[The effect of subglottic secretion drainage on prevention of ventilator-associated lower airway infection]

To assess the influence of subglottic secretion drainage (SSD) on the morbidity of ventilator-associated pneumonia (VAP) in mechanically ventilated patients.

All studied patients who received mechanical ventilation (MV) estimated for more than 48 hours were intubated with a special type endotracheal tube with a small-bore cannula in the wall for SSD. The patients were randomly divided into two groups receiving SSD (group A) and usual care (non-SSD, group B) respectively. Bacterial culture of samples from lower airway secretion taken regularly by Bagpipe Protected specimen brush were performed, and at the same time the subglottic secretion and scraping-pharynx specimen were collected for bacterial quantitative culture and antibiotic sensitivity test. The clinical data were recorded and the duration of MV, the length of stay in hospital and the time of occurrence of ventilator-associated airway infection (VAAI) and VAP were analyzed.

(1) In patients with MV < 5 days: The incidence of VAAI and VAP in group A (VAAI: 8.3% and VAP: 6.0%) was lower than those in group B (VAAI: 24.0% and VAP: 20.0%, P < 0.05). The onset of VAAI and VAP was delayed in group A [VAAI: (7.4 +/- 3.0) d and VAP: (7.7 +/- 3.2) d] as compared with group B [VAAI: (4.9 +/- 1.4) d and VAP: (4.6 +/- 2.1) d, P < 0.05]. There were no significantly statistic differences for hospital mortality, overall duration of mechanical ventilation, lengths of stay in the hospital between the two groups (P > 0.05). (2) The same organism as that previously found from subglottic secretion was isolated by PSB in 21.4% patients. (3) The concentration of bacteria in subglottic secretion from group A was decreased significantly as compared to that of group B. (4) Gram-negative bacilli were the main pathogens in the lower respiratory tract in the two groups. The dominant bacteria cultured in the lower airway secretions were Pseudomonas aeruginosa and Acinetobacter baumanii. There was no significant difference between the two groups in the spectrum of bacteria (P > 0.05).

(1) SSD reduced the incidence of VAAI and VAP in patients with MV < 5 d. The onset of VAAI and VAP was delayed in group A as compared with group B. The concentration of bacteria in the subglottic secretion was significantly reduced by subglottic secretion drainage. (2) Migration of the dominant bacteria of the subglottic secretion was one of the important factors for VALAI. (3) The dominant cultured bacteria in the lower airway secretion were gram-negative bacilli, most commonly Pseudomonas aeruginosa and Acinetobacter baumanii.