Abstract
Background: Bronchospasm is one of the most common perioperative respiratory events. Standard treatment includes administration of albuterol via a pressurized metered dose inhaler (pMDI). A laryngeal mask airway (LMA) is a supraglottic airway device used to maintain an open airway and to provide support during anesthesia. The aim of this study was to evaluate delivery of albuterol administered through an LMA using a model of a spontaneously breathing adolescent.
Methods: The experimental set-up included a ventilator (breathing frequency 15 breaths/min, tidal volume 200 or 300 mL, PEEP 5 cm H2O, FIO2 0.21) connected in series to an unheated ventilator circuit, pMDI delivery device (valved holding chamber [VHC] or adapter), LMA (size 2.5 or 3.5 modified to create a seal), filter, and test lung (Rp20, 30 mL/mbar). Tidal volume (VT) was measured with a flow analyzer placed between the LMA and filter prior to aerosol delivery. Four actuations of albuterol 90 µg were delivered during inspiration or expiration either as a single actuation, waiting at least 30 s (allowing 7 breaths) and shaking the pMDI between actuations, or multiple actuations without waiting or shaking. Albuterol mass was measured via spectrophotometer. Each condition was repeated in triplicate. The dependent variable was delivery efficiency (mass captured in the filter expressed as percentage of nominal dose). General linear regression (LMA size, VT, device, single vs. multiple actuations, and timing of actuation) and descriptive statistics were performed. Comparison between otherwise similar variables but different device, different VT, use of single and multiple actuations, timing of pMDI actuation, and LMA size were made with T-test.
Results: The VHC had higher delivery efficiency than the adapter. Larger LMA size did not improve delivery efficiency (P > .06). R2 was 0.329 with the device and mode of actuation (single vs. multiple) explaining 22% and 5% of the observed variation respectively.
Conclusions: In general, delivery efficiency of albuterol pMDI through LMAs in a model of a spontaneously breathing adolescent increased when using a VHC and using single actuations.
Footnotes
Commercial Relationships: Denise Willis discloses a relationship with Daedalus. Ariel Berlinski discloses relationships with Cystic Fibrosis Foundation, National Institute of Health, Therapeutic Development Network, Trudell Medical International, Vertex, UpTodate, Hollo Medical Inc., and the International Pharmaceutical Aerosol Consortium on Regulation and Science.
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