Albuterol Delivery Efficiency in a Pediatric Model of Noninvasive Ventilation With Double-Limb Circuit

Abstract

Background: Noninvasive ventilation (NIV) is used to treat respiratory failure in patients with concomitant need for aerosol delivery. Limited pediatric data are available on aerosol delivery efficiency, and none at all regarding aerosol delivery efficiency with a double-limb circuit. We compared the effect of position in the double-limb ventilator circuit, types of nebulizer, and ventilator settings on aerosol delivery efficiency in a pediatric model of NIV. We hypothesized that placing a vibrating mesh nebulizer at the ventilator and using the highest inspiratory pressures would increase aerosol delivery efficiency.

Methods: A breathing simulator was connected in series to a low dead-space filter holder (lung dose) and to an anatomically correct head/airway model of a 5-year-old child. A non-vented mask connected the model to a ventilator operated on noninvasive bi-level mode and assembled with a double-limb, heated-wired adult circuit. Inspiratory pressures of either 15 or 20 cm H₂O and an expiratory pressure of 5 cm H₂O were used. Two different vibrating mesh nebulizers and 2 different jet nebulizers loaded with albuterol solution were studied. Albuterol was measured with spectrophotometry. Aerosol delivery efficiency was calculated as lung dose expressed as a percentage of the nominal dose.

Results: A vibrating mesh nebulizer before the mask or Y-piece provided the highest delivery efficiency and outperformed a vibrating mesh nebulizer integrated into the mask. Vibrating mesh nebulizers delivered more drug than jet nebulizers, regardless of their position in the circuit. Increasing the inspiratory pressure only improved aerosol delivery efficiency with a jet nebulizer placed at the ventilator.

Conclusions: In a pediatric model of NIV, the effect of nebulizer position on aerosol delivery efficiency depends on the type of device and its placement in the ventilator circuit. A vibrating mesh nebulizer placed at the mask or before the Y-piece of the double-limb circuit provided the highest aerosol drug delivery during NIV. Data generated with invasive ventilation models should not be generalized to NIV models.

Keywords: aerosol delivery; airway model; albuterol; lung dose; nebulizer; noninvasive ventilation; pediatrics.