Evaluation of a reservoir device for metered-dose bronchodilator delivery to intubated adults. An in vitro study

Aerosol therapy in adult critically ill patients: a consensus statement regarding aerosol administration strategies during various modes of respiratory support

BACKGROUND

Clinical practice of aerosol delivery in conjunction with respiratory support devices for critically ill adult patients remains a topic of controversy due to the complexity of the clinical scenarios and limited clinical evidence.

OBJECTIVES

To reach a consensus for guiding the clinical practice of aerosol delivery in patients receiving respiratory support (invasive and noninvasive) and identifying areas for future research.

METHODS

A modified Delphi method was adopted to achieve a consensus on technical aspects of aerosol delivery for adult critically ill patients receiving various forms of respiratory support, including mechanical ventilation, noninvasive ventilation, and high-flow nasal cannula. A thorough search and review of the literature were conducted, and 17 international participants with considerable research involvement and publications on aerosol therapy, comprised a multi-professional panel that evaluated the evidence, reviewed, revised, and voted on recommendations to establish this consensus.

RESULTS

We present a comprehensive document with 20 statements, reviewing the evidence, efficacy, and safety of delivering inhaled agents to adults needing respiratory support, and providing guidance for healthcare workers. Most recommendations were based on in-vitro or experimental studies (low-level evidence), emphasizing the need for randomized clinical trials. The panel reached a consensus after 3 rounds anonymous questionnaires and 2 online meetings.

CONCLUSIONS

We offer a multinational expert consensus that provides guidance on the optimal aerosol delivery techniques for patients receiving respiratory support in various real-world clinical scenarios.

An in vitro visual study of fugitive aerosols released during aerosol therapy to an invasively ventilated simulated patient

COVID-19 can cause serious respiratory complications resulting in the need for invasive ventilatory support and concurrent aerosol therapy. Aerosol therapy is considered a high risk procedure for the transmission of patient derived infectious aerosol droplets. Critical-care workers are considered to be at a high risk of inhaling such infectious droplets. The objective of this work was to use noninvasive optical methods to visualize the potential release of aerosol droplets during aerosol therapy in a model of an invasively ventilated adult patient. The noninvasive Schlieren imaging technique was used to visualize the movement of air and aerosol. Three different aerosol delivery devices: (i) a pressurized metered dose inhaler (pMDI), (ii) a compressed air driven jet nebulizer (JN), and (iii) a vibrating mesh nebulizer (VMN), were used to deliver an aerosolized therapeutic at two different positions: (i) on the inspiratory limb at the wye and (ii) on the patient side of the wye, between the wye and endotracheal tube, to a simulated intubated adult patient. Irrespective of position, there was a significant release of air and aerosol from the ventilator circuit during aerosol delivery with the pMDI and the compressed air driven JN. There was no such release when aerosol therapy was delivered with a closed-circuit VMN. Selection of aerosol delivery device is a major determining factor in the release of infectious patient derived bioaerosol from an invasively mechanically ventilated patient receiving aerosol therapy.

The Use of Aerosolized Medications in Adult Intensive Care Unit Patients: A Prospective, Multicenter, Observational, Cohort Study

Background: Only limited data are available on the real-life clinical utilization of aerosolized medications in intensive care unit (ICU) patients. Exploring the utilization of aerosolized medications in the ICU may contribute to develop appropriate education and improve the quality of aerosol therapy. Methods: A 2-week, prospective, multicenter, observational, cohort study was conducted to record how the aerosolized medications were utilized in the Chinese ICUs, including indications, medications used in solo or combination, dosage, and side-effects in adult patients. Results: A total of 1006 patients from 28 ICUs were enrolled, of which 389 (38.7%) received aerosol therapy. The most common indications for aerosol therapy were difficulty in secretion management (23.1%) and chronic obstructive pulmonary disease exacerbation (18.5%). The combination of inhaled corticosteroids and short-acting muscarinic antagonist was the most commonly used medication (19.5%, 76/389). Ninety-two percent (358/389) of the patients did not have any side effects during aerosol therapy. More patients in the group with mechanical ventilation received bronchodilators than spontaneous breathing patients (81.3% vs. 55.5%, p < 0.001), and more patients who breathed spontaneously through a tracheostomy received mucus-regulating agents than other patients (70% vs. 37.9%, p = 0.004). Conclusion: In mainland China, more than one-third of adult ICU patients received aerosol therapy. Medications utilized during aerosol therapy were variable in patients with different respiratory support. To promote appropriate use of aerosolized medications, high-quality randomized, controlled trials and clinical guidance on aerosolized medication indications and dosing are needed to improve clinical outcomes.

