| ObjectiveTo establish the model of seawater respiratory distress syndrome (SW-RDS) in canine and investigate the effect of pressure-controlled ventilation and inhaled nitric oxide on respiratory function in SW-RDS.MethodsPART ONE12 normal hybrid dogs were randomly assigned into controlgroup(group C, n=4) and models group(group S, n=8).All animalswere received mechanical ventilation in the intermittent postitive pressure ventilation mode with the application of positive end-expiratory pressure(5cmH2O) after general anaesthesia and trachea intubatton.The parameters of ventilation in the two groups werealike (the fraction of inspired oxygen=50%, tidal volume=10 ~ 15mL/kg, respiratory rate=20breaths/min).The seawater(10mL/kg) were infused into the lungs of models animals twice .pH, arterialoxygen partial pressure(PaO2),arterial carbon dioxider partial pressure (PaCO2), lactic(LAC),oxygen saturation(SaO2), mean arterial pressure(MAP),heart rate(HR),central venous pressure(CVP),mean pulmonaryartery pressure(MPAP) ,pulmonary artery wedge pressure (PAWP) ,andthe concertration of lactic dehydrogenase (LDH-L) and alkaline phosphatase(ALP) in bronchoalveolar fluid (BAF) and blood were measured at 0min(T0),15min(Tl),30min(T2), lh(T3),2h(T4),3h(T5), 4h(T6) after treatment. PaO2/FiO2 ratio was calculated. And the lung pathology was assessed at the end of the trial.PART TWO18 normal hybrid dogs were randomly assigned into control group(group A,n=6),PCV group(group B,n=6) and inhaled nitric oxide(NO) group(group C,n=6).The models of SW-RDS were regarded successful when PaO2/FiO2 ratio was less than 200mmHg and PAWP was less than 18mmHg after seawater were infused. The lower inflextion point (LIP) was determined on a static pressure-volume (PV) curve in all animals,and the airway pressure in LIP was recorded to assess the best PEEP.The control group animals were received mechanical ventilation in the intermittent postitive pressure ventilation mode with the application of positive end-expiratory pressure (PLIP+3cmH2O). The PCV group animals were received mechanical ventilation in the pressure-controlled mode with PEEP(PLIp +3cmH2O) and the inhalation of 5ppm NO was additionally given in the inhaled NO group animals.The fraction of inspired oxygen was 50% in allanimals. pH, PaO2,PaCO2, LAC,SaO2, MAP,HR,CVP, MPAP andPAWP were measured at 0min(T0), 30min(Tl), lh(T2), 2h(T3), 3h(T4), 4h(T5) after treatment. PaO2/FiO2 ratio was calculated.And the lung pathology was assessed at the end of the trial.ResultsPART ONEpH, PaO2, PaCO2, SaO2 in models animals changed quickly to astable level after seawater instillation.LAC,LDH-L and ALP in blood and ALP in bronchoalveolar fluid increased significantly. PaO2/FiO2 ratio was very less than 200mmHg 30min after treatment in modeles animals. In models group,obvious lung tissue injury was observed under optical microscope after seawater perfusion. Observation with electron microscope revealed injury to type II alveolar epithelial cells,broadened respiratory mucosa,and platelet adherence.PART TWOIn group B and C,the values of MAP and HR were more than that in group A after treatment.pH,PaO2 and LAC were significantly better in group B and CAfter 2 hours of treatment, pH,PaO2 and LAC in group C were still better than those in group B. PaO2/FiO2 ratio was more than 200mmHg in group B and C from T1 to T5 and increased timely ,while that was very less than 200mmHg in group A.The inflammatory response in group B and C seemed less than that in group A from pulmonary pathology.Conclusion1.The stable SW-RDS model in canine may be established by seawater instillation twice through bronchial microscope supported with mechanical ventilation.2.Pressure-controlled mode may be helpful to respiratary function and keep stable hemodynamic during SW-RDS in canines.3.Conbined with inhaled NO may be more effective than that ofpressure-controlled mode only.4.Pressure-controlled ventilation and combined with inhaled nitric oxide can't improve the pul... |
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