Objective: To observe the formation of the biofilm in endotracheal tubes, the characteristics of etiology, drug resistance and effect on the biofilm and ventilator-associated pneumonia (VAP) of inhaled N-acetylcysteine (NAC).
Method: We selected 117 tracheally intubated and undergoing mechanical ventilation for ≥48 h in our hospital ICU from September 2010 to August 2012. All the cases were randomly divided into control group (60 cases) and study group (57 cases). The patients in the study group were treated with different doses of aerosolized NAC according to different ages, starting the first administration within 12 hours of mechanical ventilation, once every 8 hours, until stopping mechanical ventilation. Comparison was performed on the two groups in biofilm structure under the scanning electron microscopy, biofilm culture positive rate, VAP incidence, the etiology and drug resistance of the lower airway secretions and biofilms.
Result: (1) Electron microscopy showed that biofilm had formed in the endotracheal tube inner wall in early period of mechanical ventilation. With prolonged mechanical ventilation, biofilm structure improved. At the same time of mechanical ventilation, the thickness of biofilm in the study group decreased as compared with the control group. (2) Biofilm culture positive rate and incidence of ventilator-associated pneumonia decreased in the study group compared with in the control group (65%(37/57) vs. 80%(48/60), P<0.05; 11% (6/57)vs. 32%(19/60), P<0.01). (3) A large number of pathogenic bacteria colonized in the biofilm and gram-negative bacilli dominated. With prolonged mechanical ventilation, the cultured pathogens converged from the lower airway secretions and biofilm.
Conclusion: With prolonged mechanical ventilation, biofilm structure was improved. Inhalation of NAC can inhibit biofilm formation and reduce the incidence of VAP.