[Should the diagnosis of ventilator associated pneumonia be improved?]

Systematic review of studies investigating ventilator associated pneumonia diagnostics in intensive care

Background

Ventilator-associated pneumonia (VAP) is an important diagnosis in critical care. VAP research is complicated by the lack of agreed diagnostic criteria and reference standard test criteria. Our aim was to review which reference standard tests are used to evaluate novel index tests for suspected VAP.

Methods

We conducted a comprehensive search using electronic databases and hand reference checks. The Cochrane Library, MEDLINE, CINHAL, EMBASE, and web of science were searched from 2008 until November 2018. All terms related to VAP diagnostics in the intensive treatment unit were used to conduct the search. We adopted a checklist from the critical appraisal skills programme checklist for diagnostic studies to assess the quality of the included studies.

Results

We identified 2441 records, of which 178 were selected for full-text review. Following methodological examination and quality assessment, 44 studies were included in narrative data synthesis. Thirty-two (72.7%) studies utilised a sole microbiological reference standard; the remaining 12 studies utilised a composite reference standard, nine of which included a mandatory microbiological criterion. Histopathological criteria were optional in four studies but mandatory in none.

Conclusions

Nearly all reference standards for VAP used in diagnostic test research required some microbiological confirmation of infection, with BAL culture being the most common reference standard used.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01560-0.

Diagnostic value of procalcitonin in ventilator-associated pneumonia

BACKGROUND AND OBJECTIVE

Procalcitonin (PCT) can help the early diagnosis of bacterial infections and estimate the response obtained. The objective is to study the value of PCT for the diagnosis of ventilator-associated pneumonia (VAP).

PATIENTS AND METHOD

Prospective and observational study, carried out for 18 months, in a polyvalent Intensive Care Unit (ICU). Those included were over 18 years of age, with suspected pneumonia after 48h of mechanical ventilation (MV). Collected were demographic characteristics; admission pathology; reason for beginning MV; gravity scores (APACHE II, SAPS II and SOFA); C-reactive protein (CRP) and PCT. At the time of suspicion of VAP: early or late, radiological severity, presence of septic shock, SOFA, CRP, PCT and microbiology.

RESULTS

Ninety-one patients with suspected VAP were included. The mean age was 42 (17.76) and that of hospitalisation in the ICU was 18.59 (11.69) days. VAP was confirmed in 74 patients, of which 19 (25.7%) presented septic shock. The mortality was 28.4%. There were no significant differences of the PCT in the patients who presented VAP versus those who did not present VAP (P=.449). When patients without VAP, with VAP and VAP with shock, were compared, the PCT median was 0.38 (CI95%: 0.22-1.90), 0.56 (CI95%: 0.19-1.77) and 1.93 (CI95%: 0.38-10.07), respectively (P=.169).

CONCLUSIONS

In our study, PCT did not prove useful for the diagnosis of VAP.

Respiratory pathogen colonization of dental plaque, the lower airways, and endotracheal tube biofilms during mechanical ventilation

PURPOSE

In mechanically ventilated patients, the endotracheal tube is an essential interface between the patient and ventilator, but inadvertently, it also facilitates the development of ventilator-associated pneumonia (VAP) by subverting pulmonary host defenses. A number of investigations suggest that bacteria colonizing the oral cavity may be important in the etiology of VAP. The present study evaluated microbial changes that occurred in dental plaque and lower airways of 107 critically ill mechanically ventilated patients.

MATERIALS AND METHODS

Dental plaque and lower airways fluid was collected during the course of mechanical ventilation, with additional samples of dental plaque obtained during the entirety of patients' hospital stay.

RESULTS

A "microbial shift" occurred in dental plaque, with colonization by potential VAP pathogens, namely, Staphylococcus aureus and Pseudomonas aeruginosa in 35 patients. Post-extubation analyses revealed that 70% and 55% of patients whose dental plaque included S aureus and P aeruginosa, respectively, reverted back to having a predominantly normal oral microbiota. Respiratory pathogens were also isolated from the lower airways and within the endotracheal tube biofilms.

CONCLUSIONS

To the best of our knowledge, this is the largest study to date exploring oral microbial changes during both mechanical ventilation and after recovery from critical illness. Based on these findings, it was apparent that during mechanical ventilation, dental plaque represents a source of potential VAP pathogens.

[Prevention of ventilator-associated pneumonia: a comparison of level of knowledge in three critical care units]

OBJECTIVE

To determine the level of knowledge of the prevention of ventilator-associated pneumonia guidelines of nurses working in three intensive care units (ICU) in 3 university hospitals in a Spanish region, and evaluate the relationship between this level of knowledge and years worked in the ICU.

METHOD

A descriptive, prospective, cross-sectional, multicentre study was conducted using a validated and reliable questionnaire, made up by 9 questions with closed answers drawn from the EVIDENCE study. A total of 98 questionnaires were collected from ICU nurses of the three university hospitals (A, B, and C) from January to April 2014. The sample from hospital A responded the most, in contrast with the sample from hospital B, which was the one with the less participation. The Pearson correlation was calculated in order to determine the relationship between nurse years worked in ICU and level of knowledge.