Aerosol delivery via invasive ventilation: a narrative review

In comparison with spontaneously breathing non-intubated subjects, intubated, mechanically ventilated patients encounter various challenges, barriers, and opportunities in receiving medical aerosols. Since the introduction of mechanical ventilation as a part of modern critical care medicine during the middle of the last century, aerosolized drug delivery by jet nebulizers has become a common practice. However, early evidence suggested that aerosol generators differed in their efficacies, and the introduction of newer aerosol technology (metered dose inhalers, ultrasonic nebulizer, vibrating mesh nebulizers, and soft moist inhaler) into the ventilator circuit opened up the possibility of optimizing inhaled aerosol delivery during mechanical ventilation that could meet or exceed the delivery of the same aerosols in spontaneously breathing patients. This narrative review will catalogue the primary variables associated with this process and provide evidence to guide optimal aerosol delivery and dosing during mechanical ventilation. While gaps exist in relation to the appropriate aerosol drug dose, discrepancies in practice, and cost-effectiveness of the administered aerosol drugs, we also present areas for future research and practice. Clinical practice should expand to incorporate these techniques to improve the consistency of drug delivery and provide safer and more effective care for patients.

Assessment of different techniques for the administration of inhaled salbutamol in children breathing spontaneously via tracheal tubes, supraglottic airway devices, and tracheostomies

BACKGROUND

Perioperative respiratory adverse events account for a third of all perioperative cardiac arrests, with bronchospasm and laryngospasm being most common. Standard treatment for bronchospasm is administration of inhaled salbutamol, via pressurized metered dose inhaler. There is little evidence on the best method of attaching the pressurized metered dose inhaler to the artificial airway during general anesthesia.

AIM

The aim of this study is to investigate the best method to deliver aerosolized salbutamol via pressurized metered dose inhaler to the lungs of an anesthetized child.

METHODS

We measured salbutamol delivered by pressurized metered dose inhaler through different sized tracheal tubes, supraglottic airway devices, and tracheostomies in vitro for methods commonly employed for connecting the pressurized metered dose inhaler to the artificial airway. Breathing was simulated for patients weighing 3, 16, 50, and 75 kg. Pressurized metered dose inhaler actuation coincided with inspiration.

RESULTS

A pressurized metered dose inhaler combined with an in-line non-valved or valved spacer, or the direct method, when delivered via tracheal tube, was linked with improved delivered dose of salbutamol, compared to all other methods for 3 or 50 kg simulated patients weights. The delivered dose when using a non-valved spacer was greater than all methods for 16 and 75 kg patient weights. A spacer improved delivery for the flexible supraglottic airway device type, and there was no difference with or without a spacer for remaining types.

CONCLUSION

Via tracheal tube and non-valved spacer, the following doses should be delivered after single actuation of a 100 µg labeled-claim salbutamol dose: ~2 µg kg^-1 per actuation to a 3 kg neonate, ~1 µg kg^-1 per actuation to a 16 kg child, and ~ 0.5 µg kg^-1 per actuation for a 50-75 kg child. The least effective methods were the syringe, and the uni- and bidirectional adaptor methods, which require replacement by the direct method if a spacer is unavailable.

The utilization of aerosol therapy in mechanical ventilation patients: a prospective multicenter observational cohort study and a review of the current evidence

Background

Aerosol delivery via mechanical ventilation has been reported to vary significantly among different intensive care units (ICU). The optimal technique for using each aerosol generator may need to be updated with the available evidence.

Methods

A 2-week prospective multicenter observational cohort study was implemented to record aerosol delivery for mechanically ventilated adult patients in Chinese ICUs. Our data included the type of aerosol device and its placement, ventilator type, humidification, and aerosolized medication administered. A guide for the optimal technique for aerosol delivery during mechanical ventilation was summarized after a thorough literature review.

Results

A total of 160 patients (105 males) from 28 ICUs were enrolled, of whom 125 (78.1%) received aerosol therapy via invasive ventilation. Among these 125 patients, 53 received ventilator-integrated jet nebulizer, with 64% (34/53) of them placed the nebulizer close to Y piece in the inspiratory limb. Further, 56 patients used continuous nebulizers, with 84% (47/56) of them placed the nebulizer close to the Y piece in the inspiratory limb. Of the 35 patients who received aerosol therapy via noninvasive ventilation, 30 received single limb ventilators and continuous nebulizers, with 70% (21/30) of them placed between the mask and exhalation port. Only 36% (58/160) of the patients received aerosol treatments consistent with optimal practice.

