Ventilator Associated Pneumonia – an Overview
Harshal Wagh and Devaraja Acharya
Cite this article as: BJMP 2009:2(2) 16-19
Ventilator Associated Pneumonia (VAP) is pneumonia occurring in a patient within 48 hours or more after intubation with an endotracheal tube or tracheostomy tube and which was not present before. It is also the most
Ventilator Associated Pneumonia (VAP) is defined as pneumonia occurring in a patient within 48 hours or more after intubation with an endotracheal tube or tracheostomy tube and which was not present before1, 2. Early onset VAP occurs within 48 hours and late onset VAP beyond 48 hours of tracheal intubation.
Between 5-15% of hospital in-patients develop infection during admission to ICU3. Patients are 5-10 times more likely to acquire nosocomial infections than patients in the wards4and approximately 86% of hospital associated pneumonia is linked with mechanical ventilation5.
Approximately 10-28% of critical care patients develop VAP6. VAP is also the most common and fatal infection of ICU7,8 and in the United States it affects 9-27% of intubated patients and doubles the risk of mortality as compared with similar patients without VAP9-13.
VAP may account for up to 60% of all Healthcare-Associated Infections14. VAP increases length of ICU stay by 28%16 and each incidence of VAP is estimated to generate an increased cost of £6000- £2200015.
Despite the high incidence, diagnosis remains challenging because many conditions common to ICU patients like ARDS, sepsis, cardiac failure and lung atelectasis have similar clinical signs. More than 50% of patients diagnosed with VAP do not have the disease whereas upto one-third are not diagnosed17, 18. Unfortunately there is no clearly accepted gold standard for diagnosis of VAP19.
Centres for disease control and prevention (CDC) national healthcare safety network definition for VAP
Radiology signs (2 or more serial chest x-rays with at least one of the following)
Clinical signsAt least one of the following
and at least 2 of the following
Microbiological criteria (optional)
At least one of the following:
Histological landmark of VAP is multifocal disease favouring dependant lung segments, often at different stages of development and severity with cultures growing heterogenous microbial flora.20,21
Several factors affect the aetiology of VAP
VAP that occurs within 48 hours after tracheal intubation is usually termed as early onset often resulting from aspiration, which complicates intubation process22. VAP occurring after this period is late onset. Early onset VAP is often due to antibiotic sensitive bacteria (eg oxacillin-sensitive Staphylococcus aureus, Hemophilious influenza and Streptococcus pneumoniae), whereas late onset VAP is frequently caused by antibiotic resistant pathogens (eg.oxacillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, acinetobacter species and enterobacter species) 23,24,25
The pathogenesis of VAP usually requires that two important processes take place:
- Bacterial colonisation of the aero-digestive tract
- Aspiration of contaminated secretions into the lower airway26.
Therefore, the strategies to prevent VAP usually focus on reducing the burden of bacterial colonisation in the aero-digestive tract, decreasing the incidence of aspiration or both.
The presence of invasive medical devices is an important contributor to the pathogenesis and development of VAP27. Many patients have nasogastric tubes that predispose them to gastric reflux and increase the potential for aspiration. Endotracheal tubes facilitate bacterial colonisation of the tracheo-bronchial tree and lower airway aspiration of contaminated secretions through mucosal injury, pooling of contaminated secretions above the endotracheal tube cuff and elimination of the cough reflex26. The ventilator circuit and the respiratory-therapy equipment may also contribute to the pathogenesis of VAP if they become contaminated with bacteria, which usually originate in the patient’s secretions26, 28.
The National Institute of Clinical Excellence (NICE) in collaboration with National Patient Safety Agency (NPSA) is examining four technical patient safety solutions for the prevention of VAP and in the process of publishing guidelines. The latest technical patient safety solutions for VAP was published in August 2008 which says
1. Body position-mechanically ventilated and intubated patients should be positioned with their upper body elevated for as long as possible. This may be inappropriate in some patients. eg. spinal injuries.
2. Oral antiseptics e.g. 2% chlorhexidine should be included as part of oral hygiene regimen for all patients who are intubated and ventilated. There is insufficient evidence to recommend any particular antibiotic regimen.
3. Use of kinetic beds - a lack of robust evidence meant the Committee was unable to make recommendations for action on the use of kinetic beds.
4. Care bundles - although the evidence supported the use of elements of care bundles; there was insufficient evidence to recommend a care bundle of any specific design.
The Department of Health published the following ‘High impact intervention’ for ventilated patients in June 2007
- Elevation of the head of bed to 35-40 degrees
- Sedation holding
- Deep Vein Thrombosis prophylaxis
- Gastric ulcer prophylaxis
- Appropriate humidification of inspired gas
- Appropriate tubing management
- Suctioning of respiratory secretions (including use of gloves and decontaminating hands before and after the procedure)
- Routine oral hygiene as per local policy
In addition the following also may contribute to the prevention of VAP
- Prolonged nasal intubation (more than 48hrs) should be avoided because of the association between nosocomial sinusitis and ventilator-associated pneumonia29.
