Aerosol delivery in neonatal ventilator circuits: a rabbit lung model.
The benefits of inhaled therapy in ventilated neonates are recognized, but the reliability of drug delivery in nebulizer-ventilator circuits is uncertain. We quantified the effect of changing variables. Twenty-three freshly killed rabbits (1.15-1.9 kg) were ventilated via a tracheostomy by a pressure-limited, time-cycled ventilator (Neovent). A radioaerosol of 99Tcm pertechnetate from an Ultravent nebulizer (Mallinkrodt) was fed into the proximal ventilator tubing. Two 3-minute nebulizations at "standard settings" were followed by 2 at altered pressure, frequency, gas flow, I:E ratio, or position of the nebulizer in the circuit. Each nebulization was followed by a 3-minute gamma camera image and total deposited radioactivity was measured in excised lungs and trachea. Images demonstrated good peripheral aerosol deposition. At standard settings, lung deposition averaged 2.8% of the aerosol released. This was decreased markedly by reducing tidal volume (ventilator pressures) and residence time of aerosol (I:E ratio). Reduced gas flow decreased deposition slightly, presumably by increased particle size and marginally reduced tidal volume. Deposition did not change with increased frequency; increased minute ventilation was offset by decreased residence time of the aerosol. We conclude that the Ultravent nebulizer can be used to nebulize drugs in a standard neonatal circuit, although the dose delivered is small. Tidal volume and aerosol residence time are important determinants of aerosol delivery.
Cameron
D
D
Department of Pediatrics and Neonatal Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London, England.
Arnot
R
R
Clay
M
M
Silverman
M
M
D000818:Animals; D001997:Bronchopulmonary Dysplasia / Q000503:physiopathology / Q000628:therapy; D004195:Disease Models, Animal; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008170:Lung Compliance / Q000187:drug effects; D008171:Lung Diseases / Q000503:physiopathology* / Q000628:therapy; D009330:Nebulizers and Vaporizers; D010991:Plethysmography; D011817:Rabbits; D011877:Radionuclide Imaging; D012121:Respiration, Artificial / Q000379:methods; D013670:Sodium Pertechnetate Tc 99m / Q000008:administration & dosage / Q000032:analysis; D013990:Tidal Volume / Q000187:drug effects
D013670:Sodium Pertechnetate Tc 99m