Conclusions

Aerosol delivery via mechanical ventilation varied between ICUs, and only 36% of the patients received aerosol treatments consistent with optimal practice. ICU clinicians should be educated on the best practices for aerosol therapy, and quality improvement projects aim to improve the quality and outcome of patients with the optimal technique for aerosol delivery during mechanical ventilation are warranted.

RNAi therapeutic strategies for acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS), replacing the clinical term acute lung injury, involves serious pathophysiological lung changes that arise from a variety of pulmonary and nonpulmonary injuries and currently has no pharmacological therapeutics. RNA interference (RNAi) has the potential to generate therapeutic effects that would increase patient survival rates from this condition. It is the purpose of this review to discuss potential targets in treating ARDS with RNAi strategies, as well as to outline the challenges of oligonucleotide delivery to the lung and tactics to circumvent these delivery barriers.

Inhalation therapy in patients receiving mechanical ventilation: an update

Incremental gains in understanding the influence of various factors on aerosol delivery in concert with technological advancements over the past 2 decades have fueled an ever burgeoning literature on aerosol therapy during mechanical ventilation. In-line use of pressurized metered-dose inhalers (pMDIs) and nebulizers is influenced by a host of factors, some of which are unique to ventilator-supported patients. This article reviews the impact of various factors on aerosol delivery with pMDIs and nebulizers, and elucidates the correlation between in-vitro estimates and in-vivo measurement of aerosol deposition in the lung. Aerosolized bronchodilator therapy with pMDIs and nebulizers is commonly employed in intensive care units (ICUs), and bronchodilators are among the most frequently used therapies in mechanically ventilated patients. The use of inhaled bronchodilators is not restricted to mechanically ventilated patients with chronic obstructive pulmonary disease (COPD) and asthma, as they are routinely employed in other ventilator-dependent patients without confirmed airflow obstruction. The efficacy and safety of bronchodilator therapy has generated a great deal of interest in employing other inhaled therapies, such as surfactant, antibiotics, prostacyclins, diuretics, anticoagulants and mucoactive agents, among others, in attempts to improve outcomes in critically ill ICU patients receiving mechanical ventilation.

Aerosol therapy in patients receiving noninvasive positive pressure ventilation

In selected patients, noninvasive positive pressure ventilation (NIPPV) with a facemask is now commonly employed as the first choice for providing mechanical ventilation in the intensive care unit (ICU). Aerosol therapy for treatment of acute or acute-on-chronic respiratory failure in this setting may be delivered by pressurized metered-dose inhaler (pMDI) with a chamber spacer and facemask or nebulizer and facemask. This article reviews the host of factors influencing aerosol delivery with these devices during NIPPV. These factors include (1) the type of ventilator, (2) mode of ventilation, (3) circuit conditions, (4) type of interface, (5) type of aerosol generator, (6) drug-related factors, (7) breathing parameters, and (8) patient-related factors. Despite the impediments to efficient aerosol delivery because of continuous gas flow, high inspiratory flow rates, air leaks, circuit humidity, and patient-ventilator asynchrony, significant therapeutic effects are achieved after inhaled bronchodilator administration to patients with asthma and chronic obstructive pulmonary disease. Similarly to invasive mechanical ventilation, careful attention to the technique of drug administration is required to optimize therapeutic effects of inhaled therapies during NIPPV. Assessment of the patient's ability to tolerate a facemask, the level of respiratory distress, hemodynamic status, and synchronization of aerosol generation with inspiratory airflow are important factors contributing to the success of aerosol delivery during NIPPV. Further research into novel delivery methods, such as the use of NIPPV with nasal cannulae, could enhance the efficiency, ease of use, and reproducibility of inhalation therapy during noninvasive ventilation.

Aerosol delivery to ventilated newborn infants: historical challenges and new directions

There are several aerosolized drugs which have been used in the treatment of neonatal respiratory illnesses, such as bronchodilators, diuretics, and surfactants. Preclinical in vitro and in vivo studies identified a number of variables that affect aerosol efficiency, including particle size, aerosol flows, nebulizer choice, and placement. Nevertheless, an optimized aerosol drug delivery system for mechanically ventilated infants still does not exist. Increasing interest in this form of drug delivery requires more controlled and focused research of drug/device combinations appropriate for the neonatal population. In the present article, we review the research that has been conducted thus far and discuss the next steps in developing the optimal aerosol delivery system for use in mechanically ventilated neonates.