- Several investigations have suggested that secretions that pool above the inflated endotracheal tube cuffs may be a source of aspirated material and thus VAP. Endotracheal tubes with separate dorsal lumen above the cuff to suction pooled secretions from the subglottic space are now available. The pressure of the endotracheal tube cuff should be adequate to prevent the leakage of colonised subglottic secretions into the lower airway26,30.
Previous administration of antibiotics is an important risk factor for VAP because of the presence of antibiotic-resistant bacteria31. In an attempt to reverse the trend towards increasing rates of antimicrobial resistance among hospital acquired infections, more effective strategies for using antibiotics have been advocated that restrict antibiotic use or offer guidelines for their use 32, 33. Eliminating or reducing the unnecessary use of antibiotics should be the primary goal in reducing antibiotic-resistant nosocomial infections32.
The routine use of prolonged courses of empirical therapy i.e. therapy not supported by results of clinical cultures should be avoided to minimise the subsequent development of antibiotic-resistant infections.
The use of aerosolised antibiotics for the prevention of VAP has been abandoned because of its lack of efficacy and subsequent emergence of antibiotic-resistant infections28.
Similarly the routine use of selective digestive tract decontamination has not gained acceptance in the UK and USA because of its lack of demonstrated effect on mortality, emergence of antibiotic resistant infections and additional toxicity. NICE is currently in consultation for selective decontamination of digestive tract guidelines. The technical patient safety solutions for VAP in adults were published in August 2008.
The Committee examined evidence, which suggested that selective decontamination of the digestive tract (SDD) using topical antibiotics may reduce the incidence of VAP and that SDD regimes that include systemic antibiotics may also reduce mortality. However, Specialist Advisers stated that UK intensive care specialists had particular concerns about the risk of infection with Clostridium difficile and the induction and/or selection of resistant, including multiresistant, microorganisms as a result of SDD. Therefore the Committee recommended further research into SDD in a UK setting.
Use of broad-spectrum antibiotics is also not recommended for the prevention of VAP because of increasing antibiotic resistance among subsequent hospital acquired infections. Targeted antibiotic therapy with appropriate dose of appropriate antibiotic is the sensible thing to do.
Various vaccination programmes in adults and children have reduced the incidence of pneumonia caused by specific pathogens including H.influenzae type B, Streptococcus Pneumoniae and Influenza virus 34, 35.Vaccinations against these may prevent some hospital acquired infections. Pneumococcal and influenza vaccination must be considered before hospital discharge or included in the discharge planning for all patients at increased risk for subsequent respiratory infections including VAP.
There have been new advances in equipment and techniques to help prevention of VAP
- Endotracheal and tracheostomy tubes with an extra subglottic port to clear pooled secretions above the endotracheal and tracheostomy tube cuff.
- Continuous suctioning of the subglottic secretions.
- Endotracheal tubes with specially designed cuffs that do not allow pooled secretions above the cuff to trickle down causing micro-aspiration and ultimately leading to VAP. eg. Endotracheal tubes with microthin polyurethane cuff.
- Specially designed closed Tracheal Suctioning Systems (TSS) as compared to open tracheal suctioning systems. However a meta analysis of randomised controlled trial showed that closed suctioning system is not associated with a lower incidence of VAP or mortality as compared to open suctioning36
We thank Dr. S. Parida (Consultant Microbiologist) for her valuable contribution in helping us write this manuscript.
HARSHAL WAGH, Registrar in Anaesthesia, St Albans City Hospital, United Kingdom
DEVARAJA ACHARYA, Consultant in Anaesthesia and Critical Care, St Albans City Hospital, United Kingdom
CORRESPONDENCE: DR HARSHAL WAGH, Registrar, Dept of Anaesthesia, Level I, St Julians Ward, St Albans City Hospital, St Albans, UK, AL3 5PN
Email: [email protected]
- Prevention of ventilator-associated pneumonia: consultation NICE, Sept 2007
- Ventilator associated-pneumonia JAMA 2007; 297: 1616-1617
- Eggimann P, Pittet D. Infection control in the ICU. Chest 2001; 120: 2059-93
- Weber DJ, Raasch R, Rutala WA. Nosocomial infections in the ICU: the growing importance of antibiotic-resistant pathogens. Chest 1999; 115: 34S-41S
- Richards MJ, Edwards JR, Culver DH, Gaynes RP. Nosocomial infections in medical intensive care units in the United States. National Nosocomial infections Surveillance System.Crtic Care Med.1999 May; 27950: 887-92
- The prevalence of nosocomial infection in intensive care units in Europe. Results of the European Prevalence of Infection in Intensive Care (EPIC) Study. EPIC International Advisory Committee 1995.
- Legras A, Malvy D, Quinioux AI, et al. Nosocomial Infections: prospective survey of incidence in five French intensive care units. Intensive Care Med.1998; 24: 1040-1046.
- Urli T, Perone G, Acquarolo A, Zappa S, Antonini B, Ciani A. Surveillance of infections acquired in intensive care: usefulness in clinical practise. J Hosp Infect. 2002; 52: 130-135
- Heyland DK, Cook DJ, Griffith L, keenan SP, Brun-Buisson C; Canadian Critical Trials Group. The attributable morbidity and mortality of ventilator-associated pneumonia. Am J Respir Crit Care Med. 1999; 159:1249-1256
- Fagon JY, Chastre J, Vuagnat A, Trouillet JL, Novara A, Gilbert C. Nosocomial pneumonia and mortality among patients in intensive care units. JAMA 1996; 275:866-869.
