SEARCH · Search PubMed
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The technical characteristics of most frequently used devices for the production of aerosol have been described together with their effect on deposition of aerosol in tracheobronchial system. However, there are many reasons to prefer jet nebulisers for everyday application.
We assessed the effectiveness of various aerosol-generating systems. Taplin's settling method and Venticis generators had a lower efficiency (37.3 +/- 3.8% and 51.8 +/- 9.6%, respectively) than the Syntevent (88.8 +/- 6.9%, p less than 0.001), Cadema (89.8 +/- 9.9%, p less than 0.001) and Mefar (85.3 +/- 19.4%, p less than 0.001) generators. The Mass Median Aerodynamic Diameter of the particles produced by the Mefar nebulizer (2.05 +/- 0.27 micron) was larger than that of any other generators (p less than 0.001). The Syntevent (0.54 +/- 0.09 micron) generator produced smaller particles than the Mefar, Taplin (0.89 +/- 0.10 micron, p less than 0.01) and Venticis (0.79 +/- 0.06 micron, p less than 0.02) generators. Particles produced by the Cadema system (0.69 +/- 0.06 micron) were smaller than those generated by the Taplin system (p less than 0.05). We conclude: that the Syntevent, Mefar and Cadema aerosol generators are more efficient than the others, and that all the generators tested except the Mefar may be used for studies that depend on the peripheral deposition of small particles within the lungs.
Secondary electron yield measurements were used to determine the distribution of chemical components in multicomponent aerosol particles formed by crystallization from aqueous solution droplets. Yield measurements were made by measuring the charge acquired by a beam of particles as they passed through an electron beam (100-600 eV energy) inside a high-vacuum apparatus. Yields were sufficiently different for certain compounds that measurements made on two-component particles could be used to obtain information on the spatial distribution of components. Variations in chemical composition as a function of depth beneath the particle surface were ascertained from the energy dependence of the measured yields, since the electron penetration depth, and therefore the probe depth, increases with electron energy. The results for mixed NaCl-NH4Cl particles indicate that the distribution of components within these particles is relatively homogeneous, while measurements made on mixed NaCl-NaNO3 particles are indicative of particles having a heterogeneous core-shell morphology. Results for mixed Na2SO4-(NH4)2SO4 particles are ambiguous, probably because of the complexity of the phase diagram of this system. It appears that the mechanism by which aerosol particles crystallize, and therefore the resulting distribution of chemical components within particles, is strongly dependent on particle composition and environmental variables. Copyright 1997 Academic Press. Copyright 1997Academic Press
Aerosol extinction coefficients have been derived in the 375-700-nm spectral domain from measurement in the stratosphere since 1992, at night, at mid- and high latitudes from 15 to 40 km, by two balloonborne spectrometers, Absorption par les Minoritaires Ozone et NO(chi) (AMON) and Spectroscopie d'Absorption Lunaire pour l'Observation des Minoritaires Ozone et NO(chi) (SALOMON). Log-normal size distributions associated with the Mie-computed extinction spectra that best fit the measurements permit calculation of integrated properties of the distributions. Although measured extinction spectra that correspond to background aerosols can be reproduced by the Mie scattering model by use of monomodal log-normal size distributions, each flight reveals some large discrepancies between measurement and theory at several altitudes. The agreement between measured and Mie-calculated extinction spectra is significantly improved by use of bimodal log-normal distributions. Nevertheless, neither monomodal nor bimodal distributions permit correct reproduction of some of the measured extinction shapes, especially for the 26 February 1997 AMON flight, which exhibited spectral behavior attributed to particles from a polar stratospheric cloud event.
The inclusion of non-volatile components such as glycerol or polyethylene glycol in hydrofluoralkane (HFA) solution formulations for pressurised metered dose inhalers (pMDIs), greatly increases the particle size of the aerosol. Cloud characteristics can be further modulated by permuting this factor with the choice of propellant and the dimensions of the actuator, to give a chosen fine particle dose and particle diameter. This principle has been used to design solutions which closely match the performance of chlorofluorocarbon based suspension formulations containing beclomethasone dipropionate, budesonide and ipratropium bromide as assessed for pharmaceutical equivalence using the Andersen Cascade impactor.
