Experimental measurements of particle retention efficiency of filters used to prevent contamination in respiratory devices.

OBJECTIVE: Various types of filters have been designed to prevent cross contamination of ventilation and respiratory devices. The aim of this study was to experimentally measure the retention efficiency of four simple filters (antibacterial and antiviral and seven combined filters (antibacterial and antiviral plus heat and water exchangers). SETTING: The respiratory function testing (EFR) central department of a university teaching hospital. MEASUREMENTS AND RESULTS: The same aerosol test with a wide range of particle sizes (0.15 to 15 micrometers) was used to compare the retention efficiency of each filter used in various conditions. The particle sizes and the concentration of the aerosol were measured by a laser velocimeter. For all the filters studied, the retention efficiency was found to be higher than 99%. However some of them let large particles let through. CONCLUSION: These data, performed in vitro, should be assessed also by further clinical studies.

Pulmonary deposition of aerosolised pentamidine using a new nebuliser: efficiency measurements in vitro and in vivo.

The therapeutic efficacy of nebulised pentamidine in the prophylaxis of Pneumocystis carinii pneumonia (PCP) depends on the absolute pulmonary deposition of the drug. We studied the performance of a new nebuliser (Pentasave) by comparison both in vitro and in vivo with a standard nebuliser (Respirgard II). In vitro, deposition of pentamidine labelled with technetium-99m human serum albumin was measured indirectly by capturing inhaled particles on an absolute filter and measuring radioactivity with a gamma camera. The nebulisers were initially assessed with a pentamidine dose of 100 mg in 5 ml at 44 psi and an air flow of 10 l/min for Respirgard II and 16 l/min for Pentasave. Nebuliser output, expressed as the percentage of the initial nebuliser radioactivity captured by the inhalation filter, was 15% +/- 2% (mean +/- SD) for Respirgard II, and significantly increased to 23% +/- 3% for an initial version and to 33% +/- 2% for the final version of Pentasave. Measurements with a gamma camera in a group of ten patients with human immunodeficiency virus infection were made in vivo. The results revealed that pulmonary drug distributions are good using both Respirgard II and Pentasave. The literature reports that once-monthly pulmonary deposition of 9 mg pentamidine seems enough to produce prophylactic effects against Pneumocystis carinii. We measured pulmonary pentamidine deposition of 20.22 +/- 4.31 mg (mean +/- SD) using Respirgard II (with 300 mg in 5 ml) and of 16.00 +/- 7.18 mg using Pentasave (with 150 mg in 6 ml). These findings show that the therapeutic dose of pentamidine (9 mg) was widely exceeded with both nebulisers. Further investigations might demonstrate that about 200 mg and 125 mg pentamidine for Respirgard II and Pentasave, respectively, will achieve a pulmonary deposition of therapeutic dose, allowing significant savings in terms of drug and expense.

[Granulometry and measurement of a aerosol drug deposit (fusafungine) in normal and pathological airways]. / Granulométrie et mesure du dépôt d'un aérosol médicamenteux (fusafungine) dans les voies aériennes normales et pathologiques.

We measured with a laser velocimeter granulometric deposit of an aerosol anti-infectious agent, fusafungin, administered with a controlled inhalator. Total drug deposit was determined on the basis of a granulometric spectrum of the polydispered aerosol (mass mean aerodynamic diameter (MMAD) = 2.8 +/- 1.7 microns) and dispersion in the airways was estimated using the Stahlhofen model. We first compared deposits obtained with oral inhalation in 19 normal subjects and 20 patients with chronic obstructive lung disease. Total deposit in the airways of patients with chronic obstructive lung disease (82%) was not significantly different from that in normal subjects (85%). Estimated dispersion in normal airways was 27% in the alveoles, 8.4% in the tracheobronchic region and 23.5% in the extrathoracic regions. We then compared deposits after nasal inhalation in 22 normal subjects and 21 patients with rhinitis: nasal deposit was significantly greater in patients with rhinitis (54.5%) than in controls (44.7%). We conclude that such an inhalator can be adapted for local treatment of ENT infections and upper respiratory infections. Deposit is not modified in case of obstructive bronchopathy.

[Aptitude to physical effort in children with operated tetralogy of Fallot]. / Aptitude à l'effort physique des tétralogies de Fallot opérées.

