Objective To evaluate the effectiveness of Percu Twist (PT) tracheostomy comparing with that of operative tracheostomy(OT)in intensive care unit(ICU). Methods Related data were retrieved from CBM,CNKI,Wanfang Data,VIP,PubMed,EMBASE,CENTRAL,and Web of Science from the time of their establishment to May 15th 2014,and the data of randomized controlled trials(RCTs)concerning PT and OT were selected. The risk of bias assessment and data extraction were performed by two independent reviewers. Meta analysis was conducted using RevMan 5.2 software. Results A total of 12 RCTs were identified,and 893 patients in ICU were involved. The results of Meta-analysis showed that PT could significantly shorten the operation time〔mean difference (MD)=-15.11,95% confidence interval(95%CI)=-17.14 to -13.07,P<0.000 01〕,reduce the volume of blood loss(MD=-17.59,95%CI=-21.90 to-13.28,P<0.000 01),reduce the size of incision(MD=-2.20, 95%CI=-2.57 to -1.82,P<0.000 01),shor ten the time of healing(MD=-3.60,95%CI=-4.15 to -3.05, P<0.000 01),and reduce complications such as infection of the wound〔odds ratio(OR)=0.20,95%CI=0.10-0.44,P<0.000 1〕and cutaneous emphysema/mediastinal emphysema(OR=0.22,95%CI=0.10-0.47,P<0.000 1)compared with OT group. The funnel plot suggested that publication bias might be found among 12 researches. Conclusions PT was shown to be more effective than OT in ICU with lower incidence of complications. As number of RCT cases is still small with unsatis factory quality,further clinical use is warranted for a better assessment.

Objective To investigate the significance of optimization of bedside Gram staining of sputum smear in the early diagnosis and antimicrobial treatment for ventilator-associated pneumonia(VAP)patients. Methods The data of patients with VAP undergoing mechanical ventilation over 48 hours in the Department of Critical Care Medicine of Tianjin Fourth Central Hospital from June 2009 to June 2014 were analyzed. The patients were divided into two groups according to whether or not bedside Gram staining of sputum smear was used or not. The sputum samples from lower respiratory tract of all VAP patients were collected daily with tracheal catheter. In empirical examination group(from June 2009 to December 2011,n=43),the patients received antibiotics at the time of onset of VAP, selection of antibiotics depended on the information of bacterial epidemiology of the intensive care unit(ICU),and also existence of high risk factors of multi-drug resistant bacteria. In target treatment group(from January 2012 to June 2014,n=43),the patients received antibiotics according to the results of bedside instant sputum smear examination and empirical antibiotic regime. The correlation between the results of sputum smear examination and culture result was analyzed. The levels of body temperature,white blood cell(WBC)count,procalcitonin(PCT)level,and high sensitivity C-reactive protein(hs-CRP)were measured on the 1st day and 3rd day. The length of antibiotics treatment, duration of mechanical ventilation,and the time of ICU stay were recorded for both groups. Results There were 512 qualified sputum specimens for culture,from which 336 pathogens were found,and 358 strains of pathogenic bacteria were found from microscopic examination of 512 qualified sputum smear. The coincidence rate of results of bedside examination of sputum smear and that of sputum culture was 78.32%(401/512). The diagnostic acumen of the former was 85.42%(287/336),specificity was 64.77%(114/176),positive predictive value was 80.17%(287/358),and negative predictive value was 74.03%(114/154). On the 1st day,no statistical differences in infection index between the two groups could be found,but on the 3rd day,the results were significantly improved in both groups. Compared with the empirical treatment group,the body temperature,WBC,PCT and hs-CRP in the target treatment group were significantly lower〔body temperature(℃):36.83±0.69 vs. 37.64±0.71,WBC(×109/L):7.91±2.75 vs. 9.66±3.39,PCT(μg/L):7.14±3.89 vs. 10.14±4.32,hs-CRP(mg/L):12.24±6.28 vs. 15.54±5.94,P<0.05 or P<0.01〕. Compared with the empirical treatment group,the time of antibiotics use(days:6.00±2.55 vs. 9.20±3.46), the duration of mechanical ventilation(days:5.00±1.73 vs. 7.00±1.94),and the length of ICU stay(days:7.43±1.72 vs. 12.57±4.16)were significantly shortened(P<0.05 or P<0.01). Conclusions The results of bedside sputum examination and sputum culture showed a good correlation,and the former is helpful in early diagnosis and treatment of VAP. The result of high quality sputum smear in significant in guiding the first choice of antibiotics,reduce the time of antibiotic use,shorten the duration of mechanical ventilation and the length of ICU stay,and improve the outcome of the patients.