How best to deliver aerosol medications to mechanically ventilated patients

Pressurized metered-dose inhalers (pMDIs) and nebulizers are employed routinely for aerosol delivery to ventilator-supported patients, but the ventilator circuit and artificial airway previously were thought to be major barriers to effective delivery of aerosols to patients receiving mechanical ventilation. In the past two decades, several investigators have shown that careful attention to many factors, such as the position of the patient, the type of aerosol generator and its configuration in the ventilator circuit, aerosol particle size, artificial airway, conditions in the ventilator circuit, and ventilatory parameters, is necessary to optimize aerosol delivery during mechanical ventilation. The best techniques for aerosol delivery during noninvasive positive-pressure ventilation are not well established as yet, and the efficiency of aerosol delivery in this setting is lower than that during invasive mechanical ventilation. The most efficient methods of using the newer hydrofluoroalkane-pMDIs and vibrating mesh nebulizers in ventilator-supported patients also require further evaluation. When optimal techniques of administration are employed, the efficiency of aerosolized drug delivery in mechanically ventilated patients is comparable to that achieved in ambulatory patients.

Aerosol delivery during mechanical ventilation: from basic techniques to new devices

Pressurized metered-dose inhalers (pMDIs) and nebulizers are routinely employed for aerosol delivery in mechanically ventilated patients. A significant proportion of the aerosol deposits in the ventilator circuit and artificial airway, thereby reducing the inhaled drug mass. Factors influencing aerosol delivery during mechanical ventilation differ from those in spontaneously breathing patients. The English language literature on aerosol delivery during mechanical ventilation was reviewed. Marked variations in the efficiency of drug delivery with pMDIs and nebulizers occur due to differences in the technique of administration. Careful attention to five factors, viz., the aerosol generator, aerosol particle size, conditions in the ventilator circuit, artificial airway, and ventilator parameters, is necessary to optimize aerosol delivery during mechanical ventilation. Factors influencing drug delivery during NPPV are not well understood, and the efficiency of aerosol delivery in this setting is lower than that during invasive mechanical ventilaiton. With an optimal technique of administration the efficiency of aerosol delivery during mechanical ventilation is similar to that achieved during spontaneous breathing. Further research is needed to optimize aerosol delivery during NPPV.

Inhaled bronchodilator administration during mechanical ventilation: how to optimize it, and for which clinical benefit?

Bronchodilators are frequently used in ICU patients, and are the most common medications administered by inhalation during mechanical ventilation. The amount of bronchodilator that deposits at its site of action depends on the amount of drug, inhaled mass, deposited mass, and particle size distribution. Mechanical ventilation challenges both inhaled mass and lung deposition by specific features, such as a ventilatory circuit, an endotracheal tube, and ventilator settings. Comprehensive in vitro studies have shown that an endotracheal tube is not as significant a barrier for the drug to travel as anticipated. Key variables of drug deposition are attachments of the inhalation device in the inspiratory line 10 to 30 cm to the endotracheal tube, use of chamber with metered-dose inhaler, dry air, high tidal volume, low respiratory frequency, and low inspiratory flow, which can increase the drug deposition. In vivo studies showed that a reduction by roughly 15% of the respiratory resistance was achieved with inhaled bronchodilators during invasive mechanical ventilation. The role of ventilatory settings is not as clear in vivo, and primary factors for optimal delivery and physiologic effects were medication dose and device location. Nebulizers and pressurized metered-dose inhalers can equally achieve physiologic end points. The effects of bronchodilators should be carefully evaluated, which can easily be done with the interrupter technique. With the non-invasive ventilation, the data regarding drug delivery and physiologic effects are still limited. With the bilevel ventilators the inhalation device should be located between the leak port and face mask. Further studies should investigate the effects of inhaled bronchodilators on patient outcome and methods to optimize delivery of inhaled bronchodilators during non-invasive ventilation.

Mechanical ventilation: a tutorial for pharmacists

Mechanical ventilation is an integral part of the critical care environment and requires orchestration by a multidisciplinary team of clinicians to optimize therapeutic outcomes. By tradition, pharmacists have not been included on this team since this therapeutic modality is not considered relevant to their scope of practice. However, pharmacists play a critical role in the management of patients receiving mechanical ventilation by assisting in the development of institutional guidelines and protocols, by maintaining accuracy of prescribed drug dosages, by monitoring for drug-drug and drug-disease interactions, by assisting with alternative drug selections, and by maintaining continued quality assessment of drug administration. Pharmacists able to understand and integrate mechanical ventilation with the pharmacotherapeutic needs of patients are better qualified practitioners. The goal of this article is to help clinical pharmacists better understand the complexities of mechanical ventilation and to apply this information in optimizing delivery of pharmaceutical agents to critical care patients.

