Droplets Produced by Medical Nebulizers: Results (Part 3)

The effect of dilution air humidity alone on the droplet solute concentration with the nebulizer at room temperature for each jet nebulizer system can be seen in Table 1. ventolin inhalers
The droplet solute concentration reaches 1.1 to 1.5 percent with saturated dilution air at ambient temperature. Ambient dilution air with relative humidity of 65 to 75 percent at ambient temperature increased the droplet solute concentration to 1.86 and 2.46 percent for the Up-Draft and Cadema, respectively, generated with compressed oxygen. The effect with the air compressors was greater with the Up-Draft, the Flatus compressor producing a concentration of 3.45 percent and the Aerosol-One, 13.5 percent.
The droplet solution concentration generated from the ultrasonic nebulizer changes very little with time. The maximum effect is seen at the start of generation (0.93 percent saline from 0.9 percent initial value), and as nebulization progresses, the concentration returns toward isotonic, reaching it after approxisystems fall with reduced dilution air humidity and with the falling temperature in the nebulizer, in parallel with the increase in solute concentration in the aerosol droplets. Figure 5 shows the effect of nebulizer temperature on aerosol droplet size. The effect of temperature change is greater when compressed oxygen is used at 8 L/min, the droplet size falling by 33 and 36 percent of the size at ambient temperature for the Cadema and Up-Draft, respectively. With Flatus and Aerosol-One generation, the size change is smaller (19 and 11 percent fall from ambient temperature value, respectively). Conversely, the effect of dilution air humidity at ambient temperature is greater with the air compressor generation than with the compressed oxygen (Table 2). The changes that would be seen in practice with unheated nebulizers are shown in Table 3.
The ultrasonic nebulizer droplet size changes when a two-way valve is included in line but is not affected by changes in relative humidity of the dilution air (Table 4).

Table 1—Effect of Dilution Air Humidity on Droplet Solute Concentration at Ambient Temperature

Droplet Solute Concentration (% W/V Saline)

Nebulizer/Generator

100% Relative

65-75% Relative

System

Humidity

Humidity

U p- Draft/Aerosol-One

1.5±0.3

13.5± 1.8

Up-Draft/Flatus

1.1 ±0.1

3.5±0.6

Up-Draft/Compressed 02

1.3±0.2

1.9±0.3

Cadema/Compressed 02

1.5±0.2

2.5±0.2

Table 2—Effect of Dilution Air Humidity on Droplet Size at Ambient Temperature

Mass Median Aerodynamic Diameter in p,m* (Geometric Standard Deviationt)

Nebulizer/Generator

100% Relative

65-75% Relative

System

Humidity

Humidity

U p- Draft/Aerosol-One

4.2±0.3 (1.5)

2.7±0.3 (1.5)

Up-Draft/Flatus

4.1 ±0.2 (1.6)

3.1 ±0.3 (1.6)

Up-Draft/Compressed Oa

4.2±0.1 (1.4)

3.9±0.2 (1.5)

Cadema/Com pressed 02

2.7±0.1 (1.4)

2.4±0.2 (1.4)

Table 3—Change of Concentration and Droplet Size Between Ambient and Steady State Temperature, Ts (65-75% Relative Humidity Dilution Air)

N ebulizer/Generator System

Droplet Size, % Fall

Droplet Concentration, % Rise

U p- Draft/Aerosol-One

11.1

170

Up-Draft/Flatus

5.2

39.1

Up- Draft/Compressed 02

35.9

392

Cadema/Compressed 02

2.4

244

Table 4—Size of Droplets Generated by the Mist-Ot-Gen Ultrasonic Nebulizer

Ambient

Temperature,

Dilution Air Relative Humidity,

Mouthpiece

Mass Median Aerodynamic

Geometric

Standard

°C

%

and Valve

Diameter (jtm) Deviation

19.5 ±0.3

99.0± 1

Yes

3.6 ±0.1

1.1±0.1

19.0 ±0.3

53.1 ± 1

Yes

3.5±0.2

1.1±0.1

19.0 ±0.3

53.5± 1

No

5.7±0.1

1.4±0.1

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