Allan L Coates, Myrtha E Reyna, Cathy C Doyle, Mark W Nagel
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引用次数: 0
Abstract
Background: Preliminary data in a randomly selected pediatric cohort study in 8-year-olds suggested a rate of positivity to a methacholine challenge test that was unexpectedly high, roughly 30%. The current recommendation for a negative methacholine test is a 20% decrease in the forced expiratory volume in one second at a dose greater than 400 μg. This was derived from studies in adults using the obsolete English Wright nebulizer. One explanation for the high incidence of positivity in the study in 8-year-olds could be that children deposit more methacholine on a μg/kg basis than adults, due to differences in their breathing patterns. The purpose of this study was to determine if pediatric breathing patterns could result in a higher dose of methacholine depositing in the lungs of children based on μg/kg body weight compared with adults. Methods: An AeroEclipse Breath Actuated nebulizer delivered methacholine aerosol, generated from a 16 mg/mL solution, for one minute, using age-appropriate breathing patterns for a 70 kg adult and a 30 and 50 kg child produced by a breathing simulator. Predicted lung deposition was calculated from the collected dose of methacholine on a filter placed at the nebulizer outport, multiplied by the fraction of the aerosol mass contained in particles ≤5 μm. The dose of methacholine on the inspiratory filter was assayed by high performance liquid chromatography (HPLC). Particle size was measured using laser diffraction technology. Results: The mean (95% confidence intervals) predicted pulmonary dose of methacholine was 46.1 (45.4, 46.8), 48.6 (45.3, 51.9), and 36.1 (34.2, 37.9) μg/kg body weight for the 30 kg child, 50 kg child, and 70 kg adult, respectively. Conclusions: On a μg/kg body weight, the predicted pulmonary dose of methacholine was greater with the pediatric breathing patterns than with the adult pattern.
期刊介绍:
Journal of Aerosol Medicine and Pulmonary Drug Delivery is the only peer-reviewed journal delivering innovative, authoritative coverage of the health effects of inhaled aerosols and delivery of drugs through the pulmonary system. The Journal is a forum for leading experts, addressing novel topics such as aerosolized chemotherapy, aerosolized vaccines, methods to determine toxicities, and delivery of aerosolized drugs in the intubated patient.
Journal of Aerosol Medicine and Pulmonary Drug Delivery coverage includes:
Pulmonary drug delivery
Airway reactivity and asthma treatment
Inhalation of particles and gases in the respiratory tract
Toxic effects of inhaled agents
Aerosols as tools for studying basic physiologic phenomena.