Bronchodilator delivery with metered-dose inhaler during mechanical ventilation

The delivery of bronchodilators with metered-dose inhaler (MDI) in mechanically ventilated patients has attracted considerable interest in recent years. This is because the use of the MDI has several advantages over the nebulizer, such as reduced cost, ease of administration, less personnel time, reliability of dosing and a lower risk of contamination. A spacer device is fundamental in order to demonstrate the efficacy of the bronchodilatory therapy delivered by MDI. Provided that the technique of administration is appropriate, MDIs are as effective as nebulizers, despite a significantly lower dose of bronchodilator given by the MDI.

A comparison of bronchodilator therapy delivered by nebulization and metered-dose inhaler in mechanically ventilated patients

BACKGROUND

The optimal method of delivering bronchodilators in mechanically ventilated patients is unclear. The purpose of this study was to compare the pulmonary bioavailability of albuterol delivered by the nebulizer, the metered-dose inhaler (MDI) and spacer, and the right-angle MDI adaptor in ventilated patients using urinary analysis of drug levels.

METHODS

Mechanically ventilated patients who had not received a bronchodilator in the previous 48 h and who had normal renal function were randomized to receive the following: (1) five puffs (450 microg) of albuterol delivered by the MDI with a small volume spacer; (2) five puffs of albuterol delivered by the MDI port on a right-angle adaptor; or (3) 2.5 mg albuterol delivered by a nebulizer. Urine was collected 6 h after the administration of the drug, and the amounts of albuterol and its sulfate conjugate were determined in the urine by a chromatographic assay.

RESULTS

Thirty patients were studied, 10 in each group: their mean age and serum creatinine level were 62 years and 1.3 mg/dL, respectively. With the MDI and spacer, (mean +/- SD) 169+/-129 microg albuterol (38%) was recovered in the urine; with the nebulizer, 409+/-515 microg albuterol (16%) was recovered in the urine; and with the MDI port on the right-angle adaptor, 41+/-61 microg albuterol (9%) was recovered in the urine (p = 0.02 between groups). The level of albuterol in the urine was below the level of detection in four patients in whom the drug was delivered using the right-angle MDI adaptor.

CONCLUSION

The three delivery systems varied markedly in their efficiency of drug delivery to the lung. As previous studies have confirmed, this study has demonstrated that using an MDI and spacer is an efficient method for delivering inhaled bronchodilators to the lung. The pulmonary bioavailability was poor with the right-angle MDI port. This port should not be used to deliver bronchodilators in mechanically ventilated patients.

Comparing the delivery of albuterol metered-dose inhaler via an adapter and spacer device in an in vitro infant ventilator lung model

OBJECTIVE

To compare the delivery of an albuterol metered-dose inhaler (MDI) (Ventolin) via an Aerochamber (Monaghan) with an inline adapter (Medicomp Straight Swivel) in an in vitro infant lung model.

METHODS

An in vitro infant lung model was modified to compare the delivery of albuterol MDI 10 inhalations via an Aerochamber with an inline adapter. The adapter and Aerochamber were placed at the endotracheal tube. A 1000 mL intravenous bag filled with 500 mL deionized water was attached to a 3.5 mm endotracheal tube (10 cm length). An Infant Bear Cub ventilator was used at the following settings: positive inspiratory pressure 20 cm H2O, intermittent mandatory ventilation 40 breaths/min, positive end expiratory pressure 4 cm H2O, and inspiratory time 0.5 second. Each device was run at least 10 times and assayed in duplicate by HPLC. An unpaired Student's t-test was used to analyze the statistical significance of the data.

RESULTS

There was significantly greater delivery of albuterol with the Aerochamber (19.49 +/- 7.23 microg; 2.17% +/- 0.8%) as compared with an inline adapter (1.0625 +/- 1.36 microg; 0.12% +/- 0.15%) (p = 0.001).

CONCLUSIONS

The Aerochamber provides a greater delivery of albuterol metered-dose inhalations to the lung than the inline adapter in an in vitro infant lung model.

