Ventilator-Associated Pneumonia and Role of Nurses in Its Prevention

Ventilator-associated pneumonia (VAP) is one of the most frequent nosocomial infections among ventilated patients in ICUs, associated with an increase in days of ICU stay, morbidity, and mortality. Its prevention is a significant concern in every hospital. Most of the interventions and prevention strategies are part of routine nursing care. Nurses have different vital roles such as care provider, manager, educator, coordinator, and evaluator in preventing VAP. Lack of knowledge of infection prevention and proper nursing care among nurses may become a barrier in adhering to evidence-based guidelines for preventing ventilator-associated pneumonia. This study will help nurses to know about VAP and its prevention in detail so that they can apply the knowledge in clinical practice. Understanding pathophysiology of VAP, its risk factors, and care bundle is vital for the proper prevention and treatment of VAP. There must be specific protocols, strategies and active surveillance in every ICU regarding the care bundle. _______________________________________________________________________________________


INTRODUCTION
Ventilator-associated pneumonia (VAP), a subset of nosocomial pneumonia, is the common infectious complication among intensive care units (ICUs) patients who have been treated with mechanical ventilation for 48 hours or longer, with no prior signs or symptoms of lower respiratory infection before being intubated and treated with mechanical ventilation.2][3][4] Furthermore, VAP is also associated with delayed extubation, prolonged stay in the ICU and hospital, increased mortality and morbidity, and increased use of healthcare resources. 5

BACKGROUND
VAP is responsible for 25-42% of all infections that occur within ICUs and is the second most common healthcare-associated infections. 7Intubated patients are at risk of developing VAP and the incidence increases with the duration of ventilator support. 8he incidence of VAP is 22.8% in patients receiving mechanical ventilation.This is widespread in nosocomial pneumonia as 86% patients receive ventilatory support. 4evertheless, variation is found depending on criteria used for diagnosis, the type of ICU, hospital resources or study population. 8The estimated rate of VAP is 1.4 to 5.8 events per 1000 intubated patients, with a downward trend since 2000. 9,10Downward trend is more prominent in the United States, probably due to the implementation of ventilator bundles. 11It has been reported that the VAP mortality rate is between "10%" to "40%". 12LOS in the intensive care unit is increased by 5 to 7 days and hospital length of stay 2-to to 3-fold in patients with VAP.Hospital costs associated with VAP were estimated 40,000$ for each case of VAP. 2,13][16] VAP is a significant concern for ventilated patients in the intensive care units (ICUs), so a priority must be given while caring critically ill patients. 7,15,17,18

