Discussion On The Mechanism Of Lung Injury Induced By Invasive Ventilator In Newborn Rats And Clinical Study On The Application Of Non-invasive Ventilator In Premature Infants With Respiratory Distress Syndrome

Background:Invasive mechanical ventilator therapy is an important treatment for severe neonatal respiratory distress syndrome,which has saved countless newborns.But with its widespread use,the ventilation induced lung injury?VILI?has gradually attracted widespread attention.However,the specific mechanism of VILI is still unclear.Biological Injury may be the main cause of VILI.It refers to the accumulation of various inflammatory mediators and inflammatory cells in Lung tissues caused by improper mechanical stress.Activation of various signaling pathways leads to the release of various enzymes and inflammatory cytokines,A large number of inflammatory cytokines,including tumor necrosis factor-alpha?TNF??and interleukin 8?IL-8?,can induce or aggravate the inflammatory response of endothelial cells and epithelial cells,lead to these barrier dysfunction,and finally result in increased alveolar capillary permeability,non-cardiogenic pulmonary edema,Ventilator induced lung injury has been shown to be a decisive factor in the death of patients with respiratory distress syndromeNeonatal respiratory distress syndrome?NRDS?is a kind of respiratory disease of neonates,which is mainly manifested by progressive aggravation of dyspnea caused by immaturity of lungs and insufficient or complete lack of pulmonary surfactant at birth,It is more common in premature infants.The younger the gestational age,the lower the weight and the higher the incidence rate is,which is one of the main causes of neonatal death.Currently,the main treatment measures for this disease include:on the one hand,replacement therapy with pulmonary surfactant;on the other hand,respiratory support with ventilator to prevent alveolar atrophy and hypoxia,more than ever to use invasive ventilators,can significantly increase the survival rate of newborn babies,However,this method is easy to lead to a variety of serious complications,mainly lung injury,recently with the emergence of a variety of neonatal noninvasive ventilator,clinicians are more likely to use noninvasive ventilator,It can not only effectively improve the breathing and blood oxygen of infants,but also avoid all kinds of serious mechanical ventilator complications,but the noninvasive breathing pattern each have advantages and disadvantages,to seek the best mode is particularly important.Objective:On the one hand,we want to explore the mechanism of invasive ventilator induced lung injury in newborn rats and provide new direction and target for the prevention and treatment of ventilator related lung injury.On the other hand,the feasibility,safety and effectiveness of three non-invasive ventilation methods for the treatment of respiratory distress syndrome in premature infants were discussed,so as to find the best non-invasive assisted ventilation mode for neonates.Methods:1?We selected 40 SPF male newborn SD rats aged 7-14 days and randomly divided them into the sham operation group?trachea catheterization only,not ventilator ventilation?,the low-tide gas group?8ml/kg?and the high-tide gas group?three subgroups,tidal gas volumes of 20ml/kg,30ml/kg and 40ml/kg,respectively?.Newborn rats were sacrificed after 4 hours.During the experiment,the survival of the animals was observed,and indexes such as the ratio of wet/dry weight of lung tissue and the pathological score of lung injury were calculated to establish the most appropriate animal model of ventilator related lung injury in newborn rats.Then the most suitable model group?the final one was 30ml/kg?,low-tide gas volume group and sham operation group were selected to determine the changes of myeloperoxidase?MPO?,TNF alpha,il-8 and NAMPT in lung tissues in each group through Methods such as immunohistochemistry,western blotting and rna-seq.It was found that these factors were highly expressed.Since NAMPT had been reported as a potential marker of ventilator related lung injury,NAMPT inhibitor FK866 was proposed to pretreat newborn SD rats to see whether it had a protective effect on ventilator related lung injury.Specific methods:30 newborn SD rats were selected and randomly divided into the sham operation group,the H30 group?the most suitable model group?and the H30+FK866 group?FK866 10mg/kg intraperitoneal injection according to the literature?.The newborn rats were sacrificed 4 hours after the experiment,the wet/dry weight ratio of lung tissues and pathological score of lung injury were calculated.Changes in TNF alpha,il-8 and NAMPT levels in lung tissues of each group were detected by immunohistochemistry,western blotting.2?Premature infants with neonatal respiratory distress syndrome?NRDS?who were admitted to the neonatal intensive care unit of the first affiliated hospital of nanchang university from January 2016 to June 2019 were selected as subjects.It is further divided into two age groups by 32 weeks,which are less than 32 weeks and32 weeks to 36+6 weeks respectively.Each age group was randomly divided into three groups:NIPPV group?40 infants?,NHFO group?40 infants?and NCPAP group?40 infants?,NIPPV,NHFO and NCPAP interventions were performed in each group after the application of pulmonary surfactant?PS?.The time before the application of pulmonary surfactant?PS?was 0h,After PS was given,the infants in each group received NIPPV,NHFO or NCPAP respectively.PaO2,PaCO2,PaO2/FiO2 were measured at 0 hour,2hours,12 hours,24 hours and 48 hours after respiratory support.Other data were also collected,including duration of noninvasive ventilation,duration of oxygen therapy,the number of apnea events,need for reintubation and re-medication,conversion