The Effect Of Lung Recruitment Maneuvers On Arterial Oxygenation And Dynamic Compliance During One Lung Ventilation

Objective：To study the effect of lung recruitment maneuvers on arterial oxygenation anddynamic compliance during one lung ventilation. Try to definitude the duration ofonce LRM and proper frequency to do LRM.Methods:Forty patients with ASA status I-II undergoing elective open thoracotomy wererandomly allocated to two groups, aged18to70years, including male18andfemale22. Intravenous pathway was established after patient taken into operatingroom. Blood pressure, ECG, pulse oximetry were monitored. A catheter wasinserted in the radial artery of nondominant hand for invasive arterial pressuremonitoring under local anesthesia. After induction of anesthesia, a double-lumentube（DLT） of the appropriate size was intubated. After intubation, two lungs wereventilated until the patient was switched to lateral position. Control group:ventilation with6-8ml/Kg tidal volume and5cmH₂O PEEP for OLV. LRM group:same ventilator pattern with controlled group, do LRM once after20minutes ofOLV. Before performing the strategy, the ventilator was switched to pressurecontrol ventilation, adjusting the level of pressure to obtain the same tidal volumethat the patient was receiving during volume control ventilation. This wasmaintained for3minutes. Then Pip and PEEP were increased stepwise from25/5to30/10, and finally35/15cmH₂O. Every level of pressure was maintained during1minute. The difference of Pip-PEEP was limited to20cmH₂O to avoid high tidalvolume during LRM, and then the parameter was set to the original level20/5cmH₂O for1minute. After that the ventilator was set back to volume control.Before closure of thorax, the LRM group was applied for LRM, and the controlledgroup was re-expanded by a routine sustained inflation. Vital signs and artery blood samples were recorded at baseline（T₀），20minutes after OLV（T₁）,15minutes（T₂）、30minutes（T₃）、45minutes（T₄） after LRM respectively, and thebeginning of DLV. Pulmonary dynamic compliance was calculated.Results:Compared with control group, the PaO₂of LRM is higher at T2，T3，T5,respectively（204±20）,（175±14），（473±15）mmHg in LRM group, and（149±11）,（154±12）,（442±19）mmHg in the controlled group. The dynamiccompliance of LRM at T2and T5[（24.8±2.7）and（30±4）ml cm H₂O-1] is betterthan controlled group[（20±3）and（25.9±2.5）ml cm H-2O1].Conclusions:LRM can improve arterial oxygenation and dynamic compliance during onelung ventilation, the duration of one LRM is about30-45min. LRM is better thanthe routine sustained inflation.