PATHOPHYSIOLOGY
To understand and follow VAP prevention strategies, nurses should be aware of the pathophysiology of VAP.The VAP can be divided into two types according to the time elapsed from the beginning of the mechanical ventilation (MV) to the onset of pneumonia: early onset and late onset. 19Early-onset occurs 48 to 96 hours subsequent to intubation and is associated with antibiotic-susceptible organisms such as Staphylococcus aureus, Streptococcus pneumonia, Hemophilus influenza, Proteus species, Serratia marcescens, Klebsiella pneumonia and Escherichia coli.Late-onset usually occurs after 96 hours of intubation and is associated with antibiotic-resistant organisms such as Pseudomonas aeruginosin, Methicillin-resistant Staphylococcus aureus, Acinetobacter species and Enterobacter species. 2 According to the CDCP, a patient with VAP may have increased body temperature, leukopenia, new onset of purulent sputum, apnea, tachypnea, nasal flaring with retraction of the chest wall or grunting, wheezing, rales, rhonchi, and cough. 9The pathophysiology of VAP involves colonization of the respiratory and digestive tracts and microaspiration of secretions from the upper and lower parts of the airway.VAP develops when bacteria colonize the pulmonary parenchyma or lower respiratory tract of a patient receiving mechanical ventilation.Due to aspiration of secretions or the use of contaminated equipment, organisms may spread through the oropharynx, sinus cavities, nares, dental plaque, gastrointestinal tract, patient-to-patient contact and ventilator circuit leading to bacterial colonization of the lungs. 2,20,21Inhaling of colonized bacteria from the sources described above can result in an active host response, resulting VAP in the patient.
The presence of an endotracheal tube provides a direct route for colonized bacteria to enter the lower respiratory tract.Upper airway and oral secretions pool above the cuff of the tube.The pool lines along the tube forming a biofilm and contains a large amount of bacteria that can spread to the lungs by ventilator-induced breaths, which may be dislodged by instilling of saline into the tube, suctioning, coughing, or repositioning of the tube. 21,22Endotracheal tubes cause an unusual interruption between the upper airway and the trachea, providing bacteria a direct route into the lower airway, bypassing the upper airway. 21Due to the presence of bacteria in lower airway, the body's ability to filter and humidify air will decrease. 22Because of the presence of such tube, the cough reflex is frequently decreased or eliminated and mucociliary clearance can be impaired.Furthermore, an endotracheal tube provides a place for bacteria to bind in the trachea leading increment in the production and secretion of mucus. 23This leads to impairment of natural host defense mechanisms increasing the likelihood of bacterial colonization and subsequent aspiration of the colonized organisms.Micro or macro aspirations of oropharyngeal or gastric fluids are an essential step in the development of VAP. 14 As stomach may serve as a reservoir for bacteria,aspiration of gastric contents can be another potential cause of VAP.Patients receiving mechanical ventilation mostly have a nasogastric or an orogastric tube for enteral feedings, administration of medications or gastric decompression.The presence of a nasogastric or an orogastric tube interrupts the gastro-esophageal sphincter leading to increased gastrointestinal reflux, provides a route for bacteria to translocate to the oropharynx and colonizes the upper airway.Enteral feedings increase both gastric pH and gastric volume, increasing the risk of both bacterial colonization and aspiration, and subsequently may cause infection. 24

DIAGNOSIS
Accurate diagnosis and treatment of VAP are challenging as well as controversial since every intubated patient who is receiving ventilatory support is at risk. 25 The diagnosis is done on the basis of radiographic findings, clinical findings, and results of microbiological tests of sputum such as culture and sensitivity, or invasive testing such as bronchoscopy. 26Findings on chest radiographs are not reproducible and should not be used alone for the diagnosis of VAP, as pulmonary infiltrates visualized on chest radiographs of patients receiving mechanical ventilation may be because of atelectasis, aspiration, pulmonary embolism, pulmonary edema, alveolar hemorrhage, pulmonary infarction, and acute respiratory distress syndrome. 2Five of the predominant signs of VAP are significant heavy growth reported in the culture of tracheal aspirates, body temperature more than 38 0 C or less than 35 0 C, development of progressive new infiltrate on X-ray, leukocytosis WBC more than 10x 109/L or leucopenia WBC less than 3x109 /L and ten leucocytes per HPF in gram stain of tracheal aspirates.The presence of any two of the above signs can be considered as diagnostic of VAP.

