Ventilator Associated Pneumonia (VAP)

Ventilator associated pneumonia is a complication of intubation and mechanical ventilation (MV). It is the most common healthcare acquired infection (HCAI) seen in ICU, and is associated with increased morbidity, mortality and length of stay.

Causes include biofilm formation within the ETT and micro-aspiration of respiratory and gastric secretions. The presence of an ETT both provides direct access for pathogens into the lower respiratory tract, and prevents normal upper airway protective reflexes (cough and gag) that usually avoid aspiration of secretions. This means that secretions which pool on top of the inflated cuff in the trachea are able to migrate into the lungs and allows for pathogenesis. This is combined with the negative effects of critical illness on immune defences (so-called ICU-acquired immunosuppression) which make a patient more susceptible to secondary infection due to the severity of their primary insult. The risk of infection is obviously lower in immunocompetent hosts, and reduces with shorter durations of intubation.

Signs and Symptoms

By and large, symptoms of VAP are the same as for any other kind of pneumonia with a combination of systemic and respiratory indicators. Fever, large amounts of purulent respiratory secretions, increased WBCs (leukocytosis), shortness of breath, cough, decreased O2 sats and worsening gas exchange.

Diagnosis

Diagnostic criteria include subjective data, such as changes to quantity and purulence of secretions, and objective data including sampling from bronchoalveolar lavage (BAL), new or progressive consolidation/infiltrates on CXR (although this has low sensitivity and specificity, and is difficult due to other respiratory pathologies that mimic the appearance of VAP- e.g ARDS and pleural effusion- check out this post for more on x-rays), and increased WBC and worsening observations (e.g. fever). Obviously diagnosis is dependent on the patient being mechanically ventilated, or previously having been- the longer the MV, the higher the risk of VAP. Early VAP indicates a pneumonia that appears within the first 4 days of MV, compared to a late VAP appearing after 4 days of MV.

Early VAP is generally attributed to Streptococcus species, Staphylococcus aureus (methicillin-sensitive), Haemophilus species, Escherichia coli, Klebsiella pneumoniae and Enterobacter species. Later VAP is usually caused by multi drug resistant bugs, such as Methicillin Resistant Staph Aureus (MRSA), Extended Spectrum Beta Lactamase (ESBL) producing pathogens and Acinetobacter.

Prevention and Treatment

Prevention-

• Adapted ETTs have been considered as a method for reducing bacterial colonisation, biofilm formation and micro aspiration. Suggested adaptations include continuous cuff monitoring, presence of subglottic aspiration ports and antimicrobial coatings (e.g. silver, chlorhexidine or titanium dioxide) .

• Antimicrobial stewardship and appropriate use of Abx has an overall protective effect for reducing the amounts of multi-drug resistant bacteria which are more likely to cause nosocomial infection. Optimising antibiotic usage helps to reduce prevalence of antibiotic resistance.

• Spontaneous breathing trails during sedation holds- 'Wake up and breathe' as per the ABC trial, 2008.

• Avoidance of ventilator circuit changes, to avoid potentially contaminated humidified gases from being forced into the lungs. Ensuring that tubing remains free from condensation and is positioned so that any condensation does not go down the ETT and enter the lungs is also beneficial.

• Input from physiotherapists- methods including early mobilisation and deep breathing exercises. Physio input generally makes for a happier chest.

The key preventative measure, which is widely used (with a few adaptations here and there) is the VAP care bundle. In the UK, this 'High Impact Intervention' bundle contains 6 items. It was fully finalised by the Dept. of Health in 2009.

The original 2007 DoH guidance only included daily sedation holds, bed head elevation, gastric ulcer prophylaxis, and oral care. A large 2011 study (Morris et al.) considering these original 4 interventions showed varying levels of compliance with the interventions (overall bundle compliance was 70%) but also demonstrated a significant reduction in VAP rates (32 cases per 1000 ventilator days down to 12 cases), MRSA rates and antibiotic use. There was no significant difference in LOS or duration of MV. In 2009 the final 2 elements of regular suctioning and cuff pressure monitoring were added, to give the final 6 item care bundle used widely today (each aspect is discussed in more detail below)

1. HOB elevated- Having the head of the bed between 30 and 45deg helps to reduce gastric aspiration by virtue of gravity, which prevents acid reflux with the potential to be aspirated into the lungs. A super simple intervention that can make a big difference (and will also help with oxygenation in general)

2. Daily sedation hold- Unless contraindicated, sedation should be stopped daily to assess readiness for extubation from a respiratory and neurological point of view. The sooner a patient can be extubated and self ventilating, the lower the risk of pneumonias.

3. Oral care- Helps to reduce colonisation in the mouth (as well as being more comfortable for the patient, and helping to reduce dental and gingival problems). NICE, on advice from the ICS, has withdrawn its guidance recommending sue of chlorhexidine gels and mouthwashes- but this is still recommended by NHS Improvement with the Infection Prevention Society

4. Suctioning- Regular suctioning helps to reduce the volume of secretions pooling on the top of the ETT cuff. Ideally, all ETTs will have a subglottic aspiration port to facilitate this, especially if the patient is expected to be I+V for greater than 72 hours. If not, inline suction and oral suctioning should be used as required to remove secretions (this must be balanced against the ventilatory and cardiovascular stability of the patient).

5. Cuff pressure monitoring- A good seal by the ETT cuff helps to prevent aspiration of gastric and respiratory secretions around the cuff. A pressure <20cmH2O allows passage of secretions around the sides of the cuff, and a pressure >30cmH2O increases the risk of tracheal pressure damage. Cuff pressure can be monitored continuously or at least 4 hourly.

