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PubMed2002

Tobramycin as a pharmacologic tracer to compare airway deposition from nebulizers.

STUDY OBJECTIVE: To assess the utility of inhaled tobramycin as a pharmacologic tracer for comparing lung deposition from a prototypic breath-actuated jet nebulizer connected to an electronic pressure sensor designed to coordinate nebulization with inspiration with that from a continuously operating standard jet nebulizer. DESIGN: Prospective open-label study. SETTING: University-affiliated research center. SUBJECTS: Six healthy adult volunteers. INTERVENTION: All subjects received inhaled tobramycin 80, 160, and 320 mg from each nebulizer during six visits, as well as oral tobramycin 32 mg at a seventh visit to confirm the absence of significant gastrointestinal absorption. During each visit, urine was collected before drug administration and in 12-hour segments throughout the first 48 hours after administration. MEASUREMENTS AND MAIN RESULTS: Lung deposition of tracer after each of the seven treatments was quantified by measuring urinary tobramycin excretion over 48 hours with use of an enzyme-multiplied immunoassay technique. The ratio of tobramycin excreted after breath-actuated nebulization to that after standard nebulization, normalized for dose, was used to compare lung deposition by the two devices. Urinary excretion of tobramycin was linear and proportional to dose for both nebulizers. For every 1 mg of tobramycin that the standard nebulizer deposited into the lungs, the breath-actuated nebulizer deposited 1.22 mg (95% confidence interval 1.04-1.43). CONCLUSIONS: Tobramycin can be used as a pharmacologic tracer for comparison of relative airway deposition by nebulizers.

Administration, Inhalation↗

PubMed1996

Comparison of a respiratory suspension aerosolized by an air-jet and an ultrasonic nebulizer.

In the absence of USP standards and performance monographs, this research sought to determine if differences in the aerosolization mechanism (air-jet vs. ultrasonic) affected droplet and insoluble particle deposition of a nebulized model respiratory suspension. Five milliliters of a model suspension containing 0.1% w/v fluorescein (to estimate droplet deposition) and known quantities of 1, 3, and 6 microns latex spheres (representing insoluble drug particles) was aerosolized from an air-jet and an ultrasonic nebulizer. Nebulized output was collected in a modified Andersen impactor. Samples were analyzed spectrophotometrically (490.5 nm) and by a Coulter Counter to estimate droplet and sphere deposition, respectively. The distribution of droplets throughout the modified impactor for both nebulizers suggested that both the air-jet and the ultrasonic nebulizer produced droplets (0.4 to 10 microns in aerodynamic diameter) large enough to incorporate 1, 3, and 6 microns insoluble spheres. However, Coulter Counter analysis of the sphere distribution revealed that while the air-jet nebulized output contained spheres of all sizes, this was not true for the ultrasonic nebulizer. In the ultrasonic nebulizer, 99% of the spheres (irrespective of size) were not aerosolized and were recovered from the nebulizer reservoir at the aerosolization end point. The results highlight the importance of evaluating performance of a respiratory suspension in combination with a specific nebulizer. When conducting in vitro inertial deposition testing of a respiratory suspension, it is inappropriate to assume that deposition trends of droplets will predict the deposition of the insoluble dispersed phase.

Aerosols↗

PubMed2001

Nebulization of a suspension of budesonide and a solution of terbutaline into a neonatal ventilator circuit.