Evaluating the delivery of nebulized and metered-dose inhalers in an in vitro infant ventilator lung model

OBJECTIVE

To evaluate drug delivery to the lungs of nebulized and metered-dose inhalers (MDIs) in an in vitro infant lung model.

METHODS

An in vitro lung model was modified to study drug delivery. A 1000 mL intravenous bag filled with 500 mL deionized water was attached to a 3.5 mm (12 cm length) endotracheal tube. An inline Marquest Whisper Jet infant circuit nebulizer system delivered 2.5 mg/3 mL albuterol sulfate inhalation solution (Ventolin nebules) at a flow rate of 5 L/min. An Aerochamber (Monaghan) was placed at the endotracheal tube for the delivery of the MDIs. Albuterol MDI (Ventolin) 10 inhalations and beclomethasone MDI (Beclovent) 20 inhalations were delivered. A Servo 900C (Siemens-Elma) was used at the following ventilator settings: positive inspiratory pressure 30 cm H2O), intermittent mandatory ventilation 40 breaths/min, positive end expiratory pressure 4 cm H2O, inspiratory time 0.4 sec. Each formulation was run at least 10 times and assayed in duplicate by HPLC. An unpaired Student's t-test was used to analyze the statistical significance of the data.

RESULTS

There was a significantly greater percentage of drug delivery with MDI albuterol (1.96 +/- 0.50) as compared with nebulized albuterol (1.26 +/- 0.37) (p = 0.002) or beclomethasone diproprionate (0.51 +/- 0.24) (p = 0.001).

CONCLUSIONS

Albuterol MDI provides a more efficient delivery of drug to the lung as compared with nebulized albuterol and MDI beclomethasone diproprionate.

Reservoir design and dose availability with long-term metered dose inhaler corticosteroid use

The effect of reservoir design and long-term use with inhaled metered dose inhaler (MDI) corticosteroids on aerosol dose availability was examined. Beclomethasone dipropionate (Vanceril) was delivered by MDI with three brands of available reservoir devices: the AeroChamber, the OptiHaler, and the Aerosol Cloud Enhancer (ACE). An in vitro lung model simulated inspiration. Long-term use was simulated by exhausting five MDI canisters of beclomethasone through each sample of reservoir tested. Each canister exhausted through a reservoir represented approximately 1 month of use with one drug. Total inhaled dose was collected at the reservoir mouthpiece and measured using a spectrophotometric assay. Dose delivery was measured before simulated use and after each MDI canister was exhausted through the reservoir. Three samples of each brand were tested with cleaning and three samples were tested without cleaning. With cleaning, the AeroChamber, OptiHaler, and ACE delivered significantly different average doses of 16.6, 10.3, and 8.7 micrograms per MDI actuation, respectively, (P = 0.0017) over time of use. Changes in dose delivery over time of use were not significant (P = 0.2011). Without cleaning, the same three brands averaged 21.1, 9.7, and 7.8 micrograms per MDI actuation, respectively, (P = 0.0019), and changes in dose delivery over time were not significant (P = 0.3265). Reservoir design can affect the delivery of an inhaled corticosteroid, although the delivery over 4 to 5 months remained stable.

Reconciling in vitro and in vivo measurements of aerosol delivery from a metered-dose inhaler during mechanical ventilation and defining efficiency-enhancing factors

We attempted to resolve the discrepancies in reported data on aerosol deposition from a chlorofluorocarbon (CFC)-propelled metered-dose inhaler (MDI) during mechanical ventilation, obtained by in vivo and in vitro methodologies. Albuterol delivery to the lower respiratory tract was decreased in a humidified versus a dry circuit (16.2 versus 30.4%, respectively; p < 0.01). In 10 mechanically ventilated patients, 4.8% of the nominal dose was exhaled. When the exhaled aerosol was subtracted from the in vitro delivery of 16.2% achieved in a humidified ventilator circuit, the resulting value (16.2 - 4.8 = 11.4%) was similar to in vivo estimates of aerosol deposition. Having reconciled in vitro with in vivo findings, we then evaluated factors influencing aerosol delivery. A lower inspiratory flow rate (40 versus 80 L/min; p < 0.001), a longer duty cycle (0.50 versus 0.25; p < 0.04), and a shorter interval between successive MDI actuations (15 versus 60 s; p < 0.02) increased aerosol delivery, whereas use of a hydrofluoroalkane (HFA)-propelled MDI decreased aerosol delivery compared with the CFC-propelled MDI. A MDI and actuator combination other than that designed by the manufacturer altered aerosol particle size and decreased drug delivery. In conclusion, aerosol delivery in an in vitro model accurately reflects in vivo delivery, providing a means for investigating methods to improve the efficiency of aerosol therapy during mechanical ventilation.

