Contribution of water condensation in endotracheal tubes to contamination of the lungs.

We postulated that water condensate in endotracheal tubes (ETTs) transports bacteria in the ETTs into the lungs during mechanical ventilation. Thirty-two ETTs obtained from freshly extubated patients were studied under wet and dry conditions using a physiologic lung model. All bacteria expelled from the ETTs were collected on culture plates positioned beneath the ETT. The lung model was ventilated with saturated air at 37 degrees C over two time periods (60 min each), one in which condensation formation was prevented and the second in which condensation formed within the ETT. A mean of 457.6 colony-forming units (CFU)/h were expelled with condensation compared to a mean of 2.4 CFU/h without condensation. We concluded that bacteria were continuously transported from the ETT into the lungs during mechanical ventilation in water droplets. Prevention of water condensation abolishes this constant bacterial inoculation in a lung model.