DEVELOPMENT OF POST EXTUBATION PNEUMONIA: ROLE OF 24 HOURS OF ENDOTRACHEAL INTUBATION AND MECHANICAL VENTILATION. AN EXPERIMENTAL STUDY

INTRODUCTION. Tracheal intubation is a major risk factor for nosocomial pneumonia, since microaspiration of bacterial colonized secretion across the endotracheal tube cuff is considered a primary pathogenetic way for ventilator associated pneumonia (VAP). OBJECTIVES. We hypothesized that 24 h of tracheal intubation would allow the access of a conspicuous bacterial load into the lower airways to enhance the onset of pneumonia in the post extubation period. METHODS. Fourteen sheep were randomized into two groups: 1. Seven were mechanically ventilated for 24 h (control group); 2. Seven were mechanically ventilated for 24 h and then were extubated and maintained in spontaneous ventilation for 48 h (awaken group). At the end of the study all the sheep underwent to microbiology and histology of the lung. No antibiotics were administered. RESULTS. In the control group one animal developed pneumonia during mechanical ventilation while five had heavily colonized lung (median of three lobes, colonization range: 1.09E + 05–1.38E + 09). In the awaken group one animal developed pneumonia during mechanical ventilation and three developed pneumonia during the 48 h following extubation (median of 4.5 lobes, colonization range: 2.8E + 05–1.8E + 09). Two animals had sterile lungs in the control group and three in the awaken group. CONCLUSIONS. Twenty-four hours of tracheal intubation can lead to colonization of the lower airways, even without any clinical signs. This colonization can precipitate the development of pneumonia after extubation.