METHODS: The amount of nebulized budesonide and terbutaline delivered through an endotracheal tube (ETT) was measured in vitro using a test lung and filters in a neonatal ventilator circuit. Budesonide suspension (1 mg) was used in a concentration of 0.5 mg/mL and terbutaline solution (5 mg) in a concentration of 2.5 mg/mL. RESULTS: The median amount of terbutaline deposited on the inspiratory filters was significantly higher than that of budesonide: 0.4% vs 0.3% of the nominal doses with the nebulizer connected 8 cm upstream of the ETT and nebulization performed in a constant output mode (setup A), and 2.8% vs 1.0% with the nebulizer connected directly to the ETT and nebulization performed in a breath-synchronized mode (setup B) (p < 0.05 for both). The corresponding amounts of drug deposited on the waste filters with setup A were 19.2% for terbutaline and 12.6% for budesonide, and with setup B 16.2% for terbutaline and 6.2% for budesonide (p < 0.05 for both). CONCLUSIONS: The ratio between drug delivery to the inspiratory and waste filters, describing the relationship between lung deposition and wastage of drug to the ventilator circuit, was setup-dependent but not drug-dependent. The ratio with setup A was 0.02 for both budesonide and terbutaline. The respective ratios were significantly (p < 0.05) higher for budesonide (0.16) and for terbutaline (0.17) with setup B. The differences in the delivered doses of the two drugs through the ETT seems to be a function of both the drug formulation and the nebulizer-ETT setup. With the nebulizer connected directly to the ETT and nebulization in breath-synchronized mode, the differences between the two drugs were enhanced, compared with the nebulizer connected upstream of the ETT and nebulization in constant output mode. The results indicate that a solution is superior to a suspension in terms of drug delivery through an ETT.

Aerosols↗

PubMed1995

Nebulized bacteriostatic saline as a cause of bronchitis.

BACKGROUND: The purpose of this study was to determine whether nebulized bacteriostatic saline, which contains the preservative benzyl alcohol, is an irritant to the tracheobronchial mucosa in healthy adults. METHODS: A randomized, double-blind, placebo-controlled study was conducted with 10 healthy adults who inhaled 3 mL of either bacteriostatic saline or saline placebo by nebulizer four times a day for 2 weeks. Pulmonary function tests and bronchoscopy with biopsy were performed immediately before and after the 2-week nebulization period. RESULTS: Nine of 10 volunteers were compliant with the study protocol. Four of five volunteers who used nebulized bacteriostatic saline developed bronchitic symptoms and had bronchoscopic evidence of bronchitis. The fifth remained healthy. Four volunteers used nebulized saline (placebo). Two of these four became ill, one with a much more severe bronchitis than any of the bacteriostatic saline volunteers, and one with pharyngitis. Bronchoscopic biopsies showed a lymphocytic mucosal infiltrate in those who became ill while using nebulized bacteriostatic saline and a polymorphonuclear mucosal infiltrate in those who became ill while using nebulized saline placebo. CONCLUSIONS: Nebulization of bacteriostatic saline, containing benzyl alcohol as its preservative, causes bronchitis in healthy adults. Even nebulization of sterile saline may be associated with bronchitis and pharyngitis. Physicians who prescribe nebulized medications must pay close attention to the bronchodilator diluent.

Adult↗

PubMed1994

Efficient drug delivery to the lungs from a continuously operated open-vent nebulizer and low pressure compressor system.

A comparison of aerosol delivery has been made between two open-vent Pari jet nebulizers. Intermittent and continuous delivery were compared for one of the nebulizers. Ten healthy volunteers inhaled 99mTc-labelled diethylenetriamine penta-acetic acid (DTPA) aerosols on three occasions. The Pari LC device was operated both intermittently (by a manual interrupter that generated aerosol only in synchrony with inhalation) and continuously. The Pari LL nebulizer was operated only in the intermittent mode. A system of inspiratory and expiratory valves was fitted to each nebulizer in order to direct airflow. Both nebulizers were powered by Pari Boy compressors. The mean (SD) whole lung deposition for the LL nebulizer was 11.1 (4.0)% of the nominal dose, compared to 15.3 (12.8)% and 12.8 (7.9)% for the LC used with intermittent and continuous operation, respectively. These differences were not statistically significant. Regional deposition patterns within the lungs were similar for the three nebulizer systems. These data show that efficient nebulizer systems using relatively low power compressors are possible, and suggest that continuously operated open-vent nebulizers may be designed to give lung deposition comparable to that achieved by nebulizers fitted with manual interrupters.

Administration, Inhalation↗

PubMed1993

Comparison of the bronchodilator efficacy of nebulized pirenzepine and ipratropium bromide in patients with airway obstructive lung disease.