Objective To investigate the prevalent condition of endotracheal cuff pressure and risk factors for under inflation. Methods A prospective cohort study was conducted. Patients admitted to the Department of Critical Care Medicine of Fuxing Hospital Affiliated to Capital Medical University,who were intubated with a high-volume low-pressure endotracheal tube,and had undergone mechanical ventilation for at least 48 hours,were enrolled. The endotracheal cuff pressure was determined every 8 hours by a manual manometer connected to the distal edge of the valve cuff at 07:00,15:00,and 23:00. Measurement of the endotracheal cuff pressure was continued until the extubation of endotracheal or tracheostomy tube,or death of the patient. According to the incidence of under inflation of endotracheal cuff,patients were divided into the incidence of under inflation lower than 25%group(lower low cuff pressure group)and higher than 25% group(higher low cuff pressure group). The possible influencing factors were evaluated in the two groups,including body mass index(BMI),size of endotracheal tube,duration of intubation,use of sedative or analgesic,number of leaving from intensive care unit(ICU),the number of turning over the patients, and aspiration of sputum. Logistic regression analysis was used to determine risk factors for under-inflation of the endotracheal cuff. Results During the study period,53 patients were enrolled. There were 812 measurements,and 46.3%of them was abnormal,and 204 times(25.1%)of under inflation of endotracheal cuff were found. There were 24 patients(45.3%)in whom the incidence of under inflation rate was higher than 25%. The average of under inflation was 7(4,10)times. Compared with the group with lower rate of low cuff pressure,a longer time for intubation was found in group with higher rate of low cuff pressure〔hours:162(113,225)vs. 118(97,168),Z=-2.034,P=0.042〕. There were no differences between the two groups in other factors,including size of endotracheal tube,the time from intubation to first measurement of endotracheal cuff pressure,number of leaving from ICU during admission, use of sedative agent or analgesic,and the number of body turning and aspiration(all P>0.05). No risk factor was found resulting from under inflation of the endotracheal cuff by logistic regression analysis. No significant difference was found in the incidence of ventilator associated pneumonia,duration of mechanical ventilation,successful rate of weaning on 28th day,or 28-day mortality after weaning from mechanical ventilation,and ICU mortality between the two groups. However,patients in the group of higher rate of low cuff pressure had a longer ICU stay compared with that in the group of lower rate of low cuff pressure group〔days:13(8,21)vs. 10(6,18),Z=-2.120,P=0.034〕. Conclusions Abnormal endotracheal cuff pressure is common in critically ill patients with intratracheal intubation. Duration of intubation is associated with under inflation of the cuff,and it calls for strengthening monitoring and management.

