that at T2?P<0.05?.But there was no significant difference in PaO2 among T3,T4,T5 and T6 in every group?P>0.05?.ConclusionsUnder general anesthesia:two-lung ventilation at supine position was better than that at lateral decubitus position;PEEP-assisted ventilation at lateral decubitus position was better than no-PEEP ventilation.There was no significant difference in the effect of one-lung ventilation,cardiac output and dead space with different PEEP values at lateral decubitus position.The application of PEEP at lateral decubitus position could increase the lung compliance.However,there was no significant change in PaO2 between different PEEP.Based on these finding,one-lung ventilation combined with PEEP?between 4-10 cmH2O?in thoracic surgery may enhance lung compliance,and has no significant effect on cardiac output,dead space fraction and PaO2.PEEP between 4-10cmH2O has no obvious effect on increasing PaO2 and decreasing the dead space fraction. |
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