Nebulizers output

All the experiments were eondueted at the lowest volume veloeity of eompressed air that would generate a suitable mist. The volume veloeity was 5.7 liters per minute. The flow meter reading was 6 liters per minute. A horizontal glass trap 37.5 inehes long eonneeted the nebulizer with the interior of the ehamber. The internal diameter of the trap was approximately equal to that of the nebulizer output tube (approximately 5/8 internal diameter). The orifiee of the trap was flush with the inside wall of the ehamber. 

Fig. 3 Schematic diagram of nebulizer output. Droplets small enough will be carried out by air stream (route A), and the large droplets will be either recycled to the nebulizer reservoir (route B) or carried out by the outgoing air stream (route Bl). Some of the solvent will be evaporated (route C). (Adapted from Ref.. )...

The delivery efficiency, or the nebulizer output, can be expressed in many different ways, as widely documented in the literature. Sometimes it is represented as the volume output, or solution mass output. However, it is more practical to use the drug mass emitted from the nebulizer at or near the mouthpiece to estimate the nebulizer output, because the amount of aerosolized drug mass at this point in the system is the best measure of how much drug the patient has available to inhale. 

Nebulizers fitted with a T-mouthpiece have an unrestricted flow of ambient air passing through the nebulizer output, supplying inhaled air flow, which effectively increases drug output. In vented nebulizers, the inhaled air must flow through the droplet production region. Therefore, the breathing pattern of the patient has an effect on the aerosol characteristics produced by such devices. The delivery efficiency of... 

Ryan, G. Dolovich, M.B. Obminski, G. Cockroft, D.W. Juniper, E. Hargreave, F.E. Newhouse, M.T. Standardization of inhalation provocation tests influence of nebulizer output, particle size and method of inhalation. J. Allergy Clin. Immunol. 1981, 67, 156-161. 

The airflow (and the variability thereof) and its effect on nebulizer output (mass) and the respirable dose... 

With the use of a standard nebulizer, significant variation may occur in the amount of aerosol delivered per inhalation, even if inspiratory flow rate is controlled (as discussed earlier). A second important determinant of nebulizer output is related to the actual structure of the nebulizer. In the De Vilbiss 646 model, for example, the straw and baffle assembly is a detachable component of the nebulizer that is removed for washing. When this component is reattached, variable distances may result the straw and baffle assembly and the jet orifice, which is the source of pressurized air (see Fig. 2 in Dicpinigaitis 2005). This variation in distance, albeit minute, may result in variable nebulizer output. Thus, to optimize reproducibility, the author uses a nebulizer with an inspiratory flow regulator valve, as described earlier, and, with the straw and baffle assembly welded in place, thereby eliminating the variations in nebulizer output that may result when this component is detached and reattached, resulting in variable distances between the jet orifice and straw. 

Once these modifications have been performed, the exact output (milliliters per minute) of the nebulizer is measured (characterized nebulizer nSpire Health). With the exact nebulizer output known, modulation of the duration of aerosol delivery by the dosimeter allows the determination of aerosol output per inhalation. For example, the author currently uses a characterized nebulizer with an output of 1.007ml min with a dosimeter programmed to deliver pressurized air for 1.2 s, thus allowing the nebulizer to deliver exactly 0.02 ml aerosol per inhalation. Since investigators worldwide will likely continue to use different equipment for the performance of cough challenge studies, one way to achieve a measure of standardization would be to control nebulizer output per breath, with the aforementioned... 

While nebulizer output is usually diluted as a result of air entrainment in children and adults, infants may inhale pure nebulizer as a result of their low PIF (221) (Fig. 11). The quantity of aerosol that can be inspired, including that deposited in the nose and upper airways, appears to be similar in ehildren and adults once inspired flow exceeds nebulizer flow, and minute ventilation is high enough to ensure that the entire nebulizer output is inhaled. The former appears to be the case in most young children after 6 months of age (Sec. lll.B, Age-Related Changes in Aerosol Deposition ). However, the smaller minute ventilation means that younger infants will not inspire all the nebulizer output (221), unless a breath synchronized device and prolonged administration time are used (220). 

Figure 4 Cartoon depicting technique for quantification of nebulizer output and measurement of deposition. On the left, a patient inhales nebulized particles via a Y piece. The exhalation filter captures exhaled particles. On the right, the same patient performs a similar maneuver. The inhaled mass filter captures particles that would have been inhaled. Differences between filters measure deposition. Breathing pattern can be monitored using a pneumotachograph represents the sum of minute ventilation plus nebulizer flow leaving the expiratory arm of the Y piece). (From Ref. 9.)...

Tandon R, McPeck M, Smaldone GC. Measuring nebulizer output aerosol production vs gravimetric analysis. Chest 1997 111 1361-1365. 

A low thermal capacity to warm the cooled nebulizer output air-aerosol mixture, which has been reported with other cascade im-pactors to further evaporate liquid aerosol and confound interpretation of droplet size measurements (32). 

Dennis JH, Stenton SC, Beach JR, Avery AJ, Walters EH, Hendrick DJ. Jet and ultrasonic nebulizer output use of a new method to measure aerosol output directly. Thorax 1990 45 728-732. 

Figure 9 Sample PDPA results for nebulizer output...

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