6. GI ulcer prophylaxis- There remains a balance to be struck between prevention of GI bleeding (particularly as MV is a risk factor for stress related mucosal damage) and avoidance of VAP (as ulcer prophylaxis increases the pH of the stomach, leading potentially to increase bacterial colonisation in the GI tract). Therefore it's recommended that stress ulcer prophylaxis only be prescribed for high risk patients. Equally, this intervention is sometimes omitted from care bundles due to this risk.

Treatment-

Treatment mainstays match other respiratory illness- a combination of antibiotics, targeted once the organism has been identified through BAL or blood cultures, alongside supportive care including more frequent suctioning of respiratory secretions as needed and respiratory support to maintain target O2 sats and adequate gas exchange on ABG (increased FiO2, increased pressure support etc).

As always, prevention is better than treatment so ideally following the above points will reduce incidence of VAP

So there you have it, everything you might ever have wanted to know about ventilator-associated pneumonias. I spent the entire time whilst writing this post trying to come up with some pithy remix of WAP that incorporated VAP, and came up with nothing. You'd make my day if you can think of something that fits!!

As always, thank you for reading- I hope this post was useful and interesting, and that you maybe learnt something new. References are below, with any particular favourites of mine bolded. Please don't hesitate to send me a message from the website, or reach out on Instagram/Twitter (@christienursing) if you have any questions, comments or suggestions.

Love, Christie x

References-

Hunter, J. (2012) 'Ventilator associated pneumonia' in BMJ. 344, p. 3325. https://www.bmj.com/content/344/bmj.e3325

NHS Improvement, Infection Prevention Society (2017) 'High Impact Interventions: Care processes to prevent infection. 4th edition of Saving Lives: High Impact Interventions'. http://www.southernhealth.nhs.uk/EasysiteWeb/getresource.axd?AssetID=112554&type=Full&servicetype=Attachment

Gunasekera, P., Gratrix, A. (2016) 'Ventilator-associated pneumonia' in BJA Education. 16(6), pp.198-202. https://academic.oup.com/bjaed/article/16/6/198/2364844

Grimaldi, D., Pene, F (2019) 'Short and long term ICU-acquired immunosuppression' in Preiser JC., Herridge M., Azoulay E. (eds) Post Intensive Care Syndrome. New York: Springer Publishing.

Hellyer, T., Ewan, V., Wilson, P., Simpson, A. (2016) 'The Intensive Care Society recommended bundle of interventions for the prevention of ventilator-associated pneumonia' in Journal of the Intensive Care Society. 17(3), pp. 238-243. https://journals.sagepub.com/doi/full/10.1177/1751143716644461

Wip, C., Napolitano, L. (2009) 'Bundles to prevent ventilator-associated pneumonia: how valuable are they?' in Current Opinions in Infectious Diseases. 22, pp. 159-166. https://www.chpso.org/sites/main/files/file-attachments/wip.pdf

Koenig, S., Truwit, J. (2006) 'Ventilator-associated pneumonia: Diagnosis, Treatment and Prevention' in Clinical Microbiology Reviews. 19(4), pp. 637-657. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1592694/

Kalanuria, A., Zai, W., Mirski, M. (2014) 'Ventilator-associated pneumonia in the ICU' in Critical Care. 18(208). https://ccforum.biomedcentral.com/articles/10.1186/cc13775

• A gloriously detailed, well written and well evidenced article. Only drawback is that it's 6 years out of date- however on reading, it appears that the majority of guidance is the same now in 2020 so maybe there's not been any real developments in the world of VAP.

Klompas, M., Branson, R., Eichenwald, E., Greene, L., Howell, M., Lee, G., Magill, S., Maragakis, L., Priebe, G., Speck, K., Yokoe, D., Berenholtz, S. (2014) 'Strategies to prevent ventilator-associated pneumonia in acute care hospitals' in Infection Control and Hospital Epidemiology. 35(8), pp. 915-936.

• Another 6 year old article, but again, a lovely one. Includes a strong grading of the quality of evidence so you can make your own decisions, and compares a lot of different interventions. Dr Klompas is a expert in nosocomial infection, with research strongly supported by the CDC.

Morris, A., Way, A., Swann, D., Everingham, K., McCulloch, C., NcNulty, J., Brooks, O., Laurenson, I., Cook, B., Walsh, T. (2011) 'Reducing ventilator associated pneumonia in intensive care: impact of implementing a care bundle' in Critical Care Medicine. 39(10), pp. 2218-2224. https://pubmed.ncbi.nlm.nih.gov/21666444/

Department of Health (2008) 'The Health and Social Care Act 2008: Code of Practice for the NHS on the prevention and control of Healthcare associated infections and related guidance'. https://www.legislation.gov.uk/ukpga/2008/14/contents

Halyard Health (2010) 'High impact intervention: Care bundle to reduce ventilation-associated pneumonia'. https://www.halyardhealth.co.uk/media/16256404/hii_-_ventilator_associated_pneumonia.pdf

Department of Health (2009) 'High Impact Intervention No 5 Care bundle for ventilated patients (or tracheostomy where appropriate)'

Baid, H., Creed, F., Hargreaves, J. (2016) Oxford Handbook of Critical Care Nursing, 2nd edn. Oxford: Oxford University Press

Girard, T., Kress, J., Fuchs, B., Thomason, J., Schweickert, W., Pun, B., Taichman, D., Dunn, J., Pohlman, A., Kinniry, P., Jackson, J., Canonico, A., Light, R., Shintani, A., Gordon, S., Hall, J., Dittus, R., Bernard, G., Ely, W. (2008) 'Efficacy and safety of a paired sedation and ventilator weaning protocol for mechanically ventilated patients in intensive care (Awakening and Breathing Controlled trial): a randomised controlled trial' in The Lancet. 371, pp.126-134. https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(08)60105-1.pdf