Atmospheric oxidation of volatile organic compounds can lead to the formation of secondary organic aerosol (SOA) through the gas/particle (G/P) partitioning of the oxidation products. Since water is ubiquitous in the atmosphere, the extent of the partitioning for any individual organic product depends not only on the amounts and properties of the partitioning organic compounds, but also on the amount of water present. Predicting the effects of water on the atmospheric G/P distributions of organic compounds is, therefore, central to understanding SOA formation. The goals of the current work are to gain understanding of how increases in RH affect (1) overall SOA yields, (2) water uptake by SOA, (3) the behaviors of individual oxidation products, and (4) the fundamental physical properties of the SOA phase that govern the G/P distribution of each of the oxidation products. Part 1 of this series considered SOA formation from five parent hydrocarbons in the absence of water. This paper predicts how adding RH to those systems uniformly increases both the amount of condensed organic mass and the amount of liquid water in the SOA phase. The presence of inorganic components is not considered. The effect of increasing RH is predicted to be stronger for SOA produced from cyclohexene as compared to SOA produced from four monoterpenes. This is likely a result of the greater general degree of oxidation (and hydrophilicity) of the cyclohexene products. Good agreement was obtained between predicted SOA yields and laboratory SOA yield data actually obtained in the presence of water. As RH increases, the compounds that play the largest roles in changing both the organic and water masses in the SOA phase are those with vapor pressures that are intermediate between those of essentially nonvolatile and highly volatile species. RH-driven changes in the compound-dependent G/P partitioning coefficient Kp result from changes in both the average molecular weight MWom of the absorbing organic/water phase, and the compound-dependent activity coefficient zeta values. Adding water to the SOA phase by increasing the RH drives down MWom and thereby uniformly favors SOA condensation. The effect of RH on zeta values is compound specific and depends on the hydrophilicity of the specific compound of interest; the more hydrophilic a compound, the more increasing RH will favor its condensation into the SOA phase. The results also indicate that it may be a useful first approximation to assume that zeta = 1 for many compounds making up SOA mixtures.
The purpose of this research was to compare three different methods for the aerodynamic assessment of (1) chloroflurocarbon (CFC)--fluticasone propionate (Flovent), (2) CFC-sodium cromoglycate (Intal), and (3) hydrofluoroalkane (HFA)--beclomethasone dipropionate (Qvar) delivered by pressurized metered dose inhaler. Particle size distributions were compared determining mass median aerodynamic diameter (MMAD), geometric standard deviation (GSD), and fine particle fraction <4.7 microm aerodynamic diameter (FPF(<4.7 microm)). Next Generation Pharmaceutical Impactor (NGI)-size distributions for Flovent comprised finer particles than determined by Andersen 8-stage impactor (ACI) (MMAD = 2.0 +/- 0.05 micro m [NGI]; 2.8 +/- 0.07 microm [ACI]); however, FPF(<4.7 microm) by both impactors was in the narrow range 88% to 93%. Size distribution agreement for Intal was better (MMAD = 4.3 +/- 0.19 microm (NGI), 4.2 +/- 0.13 microm (ACI), with FPF(<4.7 microm) ranging from 52% to 60%. The Aerodynamic Particle Sizer (APS) undersized aerosols produced with either formulation (MMAD = 1.8 +/- 0.07 micro m and 3.2 +/- 0.02 micro m for Flovent and Intal, respectively), but values of FPF(<4.7 microm)from the single-stage impactor (SSI) located at the inlet to the APS (82.9% +/- 2.1% [Flovent], 46.4% +/- 2.4% [Intal]) were fairly close to corresponding data from the multi-stage impactors. APS-measured size distributions for Qvar (MMAD = 1.0 +/- 0.03 micro m; FPF(<4.7 micro m)= 96.4% +/- 2.5%), were in fair agreement with both NGI (MMAD = 0.9 +/- 0.03 micro m; FPF(<4.7 microm)= 96.7% +/- 0.7%), and ACI (MMAD = 1.2 +/- 0.02 microm, FPF(<4.7 microm)= 98% +/- 0.5%), but FPF(<4.7 microm) from the SSI (67.1% +/- 4.1%) was lower than expected, based on equivalent data obtained by the other techniques. Particle bounce, incomplete evaporation of volatile constituents and the presence of surfactant particles are factors that may be responsible for discrepancies between the techniques.
We have administered aerosolized pentamidine (AP) to 48 AIDS patients for secondary prophylaxis of Pneumocystis carinii pneumonia (PCP). Pentamidine 60 mg was administered by ultrasonic nebulization (Fisoneb) five times during the first two weeks and then every two weeks. The mean follow-up was 343 +/- 22 days. PCP recurred in ten patients, 297 +/- 33 days after starting AP therapy. All responded to anti-Pneumocystis therapy but two patients died of unrelated reasons (20 percent mortality). Five patients developed bilateral pneumothoraces 260 +/- 35 days after starting AP therapy. Recurrence of PCP could be documented in only one patient. All died 66 +/- 27 days after the onset of the first pneumothorax. Only 5 of 33 patients without recurrence of pneumonia or pneumothorax died during the study period (15 percent mortality). No association was found between the development of pneumothorax and age, smoking, previous respiratory or infectious problems, time from last PCP and the initiation of AP therapy, and treatment duration of last PCP. Patients with pneumothoraces had a significantly lower Dco (58.6 +/- 2.6 percent predicted) prior to AP therapy than patients with recurrence of PCP without pneumothoraces (81.1 +/- 2.1 percent predicted) or patients with no recurrence of PCP (67 +/- 2.5 percent predicted) (p less than 0.05, ANOVA). In conclusion, bilateral pneumothoraces are associated with a hastened mortality in patients receiving AP for secondary prophylaxis of PCP. Low Dco before AP therapy is associated with an increased risk of bilateral pneumothoraces in patients treated with AP for secondary prophylaxis of PCP.
