Different Effects Of Three Recruitment Maneuvers On The Heterogeneity Of Lung Gas Distribution In Acute Respiratory Distress Syndrome

Different Effects of Three Recruitment Maneuvers on the Heterogeneity of Lung Gas Distribution in Pigs with Acute Respiratory Distress SyndromeObjective:Acute respiratory distress syndrome (ARDS) is the most common syndrome in intensive care unit which requires mechanical and characterized by smalled-aerated lung region, called baby lung and heterogeneous distribution of alveolar collapse across all lung regions. Since the introduction of this disease almost 50 years ago, the mortality has been slightly but consistently improved, but the survival rate is still as low as 59.1%. Lung recruitment is the manuver which could open the lung and improve gas exchange, especially oxygenation. But lung recruitment open the atelectatic lung regions accompanied by overinflation of other lung regions at the same time. In order to develop this strategy, it is importment to monitor the regional ventilation distribution. Previous researches focus on the effect of lung recruitment on gas exchange and hemodynamics, no study explores the influence on regional venlation distribution.In this study, we expect to find out a kind of recruitment manuver that can make the lung more homogeneous.Material and methods:Ten healthy male pigs weiging 50.28 ± 1.15 kg were mechanically ventilated with volume-control at a tidal volume (VT) of 6 mL/kg, a respiratory rate of 20 breaths/min, a fraction of inspired oxygen (FiO2) 0.4, a inspiration-to-expiration time ratio (I:E) of 1:2 and PEEP 5 cmH2O and mark the situations TBaseline. ARDS was then induced by bilateral lung lavages with 30 ml/kg of isotonic saline (38℃). After that increase the FiO2 to 1.0, and mark the situations TARDS. Three lung recruitment manuvers including sustain inflation, (SI); increments of PEEP (IP) and pressure control ventilate (PCV) were performed. We use electrical impedance tomography(EIT) to monitor the gas distrubution and define four same-size contiguous regions of interests from up and down of the imaging field as regional of intreast ROI1,ROI2,ROI3, and ROI4. Then, from offline analyses of average raw EIT data of selected ten representative tidal breaths, we measured the following data:global inhomogeneity (GI) index, detal end-expiratory lung impedance(AEELI) and regional compliance(RC). Gas exchange, respiratory mechanics, hemodynamic and gas distribution parameters were measured and recorded at the following time periods: TBaseline, TaRDS, before and 3 minutes after each lung recruitment manuver.Statistical differences were evaluated by means of one-way ANOVA.Results:(1)General condition:ARDS was successfully induced by repeated bronchoalveolar lavages (2.8±1.03 times) in all 10 pigs (body length 117.5±1.65cm and body weight 50.28±1.45kg).(2)The effect of lung recruitment maneuvers on gas exchange:All maneuvers improved P/F (P/FPreSI 81.62±22.36mmHg vs P/FpostSI 145.84±26.87 mmHg, p=0.000, P/FpreIP 78.22±24.28mmHg vs P/FpostIP 167.98±36.85mmHg, p=0.000, P/FprePcv 77.54+ 24.69mmHg vs P/FpostPCV 155.83±50.85mmHg, p=0.000). Compared to the former condition, PaCO2 and pH of Tpost did not change too much.(3)The effect of lung recruitment maneuvers on gas distribution:GIpostRM decrease significantly compared with GIpreRM (GIpreSI 0.55±0.14 au vs GIpostSI 0.42±0.040 au, p=0.000; GlpreIP 0.62±0.19 au vs GIpostIP 0.42±0.07 au, p=0.000; GIprepCV 0.60±0.09 au vs GlpostPCV 0.44±0.05 au, p=0.0000). After all the lung recruitment maneuvers, △ EELI increased significantly in comparison to TARDS across all lung regions. After lung recruitment maneuvers, there were no significantly differences between three lung recruitment maneuvers.(4)The effect of lung recruitment maneuvers on static compliance and regional compliance:CrspostRM increased in comparison to CrSpreRM(p< 0.001). After all the lung recruitment maneuvers, regional compliance of ROI1,2 did not change, the RC of ROI3 increased significantly, and RC of ROI4 decreased significantly. During all the lung recruitments, Crs and RC of ROI1-4 in post RM did not differ from each other.