Delivery Efficiency of Albuterol Pressurized Metered Dose Inhaler Through Small Size Laryngeal Mask Airways in an Infant and Child Model

BACKGROUND: Intraoperative bronchospasm in pediatric patients supported through laryngeal mask airways (LMAs) is commonly treated with pressurized metered-dose inhaler (pMDI) albuterol. The aim of the study was to evaluate delivery of pMDI albuterol through LMAs under different conditions in a model of infant/child supported with a ventilator.

METHODS: We compared drug delivery efficiency of 4 actuations of albuterol pMDI (captured on a filter placed between the LMA and a test lung), drug deposition in the circuit (elbow) and in the LMA under different experimental conditions. Outcomes were expressed of percentage of nominal dose. We compared devices (valved holding chamber [VHC] and adapter), timing of administration (inspiration and expiration), tidal volumes (50 mL and 100 mL), mode of actuation (single and multiple), and LMA sizes (1, 1.5, and 2). Multiple regression analysis was used to evaluate the contribution of each to these components to the outcomes. P < .05 was considered statistically significant.

RESULTS: Results are expressed as median (interquartile range) of pooled data. Drug delivery efficiency was 0% (0–1.1) and 6.3% (3.2–14.7) for adapter and VHC, respectively. Elbow deposition was 25.8% (19.2–63.3) and 2.9% (1.4–6.4) for adapter and VHC, respectively. LMA deposition was 2.6% (1.3–4.6) and 4.6% (2.9–6.1) for adapter and VHC, respectively. Multiple regression analysis showed that device, timing of actuation, and LMA size explained 33%, 17%, and 8% of the observed variation in delivery efficiency (R² 0.63), respectively. Multiple regression analysis showed that device and timing of actuation explained 52% and 16% of the observed variation, respectively (R² 0.70). Multiple regression analysis poorly explained factors associated with LMA deposition (R² 0.22).

CONCLUSIONS: Using a VHC, actuating the pMDI during exhalation, and using a small LMA size increased drug delivery efficiency. The adapter was an inefficient add-on device for aerosol delivery with a pMDI through an LMA that caused significant circuit deposition.