- Rello J, Quintana E, Ausina V, et al. Incidence, etiology and outcome of nosocomial pneumonia in mechanically ventilated patients. Chest, 1991; 100:439-444.
- Jiménez P, Torres A, Rodriguez-roisin R, et.al. Incidence and etiology of pneumonia acquired during mechanical ventilation. Crit care Med.1998; 17:882-885.
- Safdar N, Dezfulian C, Collard HR, Saint S. Clinical and economic consequences of ventilator-associated pneumonia; a systemic review.Crit Care Med.2005; 33:2184-2193
- CDC. Guidelines for preventing Health -Care -Associated Pneumonia, 2003. Recommendation of the CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR 2004; 53(No.RR-3)
- Nosocomial pneumonia: incidence, morbidity and mortality in the intubated-ventilated patient. Pittett 1994
- Nosocomial viral ventilator-associated pneumonia in the intensive care unit: a prospective cohort study. Pfr Vincent 2005
- Petersen IS, Aru A, SkØdt V, et al. Evaluation of pneumonia diagnosis in intensive care patients. Scand J infect Dis.1999; 31:299-303
- Fagon JY, Chastre J, Hance AJ, Domart Y, Trouillet JL, Gilbert C. Evaluation of clinical judgement in the identification and treatment of nosocomial pneumonia in ventilated patients.Chest.1993; 103:547-553
- American Thoracic Society; Infectious diseases Society of America. Guidelines for the management of adults with hospital-acquired, ventilator associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med.2005; 171:388-416.
- Rouby JJ, Martin De Lassale E, Poete P, et al. Nosocomial bronchopneumonia in the critically ill: histologic and bacteriologic aspects. Am Rev Respir Dis.1992; 146:1059-1066.
- Fabregas N, Torres A, El-Ebiary M, et al. Histopathologic and microbiologic aspects of ventilator-associated pneumonia. Anaesthesiology.1996; 84:760-761
- Pingleton SK, Fagon JY, Leeper KV Jr. Patient selection for clinical investigation of ventilator-associated pneumonia: criteria for evaluating diagnostic techniques. Chest 1990; 97:170-81.
- Niederman MS,Craven DE, Fein AM, Schultz DE. Pneumonia in the critically ill hospitalised patient. Chest 1990; 97:170-81.
- Kollef MH, Silver P,Murphy DM, Trovillion E. The effect of late-onset ventilator-associated pneumonia in determining patient mortality. Chest 1995; 108:1655-62.
- Rello J, ausina V, Ricart M, Castella J, Prats G. Impact of previous antimicrobial therapy on the therapy on the etiology and outcome of ventilator-associated pneumonia. Chest 1993; 104:1230-5.
- Craven DE, Steger KA. Epidemiology of nosocomial pneumonia: new perspectives on an old disease. Chest 1995; 108: Suppl: 1S-16S.
- Kollef M. Current concepts - the prevention of VAP. NEJM 340; 8:627-634.
- Tablan OC, Anderson LJ, Arden NH, Breiman RF, Butler JC, Mcneil MM. Guideline for prevention of nosocomial pneumonia: The Hospital Infection Control Practices Advisory Committee, Centres For Disease Control And Prevention.Infect Control Hosp Epidemiol 1998; 19:304
- Rouby JJ, Laurent P, Gosnach M et al. Risk factors and clinical relevance of nosocomial maxillary sinusitis in the critically ill. Am J Respir Crit Care Med 1994; 150: 776-83
- Valles J, Artigas A, Rello J et al. Continuous aspiration of subglottic secretions in preventing ventilator associated pneumonia. Ann Intern Med 1995; 122:179-86.
- Crouch Brewer S, Wuderink RG, Jones CB, Leeper KV Jr. Ventilator-associated pneumonia due to Pseudomonas aeruginosa. Chest 1996; 109:1019-29
- Goldman DA, Weinstein RA, Wenzel RP, et al. Strategies to prevent and control the emergence and spread of antimicrobial-resistant microorganisms in hospitals: a challenge to hospital leadership. JAMA 1996; 275:234-40.
- Evans RS, Pestotnik SL, Classen DC, et al. A computer-assisted management programme for antibiotics and other anti-infective agents. N Engl J Med 1998; 338:232-8.
- Herceg A.The decline of Haemophilus influenza type b disease in Australia.Commun Dis Intell 1997; 21:173-6.
- Gross PA, Hermogenes AW, Sacks HS, Lau J, Levandowski RA. The efficacy of influenza vaccine in elderly persons: a meta analysis and review of literature. Ann Intern Med 1995; 123:518-27.
- I I Siempos, K Z Vardakas, M E Falagas. Br J Anaesth 2008; 100(3): 299-306.
- Technical patient safety solutions for Ventilator-associated pneumonia in adults. NICE August 2008
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