The criteria used for diagnosis of VAP varies by institution, but tends to be a combination of several of the following radiographic, clinical sign, and laboratory evidence:
Temperature greater than 38 °C or less than 36 °C
White blood cell count greater than 12,000/mm3 or less than 4,000/mm3
Purulent secretions, increased secretions, or change in secretions
Positive tracheal cultures or bronchoalveolar lavage cultures
Some sign of respiratory distress, such as shortness of breath, rapid breathing, abnormal breathing sounds when listening with stethoscope
Increased need for oxygen on the ventilator
Chest X-rays: at least two serial x-rays showing sustained or worsening shadowing (infiltrates or consolidations)
Positive cultures that were obtained directly from the lung environment, such as from the trachea or bronchiolesAs an example, some institutions may require one clinical symptoms such as shortness of breath, one clinical sign such as fever, plus evidence on chest xray and in tracheal cultures.There is no gold standard for getting cultures to identify the bacteria, virus, or fungus that is causing the pneumonia, and there are invasive and non-invasive strategies for obtaining the culture sample. One non-invasive strategy collects cultures from the trachea of people with symptoms of VAP. Another is more invasive and advocates a bronchoscopy plus bronchoalveolar lavage (BAL) for people with symptoms of VAP. Both strategies also require a new or enlarging infiltrate on chest x-ray as well as clinical signs/symptoms such as fever and shortness of breath. There is no strong evidence to suggest that an invasive method to collect cultures is more effective than a non-invasive method.
Prognosis
VAP occurring early after intubation typically involves fewer resistant organisms and is thus associated with a more favorable outcome. Because respiratory failure requiring mechanical ventilation is itself associated with a high mortality, determination of the exact contribution of VAP to mortality has been difficult. As of 2006, estimates range from 33% to 50% death in patients who develop VAP. Mortality is more likely when VAP is associated with certain microorganisms (Pseudomonas, Acinetobacter), blood stream infections, and ineffective initial antibiotics. VAP is especially common in people who have acute respiratory distress syndrome (ARDS). Epidemiology
Between 8 and 28% of patients receiving mechanical ventilation are affected by VAP. VAP can develop at any time during ventilation, but occurs most often in the first week of mechanical ventilation. There is some evidence for gender differences in the course of VAP: men have been found to get VAP more often, but women are more likely to die after contracting VAP. Recent reports indicate that patients with Coronavirus disease 2019 who require mechanical ventilation in an Intensive care unit are at increased risk of ventilator-associated pneumonia, compared to patients without COVID-19 ventilated in the same unit and patients who had viral pneumonitis arising from viruses other than SARS-CoV-2. Why this increased susceptibility should be present remains uncertain, as the noted reports adjusted for duration of ventilation, it is likely that the increased susceptibility relates impaired innate immunity in the lungs.