A comparison of pulmonary availability between Ventolin (albuterol) nebules and Ventolin (albuterol) Respirator Solution

Indian Guidelines on Nebulization Therapy

Inhalational therapy, today, happens to be the mainstay of treatment in obstructive airway diseases (OADs), such as asthma, chronic obstructive pulmonary disease (COPD), and is also in the present, used in a variety of other pulmonary and even non-pulmonary disorders. Hand-held inhalation devices may often be difficult to use, particularly for children, elderly, debilitated or distressed patients. Nebulization therapy emerges as a good option in these cases besides being useful in the home care, emergency room and critical care settings. With so many advancements taking place in nebulizer technology; availability of a plethora of drug formulations for its use, and the widening scope of this therapy; medical practitioners, respiratory therapists, and other health care personnel face the challenge of choosing appropriate inhalation devices and drug formulations, besides their rational application and use in different clinical situations. Adequate maintenance of nebulizer equipment including their disinfection and storage are the other relevant issues requiring guidance. Injudicious and improper use of nebulizers and their poor maintenance can sometimes lead to serious health hazards, nosocomial infections, transmission of infection, and other adverse outcomes. Thus, it is imperative to have a proper national guideline on nebulization practices to bridge the knowledge gaps amongst various health care personnel involved in this practice. It will also serve as an educational and scientific resource for healthcare professionals, as well as promote future research by identifying neglected and ignored areas in this field. Such comprehensive guidelines on this subject have not been available in the country and the only available proper international guidelines were released in 1997 which have not been updated for a noticeably long period of over two decades, though many changes and advancements have taken place in this technology in the recent past. Much of nebulization practices in the present may not be evidence-based and even some of these, the way they are currently used, may be ineffective or even harmful. Recognizing the knowledge deficit and paucity of guidelines on the usage of nebulizers in various settings such as inpatient, out-patient, emergency room, critical care, and domiciliary use in India in a wide variety of indications to standardize nebulization practices and to address many other related issues; National College of Chest Physicians (India), commissioned a National task force consisting of eminent experts in the field of Pulmonary Medicine from different backgrounds and different parts of the country to review the available evidence from the medical literature on the scientific principles and clinical practices of nebulization therapy and to formulate evidence-based guidelines on it. The guideline is based on all possible literature that could be explored with the best available evidence and incorporating expert opinions. To support the guideline with high-quality evidence, a systematic search of the electronic databases was performed to identify the relevant studies, position papers, consensus reports, and recommendations published. Rating of the level of the quality of evidence and the strength of recommendation was done using the GRADE system. Six topics were identified, each given to one group of experts comprising of advisors, chairpersons, convenor and members, and such six groups (A-F) were formed and the consensus recommendations of each group was included as a section in the guidelines (Sections I to VI). The topics included were: A. Introduction, basic principles and technical aspects of nebulization, types of equipment, their choice, use, and maintenance B. Nebulization therapy in obstructive airway diseases C. Nebulization therapy in the intensive care unit D. Use of various drugs (other than bronchodilators and inhaled corticosteroids) by nebulized route and miscellaneous uses of nebulization therapy E. Domiciliary/Home/Maintenance nebulization therapy; public & health care workers education, and F. Nebulization therapy in COVID-19 pandemic and in patients of other contagious viral respiratory infections (included later considering the crisis created due to COVID-19 pandemic). Various issues in different sections have been discussed in the form of questions, followed by point-wise evidence statements based on the existing knowledge, and recommendations have been formulated.

Sterility and Stability Testing of Preservative-free Albuterol

BACKGROUND

Continuous albuterol administration (CAA) is commonly used in hospitalized patients for treatment of asthma exacerbations. Due to higher dose requirements, CAA requires large volumes of albuterol obtained from multidose vials containing benzalkonium chloride (BAC). BAC is a common pharmaceutical preservative and potent bronchoconstrictor, which may antagonize the bronchodilation effects of albuterol. Some institutions are using preservative-free (PF) albuterol for their CAA. However, no published data currently exist to support the extended sterility or stability of this formulation.

OBJECTIVE

To evaluate the sterility and stability of PF-albuterol.