Bronchodilator response with use of OptiVent versus Aerosol Cloud Enhancer metered-dose inhaler spacers in patients receiving ventilatory assistance

OBJECTIVE

This study compared the clinical effectiveness of the OptiVent (HealthScan Products, Inc, Cedar Grove, NJ) and the ACE (DHD, Inc, Canastota, NY) metered dose inhaler (MDI) in-line spacers.

DESIGN

Two-group, split-plot design with subjects serving as their own controls.

SETTING

Data were collected in a 1000-bed urban hospital.

PATIENTS

A convenience sample of 7 intubated patients receiving mechanical ventilation.

INTERVENTION

Patients received 4 and 8 puffs of albuterol with use of both the OptiVent and ACE devices.

RESULTS

Changes in expiratory airway resistance (Raw), passive peak expiratory flow rate (PEFR), and total work-of-breathing (WOBTOT) were determined using a Bicore monitor (Bicore Monitoring System; Irvine, Calif). With the ACE, Raw decreased an average of 20.2% and 8.8% in patients receiving 4 and 8 puffs, respectively. With the OptiVent, Raw decreased an average of 34.6% and 10.8% in patients receiving 4 and 8 puffs, respectively. Improvements in WOBTOT were less than those seen in Raw, and PEFR did not trend with the other 2 variables. The performances of the 2 spacer brands were comparable, with no statistical difference (P values > 0.05) for all 3 variables with use of the nonparametric Kolmogorov-Smirnov test.

CONCLUSIONS

These data suggest that use of the OptiVent spacer yields comparable clinical results with the ACE spacer in patients receiving mechanical ventilation and merits further evaluation.

Effects of tracheal suctioning on respiratory resistances in mechanically ventilated patients

OBJECTIVE

To evaluate the effects of tracheal suctioning (TS) on respiratory resistances in sedated critical care patients receiving mechanical ventilation (MV).

SETTING

Surgical ICU of Bichat Hospital, Paris.

PATIENTS AND PARTICIPANTS

Thirteen sedated critical care patients receiving MV for various conditions.

MEASUREMENTS AND RESULTS

Airway resistances (R1), airway and pulmonary resistances (R2), and intrinsic positive end-expiratory pressure (PEEPint) were measured according to the end-inspiratory and end-expiratory occlusion methods before and after TS. R1 and R2 increased by 49.1% and 46.3%, respectively, 0.5 min after TS (p<0.01) but returned to baseline values at 1 min without any change thereafter. PEEPint decreased progressively following TS to reach a significant level (-13.3%) at 10 min (p<0.05) and was persistently reduced at 30 min (p<0.01). Nine patients received 500 microg of inhaled albuterol before another suctioning procedure. R1 and R2 decreased by 11.5% and 9.9%, respectively, 20 min after inhalation (p<0.05), but the R1 and R2 initial increase following TS did not differ between the two suctioning procedures.

CONCLUSIONS

TS evokes only a transient bronchoconstrictor response, but thereafter, does not reduce respiratory resistances below presuctioning values. However, the decrease of PEEPint following TS suggests an increase of expiratory flow. Effective beta2-adrenergic receptor blockade fails to suppress the TS-induced bronchoconstrictor response.

Salbutamol delivery from a hydrofluoroalkane pressurized metered-dose inhaler in pediatric ventilator circuits: an in vitro study

STUDY OBJECTIVES

The aim of our study was to determine the in vitro delivery of salbutamol from a pressurized metered-dose inhaler (pMDI) containing hydrofluoroalkane (HFA) propellant through various delivery devices to four models of a pediatric lung.

DESIGN

To determine the effect of electrostatic charge, delivery of salbutamol was initially assessed with a multistage liquid impinger (MSLI) through an inline nonchamber device (Baxter MDI Adapter) and a small (Aerochamber MV) and a large (Nebuhaler) inline chamber device. Following this, the delivery was assessed to four lung models appropriate for a child of 70 kg, 50 kg, 15 kg, and 4 kg, with the same three reduced static devices inserted directly into a pediatric ventilator circuit.

MEASUREMENTS AND RESULTS

Reduction of electrostatic charge improved small particle delivery through holding chambers to the MSLI by 12 to 14%. In the ventilator model, the mean delivery was between 1.9% and 5.4% for the nonchamber device, between 14.3% and 27.2% for the small holding chamber, and between 7.2% and 25.7% for the large holding chamber. Delivery was the least efficient in the 4-kg model compared to the 70-kg, 50-kg, and 15-kg models.

