Effects Of End-inspiratory Pause On Respiratory Function During One-lung Ventilation For Thoracic Surgery

Objective: To examine the effects of end-inspiratory pause (EIP) of different durations on pulmonary mechanics,pulmonary ventilation and gas exchange during one-lung ventilation (OLV) for thoracic surgery. Methods: 36 patients undergoing elective pulmonary resection,ASA gradeâ… ~â…¡.After anesthesia induction, a left-sided double-lumen endotracheal tube was intubated. Keeping all the following ventilatory parameters constant: FIO2,TV,RR,I:E during one-lung ventilation in the lateral decubitus position After OLV with 0% EIP 20 min,three levels of EIP (5%,10%,30%) were applied to the dependent lung in random order. At the same time respiratory parameters and blood gases were measured 20 min after every level of EIP was administered.Result: Comparing with two-lung ventilation (TLV),Peak inspiratory pressure (PIP),average in airway pressure (PAW), airway resistance(RAW)and pulmonary shunt fraction(Qs/Qt)were significantly increase and dynamic compliance (CDYN) show significantly decrease with different levels of EIPï¼›CDYN increased significantly when two levels of EIP(10%,30%)were administered comparing with 0% EIP(P<0.05),PIP decreased on the contary(10% and 30%).At the same time,dead space/tidal volume ratio (VD/VT) was significantly decreased(30%,P<0.05).Altering the duration of EIP from 0% to 30% resulted in a significant decrease in PaCO2(P<0.05) and a slight increase in PaO2,Qs/Qt showed no significant change. Conclusion: In normal lung during OLV,EIP can help to improve CDYN and reduce dead-spaceï¼›Qs/Qt is not affected by EIP,extending EIP without inducing a clinically significant increase in arterial oxygenation but enhances CO2 elimination.