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.

Bronchodilator delivery with metered-dose inhalers in mechanically-ventilated patients

“…In a bench model, we found that ~16% of the dose from a MDI was delivered to the lower respiratory tract when the ventilator circuit was humidified [21]; in our mechanically-ventilated patients, 2-3% of the aerosol was exhaled (unpublished data). Thus, in vitro studies indicate that 13-14% of the dose from a MDI is deposited in the lower respiratory tract when using a humidified ventilator circuit, which is greater than the value of ~6% found in the in vivo studies of FULLER and co-workers [15]. However, the latter in vivo studies did not account for tissue quenching of radioactivity [27].…”

“…1) [7]. In particular, deposition of aerosol in the endotracheal tube and ventilator circuit causes a significant reduction in the fraction of aerosol reaching the lower respiratory tract [13][14][15]. When using MDIs, a special adapter is required to connect the canister to the ventilator circuit.…”

“…Radionuclide studies noninvasively assess total and regional aerosol deposition in the lower respiratory tract. FULLER and co-workers [15] actuated a MDI containing fenoterol and 99m Tc-pertechnate into a cylindrical chamber placed in the inspiratory limb of a ventilator circuit. About 6% of the dose was deposited in the lower respiratory tract ( fig.…”

“…Few investigators have examined the efficacy of bronchodilators in mechanically-ventilated patients [8,11,12,15,[38][39][40][41][42][43][44]. Early studies showed promising results following bronchodilator administration by a MDI [42][43][44], and yet the data were ignored for several years.…”

Toxicity of prolonged high dose inhaled PGE1 in ventilated neonatal pigs

“…The most significant lesions after toxic inhalation have been reported to affect the trachea with the most severe changes being observed in the tissue adjacent to the tip of the ETT (31,37). This is because, following aerosol delivery, a large fraction of the aerosol accumulates in the conducting airways, particularly in the trachea and ETT (47). Bile aspiration, evident in five animals undergoing the experimental protocol, could also be responsible for some of the histological abnormalities observed.…”