• Allan L Coates, Kitty Leung, Jeffrey Chan, Nancy Ribeiro, Martin Charron, and Suzanne Schuh.
• Physiology and Experimental Medicine Research Institute.
• Respir Care. 2013 Dec 1;58(12):2087-92.

BackgroundIntravenous magnesium sulfate (MgSO(4)) 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 MgSO(4) has a relatively high dose (volume) requirement. This, plus the use of inefficient delivery systems, may explain the lack of efficacy of inhaled MgSO(4) 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 MgSO(4) to the respiratory system in older children, and approximately a fifth for toddlers, but no in vivo data exist.MethodsSaline mixed with a radiolabel was used as a proxy for the 100 mg/mL MgSO(4) 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 MgSO(4) and compared to the results from an in vitro model using adult respiratory patterns.ResultsThe 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.ConclusionsThese 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 MgSO(4) in children and adults with refractory asthma.

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