from noninvasive to invasive ventilation,duration of total gastrointestinal feeding,length of hospital stay,medical expenses and complications.3?Premature infants with severe neonatal respiratory distress syndrome who were admitted to the neonatal intensive care unit of the first affiliated hospital of nanchang university from January 2016 to June 2019 were selected as subjects.It is further divided into two age groups by 32 weeks,which are less than 32 weeks and 32 weeks to 36+6 weeks respectively,After birth,the patient needs invasive ventilator assisted ventilation.After birth,the patient is injected into the trachea with guersu and connected with invasive ventilator assisted ventilation.The invasive ventilation mode is ASSC,After treatment,the invasive ventilator was removed and numbered successively.According to the random number table,each age group was divided into3 groups,with 40 patients in each group.After extubation,NCPAP,NIPPV and NHFO were connected respectively for Assisted ventilation.Mean airway pressure before extubation?failure rate within 72 hours of extubation?the cause of the failed extubation?total oxygen therapy time?duration of invasive ventilation?duration of noninvasive ventilation?complications?gas leakage?abdominal distension?intraventricular hemorrhage?necrotizing enterocolitis of newborn?retinopathy of prematurity?ventilator associated pneumonia?neonatal bronchopulmonary dysplasia??duration of total gastrointestinal feeding?length of hospital stay and medical expenses in reach group were observed.Results:1?Establishment of neonatal rat lung injury model by spring tide volume mechanical ventilation and exploration of the mechanism of invasive ventilator induced lung injury in newborn rats:All the animals in the sham operation group?S?,low-tide gas group?L?and high-tide gas group?H20 and H30?survived.Six of the eight newborn rats in the H40group died during ventilation.Compared with S group,L group and H20 group,the wet/dry ratio of lung tissue and the pathological score of lung injury were significantly increased in the H30 group,and the difference between the H20 group and S group and L group was not obvious;Compared with the sham operation group and the low-tide operation group,the high-tide operation group was treated with 30m1/kg tidal air volume,and the brown staining of lung tissues was significant.The cumulative optical density value?IOD?was relatively high,and the difference was statistically significant?P<0.05?.TNF alpha,and il-8 protein levels were higher in rats treated with a tidal volume of30m1/kg in the high-tide group than in the sham group and the low-tide group.RNA-seq analysis found that the expressions of inflammatory factors such as IL6,IL8,IL16 and TNF alpha were significantly up-regulated after lung injury induced by tidal volume of 30m1/kg,Among them,the expression of NAMPT is most significantly up-regulated;Compared with the rats in the H30 group,the wet to dry ratio of the lungs in the H30+FK866 group was decreased,and the difference was statistically significant?P<0.05?.Compared with the sham group,there was no significant increase in the wet/dry ratio of the lung in the H30+FK866 group,and the difference was not statistically significant?P>0.05?.Compared with rats in the H30 group,rats in the H30+FK866group had normal lung tissue structure and no obvious inflammatory cell infiltration,and the pathological score was also significantly lower than that in the H30 group,with statistically significant difference?P<0.05?.Compared with the sham operation group,there was no significant difference in the pathological scores of the H30+FK866 group?P>0.05?.The lung tissues of rats in the H30+FK866 group showed lower chemotaxis of neutrophils,lower expression of inflammatory factors,and lower inflammatory degree.2?Comparison of basic data of the three groups of infants of all ages at the initial use and after extubation:The experimental data were all from the normal distribution,and there were no statistically significant differences?P>0.05?in the distribution of gestational age,gender,birth weight,apgar's score,mode of birth,and maternal prenatal status,as well as the comparison of invasive ventilator support time and mean airway pressure before extubation.3?Three noninvasive ventilation modes were used as initial treatment for respiratory distress syndrome in premature infants:Comparison of blood and gas results.After administration of PS and Non-invasive respiratory support,PaO₂ in all age groups was significantly increased after the application of pulmonary surfactant?PS?and Non-invasive respiratory support for 2h,12h,24h and 48h.Comparison of each time point at 2h,12h,24h and48h was statistically significant?P<0.05?;while PaCO₂ decreased in the three groups of the two age groups,In the layer of gestational age less than 32 weeks,PaCO₂ decreased less in the NCPAP group than in the other two groups,there were significant differences?P<0.05?,The decline of PaCO₂ was most obvious in the NHFO group,In the layer of gestational age of 32-36+6 weeks,At the time point of2h,the NHFO group was statistically significant compared with the NCPAP group,and there was no statistically significant difference between the three groups at other time points?P>0.05?;PaO₂/FiO₂ in all age groups was significantly increased,All age groups had statistically significant differences at different time points within the group?P<0.05?,Compared with the NCPAP group,the NIPPV group and the NHFO group showed significant improvement,with statistically significant difference?P<0.05?,while there was no significant difference between the NIPPV group and the NHFO group?P>0.05?;The comparison of treatment outcome.in the layer of gestational age less than32 weeks,total oxygen treatment time,non-invasive