Objective To evaluate the role of Toll-like receptor 2/nuclear factor-κB(TLR2/NF-κB)signaling pathway pretreatment in ventilator-induced lung injury(VILI). Methods Thirty male Sprague-Dawley(SD)rats were randomly divided into three groups by using random number scale,with 10 rats in each group. Group A:rats were given 200μL of TLR2 monoclonal antibodies(TLR2mAb,10μg/kg)by slow instillation through tracheal catheter, and then ventilated with a high tidal volume(VT)of 40 mL/kg. Group B:ventilated with a normal VT of 8 mL/kg. Group C:rats were tracheally instilled with 10 μg/kg of TLR2mAb devoid of biologic activity,and then ventilated with a high VT of 40 mL/kg. The rats were mechanically ventilated for 4 hours,the lung wet to dry weight ratio(W/D)was calculated. The changes in pathology and ultrastructure in lung tissue were observed with microscope. Enzyme linked immunosorbent assay(ELISA)was performed to determine the concentration of interleukins(IL-1β,IL-6)and tumor necrosis factor-α(TNF-α)in serum and brconchoalveolar lavage fluid(BALF). Real-time fluorescent quantitation reverse transcription-polymerase chain reaction(RT-PCR)was used to assess the mRNA expressions of TLR2, NF-κB and myeloid differentiation factor 88(MyD88)in lung tissue. Results No obvious pathological changes in lungs were found in group A and group B,and no obvious damages to ultra-microstructure were found in lung macrophages, typeⅠepithelial cell and typeⅡepithelial cell. In group C,pathological changes were observed,including pulmonary alveoli fusion,alveoli septum thickening,inflammatory cells infiltration,and damages to ultrastructure of lung macrophage,damage to cell membrane of typeⅠepithelial cells and typeⅡepithelial cells,vacuoles in cytoplasm, damage to organelle,and even pyknosis and perinuclear cistern thickening. Compared with group C,W/D ratio and mean concentration of inflammatory cytokines in serum and BALF showed a significant decrease in group A and B〔W/D ratio:1.151±0.026,1.128±0.048 vs. 1.403±0.062;concentration of IL-1βin serum(ng/L):37.05±5.61, 34.52±4.31 vs. 51.45±8.18;concentration of IL-6 in serum(ng/L):53.65±5.16,55.77±5.62 vs. 89.96±7.08;concentration of TNF-αin serum(ng/L):71.93±13.29,67.36±11.42 vs. 96.20±11.60;concentration of IL-1βin BALF(ng/L):56.48±6.16,54.44±7.26 vs. 99.77±8.41;concentration of IL-6 in BALF(ng/L):172.44±21.26, 163.47±18.70 vs. 216.22±23.90;concentration of TNF-α in BALF(ng/L):235.81±42.75,231.72±40.38 vs. 374.85±69.61,all P<0.01〕,but there were no significant differences between group A and group B(all P>0.05). The mRNA expressions of TLR2,MyD88,and NF-κB were significantly decreased in group A and group B compared with those in group C〔TLR2 mRNA(2-ΔΔCt):1.021±0.287,0.938±0.196 vs. 3.862±0.871;MyD88 mRNA (2-ΔΔCt):1.235±0.277,1.300±0.306 vs. 3.618±1.107;NF-κB mRNA(2-ΔΔCt):0.519±0.036,1.043±0.170 vs. 20.280±9.466,P<0.05 or P<0.01〕,but there was no significant difference among the parameters mentioned above between group A and B(all P>0.05). Conclusion To some extent,pre-intervention with TLR2mAb to block the TLR2/NF-κB signal pathway can inhibit the release of pro-inflammatory factors,and regulate the VILI.

