Respiratory System Deposition with a Novel Aerosol Delivery System in Spontaneously Breathing Healthy Adults

BACKGROUND: Intravenous magnesium sulfate (MgSO4) in children and adults with refractory acute asthma is effective, but therapy may be limited by systemic hypotension that might be avoided with the aerosol route. Inhaled MgSO4 has a relatively high dose (volume) requirement. This, plus the use of inefficient delivery systems, may explain the lack of efficacy of inhaled MgSO4 in some studies. An in vitro study suggested that the AeroNeb Go with the Idehaler Pocket and a face mask would deliver 16 mg/min of MgSO4 to the respiratory system in older children, and approximately a fifth for toddlers, but no in vivo data exist. METHODS: Saline mixed with a radiolabel was used as a proxy for the 100 mg/mL MgSO4 solution. In 5 adult males the rate of deposition was measured using nuclear medicine techniques. The radiolabel deposition below the vocal cords was converted to the rate of deposition of MgSO4 and compared to the results from an in vitro model using adult respiratory patterns. RESULTS: The mean SD rate of deposition was 12.6 +/- 1.9 mg/min. The reasons for this lower deposition, compared to the in vitro estimate, was most likely the exhalation of anatomical dead space aerosol, which would have been captured on the inspiratory filter in vitro. CONCLUSIONS: These in vivo data confirm the deposition data predicted in the in vitro study, although caution should be used in extrapolating the results to children. This device appears suitable for the clinical trial of inhaled MgSO4 in children and adults with refractory asthma. (C) 2013 Daedalus Enterprises