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Dilution of nebulised aerosols by air entrainment in children
G G Collis1, C H Cole, P N Le Souëf
1Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth, WA, Australia.
Insights
Nebulised aerosol drug delivery in children is inconsistent. Infants under 6 months receive undiluted medication, while older children experience significant dilution due to air entrainment, potentially requiring revised dosing regimens.
Area of Science:
- Pediatric Pulmonology
- Respiratory Drug Delivery
- Pharmacokinetics in Children
Background:
- Current guidelines for aerosolized drug administration in pediatric populations lack consistency.
- Understanding aerosol dilution is crucial for effective nebulizer therapy in infants and children.
Purpose of the Study:
- To investigate the impact of patient size on aerosol dilution during nebulizer treatments in pediatric subjects.
- To determine factors influencing aerosol concentration and drug delivery in different age groups.
Main Methods:
- A study involving 14 infants, 22 children, and 4 adults assessed inspired nebulized aerosols.
- Air entrainment was measured based on inspiratory flow exceeding nebulizer flow.
- Aerosol concentration and output were quantified in relation to subject size and respiratory patterns.
Main Results:
- Infants under 6 months did not entrain air, receiving undiluted aerosols.
- Older subjects experienced up to 5-fold dilution in aerosol concentration due to air entrainment as size increased.
- The mass of inspired drug remained largely independent of size once air entrainment occurred.
Conclusions:
- Aerosol dilution varies significantly with age and size in pediatric patients undergoing nebulizer therapy.
- Current nebulized drug delivery regimens for children may need revision to account for age-dependent air entrainment and aerosol dilution.
- Optimized dosing strategies are needed to ensure consistent therapeutic drug levels in pediatric respiratory care.
Abstract:
Guidelines for use of aerosolised drugs in children are inconsistent. In a study of 14 infants, 22 children, and 4 adults inspired nebulised aerosols were diluted more for large than for small subjects, because of air entrainment which occurred when inspiratory flow exceeded nebuliser flow. Infants under 6 months of age did not entrain air and would receive undiluted aerosols. All other subjects entrained air, which caused up to a 5-fold dilution in inspired aerosol concentration as subject size increased. In subjects who entrained air, the ratio of inspired nebuliser output versus total nebuliser output was relatively constant, and was related to the respiratory pattern. For a given nebuliser solution concentration, infants who do not entrain will inspire more concentrated aerosols than older children. Once entrainment occurs, the mass of drug inspired is largely independent of size. Regimens for nebulised drug delivery in children may require revision.