Objective To observe the changes in forkhead/winged helix transcription factor p3(Foxp3), regulatory T cells(Treg),retinoid-related orphan receptor gamma(RORγt)in rat model of chronic obstructive pulmonary disease(COPD). Methods Twenty Sprague-Dawley(SD)rats were randomly divided into normal control group and COPD model group,with 10 rats in each group. The COPD model was reproduced by smoke inhalation and tracheal instillation of lipopolysaccharide(LPS),and no such treatment was conducted in normal control group. Twenty-eight days after the model reproduction,the pulmonary function was determined,the pathological changes of lung tissue were observed with haematoxylin-eosin(HE)staining,interleukins(IL-6,IL-10)in serum were detected by enzyme-linked immunosorbent assay(ELISA),CD4+CD25+Foxp3+Treg of peripheral blood was determined by flow cytometry,and the expressions of Foxp3,RORγt,IL-17 protein in lung tissue were assayed by Western Blot. Results Under light microscope,significal interstitial infiltration of inflammatory cells was found in alveoli and interstitial tissue of the lung,and destruction of alveolar tissue,alveolar wall thinning,and even rupture to fuse into bullae,and bleeding into alveoli in different degress could be observed. Compared with the normal control group,forced vital capacity(FVC),forced expiratory volume in 0.3 second(FEV0.3),FEV0.3/FVC,peak expiratory flow(PEF)in model group were significantly decreased〔FVC(mL):8.04±2.03 vs. 9.97±2.14,FEV0.3(mL):6.16±2.23 vs. 8.84±2.12,FEV0.3/FVC:0.70±0.09 vs. 0.85±0.11,PEF(mL/s):33.56±4.76 vs. 40.14±5.64, P<0.05 or P<0.01〕. Serum IL-6 was obviously increased(ng/L:93.17±20.96 vs. 76.28±13.24,P<0.05), IL-10 was significantly decreased(ng/L:78.62±15.17 vs. 104.34±19.46,P<0.01),and CD4+CD25+FoxP3+Treg was significantly diminished〔(2.75±0.83)% vs.(4.16±1.14)%,P<0.01〕in model group compared with those in the normal control group. The expression of Foxp3 protein in lung tissue in model group was significantly down-regulated compared with that in the normal control group(gray scale:0.38±0.15 vs. 0.63±0.11,P<0.01), and RORγt and IL-17 protein expressions were significantly up-regulated〔RORγt(gray scale):0.96±0.23 vs. 0.47±0.11,IL-17(gray scale):1.02±0.24 vs. 0.34±0.08,both P<0.01〕. Correlation analysis showed that FEV0.3 was positively correlated with Foxp3(r=0.585,P<0.05),and FEV0.3/FVC was negatively correlated with IL-6 and RORγt(r=-0.655,r=-0.607,both P<0.05). PEF was positively correlated with Treg(r=0.573, P<0.05),and negatively correlated with IL-17(r=-0.198,P<0.05). IL-6 was negatively correlated with Foxp3(r=-0.603,P<0.05),and positively correlated with RORγt(r=0.588,P<0.05). IL-10 was positively correlated with Treg(r=0.573,P<0.05). Treg was positively correlated with Foxp3(r=0.607,P<0.05), and negatively correlated with IL-17(r=-0.569,P<0.05). Foxp3 was negatively correlated with RORγt(r=-0.591, P<0.05). RORγt was positively correlated with IL-17(r=0.578,P<0.05). Conclusion There is a relationship among decreased pulmonary function,inflammation and imbalance of Foxp3/Treg and RORγt/Th17 in COPD.

Objective To investigate the expression of serum microRNA-210 (miR-210) in patients with acute cerebral infarction(ACI),and to evaluate its clinical significance. Methods A retrospective study was conducted. Eighty patients with ACI admitted to Tianjin Hospital from January 2011 to March 2014 within 48 hours of onset were enrolled,and 30 healthy volunteers served as controls. The peripheral blood was collected,and the expression of serum miR-210 was determined by reverse transcription-polymerase chain reaction(RT-PCR). The receiver operating characteristic curve(ROC)was drawn to analyze the role of miR-210 in the diagnosis of ACI. According to the pathological and physiological characteristics of patients receiving treatment,the relationship between miR-210 and clinical physiology index was analyzed. Results The expression of miR-210 in serum of patients with ACI was significantly lower than that of the healthy control group(2-ΔΔCt:1.349±0.043 vs. 1.923±0.107,t=6.567, P<0.000). ROC analysis results showed that the sensitivity of miR-210 in the diagnosis of ACI was 90.4%,the specificity was 76.2%,and the area under the ROC(AUC)was 0.804〔95%confidence interval(95%CI)=0.700-0.908〕. No difference in expression of miR-210(2-ΔΔCt)in serum was found in patients of different gender,age, and infarction area(male and female:1.33±0.13 and 1.31±0.06,t=3.562,P=0.473;≤60 years and>60 years:1.32±0.12 and 1.31±0.09,t=2.351,P=0.264;large infarction,small infarction,lacunar infarction:respectively 1.31±0.02, 1.33±0.11, 1.31±0.06, F=1.236, P=0.087), or with the severity of cerebral infarction,and there was a tendency in lowering of expression of miR-210(2-ΔΔCt,light,medium,severe:1.53±0.11, 1.33±0.11,1.08±0.04,F=5.394,P=0.014).Conclusion The serum level of miR-210 in ACI was significantly lower than that in normal healthy persons,and it may be an important new serological marker in screening and diagnosis of ACI.

