Pressurized aerosol versus jet aerosol delivery to mechanically ventilated patients. Comparison of dose to the lungs.
ABSTRACT The purpose of this study was to compare deposition of aerosol to the lung from a metered-dose inhaler (MDI) and aerosol holding chamber and from a jet nebulizer in ventilator-dependent patients. Twenty-one patients were entered into the study, all receiving assisted ventilation and inhaled bronchodilators because of airflow limitation. The average age was 68 yr; there were 10 men and 11 women. The patients were randomized to receive either 4 puffs (800 micrograms) of radiolabeled fenoterol by MDI of 1.75 ml (1,750 micrograms) of radiolabeled fenoterol solution by nebulizer. Imaging of lung fields was made by a portable scintillation camera at 5-min intervals during the study. Results showed that 20 patients completed the study, 9 receiving fenoterol by MDI, and 11 by jet nebulizer. Four were excluded from analysis because of previous pneumonectomy, two from each group. Lung deposition measured as a percent of given dose from either system was 5.65 +/- 1.09 (mean +/- SEM) for MDI plus extension chamber and 1.22 +/- 0.35 for jet nebulizer (p less than 0.001). Therefore, this trial shows significantly greater efficiency of aerosol deposition to the lung in ventilator-dependent patients when using an MDI plus aerosol holding chamber than when using a jet nebulizer.
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ABSTRACT: Patients receiving invasive mechanical ventilation with an endotracheal tube (ETT) can often benefit from pharmaceutical aerosols; however, drug delivery through the ventilation circuit is known to be very inefficient. The objective of this study was to improve the delivery of aerosol through an invasive mechanical ventilation system by redesigning circuit components using a streamlining approach. Redesigned components were the T-connector interface between the nebulizer and ventilator line and the Y-connector leading to the ETT. The streamlining approach seeks to minimize aerosol deposition and loss by eliminating sharp changes in flow direction and tubing diameter that lead to flow disruption. Both in vitro experiments and computational fluid dynamic (CFD) simulations were applied to analyze deposition and emitted dose of drug for multiple droplet size distributions, flow rates, and ETT sizes used in adults. The experimental results demonstrated that the streamlined components improved delivery through the circuit by factors ranging from 1.3-1.5 compared with a commercial system for adult ETT sizes of 8 and 9 mm. The overall delivery efficiency was based on the bimodal aspect of the aerosol distributions and could not be predicted by median diameter alone. CFD results indicated a 20-fold decrease in turbulence in the junction region for the streamlined Y resulting in a maximum 9-fold decrease in droplet deposition. The relative effectiveness of the streamlined designs was found to increase with increasing particle size and increasing flow rate with a maximum improvement in emitted dose of 1.9-fold. Streamlined components can significantly improve the delivery of pharmaceutical aerosols during mechanical ventilation based on an analysis of multiple aerosol generation devices, ETT sizes, and flow rates.10/2013; DOI:10.4187/respcare.02782
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ABSTRACT: An aerosol is defined as a suspension of solid or liquid particles in a gas. Most aerosols in clinical practice are polydisperse, that is to say, the contained particles vary greatly in diameter. A dust is a suspension of solid particles in a gas. Dust particles are irregular.