ventilator-associated pneumonia

When a critically ill person cannot breathe well enough on their own, a tube is passed into the windpipe and a machine breathes for them. That life-saving tube, however, props open the airway's natural defenses and offers germs a direct path into the lungs. Ventilator-associated pneumonia is the lung infection that can take hold along this route.

By definition it is pneumonia developing in a patient who has been on mechanical ventilation through a breathing tube for more than 48 hours. The tube bypasses the filtering and coughing defenses of the upper airway, lets secretions pool above the cuff and trickle downward, and provides a surface on which bacteria form a stubborn film. The organisms are often resistant hospital strains such as Pseudomonas and MRSA, which makes the infection serious.

It is suspected when a ventilated patient develops new fever, increased or purulent secretions, falling oxygen and a new infiltrate on imaging; samples from deep in the airway help identify the germ. Treatment is prompt broad antibiotics, narrowed once cultures return. Prevention bundles — raising the head of the bed, regular mouth care, minimizing sedation and freeing patients from the ventilator as early as safely possible — meaningfully cut the risk.

Diagnosing it is notoriously tricky, because fever and lung shadows in an intensive-care patient have many causes, so over-diagnosis and unnecessary antibiotics are a recognized pitfall.