METHODS

Sterility testing was conducted for PF- and BAC-albuterol when stored at room temperature. Samples were incubated for 10 days in aerobic and anaerobic blood culture media to assess for bacterial growth. Stability of both albuterol formulations at high (0.67 mg/mL) and low (0.17 mg/mL) concentrations was determined at room temperature and under refrigeration. High performance liquid chromatography was used to evaluate samples up to 168 hours after preparation.

RESULTS

No bacterial growth was witnessed from either albuterol formulation at day 10 of observation. Both high and low concentrations of PF-albuterol and BAC-albuterol were stable at room temperature for up to 168 hours. There were no differences in stability between storage conditions for any formulation.

CONCLUSIONS

Under the current study conditions, there was no difference in sterility or stability for PF-albuterol when compared with BAC-albuterol. Thus, based on the findings of this study, PF-albuterol is sterile and stable up to 168 hours when stored at room temperature or under refrigerated conditions. The findings of this study do not confirm the therapeutic efficacy of PF-albuterol compared with BAC-albuterol for the treatment of asthma exacerbations. Further studies are warranted to determine the efficacy of PF-albuterol verses BAC-albuterol when used for CAA.

Drug Delivery Devices for Inhaled Medicines

Historically, the inhaled route has been used for the delivery of locally-acting drugs for the treatment of respiratory conditions, such as asthma, COPD, and airway infections. Targeted delivery of substances to the lungs has some key advantages over systemic administration, including a more rapid onset of action, an increased therapeutic effect, and, depending on the agent inhaled, reduced systemic side effects since the required local concentration in the lungs can be obtained with a lower dose. Fortunately, when designed properly, inhaled drug delivery devices can be very effective and safe for getting active agents directly to their site of action.

Clinical Considerations in the Use of Inhalation Delivery Devices

Medications delivered through oral inhalation represent the cornerstone of pharmacotherapy for asthma and chronic obstructive pulmonary diseases. Several options exist as methods of delivering aerosols to the lung, including metered-dose inhalers, metered-dose inhalers attached to spacers or valved holding chambers, dry powder inhalers, and nebulizers. Delivery of aerosols to the lung is affected by numerous factors including characteristics of aerosol particles, patients’ ventilatory patterns, and physical condition of the lung. It has become increasingly clear that the device used to deliver the medication is an important factor in the extent of deposition and the ultimate therapeutic effect. Further, the same therapeutic agent may exhibit differing effects depending on which delivery device is used. Each inhalation device has specific instructions for use, and the techniques for use vary significantly among the available products. In each case, patients should be instructed and observed to ensure that they have the proper technique of use to achieve an optimal effect.

A European perspective on orally inhaled products: in vitro requirements for a biowaiver

This article describes the European Union stepwise approach used for the development and assessment of second-entry orally inhaled products. This approach is similar to the approach used for systemically acting products. In some cases, in vitro data can be used to show equivalence without performing in vivo studies (e.g., solutions for nebulization in the case of inhalation products, and oral solutions or Biopharmaceutics Classification System-based biowaivers in the case of systemically acting drugs). If equivalence cannot be shown in the first step, the Applicant can show equivalence in a second step by means of conventional pharmacokinetic bioequivalence studies to assess directly systemic exposure and lung deposition indirectly. The dose absorbed from the lungs should be distinguished from the dose absorbed from the gastrointestinal tract. Then the fraction of dose absorbed (area under the curve) represents the dose that reached the site of action, and the peak exposure gives information on the pattern of deposition within the lungs. This information is more discriminative than any pharmacodynamic or clinical endpoint, because these have flat dose-response curves. If equivalence is not shown with pharmacokinetic data, the Applicant can decide to show equivalence by means of pharmacodynamic or clinical trials, but assay sensitivity must be demonstrated within the study and relative potency should be estimated. This article focuses on the in vitro requirements applicable in the European Union for a waiver of in vivo studies and for waiving studies with all drug product strengths or pharmacokinetic studies in patients. The reasons why in the European Union in vitro data alone can be used to show equivalence are discussed, and some examples are given.

