PROSPECTIVE-STUDY OF NOSOCOMIAL PNEUMONIA AND OF PATIENT AND CIRCUIT COLONIZATION DURING MECHANICAL VENTILATION WITH CIRCUIT CHANGES EVERY 48 HOURS VERSUS NO CHANGE

Circuits on mechanical ventilators with cascade humidifiers are are routinely changed every day or every other day, although humidifying cascades have been considered unlikely to increase the risk of respiratory infection because they do not generate aerosols. Moreover, changing ventilator tubings every 24 rather than every 48 h increases the risk of ventilator-associated pneumonia. To study the effects of ventilator circuit changes on the rate of nosocomial pneumonia and on patient and circuit colonization, 73 consecutive patients requiring continuous mechanical ventilation for more than 48 h were randomly assigned to either ventilator circuit changes every 48 h (Group 1, n = 38) or no change (Group 2, n = 35). Patients dying or being weaned before 96 h were not analyzed (Group 1 n = 3; Group 2 n = 7; leaving Group 1 n = 35 and Group 2 n = 28; p = 0.13). Ventilator-associated pneumonia was defined as the occurrence during mechanical ventilation or within 48 h after weaning of a new and persistent infiltrate on chest X-ray, purulent tracheal secretions, and a positive culture of a protected brush specimen (greater-than-or-equal-to 10(3) cfu/ml). Bacterial colonization was assessed every 48 h by quantitative cultures of pharyngeal swab, tracheal aspirate, humidifying cascade, and expiratory tubing trap. The two groups were similar in terms of age, indication for and duration of ventilation, and severity of illness. The incidence of pneumonia was similar in both groups (11 of 35 and 8 of 28 in Groups 1 and 2, respectively; p = 0.8), as was the duration of ventilation before pneumonia (10.1 +/- 5.8 versus 9.1 +/- 2.9 days; p = 0.7). The level of colonization by both gram-positive and gram-negative bacteria was the same in both groups. We conclude that not changing ventilator circuits during mechanical ventilation has no adverse effect on the rate of nosocomial pneumonia or on patient and circuit colonization. Substantial savings in expenses of tubing and personnel time could be obtained without apparent adverse effect.