below 5.79 mm and the median diameter. Indeed,particles must have a diameter below 5.79 mm to reach the lungs.

 Percentage of Solution Nebulized

The amount of solution remaining in the nebulizer was subtracted from the mass initially placed in the system, making it possible to calculate the percentage of solution nebulized.

 Nebulization Time

The nebulization time parameter is important for patient compliance and must be taken into consideration.

Table 1

Characteristics of Ultrasonic Nebulizers

Vibration Vibration Ventilation Coupling

Nebulizer Frequency (MHz) Intensity Level Liquid

A 1.5 Does not vary 0–20 L/min No

B 1.63 3 positions: 0–30 L/min Yes

. minimum

. median

. maximum

C 2.4 6 positions: 1 to 6 0–50 L/min Yes

 Temperature of the Solution

We measured the temperature of dead volume to show a possible increase in temperature due to ultrasonic nebulization.

RESULTS AND DISCUSSION

Table 2 presents the influence of vibration intensity and ventilation level on the size of emitted droplets. During previous assays, we noted that results relating to the 9% sodium chloride solution and the 2% aqueous solution of 1 PI were comparable. Indeed, the concentrations of the two solutions were low, so they were very fluid and had a Newtonian rheologic behavior. Their surface tensions were 53 mN/m for the 2%   PI solution and 50.6 mN/m for the 9% sodium chloride solution.

In a previous work (9), jet nebulization of 2% and 3.5% aqueous solutions of   PI was comparable because surface tension and viscosity were not different. Protein level will have no influence on nebulization parameters if surface tension and viscosity are not significantly different.

Whatever the nebulizer considered, for a given intensity, an increase in ventilation increased the size of emitted droplets. Droplet size was greater because higher turbulence in the airstream makes droplets aggregate.

For a given nebulizer and ventilation, the increase in intensity did not influence the size of emitted droplets.

Table 3indicates the influence of vibration intensity

and ventilation level on the quantity of solution nebulized and nebulization time. For a given intensity,an increase in ventilation did not influence thepercentage of solution nebulized, but decreased nebulization time. The observations are the same when vibration intensity increased for a given ventilation.A decrease in the quantity of drug nebulized was

associated with the increase in nebulization time for the same ventilation. This decrease is explained by the concentration of the solution due to water evaporation(10). On the other hand, an increase in ventilation decreased the quantity of   PI nebulized because of higher turbulence in the airstream, which

increases the loss of drug to the wall of the nebulizer.It means that the antielastase activity of the protein,evaluated during the dosage of   PI,was maintained during ultrasonic nebulization in presence of a coupling liquid. These results are in concordance with those of Taylor et al. (11). They observed that operating the nebulizer at maximum setting decreased the time required to nebulize pentamidine isethionate solution, but also decreased delivery efficiency.