RISK FACTORS
Every intubated patient receiving ventilatory support is at risk for VAP.There are different types of risk factors, which can be divided into three categories: host related, device related, and personnel related.
Host-related risk factors include preexisting conditions such as immunosuppression, chronic obstructive lung disease, and acute respiratory distress syndrome.Other host-related factors include patients' body positioning, advanced age, the level of consciousness, the number of intubations, blood transfusion and medications including sedative agents and antibiotics. 2,27Decreased in the level of consciousness results in the loss of a cough and gag reflexes and increased the risk of aspiration and VAP. 28vice-related risk factors include the endotracheal tube, the ventilator circuit, and the presence of a nasogastric or an orogastric tube.When a patient is in the supine position, pulmonary aspiration increases and secretions pool above the cuff of an endotracheal tube.In low cuff pressure, such pools may lead to microaspiration or leakage of bacteria around the cuff into the trachea.In addition, nasogastric and orogastric tubes also disrupt the gastro-esophageal sphincter leading to reflux and an increased risk for VAP. 2,29rsonnel-related risk factors include improper hand washing , failure to change gloves between contacts with patients and not wearing personal protective equipment when antibiotic-resistant bacteria have been identified.If healthcare staffs do not use proper hand-washing techniques during interventions such as suctioning or manipulation of the ventilator circuit of an intubated patient, the likelihood of cross-contamination between patients will increase the risk of VAP.Failure to wash hands and change gloves between contaminated patients has also been associated with an increased incidence of VAP. 30 Not only this but also failure to wear proper personal protective equipment when antibioticresistant organisms have been identified increased the risk of cross-contamination between patients. 25

MANAGEMENT
The management of VAP is important as well as challenging job for healthcare team in the ICU.It depends on the interaction between the infective agent, the host response, and the antimicrobial drug used.The pulmonary infection may occur when the pathogen spreads to the lungs.However, the vigorous approach has evolved in VAP management, updating local epidemiology, evaluating VAP, diagnostic tools every day, and assessing host response using clinical and biochemical parameters.The two important steps recommended for the treatment of a patient with VAP are etiologic diagnostic testing and the immediate initiation of antibiotics. 31Antibiotic Management: As the initial management of VAP, appropriate antibiotics should be selected for each patient based on the individual risk factors for multidrug-resistant pathogens and time of onset of disease.Furthermore, antimicrobial spectrum of activity, effective doses of antibiotics, pharmacokinetic profiles and adverse effects of individual antimicrobials should be carefully reviewed. 32For the patients with early-onset VAP and no risk factors for multidrugresistant (MDR) pathogens, currently recommended initial empiric antibiotics include one of the following options: Ceftriaxone, Fluoroquinolones, Ampicillinsulbactam and Ertapenem.For patients with VAP and risk factors for MDR pathogens or for patients with lateonset VAP, initial antibiotic therapy may consist of one of the following options: Antipseudomonal cephalosporins (eg, cefepime, ceftazidime), Antipseudomonal carbapenems (imipenem or meropenem), Beta-lactam/ beta-lactamase inhibitors (piperacillin-tazobactam) with an antipseudomonal fluoroquinolone (ciprofloxacin) or aminoglycoside plus linezolid or vancomycin (if risk factors for methicillin-resistant Staphylococcus aureus are present) and Telavancin is indicated for HABP/ VAP caused by susceptible isolates of Staphylococcus aureus, including methicillin-susceptible and resistant isolates, when alternative treatments are not suitable. 33

