The equivalence of compressor pressure-flow relationships with respect to jet nebulizer aerosolization characteristics

Bronchial allergen challenge using the Medicaid dosimeter

BACKGROUND

Bronchial allergen provocations are well established in asthma research. We evaluated the reproducibility of single-concentration, single-step allergen challenges in volunteers with grass pollen allergy.

METHODS

Forty-seven subjects underwent bronchial challenges using the aerosol provocation system nebulizer (Medicaid Sidestream) with incremental doses of grass pollen to define the individual allergen dose that causes a 20% drop in FEV(1) (PD(20)FEV(1)). In 39 subjects this procedure was followed by single-step challenges. Early and late asthmatic responses were monitored, and increases in exhaled nitric oxide were measured before and 24 h after single-step challenges.

RESULTS

After the first single-step challenge, the maximum drop in FEV(1) was 21.3% ± 8.0. A comparison of the drop in FEV(1) to the initial incremental challenge (29.7% ± 7.5) revealed an intraclass correlation of -0.30 (p < 0.05). In the second single-step challenge, the mean drop in FEV(1) was 20.9% ± 7.2. Compared with the first single-step challenge, the intraclass correlation was 0.37 (p < 0.05) and the 95% limits of agreement according to Bland and Altman were -17.5 to 18.1%. The increases in exhaled nitric oxide revealed substantial agreement in repeated single-step challenges (26.8 ppb ± 27.8 and 21.8 ppb ± 21.9, ICC 0.62, p < 0.001).

CONCLUSIONS

The use of aerosol provocation system to calculate the PD(20)FEV(1) allergen is a timesaving procedure and is less prone to errors because only one dilution of the allergen is used. The repeatability in well-defined subjects is excellent to study the mechanisms of allergen-induced airway inflammation and the development of new treatments for allergic diseases.

Dry powder inhalation of colistin in cystic fibrosis patients: a single dose pilot study

BACKGROUND

Dry powder inhalation (DPI) may be an alternative to nebulisation of drugs in the treatment of chest infections in cystic fibrosis (CF) patients. In a pilot study the feasibility of a colistin dry powder inhaler (prototype Twincer) by a single dose in CF-patients was assessed and compared to nebulised colistin.

METHODS

Ten CF-patients, chronically infected with P. aeruginosa, participated in a randomised cross over study. On two visits to the outpatient clinic, patients inhaled colistin sulphomethate as 25 mg dry powder (Twincer) or as 158 mg nebulised solution (Ventstream nebuliser, PortaNeb compressor). Pulmonary function tests were performed before, 5 and 30 min after inhalation. Serum samples were drawn prior to each dose and at 15, 45 min, 1.5; 2.5; 3.5 and 5.5 h after inhalation.

RESULTS

The DPI was well tolerated by the patients: no significant reduction in FEV1 was observed. Relative bioavailability of DPI to nebulisation was approx. 140% based on actual dose and approx. 270% based on drug dose label claim.

CONCLUSIONS

The colistin DPI (Twincer inhaler) is well tolerated and appreciated by CF-patients. Optimisation with respect to particle size and internal resistance of the inhaler is necessary to attain equivalent pulmonary deposition to liquid nebulisation.

The choice of a compressor for the aerosolisation of tobramycin (TOBI®) with the PARI LC PLUS® reusable nebuliser

The performance of five different compressors (CR60), Porta-Neb, Pulmo-Aide, TurboBoy and Freeway Freedom) was studied in combination with the widely recommended PARI LC PLUS nebuliser for the aerosolisation of a marketed tobramycin solution (TOBI). The droplet size distribution of the generated aerosol was measured with laser diffraction technique at stationary inspiratory flow rates through the nebuliser cup of 20, 30 and 40l N/min. The different compressors showed a distinct difference in droplet size distribution of the aerosol and nebulisation time till dry running. The finest droplets with a volume (equals mass) median diameter (mmd) of 1.84 microm (which was the same at all flow rates), as well as the narrowest size distribution were obtained with a CR60. The Freeway Freedom generated the largest droplets: mmd ranged between 2.63 and 3.72 microm depending on the inspiratory flow rate. The aerosol produced with this compressor also had the widest size distribution. The differences between the compressors could be explained with differences in the jet flow. A higher jet flow resulted in finer droplets, less dependence on the inspiratory flow rate and a shorter time till dry running. Thus, to obtain the required fineness of the aerosol for peripheral airway deposition of the tobramycin, independent of the inspiratory flow rate, the use of the CR60 compressor is preferred over the use of Porta-Neb, Pulmo-Aide, TurboBoy and Freeway Freedom (in order of decreasing preference). Finally, it was found that careful cleaning with warm water and liquid soap of the nebuliser cup is essential to obtain adequate performance of the LC PLUS.

Improving drug delivery from medical nebulizers: the effects of increased nebulizer flow rates and reservoirs

Drug delivery from jet nebulizers can be considered in terms of the dose inhaled and the respirability of that dose. It is proposed that dose respirability and dose per breath can be controlled through specification of the driving gas flowrate, and that the dose inhaled per breath can also be increased through the use of nebulizer reservoirs. When a Hudson Micromist nebulizer was used and assessments of respirability were made utilizing phase Doppler interferometry, it was noted that the portion of the spray mass in droplet sizes of <or=5 microm (general respirability) and in droplet sizes of <or=3 microm (deep lung respirability) increased linearly with gas flowrate for both tank air and helium-oxygen (70/30). Drug mass in the 2-6 microm range (tracheobronchial respirability) peaked at air flowrates of 8-10 LPM and decreased slightly for higher flowrates. Two portable compressors provided respirabilities similar to tank air at the same flowrates. Changing the nebulizer flowrate did not affect the ratio of the inhaled dose to the dose expelled by exhalation when a typical breathing pattern was simulated. A version of the Micromist with an attached reservoir (the Hudson AeroTee) provided a higher dose per breath to the patient and a higher total dose for the same treatment time by conserving the aerosol generated during exhalation. The inhaled dose increased approximately 28% when compared to a standard Micromist, despite significant deposition in the reservoir bag. Nebulizer reservoirs could be used to attain higher doses or to more efficiently utilize expensive medications.