STUDY OBJECTIVE: To compare the effectiveness of a standard jet nebulizer, Respirgard II, and a standard ultrasonic nebulizer, Fisoneb, for the administration of aerosolized pentamidine (AP) as primary and secondary prophylaxis against Pneumocystis carinii pneumonia (PCP) in HIV-infected individuals. DESIGN: A retrospective, nonrandomized, parallel group comparative study. SETTING: Patients were enrolled in a community-based AP program (APP) between May 1989 and April 1992 in Ontario, Canada. They received AP in either (1) a centralized treatment facility ("clinic") or (2) their attending physician's office or regionalized centers ("nonclinic"). Clinic administration of pentamidine was via Fisomeb; nonclinic via Respirgard II. PATIENTS: The study group comprised of 1,762 HIV-infected individuals requiring AP for either primary (CD4 < 200/mm3) or secondary PCP prophylaxis. Of these, 1,151 used Fisoneb (clinic) and 611 used Respirgard II (nonclinic). RESULTS: In the primary prophylaxis group, 41 of the 892 patients using Fisoneb (4.6%; mean follow-up, 18 months) compared with 16 of 435 patients using Respirgard II (3.7%; mean follow-up, 14.6 months) developed PCP (p = 0.44). A total of 28 of 259 (10.8%; mean follow-up, 15.3 months) patients using Fisoneb for secondary prophylaxis compared with 11 of 176 (6.3%; mean follow-up, 14.4 months) patients using Respirgard II for secondary prophylaxis developed PCP (p = 0.1). CONCLUSIONS: Despite the difference in dosage (120 mg/mo vs 300 mg/mo), type of nebulizer (ultrasonic vs jet), and frequency of administration (twice vs once monthly), the results of this study indicate that both regimens of AP provide comparable protection against PCP. This study further supports the effectiveness of AP as a solid second-line prophylaxis for HIV-infected individuals who are intolerant to trimethoprim/sulfamethoxazole or dapsone.
Aerosolized pentamidine (AP) has been widely used for prophylaxis of pneumocystis carinii pneumonia (PCP) since 1988. The objective of this study was to evaluate the long-term effects of AP on pulmonary function. Of 36 patients with AIDS who were receiving AP for secondary prophylaxis of PCP, 13 patients had been using AP continuously for more than 52 weeks. AP was given using a Fisoneb ultrasonic nebulizer with five loading doses of 60 mg over two weeks, followed by one dose of 60 mg every two weeks. Baseline PFT were TLC 92 +/- 14% pred, FVC 90 +/- 11% pred, FEV1 91 +/- 11% pred, FEF25-75 95 +/- 17% pred, and DLCO (corrected for hemoglobin) 70 +/- 22% pred. No significant change in TLC, FVC, FEV1, or DLCO was seen after 56 weeks of AP. There was a 20% fall in FEF25-75 seen after 56 weeks, which was statistically significant. However, the clinical significance of a fall of this magnitude in the FEF25-75 is uncertain. Similar results were seen in a smaller subset of patients who received AP for at least 76 weeks. Although the small sample size must be considered, this data suggests that there is no clinically significant change in pulmonary function associated with the use of AP for up to 76 weeks.
The bronchodilator efficacy of two doses of dry salbutamol powder (rotacap) was compared with the conventional dose of metered dose inhaler (MDI). The doses used were: 200 micrograms rotacaps, 400 micrograms rotacaps and 200 micrograms MDI. All the three doses resulted in a significant bronchodilation, increasing the FEV1. The increase in FEV1 was 11.4%, 23.2% and 24% respectively. The improvement following 400 micrograms rotacap was similar to that seen after 200 micrograms MDI. Both 200 micrograms MDI and 400 micrograms rotacap resulted in significantly greater increase in FEV1 as compared to 200 micrograms rotacaps. It was concluded that bronchodilator effect is superior with an MDI and a double dose of powder aerosol is required to achieve the same results.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.