Regulatory Considerations for Approval of Generic Inhalation Drug Products in the US, EU, Brazil, China, and India

This article describes regulatory approaches for approval of "generic" orally inhaled drug products (OIDPs) in the United States, European Union, Brazil, China and India. While registration of a generic OIDP in any given market may require some documentation of the formulation and device similarity to the "original" product as well as comparative testing of in vitro characteristics and in vivo performance, the specific documentation approaches, tests and acceptance criteria vary by the country. This divergence is due to several factors, including unique cultural, historical, legal and economic circumstances of each region; the diverse healthcare and regulatory systems; the different definitions of key terms such as "generic" and "reference" drug; the acknowledged absence of in vitro in vivo correlations for OIDPs; and the scientific and statistical issues related to OIDP testing (such as how best to account for the batch-to-batch variability of the Reference product, whether to use average bioequivalence or population bioequivalence in the statistical analysis of results, whether to use healthy volunteers or patients for pharmacokinetic studies, and which pharmacodynamic or clinical end-points should be used). As a result of this discrepancy, there are ample opportunities for the regulatory and scientific communities around the world to collaborate in developing more consistent, better aligned, science-based approaches. Moving in that direction will require both further research and further open discussion of the pros and cons of various approaches.

Challenging the two-minute tidal breathing challenge test

BACKGROUND

In the adenosine 5'-monophosphate (AMP) bronchial challenge test, AMP is usually administered according to dosing protocols for methacholine. We investigated whether the 2-min tidal breathing challenge test for methacholine is applicable to AMP. Parameters known to affect nebulizer output were studied. Our aim was to determine whether control of additional parameters is needed for currently standardized protocols.

METHODS

The study was performed with the Sidestream nebulizer from the APS Pro Aerosol Provocation System (CareFusion Respiratory). The effects of AMP concentration, jet pressure, and suction flow rate on nebulizer output rate and aerosol droplet size distribution were determined.

RESULTS

The volume median diameter for water increased from 5.10 μm to 8.49 μm when the jet pressure was reduced to obtain the prescribed output rate of 0.13 mL/min. The output rate was increased when a suction flow rate was used to remove the aerosol. Increasing the AMP concentration resulted in smaller droplets and a lower output rate when a suction flow was applied.

CONCLUSIONS

The effects of AMP concentration on nebulizer performance may result in changes in the administered dose and site of deposition of AMP at dose escalation. All of the investigated parameters influence nebulizer performance, hence the outcome of a bronchial challenge test. Therefore, these parameters should not only be specified in challenge testing, but be actively controlled as well.

Modeling breath-enhanced jet nebulizers to estimate pulmonary drug deposition

BACKGROUND

Predictable delivery of aerosol medication for a given patient and drug-device combination is crucial, both for therapeutic effect and to avoid toxicity. The gold standard for measuring pulmonary drug deposition (PDD) is gamma scintigraphy. However, these techniques expose patients to radiation, are complicated, and are relevant for only one patient and drug-device combination, making them less available. Alternatively, in vitro experiments have been used as a surrogate to estimate in vivo performance, but this is time-consuming and has few "in vitro to in vivo" correlations for therapeutics delivered by inhalation. An alternative method for determining inhaled mass and PDD is proposed by deriving and validating a mathematical model, for the individual breathing patterns of normal subjects and drug-device operating parameters. This model was evaluated for patients with cystic fibrosis (CF).

METHODS

This study is comprised of three stages: mathematical model derivation, in vitro testing, and in vivo validation. The model was derived from an idealized patient's respiration cycle and the steady-state operating characteristics of a drug-device combination. The model was tested under in vitro dynamic conditions that varied tidal volume, inspiration-to-expiration time, and breaths per minute. This approach was then extended to incorporate additional physiological parameters (dead space, aerodynamic particle size distribution) and validated against in vivo nuclear medicine data in predicting PDD in both normal subjects and those with CF.

RESULTS

The model shows strong agreement with in vitro testing. In vivo testing with normal subjects yielded good agreement, but less agreement for patients with chronic obstructive lung disease and bronchiectasis from CF.

CONCLUSIONS

The mathematical model was successful in accommodating a wide range of breathing patterns and drug-device combinations. Furthermore, the model has demonstrated its effectiveness in predicting the amount of aerosol delivered to "normal" subjects. However, challenges remain in predicting deposition in obstructive lung disease.