Objective To determine the expression spectrum of microRNA(miRNA)in the lung homogenate of rats with chronic obstructive pulmonary disease(COPD)or healthy rats,to look for differentially expressed miRNA, and to explore their potential role in pathogenesis of COPD. Methods Twenty male Sprague-Dawley(SD)rats were randomly divided into normal control group and COPD model group,with 10 rats in each group. COPD rat models were reproduced by smoke inhalation as well as intratracheal instillation of lipopolysaccharide(LPS). The samples of the lung were harvested,and the histopathological examination of the right lung was carried out to evaluate the degree of lung injury. Total RNAs were isolated from the left lung. The miRNA expressions in lung tissue of rats with COPD or normal rats were determined by miRNA chip eichnology to screen the miRNA with differential expression, and hierarchical clustering analysis was made. The data were analyzed to study the expression difference of miRNAs between the two groups,and to construct the miRNA-Target network. Results Compared with normal control group, 20 miRNA with increased expression were found in COPD model group,the top 10 were miR-30c-2,miR-199a-5p, miR-30a, miR-145, miR-151, miR-674-5p, miR-214, miR-423, miR-28 and miR-181b, and only miR-376b-3p showed down-regulation. Hierarchical clustering analysis showed that significant differences in individual miRNA in lung tissue between rats of two groups were found. However,similar samples could not be gathered well,thus it may give rise to inconsistency during the sample preparation. Many miRNAs had multiple target genes in miRNA-Target network, such as miR-30c-2, miR-145, miR-181b, miR-181a, miR-181d, miR-199. Conclusions The study reveals that there is a variance of miRNAs expression profile in lung homogenates between COPD group and the normal control group of rats,and many miRNAs have multiple target genes,such as miR-30c-2,miR-145,miR-181b,miR-181a,miR-181d,and miR-199. Therefore,the results may be valuable to centain extent for the interpretation of COPD pathogenesis.

Objective To explore the effect of the transcutaneous tracheostomy tube in patients with pneumothorax and its clinical value. Methods A prospective randomized controlled trial was conducted. Thirty-two patients with pneumothorax admitted to Department of Critical Care Medicine of Harrison International Peace Hospital of Hebei Medical University from June 2010 to June 2014 were enrolled. The patients were divided into control group and observation group,with 16 cases in each group. Beside the treatment for primary disease,the patients in control group received thoracic close drainage with traditional silica gel tube as performed by thoracic surgeons,and those in observation group received thoracic close drainage with transcutaneous tracheostomy tube by intensive care doctors. The curative effect and complications of the two groups were observed. Results Compared with control group,the time from diagnosis to operation(minutes:8.00±1.36 vs. 23.06±3.83,t=14.790,P=0.000)and the operation time were significantly shortened(days:5.37±1.02 vs. 7.31±1.70,t=7.286,P=0.000),the frequency of drainage tube replacement(times:0.18±0.40 vs. 3.87±1.14,t=12.128,P=0.000)and the times of repeated chest radiography(times:1.12±0.34 vs. 2.93±0.77,t=8.589,P=0.000)in observation group were significantly reduced,the length of hospital day was significantly shortened(days:8.30±1.37 vs. 24.56±5.62,t=17.289, P=0.000),the rates of dislocation of drainage tube(0 vs. 3 cases),obstruction of the tube(0 vs. 5 cases),and subcutaneous emphysema(3 vs. 16 cases)were reduced obviously,but there was no difference in incidence of incision infection(1 vs. 3 cases)and infection of thoracic cavity(0 vs. 2 cases). Conclusions The usage of transcutaneous tracheostomy tube in patients with pneumothorax is safe and simple. Doctors in ICU can independently do this procedure,and its effect is positive.