Ipratropium bromide (IB) is a non-selective muscarinic antagonist, whose bronchodilator efficacy has been shown in reversible and irreversible obstructive airway diseases. Pirenzepine is a M1 receptor antagonist and effective in vagally-induced bronchoconstriction. To investigate the bronchodilator efficacy of nebulized pirenzepine, we compared nebulized pirenzepine with nebulized IB and nebulized isotonic saline (placebo). Eighteen patients with reversible and 18 patients with irreversible obstructive airway disease were studied. Nebulized isotonic saline (placebo), 100 mcg nebulized pirenzepine and 125 mcg nebulized IB were given on three consecutive days. Spirometry was performed prior to nebulization and repeated at 5, 30, 60, 90 and 120 minutes following nebulized medication. A dose of 125 mcg IB resulted in a significant increase in FEV1 in patients with both reversible or irreversible bronchoconstriction (p < 0.00001, p < 0.03). IB at the same dose resulted in an increase in FVC in patients with irreversible bronchoconstriction (p < 0.001) and an increase in FEF25-75 in patients with reversible bronchoconstriction (p < 0.0003). Pirenzepine therapy resulted in no significant change in the same parameters. It is concluded that nebulized pirenzepine at a dose of 100 mcg does not have bronchodilator effect in patients with reversible or irreversible bronchoconstriction.

Administration, Inhalation↗

PubMed1998

Surfactant nebulization versus instillation during high frequency ventilation in surfactant-deficient rabbits.

Surfactant nebulization improves lung function at low alveolar doses of surfactant. However, efficiency of nebulization is low, and lung deposition seems to depend on lung aeration. High frequency ventilation (HFV) has been shown to improve lung aeration. We hypothesize that the combination of HFV and surfactant nebulization may benefit lung deposition of surfactant and consequently, lung function. The aim of this study was to compare the effect of surfactant nebulization versus instillation during HFV on lung function, surfactant distribution, and cerebral blood flow. Therefore, severe respiratory failure was induced by lung lavages in 18 rabbits. HFV was applied: frequency = 8 Hz, mean airway pressure = 12 cm H2O, amplitude = 100%, fraction of inspired O2 = 1.0. Technetium-99m-labeled surfactant (Alveofact, 100 mg/kg of BW) was nebulized or instilled (n = 6 each). Six other rabbits did not receive surfactant (control, HFV only). We found that after instillation partial arterial O2 tension increased from 7.0 kPa (95% confidence interval, 6.3-8.0 kPa) to 34 kPa (16-51 kPa), and during nebulization from 7.0 kPa (6.0-9.0 kPa) to 46 kPa (27-58 kPa). Partial arterial CO2 tension decreased after instillation from 6.1 kPa (5.3-7.1 kPa) to 4.8 kPa (3.9-5.6 kPa), and during nebulization, after an initial rise, it decreased from 6.3 kPa (5.3-7.4 kPa) to 4.9 kPa (4.4-5.6 kPa). Both treatments resulted in nonuniform distribution. Surfactant deposition after nebulization was 9.8%. Instillation resulted in a drop of mean arterial blood pressure of 17% (8-31%), and an even more pronounced drop in cerebral blood flow of 39% (18-57%). Nebulization did not affect blood pressure. Cerebral blood flow decreased with a maximum of 27% (10-37%). We conclude that surfactant nebulization during HFV improves lung function in rabbits with severe respiratory failure, without improving distribution, but with less effects on blood pressure and cerebral blood flow, when compared with surfactant instillation.

Aerosols↗

PubMed2005

A miniaturized nebulization catheter for improved gene delivery to the mouse lung.

BACKGROUND: The available methods for administration of gene delivery systems to the lungs of small animals via nebulization have several drawbacks. These include lack of control over the delivered dose and a negative impact on the stability of the formulation. This paper describes a new nebulization catheter device for the administration of plasmid-based gene delivery systems (polyplexes) as aerosols to the mouse lung in vivo. METHODS: The physical stability of naked pDNA and polyplexes formulated with chitosan oligomers and PEI was examined following nebulization with the catheter device. We also examined the in vitro transfection efficiency of the polyplexes recovered after nebulization. Lung distribution and gene expression after administration of the selected gene delivery systems to the mouse lung were also investigated. RESULTS: In contrast to previously described nebulization methods, the structural integrity of the unprotected naked pDNA was maintained following nebulization by the catheter device, which indicates relatively mild nebulization conditions. In addition, the nebulization procedure did not affect the physical stability of the formulated polyplexes. Small volumes of the pDNA aerosol (10-20 microl) were delivered in a highly controlled and reproducible manner. The aerosol droplet size varied with the molecular weight of the polycations. Aerosol delivery via this method resulted in improved lung distribution of pDNA polyplexes and a six-fold increase in the efficiency of gene delivery in vivo over that seen with the commonly used intratracheal instillation method. CONCLUSION: The use of the nebulization catheter device provides a promising alternative for aerosol gene delivery to the mouse lung.

