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Biomedical subjects

M Dolovich

Publications and source records attributed to M Dolovich.

62 records · Page 4Linked to original sources
PubMedDate not supplied

Aerosol delivery to the rabbit lung with an infant ventilator.

Little is known about delivery of aerosolized medications to infants undergoing assisted positive pressure ventilation. To assess delivery of medications to the lung with an infant ventilator (Bournes LS104), 27 experiments were performed on anesthetized adult rabbits. Lung deposition was determined by using aerosol radiolabeled with 99m technetium sulfur colloid. Initially a traditional nebulizer was studied and very inefficient delivery to the lung was observed (0.19 +/- 0.10 SD% of the initial nebulizer dose). Subsequent experiments using a nebulizer that generates submicronic aerosol particles, at equivalent aerosol output, achieved a highly significant increase in delivery (1.96 +/- 1.19 SD%, P less than 0.001). Our experiments demonstrated that modifications to to traditional nebulizer systems can enhance delivery of aerosolized medication to the lungs of rabbits.

Aerosols↗
PubMedDate not supplied

Effect of TLV levels of SO2 and H2 SO4 on bronchial clearance in exercising man.

Pulmonary mucociliary function was assessed following exposure to industrial threshold limit values (TLV) of sulfur dioxide (5 ppm) SO2) and sulphuric acid mist (1 mg/m3 H2SO4). Bronchial clearance was measured in two sets of ten healthy exercising non-smoking adults under control and exposure conditions. A 99mTc-albumen saline aerosol (MMD 3 micrometer) was inhaled as a bolus in late inspiration under controlled conditions to produce reproducible deposition in large airways. Lung retention of radioactivity was quantified using a gamma camera and computer analysis. Clearance was significantly faster (P less than .05) on exposure to both SO2 and H2SO4 compared to control values. Maximum mid-expiratory flow rates (MMFR) were significantly reduced (P less than .01) on exposure to SO2 (mean decrease 8.5%), but only slightly reduced for H2SO4 (1.4%). The speeding in clearance was probably an irritant response in both cases. For SO2 the response appeared predominantly reflex, while H2SO4 showed evidence of a direct effect.

Adult↗
PubMedDate not supplied

Emitted doses of salbutamol pressurized metered-dose inhaler from five different plastic spacer devices.

In a recent clinical study we have demonstrated that the bronchodilator effect of 200 microg salbutamol (Ventoline) was spacer device-dependent in 100 tested asthmatic children, with the Babyhaler providing greater efficacy for improving peak expiratory flow rate compared to Aeroscopic, Nebuhaler, Aerochamber and Volumatic. The aim of this present study was to correlate our clinical results to in vitro determinations of the emitted dose (ED) of Ventoline administered via these five different plastic spacer devices. ED was determined from the mean of single doses collected in unit dose sampling tubes using a constant suction flow of 28.3 L/min. Three pressurized metered-dose inhalers and three sets of spacer devices were used to obtain a total of 30 measurements per group. Inter-group results were compared by RM-ANOVA or Student-Newman-Keuls method when indicated. Babyhaler delivered significantly (P < 0.05) more salbutamol than Nebuhaler, Aerochamber and Aeroscopic (mean +/- standard deviation: 63.6 +/- 2.9 microg/100 microg actuation for Babyhaler vs. 59.4 +/- 8.6 for Nebuhaler, 50.8 +/- 5.0 for Aerochamber and 47.5 + 2.5 for Aeroscopic). The ED from Volumatic (61.5 +/- 7.9 microg/100 microg actuation) was similar to that from the Babyhaler. The variability in the ED was greatest with the large volume spacers. Despite a greater ED from the Babyhaler, in vitro results do not fully explain the in vivo results. However, the previously described clinical improvement seen with the Babyhaler may be due to the quantitatively different aerosol production in a more 'useful' size range, as well as the different breathing patterns of the children tested. The results of this present study question the relevance of mouthpiece filter collection studies using a constant sampling in predicting clinical or physiological outcomes.

Albuterol↗
PubMedDate not supplied

New delivery systems and propellants.

The removal of chlorofluorocarbon (CFC) propellants from industrial and household products has been agreed to by over 165 countries of which more than 135 are developing countries. The timetable for this process is outlined in the Montreal Protocol on Substances that Deplete the Ozone Layer document and in several subsequent amendments. Pressured metered dose inhalers (pMDIs) for medical use have been granted temporary exemptions until replacement formulations, providing the same medication via the same route, and with the same efficacy and safety profiles, are approved for human use. Hydrofluoroalkanes (HFAs) are the alternative propellants for CFCs-12 and -114. Their potential for damage to the ozone layer is nonexistent, and while they are greenhouse gases, their global warming potential is a fraction (one-tenth) of that of CFCs. Replacement formulations for almost all inhalant respiratory medications have been or are being produced and tested; in Canada, it is anticipated that the transition to these HFA or CFC-free pMDIs will be complete by the year 2005. Initially, an HFA pMDI was to be equivalent to the CFC pMDI being replaced, in terms of aerosol properties and effective clinical dose. However, this will not necessarily be the situation, particularly for some corticosteroid products. Currently, only one CFC-free formulation is available in Canada - Airomir, a HFA salbutamol pMDI. This paper discusses the in vitro aerosol characteristics, in vivo deposition and clinical data for several HFA pMDIs for which there are data available in the literature. Alternative delivery systems to the pMDI, namely, dry powder inhalers and nebulizers, are briefly reviewed.

Administration, Inhalation↗