Effect Of Tidal Volume On Intrapulmonary Shunt And Arterial Oxygenation During One Lung Ventilation

Objective:To investigate the effects of different tidal volume ventilation(OLV) on arterial oxygenation and intrapulmonary shunt and the correlation between PaCO₂ and P_ETCO₂ during one lung。Methods:sixty patients with ASAâ… -â…¡, scheduled for selective lobectomy under left lateral decubitus position were randomly divided into A, B and C with 20 cases each. After induction of anesthesia, two lung ventilation(TLV) was performed with tidal volume (V_T)=10ml/kg, frequency(f)=12 breaths per minute (bpm), ratio of inspiratory to expiratory (I:E)was 1:2 at first; During OLV I:E was keep steady, V_T= 6ml/kg, f=20bpm were chosed in group A, V_T=8ml/kg,f=15bpm in group B, V_T=10ml/kg, f=12bpm in group C. Laboratory examination was determined before OLV and 10min, 20min, 30min after OLV, Q_S/Q_T and lung compliance(Cdyn) was calculated. Results:OLV have lower PaO₂(p<0.05), higher intrapulmonary shunt(p<0.05), higher airway pressure (p<0.05)and lower Cdyn (p<0.05) compaired with TLV; The decrease of PaO₂ was more in group A and C than that in group B(p<0.05). Regression equation of A, B, C three groups by means of P_ETCO₂ and PaCO₂ during OLV are y_A=13.886+0.768xA, yB=12.218+0.820xB, y_C=14.936+0.747x_C respectively. Coefficient of correlation are rA=0.793, rB=0.786, rC=0.790 respectively. Conclusion:During OLV, a better may be maintained with the ventilation parameter of V_T=8ml/kg and f=15bpm with less increase in Q_S/Q_T and higher arterial oxygenation and Cdyn. P_ETCO₂ are close correlated with PaCO₂ during one lung ventilation, PaCO₂ level can be reflex by P_ETCO₂ through dynamic overview, it is provided a species method for CO₂ monitoring.