Administration, Inhalation↗

PubMed2000

Costs and effectiveness of spacer versus nebulizer in young children with moderate and severe acute asthma.

OBJECTIVE: To compare the costs and effectiveness of albuterol by metered dose inhaler (MDI) and spacer versus nebulizer in young children with moderate and severe acute asthma. DESIGN: Randomized, double-blind, placebo-controlled trial in an emergency department at a children's hospital. The participants were children 1 to 4 years of age with moderate to severe acute asthma. Patients assigned to the spacer group received albuterol (600 microg) by MDI by spacer (AeroChamber) followed by placebo by nebulizer (n = 30). The nebulizer group received placebo MDI by spacer followed by 2.5 mg albuterol by nebulizer (n = 30). Treatments were repeated at 20-minute intervals until the patient was judged to need no further doses of bronchodilator, or a total of 6 treatments. RESULTS: Clinical score, heart rate, respiratory rate, auscultatory findings, and oxygen saturation were recorded at baseline, after each treatment, and 60 minutes after the last treatment. Baseline characteristics and asthma severity were similar for the treatment groups. The spacer was as effective as the nebulizer for clinical score, respiratory rate, and oxygen saturation but produced a greater reduction in wheezing (P =.03). Heart rate increased to a greater degree in the nebulizer group (11.0/min vs 0.17/min for spacer, P <.01). Fewer children in the spacer group required admission (33% vs 60% in the nebulizer group, P =.04, adjusted for sex). No differences were seen in rates of tremor or hyperactivity. The mean cost of each emergency department presentation was NZ$825 for the spacer group and NZ$1282 for the nebulizer group (P =.03); 86% of children and 85% of parents preferred the spacer. CONCLUSION: The MDI and spacer combination was a cost-effective alternative to a nebulizer in the delivery of albuterol to young children with moderate and severe acute asthma.

Acute Disease↗

PubMed1998

Comparative study of budesonide as a nebulized suspension vs pressurized metered-dose inhaler in adult asthmatics.

The study objective was to compare the effect of budesonide administered as a nebulized suspension as compared to a spray with a spacer in adult asthmatics. In a double-blind, double-dummy crossover study, 26 adult patients with moderately severe unstable asthma were randomized to three 4-week treatment periods with budesonide 0.8 mg b.i.d. administered by a pressurized metered-dose inhaler (pMDI) with spacer (Nebuhaler) and budesonide 1 mg and 4 mg b.i.d. administered by a Pari Inhalier Boy jet nebulizer. The nebulizer was activated only during inspiration. The total mass output was similar from the two devices but their fraction of small particles differed by a factor of 2 in favour of pMDI. Effect was evaluated from daily home measurements of peak expiratory flow (PEF), need of beta 2-agonist and symptom scores. Plasma cortisol and budesonide levels were measured in a subgroup of 10 patients. A consistent trend showed the nebulizer treatment to be at least as efficient as the pMDI plus spacer treatment. In actual fact, the apparent order of effect was: 4 mg nebulized suspension treatment > or = 1 mg nebulized suspension treatment > or = 0.8 mg pMDI with spacer treatment. Plasma budesonide and plasma cortisol also exhibited dose-related levels independent of device. The adverse effects reported appeared to be related to the dose rather than delivery device. Accordingly, the effect was related to total mass output, rather than to the small particle fraction of the budesonide aerosol. These results attest to the efficiency of jet-nebulized budesonide suspension, and indicate nebulized budesonide to be equipotent to standard budesonide therapy delivered by pMDI with Nebuhaler, provided nebulization is synchronized with inspiration and no loss of aerosol occurs during expiration.

Adult↗

PubMed2006

Use of nebulized inhaled corticosteroids among older adult patients: an assessment of outcomes.