BACKGROUND: Long-term follow-up of patients after total surgical correction of tetralogy of Fallot indicates that they have a smaller working capacity than controls, with an increased incidence of late onset complete heart block and sudden death. These abnormalities may be less frequent when surgery is undertaken at an early age. POPULATION AND METHODS: A cardio-pulmonary stress test was performed on 18 patients aged 8 to 20 years who had undergone correction of tetralogy of Fallot when they were 3 months to 7 years (mean age: 3 years). The basic ventilatory tests, exercise ventilatory tests and gas exchange were also performed. RESULTS: The cardiopulmonary stress test was maximal in 16 of the 18 cases. No stress-induced PVCs, or chronotropic insufficiency was found despite a basic long PR interval in 4 cases. A restrictive ventilatory syndrome was seen in 4 cases with low respiratory reserve at exercise (defined as the ratio between maximal observed ventilation and maximal theoretical ventilation, VEMS x 40). The respiratory function was normal in 14 cases with an aerobic capacity of over 40 ml/kg/min. CONCLUSION: Patients with a normal chronotropic function and preserved aerobic capacity show no post-operative restriction or cardiac of pulmonary exercise capacity.

Particle deposition and resistance in the noses of adults and children.

Nasal filter efficiency for particles has been described by several authors as showing large individual variations, probably somehow related to airflow resistance. Twelve children, aged 5.5-11.5 yrs and 8 aged 12-15 yrs were compared to a group of ten adults. Deposition of polystyrene beads (1, 2.05, 2.8 microns mass median aerodynamic diameter (MMAD] was measured by comparing inhaled aerosols and exhaled air concentrations, for both nose and mouth breathing. Ventilation was controlled to scale breathing patterns appropriate for each age either at rest or during moderate exercise to allow comparison between subjects in similar physiological conditions. Anterior nasal resistance (as a function of flow rate) and standard lung function were measured for each subject. For the same inhalation flow rate of 0.300 l.s-1, children had much higher nasal resistances than the adults, 0.425 +/- 0.208 kPa.l.1.s under 12 yrs, 0.243 +/- 0.080 kPa.l.1.s over 12 yrs and 0.145 +/- 0.047 kPa.l.1.s in adults. Individually, nasal deposition increased with particle size, ventilation flow rate and nasal resistance, from rest to exercise. The average nasal deposition percentages were lower in children than in adults, in similar conditions: at rest, 12.9 and 11.7 versus 15.6 for 1 microns; 13.3 and 15.9 versus 21.6 for 2.05 microns; 11 and 17.7 versus 20 for 2.8 microns. This was even more significant during exercise, 17.8 and 15.9 versus 29.2 for 1 microns; 21.3 and 18.4 versus 34.7 for 2.05 microns; 16 and 16.1 versus 36.8 for 2.8 microns.(ABSTRACT TRUNCATED AT 250 WORDS)

[Which compressor should be used to deliver pentamidine aerosols with the Respirgard II?]. / Quel compresseur faut-il utiliser pour délivrer des aérosols de pentamidine avec le Respirgard II?

Prophylaxis against pneumonia due to Pneumocystis carinii is most often carried out using pentamidine administered as an aerosol. For reasons both of comfort and cost this technique should be developed at home or at least in an extra-hospital environment. Using the Respirgard II as the nebuliser of reference this requires a compressor. We have assessed four different compressors and compared these to pressurised oxygen used in a hospital environment. During the course of nebulisation with a pentamidine aerosol two physical factors may coincide to limit their efficacy. First the deposition of some of the particles on the walls of the apparatus and secondly the production of a particle size which is incompatible with alveolar deposition. This study showed that according to the source of compressed air: 1) the fraction of the pentamidine solution found in an aerosol at the mouthpiece varies from 29 to 62%; 2) the fraction of the aerosol whose particle size is suitable for alveolar deposition (1 to 3 microns) varies from 35 to 48%. The product of these two fractions enables an assessment of the efficiency of each apparatus: 14 to 24% of the pentamidine solution may be deposited at the alveolar level. In addition to this efficiency the duration of the session (from 25 to 50 minutes) for each machine should be taken into consideration when considering the choice of the compressor to be coupled with the Respirgard II in order to improve the comfort and therefore the compliance to the treatment.

Particle size study of nine metered dose inhalers, and their deposition probabilities in the airways.

This study deals with the particle size measurement of nine aerosol metered dose inhalers. Calibration was made possible by the use of a laser particle velocimeter (aerodynamic Particle Sizer from TSI). The count median aerodynamic diameters (CMAD) show little variation, from 0.63 to 0.73 micron, with standard deviations (sigma g) between 1.2 and 1.8. Aerodynamic diameter aerosol diagram analysis showed multimodal mass distribution for all the tested dose inhalers. Calculations for the airway deposition probabilities (extrathoracic, tracheobronchial and alveolar) refer to the studies made by W. Stahlhofen and co-workers. As most aerosol metered dose inhalers have a predominantly bronchial therapeutic destination, the deposition at the bronchial level could be enhanced with the following parameters: inspired volume of 1500 ml, inspiratory time of 2 sec, aerosol mass median aerodynamic diameter (MMAD) of 7.5 microns, with a monodispersed distribution. The respective influences of the excipients and propellents used for the aerosolization of these dose metered inhalers are also discussed.