RESULTS

Hospital A obtained in the best mean score in the questionnaire, 6.33 (SD 1.4) points, followed by hospital C with 6.21 (SD 1.4), and finally, the hospital B with 6.06 (SD 1.5) points. A p=.08 was obtained on relating years worked with the level of knowledge.

CONCLUSION

The results showed a high level of knowledge compared other studies. There was a tendency between the years worked in the unit and the level of knowledge in ventilator-associated pneumonia prevention.

Microbial profiling of dental plaque from mechanically ventilated patients

Micro-organisms isolated from the oral cavity may translocate to the lower airways during mechanical ventilation (MV) leading to ventilator-associated pneumonia (VAP). Changes within the dental plaque microbiome during MV have been documented previously, primarily using culture-based techniques. The aim of this study was to use community profiling by high throughput sequencing to comprehensively analyse suggested microbial changes within dental plaque during MV. Bacterial 16S rDNA gene sequences were obtained from 38 samples of dental plaque sampled from 13 mechanically ventilated patients and sequenced using the Illumina platform. Sequences were processed using Mothur, applying a 97 % gene similarity cut-off for bacterial species level identifications. A significant ‘microbial shift’ occurred in the microbial community of dental plaque during MV for nine out of 13 patients. Following extubation, or removal of the endotracheal tube that facilitates ventilation, sampling revealed a decrease in the relative abundance of potential respiratory pathogens and a compositional change towards a more predominantly (in terms of abundance) oral microbiota including Prevotella spp., and streptococci. The results highlight the need to better understand microbial shifts in the oral microbiome in the development of strategies to reduce VAP, and may have implications for the development of other forms of pneumonia such as community-acquired infection.

Guidelines for the prevention of ventilator-associated pneumonia and their implementation. The Spanish "Zero-VAP" bundle

BACKGROUND

"Zero-VAP" is a proposal for the implementation of a simultaneous multimodal intervention in Spanish intensive care units (ICU) consisting of a bundle of ventilator-associated pneumonia (VAP) prevention measures.

METHODS/DESIGN

An initiative of the Spanish Societies of Intensive Care Medicine and of Intensive Care Nurses, the project is supported by the Spanish Ministry of Health, and participation is voluntary. In addition to guidelines for VAP prevention, the "Zero-VAP" Project incorporates an integral patient safety program and continuous online validation of the application of the bundle. For the latter, VAP episodes and participation indices are entered into the web-based Spanish ICU Infection Surveillance Program "ENVIN-HELICS" database, which provides continuous information about local, regional and national VAP incidence rates. Implementation of the guidelines aims at the reduction of VAP to less than 9 episodes per 1000 days of mechanical ventilation. A total of 35 preventive measures were initially selected. A task force of experts used the Grading of Recommendations, Assessment, Development and Evaluation Working Group methodology to generate a list of 7 basic "mandatory" recommendations (education and training in airway management, strict hand hygiene for airway management, cuff pressure control, oral hygiene with chlorhexidine, semi-recumbent positioning, promoting measures that safely avoid or reduce time on ventilator, and discouraging scheduled changes of ventilator circuits, humidifiers and endotracheal tubes) and 3 additional "highly recommended" measures (selective decontamination of the digestive tract, aspiration of subglottic secretions, and a short course of iv antibiotic).

DISCUSSION

We present the Spanish VAP prevention guidelines and describe the methodology used for the selection and implementation of the recommendations and the organizational structure of the project. Compared to conventional guideline documents, the associated safety assurance program, the online data recording and compliance control systems, as well as the existence of a pre-defined objective are the distinct features of "Zero VAP".

[Role of plasma procalcitonin in the diagnosis of ventilator-associated pneumonia: systematic review and metaanalysis]

OBJECTIVE

To determine the role of plasma procalcitonin (PCT) levels in diagnosing ventilator-associated pneumonia.

DESIGN

A systematic review of publications prospectively assessing the diagnostic role of PCT in ventilator-associated pneumonia was carried out. The search was performed using Medline, Embase, the Cochrane Collaboration and MEDION, with reviewing of the references of retrieved articles. We extracted data that allowed the calculation of sensitivity, specificity, likelihood ratios and diagnostic odds ratio. Intervention Metaregression was performed to determine whether exposure to previous antibiotic treatment, the time to occurrence of ventilator-associated pneumonia and the type of patients had an impact upon the diagnostic performance of procalcitonin.

RESULTS

Seven studies were considered (373 patients, 434 episodes). We found no publication bias or threshold effect. High plasma PCT levels were associated to an increased risk of suffering ventilator-associated pneumonia (OR: 8.39; 95% CI: 5.4-12.6). The pooled data on sensitivity, specificity, positive and negative likelihood ratio, and diagnostic odds ratio found were 76% (69-82), 79% (74-84), 4.35 (2.48-7.62), 0.26 (0.15-0.46) and 17.9 (10.1-31.7), respectively. Diagnostic yield was modified by prior exposure to antibiotics (rDOR 0.11, 0.02-0.069), but not by the type of critically ill patient or the time to occurrence of ventilator-associated pneumonia.

CONCLUSIONS

Our results suggest that PCT provides additional information on the risk of VAP. Inclusion of PCT in diagnostic algorithms could improve their effectiveness.