BACKGROUND: Inhaled corticosteroids (ICSs) are used by patients of all ages, but older patients may have difficulty with conventional inhalation devices and therefore may benefit from the easy-to-use delivery mechanism of the nebulizer. OBJECTIVE: To compare the outcomes, resource use, and health care costs of patients prescribed nebulized ICSs before and after treatment. METHODS: All patients 50 years and older prescribed nebulized ICSs were identified from a nationally representative managed care claims database (1999-2003). Patients with 1 year of continuous enrollment were analyzed using a retrospective cohort design; outcomes, resource use, and costs were measured and compared 6 months before and 6 months after the initial nebulized ICS prescription. RESULTS: A total of 2,178 patients were identified for participation in the study, of whom 668 were analyzed. Patients were prescribed nebulized ICSs primarily for asthma (57.4%) and chronic obstructive pulmonary disease (52.1%). Nebulized ICSs were prescribed mostly by primary care physicians and pulmonologists. More than 40% of patients used nebulized ICSs persistently (at least 1 refill); persistent users averaged 123.4 days of use during 6 months of follow-up. There was a significant decrease in systemic corticosteroid use among persistent users (48.0% vs 38.8%; odds ratio, 0.7; 95% confidence interval, 0.5-1.0; P = .03). There was an emergency department visit in 20.2% and 15.0% of persistent users before and after the index date, respectively (odds ratio, 0.7; 95% confidence interval, 0.45-1.09; P = .12); 20.5% and 17.5% were hospitalized before and after the index date, respectively (odds ratio, 0.8; 95% confidence interval, 0.54-1.27; P = .38). No significant difference occurred in total health care costs during follow-up compared with baseline. CONCLUSIONS: In this retrospective cohort study, older patients who used nebulized ICSs persistently demonstrated fewer emergency department visits and systemic corticosteroid use than before nebulized ICS use. These improved outcomes were not associated with an increase in health care costs.

Administration, Inhalation↗

PubMed2005

Importance of dosimeter calibration method on nebulizer output.

BACKGROUND: We have observed that dosimeter-run nebulizers have a much smaller output when manually activated than when breath activated; however, this has not been adequately investigated. OBJECTIVE: To evaluate the effect of different calibration methods on nebulizer output. METHODS: Six healthy subjects performed all calibrations. The nebulizers were operated by 2 different dosimeters and were calibrated to produce 9 microL per actuation by breath activation followed by exhalation to the room. The nebulizers were then operated at these identical settings, and the output determined in 3 ways: (1) breath activation followed by exhalation to the room, (2) breath activation with exhalation into the nebulizer, and (3) manual activation (with no subject using the nebulizer). These 3 methods were termed regular, rebreathe, and manual, respectively. RESULTS: There was a large and statistically significant difference in nebulizer output among the 3 methods. The measured rebreathe outputs (5.6 and 5.7 microL per actuation) were approximately two thirds and the manual outputs (3.2 and 3.9 microL per actuation) were approximately one third of the regular calibration outputs (8.6 and 8.9 microL per actuation); the 2 values are for the 2 dosimeters. The results were highly statistically significant (P < .001). CONCLUSIONS: The method by which a nebulizer-dosimeter system is calibrated results in different nebulizer outputs. This has a high likelihood of influencing the concentration of methacholine causing a 20% decrease in volume in the first second of forced expiration.

Adult↗

PubMed1998

Continuous nebulization therapy for asthma with aerosols of beta2 agonists.