(5)The effect of lung recruitment maneuvers on hemodynamic:Heart rate(HR), mean arterial pressure(MAP), central venous pressure(CVP), cardic output(CO) and pulmonary arterial wedge pressure(PAWP) did not change significantly with introduction of three lung recruitment maneuvers.Conclusion:These results suggested that lung recruitment manuvers improve oxygention and heterogeneous distribution of ARDS. It is better to use PCV when you want to improve the regional compliance.Different Effects of Three Recruitment Maneuvers on the Heterogeneity of Lung Gas Distribution in Patients with Acute Respiratory Distress SyndromeObjective:The acute respiratory distress syndrome (ARDS) is an important cause of acute respiratory failure that is often associated with multiple organ failure. ARDS is characterized by smalled-aerated lung region, called baby lung and heterogeneous distribution of alveolar collapse across all lung regions. Since the original description of ARDS in 1967, considerable progress has been made in understanding the pathogenesis and pathophysiology of acute lung injury, but the survival rate is still as low as 59.1%. Lung recruitment is the maneuver which could open the lung and improve gas exchange, especially oxygenation. But lung recruitment open the atelectatic lung regions accompanied by overinflation of other lung regions at the same time. It is important to monitor the regional ventilation distribution. Previous researches focus on the effect of lung recruitment on gas exchange, no study explores the influence on regional venlation distribution. In this study, we expect to find out a kind of recruitment manuver that can make the lung more homogeneous.Material and methods:Forty-one mechanically ventilated patients with ARDS were included in the study. These patients were mechanically ventilated with volume-control at a tidal volume (VT) of 4-6 mL/kg, a respiratory rate less than 20 breaths/min, fraction of inspired oxygen (FiO2) and PEEP titrated according to ARDSnet and mark the situation TBaseline. Three lung recruitment manuvers including sustain inflation (SI); increments of PEEP (IP) and pressure control ventilate (PCV) were performed randomly. After lung recruitment. PEEP were adjusted to the Tbasline. After each of lung recruitment manuvers, we exam the gas change to make sure that the lung recruitment manuvers have been maximum-recruitment. We use electrical impedance tomography(EIT) to monitor the gas distrubution and define four same-size contiguous regions of interests from up and down of the imaging field as regional of intreast ROI1,ROI2,ROI3, and ROI4. Then, from offline analyses of average raw EIT data of selected ten representative tidal breaths, we measured the following data:global inhomogeneity (GI) index, detal end-expiratory lung impedance(△EELI) and regional compliance(RC). Gas exchange, gas distribution, respiratory mechanics and hemodynamic parameters were measured and recorded at the following time periods: TBaseline, TARDs, before and 3 minutes after each lung recruitment manuver. Statistical differences were evaluated by means of one-way ANOVA.Results:(1)General Information:Forty-one ARDS patients were recruited in the study from March 2014 to June 2015 with the age of 69 ±15.01 years old, APACHE Ⅱ 19.28± 5.46. Among adults with ARDS, the proportion who had ARDS ranged from 51.2% for mild,43.9% for moderate and 4.8% for severe.(2)Effects of lung recruitment manuvers on gas change:All the manuvers improve P/F (P/FpreSI202.26±58.08mmHg vs P/FpostSI325.69±95.82mmHg, p=0.000, P/F preIP 210.63±58.85mmHg vs P/FpostIP±338.02±80.96mmHg, p=0.000, P/FprePCV202.44± 53.89mmHg vs P/FpostPCV 319.50±90.57mmHg, p=0.000) without change of PaCO2.(3)Effects of lung recruitment manuvers on gas distrbution:In comparison with baseline across all lung regions △EELI increased and GI decreased (GIpreSI0.53± 0.13au vs GIpostSI0.45±0.12 au, p<0.01, GIpreIP 0.51±0.20 au vs GIpostIP 0.45±0.11 au, p<0.05,GIprePCV 0.52±0.13 au vs GIpostPCV 0.43±0.09 au, p<0.01).(4)Effects of lung recruitment manuvers on static compliance and RC:Static compliance was significantly increased after all the lung recruitment maneuvers (p< 0.001). PCV improve the regional compliance of ROI3 significantly (p<0.05).(5)Effects of lung recruitment manuvers on hemodynamic:There were no significant differences in heart rate(HR), mean arterial pressure(MAP), central venous pressure(CVP), cardic output(CO) and pulmonary arterial wedge pressure(PAWP) between before and after lung recruitment manuvers.Conclusion:These results suggested that lung recruitment manuvers improve oxygention and gas distribution of ARDS. PCV seems to improve regional compliance in ROI3.