ventilation time,hospital stay time and total gastrointestinal feeding time were shorter in the NIPPV group and the NHFO group than in the NCPAP group,with statistically significant differences?P<0.05?,the incidence of apnea,probability of reintubation,and hospitalization costs of the NIPPV group and the NHFO group were lower than those of the NCPAP group,with statistically significant differences?P>0.05?,while there was no significant difference between the NIPPV group and the NHFO group?P>0.05?.The number of infants repeatedly using pulmonary surfactant?PS?showed no statistically significant difference among the three groups?P>0.05?.In the layer of gestational age of32-36+6 weeks,the occurrence of apnea,total oxygen treatment time,non-invasive ventilation time,hospitalization time,total gastrointestinal feeding time,the number of children repeatedly using pulmonary surfactant,and hospitalization costs of the three groups were not statistically significant?P>0.05?;The comparison of complications.in the layer of gestational age less than 32weeks,The incidence of bronchopulmonary dysplasia?BPD?,retinopathy of prematurity?ROP?,gas leakage and abdominal distension?all children in the three groups were given indwelling gastric tube to reduce abdominal distension?was significantly higher in NCPAP group than in NIPPV group and NHFO group,with statistical significance?P<0.05?.No significant difference was found in the other complications in three groups,with no statistical significance?P>0.05?.In the layer of gestational age of 32-36+6 weeks,all the complications in the three groups showed no significant difference,with no statistical significance?P>0.05?.4?Three noninvasive ventilation modes were used for sequential treatment of severe preterm respiratory distress syndromeThe comparison of treatment outcome.in the layer of gestational age less than 32weeks,compared with NIPPV group and NHFO group,the incidence of extubation failure at 72 hours,time of non-invasive ventilator ventilation and total time of oxygen use in NCPAP group were significantly increased,with statistically significant differences?P<0.05?,there was no statistically significant difference in the use time of invasive ventilator among the three groups?P>0.05?.In the layer of gestational age of 32-36+6 weeks,there was no significant difference between the three groups in failure rate of extubation at 72 hours,time of non-invasive ventilator ventilation,time of total oxygen use,and time of total invasive ventilator use?P>0.05?;The comparison of treatment results and related complications,in the layer of gestational age less than 32 weeks,results of total gastrointestinal feeding time,number of apnea,length of stay,and hospitalization costs showed significant higher in NCPAP group than NIPPV group and NHFO group?P<0.05?,the incidence of bronchopulmonary dysplasia?BPD?,retinopathy of prematurity?ROP?,gas leakage and abdominal distension?all infants in the three groups were given indwelling gastric tube to reduce abdominal distension?showed that the incidence of NCPAP group was significantly increased,compared with NIPPV group and NHFO group,which was statistically significant?P<0.05?,there was no difference between the NIPPV group and the NHFO group.Other complications?NEC,nasal injury,ventilator associated pneumonia,IVH?were not significantly abnormal in the three groups,showing no statistical significance?P>0.05?.In the layer of gestational age of 32-36+6 weeks,all the complications in the three groups showed no significant difference,with no statistical significance?P>0.05?.Conclusion:1?During the establishment of invasive ventilator induced lung injury model in newborn rats,mechanical ventilation with tidal air volume of 30m1/kg was used to establish the ventilator induced lung injury model.During the course of lung injury in newborn rats,the expression of NAMPT in lung tissues was significantly up-regulated,and the treatment of rats with NAMPT inhibitor could significantly reduce ventilators induced lung injury in newborn rats.Therefore,NAMPT may be an important target for the treatment of ventilators related lung injury in the future.2?Three non-invasive ventilation modes?NCPAP,NIPPV,and NHFO?combined with pulmonary surfactant?guersu?for the treatment of neonatal respiratory distress syndrome have good therapeutic effects,which can quickly correct hypoxemia and improve the respiratory and pulmonary oxygenation function of the infants.3?NIPPV and NHFO can significantly improve pulmonary oxygenation function in a short period of time,clinical symptoms of infants can be alleviated.Meanwhile,they can shorten non-invasive ventilation time,oxygen treatment time,hospitalization time and hospitalization costs.Therefore,for infants with small gestational age and weak spontaneous breathing,they have more therapeutic advantages over NCPAP.4?Infants with NIPPV and NHFO have less abdominal distension,and the whole gastrointestinal feeding time can be achieved as soon as possible,which is conducive to the recovery of gastrointestinal function,thereby reducing the corresponding complications of long-term intravenous nutrition,Reducing hospitalization time and expenses.5?NHFO is a new and effective non-invasive ventilation mode,which can rapidly improve the oxygenation of neonates with respiratory distress syndrome and effectively remove carbon dioxide with few side effects.Therefore,it is worth promoting.6?All three non-invasive ventilation modes?NCPAP,NIPPV,and NHFO?can be used for the initial treatment of neonatal respiratory distress syndrome and sequential treatment after the extubation of invasive ventilation.For newborns with small gestational age and weak spontaneous breathing,NIPPV and NHFO have stronger advantages over NCPAP,They have good efficacy and safety.