BACKGROUND: Various studies have demonstrated the benefits of continuous nebulization therapy for delivering aerosols of the beta2 agonists such as terbutaline sulfate or albuterol sulfate to patients with severe asthma and/or impending respiratory failure. OBJECTIVE: The purpose of this investigation was to explicate the operational factors associated with the use of nebulizers for extended aerosol respiratory therapy including those factors that affect the prescribed aerosol dosages and the relationship to actual delivery of prescribed drugs to the respiratory airways of the lungs of a patient under treatment conditions. METHODS: Operational characteristics and methods have been investigated for use of long-running nebulizers for continuous nebulization therapy. Factors considered were particle size distribution, setup conditions, aerosolization concentrations and rates, delivery fraction of aerosol reaching patient, and changes in medication concentration during extended operation. With a large volume nebulizer, aerosols can be delivered to the patient without dilution via a standard open mask for up to eight hours without refill. The pneumatic HEART nebulizer with 240 mL reservoir was evaluated. RESULTS: The nebulizer was operated from a single compressed air or oxygen source and found to provide from 10 to 15 L/min of aerosol with 38 to 50 microL of aerosolized medicine per liter of air (or oxygen) and utilize from 30 to 56 mL/hour of medicinal liquid. The mass median aerodynamic diameter of the aerosol droplets was found to be about 2.0 microm (sigma(g) = 2.7). Delivery efficiency to the patient mask was about 90%. The aerosolized medicine delivered to the patient can be increased by adjusting the flow rate of the gas source or changing the solution concentration of medicine. Typically, several milligrams of drug can be delivered to the patient as inhaled aerosol per hour of treatment of which about one-quarter can be expected to be deposited in the lungs. During eight hours of operation the concentration of medicinal solution increased by about a factor of two because of water evaporation. CONCLUSIONS: Continuous nebulization therapy is an important means of treating patients with severe asthma. Dosage criteria can be established based on the operating characteristics of the nebulizer system, drug solution concentration, and patient respiration.

Adrenergic beta-2 Receptor Agonists↗

PubMed2006

Hood versus mask nebulization in infants with evolving bronchopulmonary dysplasia in the neonatal intensive care unit.

OBJECTIVE: To compare infants' discomfort, nursing-time and caregiver preference, and assess the clinical efficiency (as a secondary outcome) of hood versus facemask nebulization in infants with evolving bronchopulmonary dysplasia (BPD) in the neonatal intensive care unit. STUDY DESIGN: A prospective, open, randomized, controlled crossover clinical trial. In total, 10 infants with BPD who were on inhaled beta-agonist bronchodilators and corticosteroids were randomly assigned to receive their nebulized treatments either by a facemask, or by a hood for 2-3 days, and then crossover to receive the same treatments with the other technique for another 2-3 days. Infants' discomfort, nursing-time, caregiver preference and clinical efficiency were compared. RESULTS: At baseline there was no significant clinical difference between the groups. Nurse-time required for administering the hood nebulization (mean+/-s.e.m.: 1.9+/-0.1 min) was significantly shorter than the time for mask nebulization (12.0+/-0.6 min, P<0.0001). Infants' discomfort score was significantly lower (0.1+/-0.04) for hood versus mask nebulization (2.5+/-0.2, P<0.0001). Nurses and parents unequivocally preferred the hood treatment. During both mask and hood nebulization therapies (2-3 days) clinical efficiency was comparable. While both methods caused an immediate (20 min post) clinical improvement, the immediate respiratory assessment change score was significantly greater for the hood versus the mask nebulization (0.62+/-0.27 versus 0.13+/-0.14, P<0.05). CONCLUSIONS: Nebulization of aerosolized medications in infants with evolving BPD by hood was less time-consuming for caregivers and was much better tolerated by the infants while being at least as effective as the conventional facemask nebulization.

Administration, Inhalation↗

PubMed1990

Physical properties of antibiotic aerosols produced by jet and ultrasonic nebulizers.

The drug stability and the physical properties of aerosol of five different antibiotics were compared for ultrasonic and jet-type nebulization. These antibiotics were used alone, as well as combined with betamethasone sodium phosphate and/or tyloxapol glycerol sodium bicarbonate. The parameters investigated were changes in appearance, pH, temperature, viscosity, specific gravity and the residual potency of the antibiotics. No significant change was shown in appearance, viscosity and specific gravity. Temperatures of the solutions in the ultrasonic nebulizer cup increased with time, though almost no change after 10 minutes in the jet nebulizer. For pH, with antibiotics alone in the ultrasonic nebulizer, some drugs showed an increase, and other drugs showed a decrease, while generally a little change in the jet nebulizer. For residual potency, one drug showed decreased potency in the aerosol, though it was increased in the remnant solution, in contrast, another drug showed a tendency to increased potency in the aerosol and decreased potency in the remnant solution in the ultrasonic nebulizer. In the jet nebulizer, drugs showed generally slight increased potency and no difference among drugs. It was suggested that, with ultrasonic nebulization, in some drugs the solvents were nebulized and the principal ingredient tended to remain behind, while in other drugs the opposite occurred so that the effects were not uniform.