Objective To investigate the related factors of serum carnitine deficiency in critical ill patients, and the influence of its deficiency on the length of hospital stay. Methods A prospective study was conducted. Critical ill patients with acute physiology and chronic health evaluationⅡ(APACHEⅡ)score>12 admitted to Department of Critical Care Medicine of the First Affiliated Hospital of Sun Yat-sen University from March 2013 to September 2013 were enrolled. Serum carnitine concentration and indexes of organ function were determined,and the tolerance of enteral nutrition within 5 days,the length of hospital stay,the length of intensive care unit(ICU)stay,and the hospital mortality were recorded. The relationship between serum carnitine and indexes mentioned above was analyzed. Results Thirty critically ill patients were enrolled. Serum carnitine concentration was very low in all critically ill patients,i.e. (8.92±5.05)μmol/L(normal reference value at 43.5 μmol/L)at hospital admission. Serum carnitine concentration in patients with APACHEⅡscore>23(7 cases)was significantly lower than that in those with APACHEⅡscore 12-23(23 cases,μmol/L:5.33±1.72 vs. 10.02±5.24,t=2.300,P=0.001). Serum carnitine concentration in patients with serum total bilirubin(TBil)>19μmol/L(9 cases)was significantly lower than that in those with TBil≤19μmol/L(21 cases,μmol/L:5.54±2.70 vs. 9.84±5.08,t=2.750,P=0.014). Serum carnitine concentration was negatively correlated with the APACHEⅡscore and the TBil(r=-0.387,P=0.035;r=-0.346,P=0.048). During the 5-day observation period,enteral feeding amount〔(5 134±1 173)mL〕was positively correlated with serum carnitine concentration(r=0.430,P=0.022). In 30 critical patients,the incidence of abdominal distension was 40.0%(12/30),and the serum carnitine concentration of patients with abdominal distension was lower compared with that of patients without abdominal distension(μmol/L:7.83±4.98 vs. 9.12±5.35,t=0.707,P=0.383). The incidence of diarrhea was 26.7%(8/30),and the serum carnitine concentration of diarrhea patients was lower compared with that of patients without diarrhea(μmol/L:8.27±5.78 vs. 9.73±4.78,t=0.607,P=0.576). The mean length of hospital stay was(34.72±16.66)days. The serum carnitine concentrations in patients with hospital stay≥45 days (8 cases)were lower compared with those in those<45 days(22 cases,μmol/L:5.71±3.23 vs. 9.95±5.26,t=1.627,P=0.020). No correlation was found between serum carnitine concentrations and the hospital stay(r=-0.165, P=0.385). The length of ICU stay was(18.60±10.72)days. Serum carnitine concentration in patients with the length of ICU stay>7 days(27 cases)was slightly lower than that in those with the length of ICU stay≤7 days (3 cases,μmol/L:8.44±5.00 vs. 13.24±3.65,t=1.610,P=0.119). No correlation was found between serum carnitine concentrations and the length of ICU stay(r=-0.019,P= 0.293). In-hospital mortality was 26.67%(8/30). No significant difference in serum carnitine concentrations was found between the death group and the survival group(μmol/L:12.24±6.52 vs. 7.72±3.91,t=-1.846,P=0.098). No correlation was found between serum carnitine concentrations and in-hospital mortality(r=0.340,P=0.066). Conclusions Carnitine deficiency is significant in critically ill patients,and it is correlated with disease severity and serum TBil. The total amount of lenteral feeding was lower,and hospital stay was prolonged in critically ill patients with low serum carnitine level.

