Abstract
Background: Intravenous magnesium sulphate (MgSO4) in children and adults with refractory acute asthma is effective but therapy may be limited by systemic hypotension which 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® using a face mask would deliver 16 mg/min of MgSO4 to the respiratory system for older children and approximately a fifth for toddlers but no in vivo data exist.
Materials and 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 deposition below the vocal cords of the radiolabel was converted to the rate of deposition of MgSO4 and was compared to the results from an in vitro model using adult respiratory patterns.
Results: The mean rate of deposition was 12.6±1.9 mg/min (mean±SD). The reasons for this lower deposition compared to the in vitro estimate was likely 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 extrapolating to children. This device appears suitable for the clinical trial of inhaled MgSO4 in children and adults with refractory asthma.
- asthma
- inhaled magnesium sulphate
- Idehaler Pocket®
- AeroNeb Go®
- nuclear medicine
- respiratory system deposition
- pulmonary deposition
Footnotes
- Address Correspondence to Dr Allan L Coates, Physiology and Experimental Medicine, Research Institute — Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8 email allan.coates{at}sickkids.ca Tel 416 813-6215
- Copyright © 2013 by Daedalus Enterprises Inc.