Administration, Inhalation↗

PubMed1994

Why do medical nebulizers differ in their output and particle size characteristics?

Previous work done on the characterisation of nebulizers has focused on gravimetrical output and particle/droplet size distribution at various air flow rates. This paper investigates six different nebulizers, with regard to droplet generation and separation properties, at a single air flow rate. Droplet generation and separation properties were measured with laser diffraction and impactor techniques. For each of the nebulizers the air velocity was calculated and both liquid and air volumetric flow rate was measured. The primary generated droplets (nebulizer without impaction baffle) had a mean size of between 15 microns and > 500 microns. The secondary generated droplets (nebulizer with baffle) were in the size range of 1 to 10 microns. It was found that the baffle system of the investigated nebulizers could be described according to ordinary impaction theory. The mass median diameters (MMD) of these nebulizers were found to be dependent on air velocity (vg), and ratio of liquid to air volumetric flow rate (Ql/Qa). In all of the nebulizers, between 93% and 99% of the generated primary droplets were caught by the baffle system which resulted in a very low output. Thus, the nebulizers examined do not appear to be optimised, with regard to observed droplet generation and baffle arrangements, if secondary droplets with a size approximately 1 micron are desired. By changing the design at the primary generation point, air velocity (vg) and liquid to air flow rate (Ql/Qa), the primary generated droplet size could be decreased. This would result in an increase in the number concentration of smaller droplets that pass the baffle system.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Design↗

PubMed1990

Evaluation of nebulizers for use in neonatal ventilator circuits.

The use of nebulizers in neonatal ventilator circuits offers a new and relatively uncharted route of therapy for infants in respiratory failure. We used a model lung to investigate and compare different nebulizer types and therapeutic agents and to make practical observations. Five different nebulizers (Ultravent, Acorn, MAD2, Small Particle Aerosol Generator, and Pulmosonic) were compared for efficiency of delivery of an amino-phylline aerosol to the model lung, and the particle size of aerosol produced by them was measured. A Nebulizer Efficiency Index (NEI) was created, representing the deposition rate of the original solution as aerosol upon the model lung filter. The Acorn (2.8.10(3) ml/min) and MAD2 (2.4.10(-3) scored highest NEI. When a suspension of budesonide was nebulized, minimal amounts of drug were recovered from the filter when the nebulizer producing the smallest particle size (Ultravent) was studied, suggesting that suspensions of drugs behave differently from solutions. Significant changes need to be made to a conventional circuit when jet nebulizers are used; most of these are obviated by the use of an ultrasonic nebulizer, which also avoids the potential problem of marked cooling of the gas flow produced by jet nebulizers.

Aerosols↗

PubMed1998

Drug output from nebulizers is dependent on the method of measurement.

The objective of this study was to determine whether current regulatory methods for assessing the output of nebulizers are appropriate for the delivery of nebulized steroid suspensions to patients. We studied a conventional jet nebulizer (the Intersurgical Cirrus), an open-vent nebulizer (the Medicaid Sidestream) and a breath-enhanced nebulizer (the Pari LC Plus), using a constant sampling flow or a sinusoidal pump to represent the breathing pattern of children from 6 months to adulthood. Recovery of budesonide released from the nebulizers onto filters was reduced when using breathing simulation compared with constant flow, and this reduction was greatest for the conventional nebulizer (Cirrus, 103 microg with constant flow to 4.4 microg with a 50 mL tidal volume; Pari, 176 microg to 25 microg). The open-vent nebulizer deposited very little budesonide on the filter at lower tidal volumes (4.5 microg with a 50 mL tidal volume), possibly because the enhanced flow of aerosol laden air was greater than the inspiratory flow from the breathing simulator. The output of the LC plus was reduced at high flow, from 176 microg at 20 L x min(-1) to 93 microg at 60 L x min(-1). Overall, the measured output varied by up to 700%, depending on the method used. These results suggest that breathing patterns dramatically alter the measured output of different nebulizers and that breathing simulation should be included as part of their assessment.

Adolescent↗