Application Of Bedside Lung Ultrasound In The Diagnosis And Severity Assessment Of Ventilator-associated Pneumonia

Objective To explore the specific lung ultrasound signs of ventilator associated pneumonia（VAP）,and evaluate the diagnostic performance of lung ultrasound in VAP and its application value in the assessment of disease severity.Methods A prospective research method was used to select 60 VAP patients（VAP group）who were admitted to the intensive care unit（ICU）of General Hospital of Ningxia Medical University from September 1,2018 to July 1,2020.62 patients who were admitted to the ICU with age,gender and basic diseases matched with the VAP group during the same period and received mechanical ventilation without VAP were selected as the non-VAP group.At the same time,healthy people who matched the age,gender,BMI and the VAP group and the non-VAP group were selected 15 as the healthy control group.After 48 hours of mechanical ventilation,patient’s body temperature,white blood cell count,sputum characteristics and the change of the lung ultrasound were dynamically observed.If the patient had suspected infection manifestations such as elevated body temperature,leukocytosis/leukopenia,purulent airway secretions,and abnormal lung ultrasound signs,airway secretions were immediately extracted and chest CT examination was improved.At the same time,general clinical data such as age,gender,department source,basic diseases,APACHE II score and SOFA score were collected.The body temperature,white blood cell count,procalcitonin level,Pa O₂/Fi O₂,P_A-aDO₂,the nature of airway secretions and the results of endotracheal aspirate gram staining/culture were recorded.The lung ultrasound examination results of the two groups of patients were recorded,VPLUS score,LUSS score were performed,and prognostic indicators such as mechanical ventilation time,ICU length of stay and 28-day mortality rate were recorded.Results 1.There was no statistically significant difference in age,gender and BMI between the healthy control group,the VAP group and the non-VAP group（all P>0.05）.2.There was no difference in age,gender,BMI,basic diseases composition,white blood cell count,Pa O₂/Fi O₂ between the VAP group and the non-VAP group（all P>0.05）.In terms of the source of patients,the VAP group had most emergency surgery patients（51.7%vs.33.9%,P=0.047）,and the non-VAP group had more elective surgery patients（51.6%vs.26.7%,P=0.005）.More patients in the VAP group had purulent airway secretions（65.0%vs.41.9%,P=0.011）,and the body temperature tended to increase compared with the non-VAP group（℃,38.3±0.8 vs.38.0±0.9,P=0.054）.The VAP group’s APACHE II score（15.4±5.7vs.13.4±3.4,P=0.021）,SOFA score（8.8±4.2 vs.6.3±3.3,P<0.001）,and 28-day mortality rate（31.7%vs.9.7%,P=0.003）were higher than those of the non-VAP group,and had longer mechanical ventilation time（d,10.5 vs.4.3,P<0.001）and ICU length of stay（d,14.8 vs.6.0,P<0.001）than the non-VAP group.3.In the healthy control group,2 cases（13.33%）had abnormal pleural line,and the other abnormal signs did not appear.In the non-VAP group,the most abnormal signs were pleural line abnormalities in 31 cases（50.00%）,and the least abnormal signs were dynamic bronchial signs in 3 cases（4.84%）.In the VAP group,the most abnormal signs were pleural line abnormalities in 59 cases（98.33%）,and the least abnormal signs were static bronchial signs in 15 cases（25.00%）.4.In the healthy control group and the non-VAP group,pleural line abnormalities,B’signs and A/B signs were significantly different（all P<0.05）.In the healthy control group and the VAP group,pleural line abnormalities,B’signs,A/B signs,subpleural small piece of lung consolidation,large piece of lung consolidation,dynamic bronchial signs,static bronchial signs were statistically different（all P<0.05）.In the non-VAP group and the VAP group,there was no significant difference in static bronchial signs（P>0.05）,in addition,the other six kinds of abnormal lung ultrasound signs were statistically different（all P<0.05）.5.When seven kinds of abnormal lung ultrasound signs were used in the diagnosis of VAP,abnormal pleural line had the highest sensitivity（98.33%）,static bronchial signs had the lowest sensitivity（25.00%）,dynamic bronchial signs had the highest specificity（95.16%）,abnormal pleural line had the lowest specificity（50.00%）.6.When LUS positive,VPLUS≥3,EAgram positive,EAquant positive and PCT>0.5ng/m L were used alone in the diagnosis of VAP,LUS positive had better sensitivity（73.3%）and specificity（80.6%）.7.When LUS positive,VPLUS≥3,EAgram positive,EAquant positive and PCT>0.5ng/m L were combined with each other,the specificity of LUS positive combined with PCT>0.5ng/m L was the highest（95.2%）.8.LUSS was significantly positively correlated with APACHE II score（r=0.407,P=0.001）and SOFA score（r=0.399,P=0.002）,but there was no correlation with Pa O₂/Fi O₂（r=﹣0.064,P=0.629）and Pa O₂/Fi O₂（r=0.189,P=0.149）.Conclusion The specific lung ultrasound signs of VAP mainly include small subpleural consolidation,large lung consolidation,dynamic bronchial signs and static bronchial signs,among which the dynamic bronchial signs had the highest specificity.The specificity of LUS positive combined with PCT>0.5ng/m L in the diagnosis of VAP is high,which can be used in clinical diagnosis of VAP.Lung ultrasound score（LUSS）is closely related to the severity of VAP.