Aerosol drug delivery: developments in device design and clinical use

Aerosolised drugs are prescribed for use in a range of inhaler devices and systems. Delivering drugs by inhalation requires a formulation that can be successfully aerosolised and a delivery system that produces a useful aerosol of the drug; the particles or droplets need to be of sufficient size and mass to be carried to the distal lung or deposited on proximal airways to give rise to a therapeutic effect. Patients and caregivers must use and maintain these aerosol drug delivery devices correctly. In recent years, several technical innovations have led to aerosol drug delivery devices with efficient drug delivery and with novel features that take into account factors such as dose tracking, portability, materials of manufacture, breath actuation, the interface with the patient, combination therapies, and systemic delivery. These changes have improved performance in all four categories of devices: metered dose inhalers, spacers and holding chambers, dry powder inhalers, and nebulisers. Additionally, several therapies usually given by injection are now prescribed as aerosols for use in a range of drug delivery devices. In this Review, we discuss recent developments in the design and clinical use of aerosol devices over the past 10-15 years with an emphasis on the treatment of respiratory disorders.

In vitro deposition properties of nebulized formoterol fumarate: effect of nebulization time, airflow, volume of fill and nebulizer type

OBJECTIVE

The aim of this study was to investigate in vitro the delivery of a new long-acting beta2-agonist (LABA) drug formoterol fumarate inhalation solution (20 microg/2 mL) nebulized with and without ipratropium bromide (0.5 mg/2.5 mL) at different administration times (2.5-22.5 min), airflows (5-28.3 L/min), nebulizer fill volumes (2-6 mL),and nebulizer brands (Pari LC+, Ventstream and DeVilbiss).

METHOD

Formoterol fumarate with and without ipratropium bromide was aerosolized at different administration times, airflows, nebulizer fill volumes, and nebulizer brands. The drug deposited on the throat, filter and stage plates was collected and analyzed by HPLC to determine the aerodynamic profiles of the nebulized drugs under each variable.

RESULTS

In addition to altering the aerosol characteristics,increasing the nebulizer fill volume including the addition of ipratropium bromide produced a significant(p50.05) increase in the drug output. As expected, sputtering time was significantly longer at low airflows, and vice versa at higher airflows but with a significant loss of drug delivered presumably due to greater solvent evaporation at higher airflows. Airflows between 10 and 28.3 L/min and a nebulization time of approximately 10 min appear sufficient for producing aerosols within the respirable range (1-5 mm MMAD) with the nebulizer/compressor combination used.While the drug output varied significantly (p50.05) among the three brands of nebulizers tested, the LC+ nebulizer appears to produce aerosols (2.7 0.1 microm MMAD) capable of penetrating more deeply into the lung than the other nebulizers evaluated under the current test conditions. This study did not attempt to evaluate different nebulizer/compressor combinations. Also, the cascade impaction data may not necessarily reflect aerosol deposition in the airways in vivo, which may be different depending on the health status of the patient.

CONCLUSION

The results demonstrated that administration of nebulized formoterol fumarate require proper selection of a delivery system/method for safe and effective therapy of the medication with and without ipratropium bromide.

Calculating expected lung deposition of aerosolized administration of AAV vector in human clinical studies

BACKGROUND

Cystic fibrosis is an autosomal recessive disease affecting approximately 1 in 2500 live births. Introducing the cDNA that codes for normal cystic fibrosis transmembrane conductance regulator (CFTR) to the small airways of the lung could result in restoring the CFTR function. A number of vectors for lung gene therapy have been tried and adeno-associated virus (AAV) vectors offer promise. The vector is delivered to the lung using a breath-actuated jet nebulizer. The purpose of this project was to determine the aerosolized AAV (tgAAVCF) particle size distribution (PSD) in order to calculate target doses for lung delivery.

METHODS

A tgAAVCF solution was nebulized using the Pari LC Plus (n = 3), and the PSD was determined by coupling laser diffraction and inertial impaction (NGI) techniques. The NGI allowed for quantification of the tgAAVCF at each stage of impaction, ensuring that rAAV-CFTR vector is present and not empty particles. Applying the results to mathematical algorithms allowed for the calculation of expected pulmonary deposition.

