Placement of the nebulizer before the humidifier during mechanical ventilation: Effect on aerosol delivery

Background

Therapeutic aerosols are commonly used in mechanically ventilated patients. The position of the nebulizer in the ventilator circuit and the humidification of inhaled gases can influence the efficiency of aerosol delivery. We evaluated the effect of nebulizer position on the pulmonary bioavailability of nebulized ipratropium in ventilated patients without known preexisting respiratory disease.

Methods

The study included 38 mechanically ventilated and sedated patients after open heart surgery. Ipratropium (500 μg) was delivered by an ultrasonic nebulizer. Patients were randomized into 2 groups: the nebulizer positioned before the heat humidification system (group 1, n = 19) or at the end of the inspiratory limb before the Y-piece (group 2, n = 19). The amount of ipratropium in the urine collected during the 4 hours after drug administration was measured by mass spectrometry.

Results

There were no statistically significant differences in tidal volume or respiratory rate between groups. There were no significant differences between the 2 groups in the amount of drug excreted (group 1 vs 2: 13,237 ± 2313 pg/mL vs 15,529 ± 3204 pg/mL) or in pulmonary bioavailability (.9% ± .1% vs 1.1% ± .2%).

Conclusion

The position of the nebulizer in the ventilatory circuit had no effect on the pulmonary bioavailability of ipratropium.