Effects Of Two Kinds Of Lung Recruitment Maneuvers On Centre Venous Pressure In Newborn Piglets With Acute Lung Injury

Objective:1. To compare the effects of two lung recruitment maneuvers (RM) on gas exchange、hemodynamics in newborn piglets with acute lung injury (ALI), to investigate the feasibility, effectiveness, safety of the lung recruitment maneuvers;2. To investigate the relationship between the pressure and central venous pressure (CVP) along with the effects of growing positive end-expiratory pressure (PEEP)/mean airway pressure (mPaw) in lung recruitment maneuvers.Methods: All experimental animals were repeatedly lavaged by normal saline after anesthesia, intubation, ventilation. It is succeed in ALI modeling when the arterial oxygen pressure (PaO2) remained below100mmHg under the fraction of inspired oxygen (FiO2) being1.0for one hour. All experimental animals were randomly assigned to two groups: conventional mechanical ventilation (n=6) and high frequency oscillatory ventilation (n=6).Based on the smaller tidal volumes/low volume,we fully open the lung. In conventional mechanical ventilation (CMV) group,when the end‐tidal CO2pressure (PETCO2) decreased instead of increased,it points out that the lung were fully opened.Then treating the point of the dynamic compliance (Cdyn) becoming decrease as the closing pressure by the titration. Optimum PEEP was the addition of the closing pressure and2cmH2O. In high frequency oscillatory ventilation (HFOV) group, it is called optimal oxygenation that the PaO2/FiO2≥400mmHg under the FiO2less than0.6,which pointed out that the lung were fully opened. Also by the titration, treating the point as the closing pressure when PaO2/FiO2fell to400mmHg,which showed that a part of alveolar began to collapse. The addition of the closing pressure and2cmH2O was regarded as optimum Paw.After the lung recruitment maneuvers, readjusting the parameter of ventilation according to the outcome of arterial blood gas analysis. Dynamically observing elemental status、ALI0h、RM5min、RM1h、RM2h、RM3h and the gas exchange and hemodynamic indicators including heart rate (HR), pulse, oxygen saturation (SpO2), CVP, invasive arterial blood pressure, arterial blood gas analysis at the process of lung recruitments.Results:1. There was no significant difference between two groups in Weight, HR, mean artery blood pressure (MABP), CVP and oxygen index (OI) recorded at elemental status. There was also no significant difference between two groups as for the times of bronchoalveolar lavage, HR, MABP, CVP and OI at ALI0h.2.After lung recruitment maneuvers, optimum PEEP in CMV group was (9.67±1.51) cmH2O, open pressure (22.00±1.79) cmH2O; optimum mPaw in HFOV group was (16.33±1.51) cmH2O; open pressure (26.33±1.63) cmH2O.3. In CMV group, there was significant difference between HR, CVP, MABP recorded at elemental status and those recorded at ALI0h. It appeared in HFOV group as well. In the two group, there was significant difference between HR, CVP, MABP recorded at different time points and those recorded at elemental status within each group(P＜0.05).But it showed no significant difference between HR, CVP, MABP recorded at different time points and those recorded at ALI0h within each group. Among the parameters of the same time point in CMV group and HFOV group, the difference was not statistically significant.4.There was significant difference between OI at elemental status and that at ALI0h both in CMV group and HFOV group(P＜0.05).However, there was no significant difference between CMV group and HFOV group as for every parameter recorded at the same points. There was a positive correlation between OI values and ventilation time(in CMV group,r=‐0.850,p=0.00; in HFOV group, r=‐0.844, p=0.00). 5. HR and CVP was positively correlated with PEEP/mPaw both in CMV group and HFOV group(HR: in CMV group,r=‐0.729,p=0.00; in HFOV group, r=‐0.890, p=0.00.CVP: in CMV group,r=‐0.651,p=0.00; in HFOV group, r=‐0.681,p=0.00). With the increase of pressure, the HR/CVP augmented. Under condition of the same MAP, ranging from8to18cmH2O, there was no significant difference between the two groups as for HR. Under condition of the same MAP, ranging from20to22cmH2O, it showed significant difference between the two groups as for HR(P＜0.05).What is more, HR in CMV group was higher than that in HFOV group. When the CVP was8cmH2O, there was no significant difference between the two groups as for CVP. Under condition of the same CVP, ranging from10to22cmH2O, there was significant difference between the two groups as for CVP(P＜0.05). What is more, CVP in CMV group was higher than that in HFOV group. MABP had no correlation with PEEP/mPaw.Conclusions:1. In CMV group, the expansion pressure was (22.00±1.79)cmH2O, the optimum PEEP (9.67±1.51) cmH2O; in HFOV group, the expansion pressure was (26.33±1.63) cmH2O, the optimum mPaw (16.33±1.51) cmH2O.2.Two kinds of lung recruitment maneuvers can offer efficient improvement in oxygenation, but no remarkable effect on hemodynamics of the optimal PEEP/mPaw.3. During the process of RM, with the increase of PEEP/mPaw, HR and CVP also increased, but no change take place in arterial blood pressure.4. The impact of high frequency oscillation ventilation group on CVP and HR is smaller than conventional mechanical ventilation group under the same mean airway pressure.