RESULTS

The mass median diameter (MMD) for the tgAAVCF was 2.78 +/- 0.43 microm. If the system works ideally and the patient only receives aerosol on inspiration, the patient would receive 47 +/- 0% of the initial dose placed in the nebulizer, with 72 +/- 0.73% of this being deposited beyond the vocal cords.

CONCLUSIONS

This technology for categorizing the pulmonary delivery system for lung gene therapy vectors can be adapted for advanced aerosol delivery systems or other vectors.

Nebulized therapies for childhood pulmonary hypertension: an in vitro model

OBJECTIVES

Sildenafil, tezosentan, and prostacyclin reduce pulmonary vascular pressures in pulmonary hypertension, but have potential to vasodilate the systemic circulation. Nebulized vasodilators allow targeted drug delivery, high local drug concentrations, less systemic hypotension, and better matching of the lung's ventilation and perfusion. We aimed to estimate pulmonary deposition of these drugs from commonly employed nebulizers using in vitro techniques and to create a mathematical model to predict inspired mass of aerosol.

DESIGN

Lung deposition was estimated by characterization of drug output and particle size distribution (PSD) of nebulizers using helium-neon laser diffraction techniques. A mathematical model for each device was created to estimate pulmonary deposition using patients' breathing patterns and was verified with a mechanical-breathing model.

RESULTS

Total output and PSD were similar for the Hudson Updraft II and Whisperjet nebulizers, consisting of half the nebulizer's charge, with (1/4) of particles < or = 5 microm, in the respirable fraction (RF). Drug output increased with inspiratory flow for the Pari LC Star. Differences were noted in device performance, depending on the drug tested. Estimated pulmonary deposition (mean, 95% CI) was 8.1 (7.2, 9.0)% of the initial drug charge for the Hudson Updraft II, 6.4 (5.8, 7.0)% for the Whisperjet, and 33.0 (28.3, 37.9)% for the Pari LC Star. A mechanical model was consistent with our mathematical model.

CONCLUSIONS

All drugs could be nebulized, but expected pulmonary deposition varied depending on the nebulizer and drug.

Bronchial constriction and inhaled colistin in cystic fibrosis

STUDY OBJECTIVE

Inhaled colistin is used for the treatment of Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients despite reports of chest tightness and bronchospasm. The main objective of the study was to assess whether bronchospasm occurred in pediatric CF patients with or without clinical evidence of airway hyperreactivity.

DESIGN AND METHODS

A prospective placebo-controlled clinical trial with crossover design was devised using challenge tests with 75 mg colistin in 4 mL saline solution and a placebo solution of the same osmolarity using a breath-enhanced nebulizer for administration. Subjects were recruited as follows: high risk (HR) for bronchospasm due to a personal history of recurrent wheezing, a family history of asthma and/or atopy, or bronchial lability, as demonstrated in pulmonary function tests; or low risk (LR) without these characteristics.

RESULTS

The mean FEV(1) (expressed as the mean [+/- SD] fall from baseline) of the HR group (n = 12) fell 12 +/- 9% after placebo was administered, and fell 17 +/- 10% after colistin was administered. For the LR group (n = 8), the mean FEV(1) fell 9 +/- 4% following placebo administration and 13 +/- 8% following colistin administration. There was a greater number of subjects in the HR group compared to the LR group, which had a mean fall in FEV(1) of >/= 15% (p < 0.01) after inhaling colistin. The differences between placebo and colistin therapy in the LR group were not significant.

CONCLUSION

The results demonstrated that colistin can cause bronchospasm, particularly in those patients with coexisting CF and asthma.