Objective To explore the effect of airway humidification on lung injury as a result of mechanical ventilation with different tidal volume(VT). Methods Twenty-four male Japanese white rabbits were randomly divided into four groups:low VT with airway humidification group,high VT with airway humidification group,low VT and high VT group without humidification,with 6 rabbits in each group. Mechanical ventilation was started after intubation and lasted for 6 hours. Low VT denoted 8 mL/kg,while high VT was 16 mL/kg,fraction of inspired oxygen (FiO2)denoted 0.40,positive end-expiratory pressure(PEEP)was 0. Temperature at Y piece of circuit in airway humidification groups was monitored and controlled at 40℃. Arterial blood gas analysis,including pH value,arterial partial pressure of oxygen(PaO2),arterial partial pressure of carbon dioxide(PaCO2),lung mechanics indexes, including peak airway pressure(Ppeak)and airway resistance(Raw),and lung compliance was measured at 0,2,4, 6 hours of mechanical ventilation. The levels of tumor necrosis factor-α(TNF-α)and interleukin-8(IL-8)in plasma and bronchoalveolar lavage fluid(BALF)were determined by enzyme linked immunosorbent assay(ELISA). The animals were sacrificed at the end of mechanical ventilation. The wet to dry(W/D)ratio of lung tissues was calculated. Histopathologic changes in the lung tissueies were observed with microscope,and lung injury score was calculated. Scanning and transmission electron microscopies were used to examine the integrity of the airway cilia and the tracheal epithelium. Results Compared with low VT group,pH value in high VT group was significantly increased,PaCO2 was significantly lowered,and no difference in PaO2 was found. Ppeak,Raw,and lung compliance were significantly increased during mechanical ventilation. There were no significant differences in blood gas analysis and lung mechanics indexes between low VT with airway humidification group and low VT group. Compared with high VT group,PaCO2 in high VT with airway humidification group was significantly decreased,Ppeak raised obviously,and no difference in pH value,PaO2,Raw and pulmonary compliance was found. Compared with low VT with airway humidification group,no difference in blood gas analysis(PaCO2,mmHg,1 mmHg=0.133 kPa)was found,but Ppeak(cmH2O,1 cmH2O=0.098 kPa),Raw(cmH2O),and lung compliance(mL/cmH2O)were increased significantly in high VT with airway humidification group(PaCO2 at 2 hours:27.96±4.64 vs. 36.08±2.11,4 hours:28.62±2.93 vs. 34.55±5.50, 6 hours:29.33±2.14 vs. 35.01±5.53;Ppeak at 0 hour:14.34±1.97 vs. 8.84±1.32,2 hours:17.33±0.52 vs. 11.17±2.14,4 hours:17.83±0.98 vs. 12.67±2.06,6 hours:18.67±1.22 vs. 13.50±2.16;Raw at 0 hour:37.36±5.14 vs. 27.05±2.93,2 hours:43.94±6.58 vs. 31.95±3.56,4 hours:48.04±6.07 vs. 35.24±3.50, 6 hours:50.33±6.34 vs. 36.66±3.64;pulmonary compliance at 6 hours:2.28±0.18 vs. 1.86±0.37,all P<0.05). The lung W/D ratio in high VT group was significantly higher than that of the low VT group(6.17±2.14 vs. 3.50±1.52, P<0.05). W/D in high VT with airway humidification group was higher than that of low VT with airway humidification group but without statistically significant difference(5.17±2.14 vs. 3.00±1.10,P>0.05). Microscopic observation showed that cilia were partially detached,adhered and sparse in low VT group,while cilia in high VT group showed serious detachment and lodging. Remaining cilia were sparse,with lodging,and cellular structure was damaged. Lung tissue pathological injury score in the high VT group was significantly higher than that of low VT group(6.17±2.14 vs. 3.50±1.52,P<0.05). Cilia density and cellularity were normal in low VT with airway humidification group,and no difference in lung tissue pathological injury score was found compared with low VT group(3.00±1.10 vs. 3.50±1.52, P>0.05). Cilia were severely detached,adhered and lodging,and cellularity were not obvious in high VT with airway humidification group,and lung tissue pathological injury score was elevated significantly than that of the low VT with airway humidification group but without statistically significant difference(5.17±2.14 vs. 3.00±1.10,P>0.05). TNF-α and IL-8 concentrations showed no change in plasma and BALF in all groups during ventilation,and no significant difference was found among the groups. Conclusions Airway humidification can alleviate pathological lung injury,damage of cilia and cellular structure in trachea caused by mechanical ventilation with low and high VT. High VT with humidification can result in serious pulmonary edema.