PREVENTION
5][36] It is based on pathophysiology and etiology of pneumonia, mode of mechanical ventilation and duration of ventilation, which offers prompt and consistent preventive strategies. 4Implementing care bundles in clinical practice for mechanically ventilated patients admitted to ICUs 34 and active surveillance 28 are associated with a reduced risk of VAP.
For prevention and reduction of VAP, appropriate multidisciplinary approaches and interventions should be applied in ICUs which should begin at the time of intubation, or if possible prior to intubation and should be continued until extubation. 2,37It should focus on avoiding microaspiration of subglottic secretions, preventing oropharyngeal colonization, and preventing contamination of ventilator equipment. 38any strategies and guidelines have been developed and proposed.However, in clinical practice, the implementations of evidence-based guidelines for VAP are variable and are adversely affected by the lack of training, lack of an adequate infection control program, and lack of knowledge among healthcare providers of such guidelines.
Protocols for non-invasive mechanical ventilation (NIMV) in acute exacerbations of chronic obstructive pulmonary disease (COPD), weaning and sedation promoting lower infusion doses or its daily interruption should be available in every ICU. 19,39,40Strategies should be developed to incorporate evidence-based practices into the daily care provided to patients receiving mechanical ventilation. 41Daily assessments of readiness to wean and use of weaning protocols are very essential because the risk of VAP development increases with duration of mechanical ventilation. 40,42,43Proper implementation of the VAP bundle will decrease the ventilator days, LOS, and ultimately the VAP rates. 15rses are the first line of defense in preventing bacterial colonization of the oropharynx and the gastrointestinal tract.However, multidisciplinary persons like nurses, physicians, respiratory therapists and clinical pharmacists should be a part of VAP practices for high effectiveness.Critical care unit should ensure the availability of practice documents such as a policy, procedure or standards of care. 2,14Hand washing is the cost-effective measures to minimize nosocomial infection like VAP, so, the hand should be washed properly for 10 seconds prior and subsequent to all contact with patients. 25,44imilarly, wearing gloves is also an important action in the prevention of VAP. 41Bacterial colonization of the oropharynx and the gastrointestinal tract can be prevented by following the certain strategies such as proper hand washing, using oral decontamination , using stress ulcer prophylaxis, avoiding saline lavage with suctioning, turning patients at least every 2 hours and changing ventilator circuit when it is contaminated.Aspiration of oropharyngeal secretions and gastric contents containing bacteria are considered an essential step in the pathogenesis of VAP. 26 Aspiration can be prevented by positioning the head of the bed at an angle of 30° to 45° unless medically contraindicated, minimizing the use of narcotic and sedative agents , thoroughly suctioning the oropharynx, using endotracheal tubes that comprise continuous subglottic suction ports, monitoring gastric residual volumes for overdistention and maintaining adequate endotracheal tube. 2,14,44Head elevation prevents reflux and aspiration of bacteria from the stomach into the airways. 15,37,40,45,46,47Routine turning of patients at least every two hours can also increase pulmonary drainage and decrease the risk of VAP. 48e of noninvasive ventilation whenever possible and the minimization of the duration of ventilation can also aid in preventing VAP. 40,42Re-intubation has also been considered a risk of VAP due to an increased risk of aspiration of pathogens from the oropharynx of patients with subglottic dysfunction subsequent to several days of endotracheal intubation.Re-intubation should be avoided as far as possible and planned extubations should be improved with the design of protocols to enhance the quality of weaning, and planned tracheostomy for long-term ventilation. 49Preferable use of orotracheal instead of nasotracheal intubation 42 and prevention of airway contamination and maintenance of aseptic technique subsequent to intubation is essential while performing endotracheal suctioning.Proper oral hygiene decreases the risk of translocation and colonization of bacteria. 47Oral decontamination by both mechanical and pharmacological interventions decreases the likelihood of colonization of the oropharynx.Mechanical interventions such as tooth brushing and rinsing of the oral cavity or thoroughly suctioning secretions from the mouth to remove dental plaque and pharmacological interventions such as the use of chlorhexidine mouthwash, gentamicin, colistin, and vancomycin decrease the incidence of VAP by decreasing colonization. 2,37,46,50Appropriate antibiotic should be used for treating the patient in ICUs because extensive use of antibiotics has resulted in the emergence and rapid dissemination of Multidrugresistant (MDR), Methicillin-Resistant Staphylococcus aureus (MRSA), Extended-Spectrum β-Lactamase (ESBL) and Metallo-β-Lactamase (MBL) bacteria.Thus, their detection is crucial for the optimal treatment of patients and to control the spread of resistance. 51Saline lavage has long been considered a means to liquefy secretions and prevent plugs of mucus in endotracheal tubes.However, saline installation does not thin secretions, it reduces the amount of oxygen that reaches the lungs and increases blood pressure, heart rate, intracranial pressure and dislodges bacteria from the endotracheal tube into the lower airways increasing the risk of VAP.Maintaining adequate hydration, ensuring proper humidification of the ventilator circuit and using the nebulizer or mucolytic agents can help decrease the viscosity of secretions and eliminate the need for saline lavage. 2 The CDCP does not recommend changing the ventilator circuit more than once every 48 hours but only when visibly soiled. 25As the prolonged endotracheal intubation and subsequent aspiration of secretions around the endotracheal tube cuff are the major but not easily preventable determinants of VAP development, 52 daily interruptions of sedation and daily assessment of readiness for extubation are other integral components of the ventilator bundle, which helps in reducing duration of mechanical ventilation and LOS in the intensive care unit. 11e decrease in the use of narcotic and sedative agents prevents aspiration of gastric contents.Monitoring gastric residual volumes and administering agents to increase gastric motility have also been suggested to prevent gastric over distention. 15Prophylaxis to reduce deep-vein thrombosis (DVT) and peptic ulcer disease (PUD) are the important aspects of the VAP bundle.Patients treated with mechanical ventilation are sedated.So, DVT prophylaxis with administration of antithrombotic medications and antiembolism stockings are used.PUD prophylaxis such as histamine2 blockers increases the pH of gastric contents and protects the airway against acidic contents. 46e oropharynx should be suctioned thoroughly to prevent aspiration of the pooled secretions prior to replacing an endotracheal tube. 46Continuous low suction drainage of oral secretion from above the cuff decreases the chance to seep secretions into the lungs. 41he pressure within the cuff should be measured and maintained between 20 and 30 cm H2O to prevent aspiration of the secretions. 37Prevention of aspiration leads to prevention of colonization which decreases the risk of VAP.
Patients should be assessed daily for potential weaning and extubation from mechanical ventilation to decreases the risk of VAP by using methods like T-piece trials, weaning intermittent mandatory ventilation, and pressure-support ventilation as the presence of an endotracheal tube predisposes patients to VAP. 15,53 Daily assessment of the patient with an interruption in sedation and a spontaneous breathing trial for patient's readiness to be weaned from mechanical ventilation can reduce its duration, preventing VAP. 47The important VAP prevention bundle components discussed above are summarized in Table 1.
Subglottic suctioning prior to deflating the cuff of an endotracheal tube or moving the tube. 26.
Maintenance of endotracheal and tracheostomy cuff pressures between 20 and 30 cmH2O. 37.Planned tracheostomy for long-term ventilation. 49