Effect of driving pressure and nebulizer model on aerosol output during intermittent delivery with a dosimeter

Recent guidelines reinforce the need for a standardized technique during inhalational bronchoprovocation challenge testing. We investigated the effects of nebulizer model and dosimeter driving pressure on nebulizer output using a nebulized saline model. Four nebulizers (Hudson 1720, Salter 8900, Baxter Airlife, and DeVilbiss 644) were evaluated at two driving pressures (20 and 50 pounds per square inch [psi]) via a dosimeter (Salter 700) that delivered a 0.6-sec actuation. Output was determined gravimetrically after 20 actuations of saline at constant respiratory flow and volume. Output per actuation at 20 psi was 2.83 +/- 0.41 mg (mean +/- SD), 4.58 +/- 0.66, 4.75 +/- 0.42, and 4.75 +/- 1.37 for the Hudson, Salter, Baxter, and DeVilbiss, respectively, and 6.75 +/- 0.61 mg, 9.17 +/- 0.88, 9.42 +/- 1.32, and 9.83 +/- 1.75 at 50 psi. The Hudson delivered a lower volume than the other nebulizers (p < 0.0005). At 20 psi, output from the DeVilbiss had greater variability (coefficient of variation = 28.8%) compared to the Baxter (CV = 8.8%; p = 0.045). The output was greater at 50 psi than 20 psi for all models (p < 0.0005). These results demonstrate that, when choosing a nebulizer driven by a dosimeter, it is important to base that selection on published data describing aerosol output under different driving pressures.

Accounting for radioactivity before and after nebulization of tobramycin to insure accuracy of quantification of lung deposition

The ability to predict drug deposition of inhaled drugs used in cystic fibrosis (CF) is important if there is a need to target specific doses of drug to the lungs of individual patients. The gold standard of measuring pulmonary deposition is the quantification of an aerosolized radiolabel either mixed with the drug solution or tagged directly to the compound of interest. Accuracy of the quantification could be assured if there is agreement between the amount of radioactivity before and after administration. Before administration, the radiolabel is concentrated in the well of the nebulizer, whereas after administration, it is distributed throughout the nebulizer, the expiratory filter and connectors, and the upper airway, stomach, trachea, and lung. Not only is the geometry of the distribution that is presented to the gamma camera different, but there are different attenuation factors for the various body tissues. The primary aim of this study was to evaluate the accuracy of the quantification of deposition. Secondary goals were to compare in vitro nebulizer performance with that measured in vivo during the deposition study. Eighty milligrams of tobramycin and technetium bound to human serum albumin was administered to 10 normal adults using a Pari LC Jet Plus (Pari Respiratory Equipment, Inc., Richmond, VA) breath-enhanced nebulizer. Techniques were developed that allowed for the accounting of 99 +/- 2% of the initial radioactivity. The fraction of the rate of lung deposition to total body deposition was the in vivo respirable fraction (0.62 +/- 0.07), which closely agreed with in vitro measurements of respirable fraction (0.62 +/- 0.04). Drug output measured from the change in weight and concentration in the nebulizer systematically overestimated drug output measured by the deposition study. The results indicate that 11.8 of the initial 80 mg would be deposited in the lungs. This technique could be adapted to accurately quantify the amount of deposition on any inhaled therapeutic agent, but caution must be used when extrapolating performance of a nebulizer on the bench to expected deposition in patients.

Effect of size and disease on estimated deposition of drugs administered using jet nebulization in children with cystic fibrosis

STUDY OBJECTIVES

To develop a model that quantified the nebulizer output that was inhaled by subjects with cystic fibrosis (CF) in order to predict the amount of drug likely to enter the upper airway contained in particles small enough to be deposited in the lower respiratory tract of individual patients.

DESIGN

Forty-three patients (age, 6 to 18 years) with CF, with FEV(1) of 26 to 124% of predicted, breathed through a nebulizer circuit with a pneumotachograph in place at the distal end. Algorithms were developed from the measured flows through the pneumotachograph, allowing partitioning of inspiration into undiluted aerosol and fresh gas. In order to validate the algorithms, argon was added to the nebulizing gas flow and then its concentration was analyzed at the mouth by mass spectrometry.

RESULTS

Predictions of the concentration of argon at the mouth were concordant with that measured by mass spectrometry, thus validating the model. Combining data from the model with in vitro nebulizer performance data, predictions for estimates for lung deposition for individuals were possible. Total estimate was independent of patient size or FEV(1). The respiratory duty cycle was 0.44 +/- 0.05 (mean +/- SD) and correlated (r = 0.91, p < 0.001) with estimated deposition and minute ventilation (r = 0.60, p < 0.01). However, when expressed in milligrams per kilogram of body weight, the estimated deposition in smaller children was fourfold higher than in larger children.

