Effect of Oxygen Flow on Aerosol Delivery From a Nebulizer With a Holding Chamber

A new holding chamber was designed to be used with a vibrating mesh nebulizer to increase the total inhalable dose for patients. It facilitates intermittent and continuous nebulization as well as the optional supply of supplemental oxygen via a T-piece with a mouthpiece adapter. This study aimed to evaluate the effect of oxygen introduction in the new holding chamber on aerosol delivery using a vibrating mesh nebulizer.

The study was divided into 2 parts. First, the total inhalable dose of 1 mL of a respirable solution (nominal dose of 5,000 μg-salbutamol) was determined using a breathing simulator set to provide a tidal volume of 500 mL, a breathing frequency of 15 breaths/min, and an inspiratory:expiratory ratio of 1:1 for adults as a quiet-breathing pattern. Three experimental nebulizer setups were used: a vibrating mesh nebulizer with the holding chamber and oxygen set at 6 L/min, a vibrating mesh nebulizer with the holding chamber and no oxygen, and a vibrating mesh nebulizer with the T-piece. Aerodynamic particle size characterizations were determined using cooled Andersen cascade impaction at an inhalation flow of 15 L/min. Second, we performed an in vivo study involving 12 healthy non-smoking subjects (6 female) who were > 18 y old with an average FEV₁ > 90% of predicted. Using normal tidal breathing, subjects inhaled 1 mL of nebulized salbutamol (5,000 μg) through the vibrating mesh nebulizer with the holding chamber with and without oxygen and through the vibrating mesh nebulizer with a T-piece. To analyze salbutamol content, urine samples were obtained 30 min after dosing as an index of lung deposition, and their urine was cumulatively collected for 24 h as an index of systemic absorption.

The holding chamber significantly increased the total inhalable dose or amount of salbutamol excreted in the first 30 min, as well as the amount of salbutamol excreted over a 24-h period compared to the dose received with the vibrating mesh nebulizer with a T-piece (P = .005, P = .034, and P = .02, respectively), and relatively decreased the mass median aerodynamic diameter, although the difference was not significant. However, when oxygen was introduced in the holding chamber, the total inhalable dose, or amount of salbutamol excreted in the first 30 min, significantly decreased compared to use without oxygen (P = .003, P = .03 respectively). No significant difference was found between the vibrating mesh nebulizer with the holding chamber with oxygen and the vibrating mesh nebulizer with a T-piece.

The vibrating mesh nebulizer with a holding chamber and without oxygen resulted in much better aerosol delivery compared to vibrating mesh nebulizer with a holding chamber and with oxygen delivery and to the vibrating mesh nebulizer with a T-piece. The use of oxygen with the holding chamber significantly decreased aerosol delivery and its benefit, and recommended flow should be reevaluated.