Background: A heated tracheostomy collar (HTC) is frequently used for humidification at our institution for spontaneously breathing tracheostomized children. Nebulized medications are commonly administered using different methods. The purpose of this study was to evaluate aerosol delivery using a vibrating mesh nebulizer (VMN) and jet nebulizer (JN) in-line with an HTC. Methods: A model of a spontaneously breathing tracheostomized child was used. The model consisted of a breathing simulator connected in series to a collecting filter (lung dose), a tracheal model with 4.5 mm uncuffed tracheostomy tube and an expiratory filter. The HTC was used with a heated humidifier set to 37°C with 15 L/min airflow (FIO2 0.21). A heated-wired circuit was used with a tracheostomy direct connection adapter. Different breathing patterns were used for an infant (30 breaths, 80 mL, I:E 1:3), child (25 breaths, 155 mL, I:E 1:2), and older child (20 breaths, 310 mL, I:E 1:2). A VMN or JN was used in 3 different positions: on the dry side of the humidifier (distal) with and without the adapter and between the circuit and the tracheostomy (proximal). Albuterol 2.5 mg/3 mLs and 5 mg/6 mLs were used for VMN and JN respectively. The JN was operated at 6 L/min and additional 9 L/min was provided at the humidifier inlet. Each condition was repeated in triplicate. Albuterol mass was measured via spectrophotometer (276 nm) and reported as absolute mass. Mann-Whitney was used to compare outcome measures at each scenario. Friedman test/Dunn’s test were used to compare different breathing pattern for each scenario as well as different configurations. Results: No differences in absolute lung dose were found between nebulizers (P value ranged from .10 to .70) (Figure 1, median + 95% CI). Lung dose was higher for the older child when compared to infant both for VMN and JN (P = .043). Adding the connector to the circuit resulted in a 37 and 17% decrease in lung dose for VMN and JN respectively (P = .49). Moving the nebulizer from a distal to a proximal position resulted in in a resulted in a 16 and 66% increase in lung dose for VMN and JN respectively P = .16). Conclusions: Doubling loading albuterol in a JN resulted in similar absolute lung dose to VMN when delivering aerosols through an HTC system. Tracheostomy connector reduced lung dose while moving the nebulizer from distal to proximal increased it.
Downs et al. (Tue,) studied this question.