CONCLUSIONS

If the effect of patient size and pattern of breathing on estimated drug deposition are not considered when prescribing drugs given by nebulization, the result may be overdosing younger children, underdosing older children, or both.

Inhaled tobramycin and bronchial hyperactivity in cystic fibrosis

The use of inhaled tobramycin for prophylaxis and treatment of respiratory symptoms in cystic fibrosis (CF) is now widespread. There have been concerns that inhaling the intravenous (I.V.) formulation of tobramycin causes bronchoconstriction. Previous studies using this formulation have either not specified the nebulizing equipment, or studied older, more severely affected patients. This study investigated the incidence of bronchoconstriction with tobramycin inhalation in children with mild to moderate CF. We studied 26 patients between the ages of 7 and 17 years, with mild to moderate CF (20 female). Prior to being placed on prolonged inhaled tobramycin therapy, they underwent a "tobramycin challenge." FEV(1) was measured pre and post challenge. For the test, standard I.V. solution (80 mg/2 mL) diluted with 2 mL of normal saline was nebulized, using the Hudson (Temecula, CA) RCI Updraft II nebulizer. The nebulization lasted 2 min. There was a 3-min "quiet period," following which FEV(1) was measured. A decrease in FEV(1) by at least 10% post-tobramycin inhalation was considered to be a positive test. Results were analyzed using the Pearson Chi-square test. Five of 26 (19%) had a positive reaction to tobramycin. Sixteen of 26 (61.5%) were using salbutamol on a daily basis at the time of testing but not for 48 hr before the challenge, and 16 of 26 (61.5%) had a pre-tobramycin FEV(1) of < or =80%. Neither an FEV(1) of <80% (P = 0.93) nor regular use of salbutamol (P = 0. 34) were associated with a positive tobramycin challenge. This study suggests that, while bronchoconstriction does occur, many patients do not exhibit bronchoconstriction in response to the standard I.V. preparation and, as prior work suggests, this may be reduced further by pretreatment with salbutamol.

Do sinusoidal models of respiration accurately reflect the respiratory events of patients breathing on nebulizers?

The amount of drug that is delivered by nebulization is a combination of the physical properties of the agent being nebulized, the performance of the nebulizer, and the pattern of breathing of the patient. To avoid biological variation, mechanical models of breathing are frequently employed during the evaluation of the performance of a device. For simplicity, many investigators use sinusoidal models of breathing to calculate the expected inhaled mass, although some use square waves and other more complex models. Most assume that the duration of inspiration (Ti) is half of the total respiratory time (Ttot). This study compared the calculated inhaled mass from which the expected pulmonary deposition was estimated from the actual pattern of breathing of 43 children with cystic fibrosis (CF) breathing from an unvented nebulizer with a low dead volume and appropriate particle size distribution with that from a sinusoidal pattern of breathing using the same tidal volume (VT) and respiratory rate. The respiratory duty cycle (Ti/Ttot) was 0.45 +/- 0.05, which meant that less time was spent during inspiration than that found in a pure sinusoidal pattern. The difference between the predicted deposition from the actual pattern of breathing and that calculated from the sinusoidal model was 12 +/- 7%, which correlated with the respiratory rate (r = 0.67, P < 0.001). The degree of lung disease did not influence the discrepancy between the two values. In general, the actual VTs and respiratory rates were less in the patients than those employed in mechanical models of pediatric breathing. Although some patients had respiratory patterns that could be represented accurately with a sinusoidal model, most did not, and there were wide variations from child to child. These results suggest that there are both systematic and random errors arising from the use of a sinusoidal waveform to mimic respiratory events in patients.