17.
8. Turn patients at least every 2 hours. 2,14,44,48 Elevation of the head of bed 30°-45°, if not contraindicated. 2,14,15,37,40,44,45,46,47  Nes perform most procedures related to mechanical ventilation, so they should have appropriate knowledge regarding non-invasive positive pressure ventilation, daily weaning trials, sedation holidays, aspiration prevention, subglottic suctioning of endotracheal tubes, ET tube cuff pressure and head of the bed elevation.This knowledge should be applied correctly in practice to reduce the risk of VAP. 43,55Nurses should keep the records and reports accurately, manage in-service education to the nursing staff regarding infection prevention and proper health education counseling to the visitors.
As a whole, nurses are responsible for the overall care of the patient from admission till discharge.They are one of the members of the health team who spend most of the time caring patient and thus, have a vital role in the prevention of VAP.However, only having the knowledge is not sufficient but also applying it in the right place at the right time by providing overall nursing care as per the need of patient is essential.That is why critical care nurses play the most important role in the prevention of VAP.

WAY FORWARD
VAP is the common infectious complication among ICUs patients who have been treated with mechanical ventilation for 48 hours or longer, contributing to the substantial increase in morbidity, mortality, hospital costs and LOS.Healthcare systems play an important role in preventing VAP by developing strategies and guidelines and implementing it strictly.For the prevention and reduction of VAP rate, the successful multidisciplinary approaches should be applied in ICUs and education should be provided for all healthcare providers focusing on the risk factors and preventive measures of VAP.Most of the interventions and prevention strategies are part of routine nursing care, which they provide by playing different roles such as care provider, manager, educator, coordinator, and evaluator.