Evidence for dynamic phenomena in residual tracheal tube biofilm.

It has been proposed recently that a dynamic physical process occurring in the tracheal tube might account for the dissemination of bacteria and biofilm fragments into the lungs during mechanical ventilation, and the subsequent development of ventilator-associated pneumonia. In this study of tracheal tubes from consecutive adult intensive care patients, biofilms were detected radiographically in 45 of 50 tubes, and were found at the lower end of the tube more often than at the upper end (P < 0.005). In 37 of 50 tracheal tubes, the maximum biofilm thickness was equal to or greater than the 0.5 mm required for gas-liquid interaction in a tube with an i.d. of 8.5 mm. In 23 of 50 tubes, wave-like patterns were found. Five tubes had no biofilm inside the bevelled tip and another six showed evidence of biofilm loss for a greater distance from the tip. These observations suggest that the distribution of tracheal tube biofilm is caused at least in part by dynamic phenomena in the tracheal tube.