Aerosol therapy for asthma

Inhaled drugs play an important role in asthma management. The correct use of an appropriate delivery device is necessary to achieve the desired therapeutic effects of the drug. Currently, chlorofluorocarbon-propelled metered-dose inhalers, with or without spacers, are the most popular aerosol delivery devices. With the planned phase out of the chlorofluorocarbon metered-dose inhalers, the use of other delivery devices is being emphasized. To achieve optimal therapeutic effects, the drug and the delivery device should be considered a "couple". Aerosol delivery devices should provide an adequate "drug dose to the lung", be cost effective, simple to operate, minimize oropharyngeal deposition and systemic side effects, and match the patient's requirements. A new generation of aerosol delivery devices, incorporating the latest advances in aerosol technology, is likely to fulfill many of the goals mentioned above.

A comparison of the availability of tobramycin for inhalation from vented vs unvented nebulizers

STUDY OBJECTIVE

To compare drug output from a vented nebulizer (Pari LC Jet Plus) with a traditional unvented nebulizer (Hudson 1730 T Up-Draft 11) using aerosolized tobramycin, which is frequently used in the treatment of cystic fibrosis.

DESIGN

Six nebulizers of each type were filled with a 4 mL tobramycin (80 mg) solution and were driven by a compressor (Pulmo-Aide). Various inspiratory flows (VI) (0, 5, 10, 15, 20 L/min for the Pari LC Jet Plus and 0, 5, and 10 L/min for the Hudson 1730, all at 40% relative humidity) were directed through each nebulizer. Drug output was measured from changes in weight and concentration (assessed by changes in osmometry) within the nebulizer. Particle size distributions were determined by laser diffraction allowing the calculation of the amount of aerosol output in the respirable range (<5 microm). The nebulizers were first run until end-nebulization to establish total drug output and then for either 4 or 5 min to determine the rate of drug output (mg/min) before intermittent aerosol output.

RESULTS

The total drug output without VI for both the unvented and the vented nebulizers was not significantly different, 55 (51, 60) mg for the Hudson 1730 vs 51 (49, 53) mg for the Pari LC Jet Plus (mean [95% confidence limits]). Inspiratory flow had no effect on the unvented Hudson 1730 nebulizer but significantly increased the rate of total drug output and the rate of drug output in the respirable range for the vented Pari LC Jet Plus nebulizer (VI=0, 3.35 [2.84, 3.85] and 1.72 [1.48, 1.96] compared with VI=20, 9.87 [9.03, 10.70] and 6.11 [5.33, 6.88] mg/min).

CONCLUSIONS

These findings indicate that the increase in the rate of drug output with VI for the vented nebulizer would result in shorter nebulization times and a relative decrease in drug loss during the expiratory phase.

The choice of jet nebulizer, nebulizing flow, and addition of albuterol affects the output of tobramycin aerosols

The use of inhaled antibiotics in the treatment of cystic fibrosis has become widespread despite controversy in the literature as to the appropriate dosing regimen and its effectiveness. This study compared two tobramycin (T) preparations (one with and one without the addition of albuterol) using two different jet nebulizers in order to determine if drug output would be affected. Using calibrated flows from a dry compressed gas source of 6 and 8 L/min as well as a specific compressor (Pulmo-Aide), the Hudson 1720 nebulizer was compared with the newer disposable Hudson 1730. The albuterol preparation used in this study was the Ventolin (albuterol) Respirator Solution (VRS). The nebulizers were charged with (1) 2 mL T (80 mg/2 mL) with 0.5 mL VRS (5 mg/mL) and normal saline solution to make the total nebulizer charge of 3 or 4 mL, or (2) 2 mL T and either 1 or 2 mL normal saline solution. A laser diffraction analyzer (Malvern 2600) was used to determine the aerosol particle size distribution. From the distribution, the respirable fraction, which is the fraction of aerosol that could enter and remain in the lungs, was calculated. For all solutions and each particular flow, the Hudson 1730 had a larger respirable fraction of T. The addition of VRS lowered the surface tension of the solution in the nebulizer and resulted in a greater output of T. This effect was most apparent for the 3-mL volume fills of the Hudson 1720. The greatest differences were between the 3-mL nebulizer charges of T using the Hudson 1720 driven by a flow of 6 L/min, which produced 8 mg of T in the respirable fraction, compared with 35 mg produced by the Hudson 1730 driven by a flow of 8 L/min. These results suggest that different nebulizers, different nebulizer solutions, and different techniques of nebulization may result in very different amounts of T aerosol output in the respirable fraction.