Ventilator-Associated Pneumonia (VAP)
Pneumonia ranks as the second most common nosocomial infection in this county, according to the Centers for Disease Control and Prevention. The mechanical ventilation required for critical care patients is one reason why this infection ranks so high.
Ventilator-associated pneumonia, VAP, occurs in approximately 22.8 percent of patients put on a ventilator for less than 48 hours. Understanding the pathophysiology of VAP and the risk factors associated with it is how medical professionals can help prevent this potentially deadly infection in ventilated patients.
What is Ventilator-Associated Pneumonia?
Ventilator-associated pneumonia is divided into two categories: early and late. The reason for this distinction lies in the pathophysiology of the infection. Patients diagnosed with pneumonia within 96 hours of intubation will have an antibiotic-susceptible infection while those who get sick after the 96 hour marker are more likely to have an antibiotic-resistant infection. A physician can prescribe an intervention to prevent the infection before or immediately after the patient is put on the respirator to ward off the disease.
Processes of VAP
There are two main processes association with VAP infections. The first occurs due to colonization of the respiratory and digestive tracts. The colonization can come from a number of sources such as the sinus cavities, dental plaque or cross-contamination. The endotracheal tube provides a direct route for bacteria to travel into the lungs. The inhalation of colonized bacteria leads to an active host response and triggers the pneumonia.
The second means of infection occurs when the patient aspirates gastric contents into the lungs. The introduction of a nasogastric or orogastric tube interferes with the body’s natural defense against aspiration, causing an increase in gastrointestinal reflux.
Since any patient who receives mechanical ventilation is at risk for pneumonia, an accurate diagnosis is critical, but difficult. Delaying treatment leads to higher mortality rates, however.
The initial diagnosis can be made based on the progressive infiltration seen in chest x-rays. Additionally, doctors will order sputum samples for microbiological testing and possibly rely on more invasive tests done via bronchoscopy. The additional tests are necessary to confirm the diagnosis and define the treatment by identifying the pathogen. Additional testing will rule out other causes of the infiltration, such as acute respiratory distress syndrome or pulmonary embolism, as well.
Other signs of ventilator-associated pneumonia include:
- Purulent sputum
Certain patients have a higher risk of developing VAP. Risk factors are divided into three categories:
Host-related risks include comorbid conditions such as chronic obstructive pulmonary disease. The body positioning of the patient falls into this category, as well. Ventilated patients kept in a supine position are at higher risk than those with even slightly elevated heads. Level of consciousness plays a role, too.
Device-related risk factors would include:
- Endotracheal tube
- Ventilator circuit
- Nasogastric tube
- Orogastric tube
For example, secretions can pool around an endotracheal tube creating an ideal environment for bacterial growth.
Personnel-related risks are related to cross-contamination issues such as poor hand-washing techniques or failure to reglove between patients.
Tips for Preventing Ventilator-Associated Pneumonia
Just understanding that any patient put on a ventilator is at risk for this potentially deadly infection is the first step in preventing the disease. Staff working with ventilated patients must take precautions to reduce the risk factors and improve the outcomes.
- Patients must have their heads elevated between 30 to 45 degrees unless they have a medical condition that prevents this body positioning.
- Practice good hand washing hygiene
- Reglove between patients to prevent cross-contamination
- Wear necessary personal protection
- Conduct daily checks to see if the patient is able to breathe without mechanical assistance
- Perform proper disinfection on ventilator equipment between patients
- Follow protocols for cleaning the patient’s mouth regularly
Nurses serve as the first line of defense when it comes to preventing nosocomial infections caused by bacterial colonization. Things like requiring vaccinations and putting up signs to remind the nurses to wash their hands and reglove are cost-effective ways to reduce the incidence of this disease.
Physicians can order pharmacological interventions that reduce the risks, as well. Chlorhexidine oral rinse, for example, improves oral hygiene and decreases bacterial colonization in the mouth. A 2004 study published in Critical Care Medicine shows this intervention every six hours reduces the number of VAP infections by 16 percent.
With the risk of antibiotic-resistant infections increasing exponentially over the last decade, ventilator-associated pneumonia becomes an even more prevalent concern. VAP is often preventable with only a few minor precautions.