CONCLUSIONS

Salbutamol from an HFA pMDI is delivered efficiently through inline holding chambers with reduced static in pediatric ventilator settings. A large holding chamber has no advantage over a small holding chamber. In addition, salbutamol delivery is more efficient through a holding chamber than through a nonchamber device.

Status asthmaticus

Despite improved understanding of the pathophysiology and treatment of asthma, significant morbidity and mortality exist for both the pediatric and adult patient. The critical care practitioner must understand the chronic as well as the acute nature of the condition in order to provide effective intervention. This article reviews the epidemiology and pathophysiology of asthma, clinical assessment, management principles, therapeutic modalities, and future approaches to the management of asthma.

Medication nebulizer performance. Effects of diluent volume, nebulizer flow, and nebulizer brand

BACKGROUND

Medication nebulizers are commonly used to delivery aerosolized medications to patients with respiratory disease. We evaluated output and respirable aerosol available to the patient (inhaled mass) for 17 medication nebulizers using a spontaneous breathing lung model.

METHODS

Three nebulizer fill volumes (3, 4, and 5 mL containing 2.5 mg of albuterol) and 3 oxygen flows (6, 8, and 10 L/min) were evaluated using the 17 nebulizers. A cotton plug at the nebulizer mouthpiece was used to trap aerosol during simulated spontaneous breathing. Following each trial, the amount of albuterol remaining in the nebulizer and the amount deposited in the cotton plug were determined spectrophotometrically. Aerosol particle size was determined using an 11-stage cascade impactor.

RESULTS

Increasing fill volume decreased the amount of albuterol trapped in the dead volume (p < 0.001) and increased the amount delivered to the patient (p < 0.001). Increasing flow increased the mass output of particles in the respirable range of 1 to 5 microns (p = 0.004), but the respirable mass delivered to the patient was affected to a greater extent by nebulizer brand (p < 0.001) than flow. Although 2.5 mg of albuterol was placed into the nebulizers, less than 0.5 mg in the respirable range of 1 to 5 microns was delivered to the mouthpiece.

CONCLUSIONS

The performance of medication nebulizers is affected by fill volume, flow, and nebulizer brand. When they are used for research applications, the nebulizer characteristics must be evaluated and reported for the conditions used in the investigation.

Optimal pharmacologic treatment of the critically ill patient with obstructive airways disease

There are few experimental data evaluating the effect of inhaled bronchodilator treatment in the critically ill patient in the intensive care unit. Extrapolating from the data that are available in chronic and acute asthma and chronic obstructive pulmonary disease (COPD) studies, it appears that both agents may be beneficial. Beta-adrenergic receptor agonists are first-line agents in asthma. However, anticholinergics may be valuable as additive agents or as single agents if the patient is intolerant of beta-adrenergic side effects. This may be especially important in the critically ill patient with multiple organ failure in whom excessive tachycardia may reduce oxygen delivery. Anticholinergics and beta 2-adrenergic agonists both appear to be beneficial in smoking-related chronic bronchitis. Finally, because of the severity of illness in the critical care setting, both drugs should be titrated to maximal effect when possible, monitoring closely for adverse effects of the larger than normal doses that are used.

In vitro assessment of drug delivery through an endotracheal tube using a dry powder inhaler delivery system

BACKGROUND

Jet nubulisers and metered dose inhalers are widely used to deliver aerosolised drugs to the lungs of intubated patients in adult intensive care units. Drug delivery using these systems has been shown to be inefficient and both forms of delivery have the potential to induce paradoxical bronchoconstriction in patients with reactive airways disease.

METHODS

Experiments were carried out to determine whether it was possible to deliver drug from a dry powder delivery system through an endotracheal tube. A 200 micrograms budesonide Turbohaler was enclosed in a chamber which allowed it to be inserted into a ventilator circuit. Experiments were performed with a multistage liquid impinger in which drug was drawn through the Turbohaler and endotracheal tube at 60 l/min providing an index of the maximum drug delivery achievable via this route. A second series of experiments was performed in which the Turbohaler was placed in a ventilator circuit using a Servo 900C volume cycled ventilator. Drug delivered from the Turbohaler during the inspiratory phase was collected on a filter placed between the end of a 9 mm endotracheal tube and a model lung. A tidal volume of 500 ml and inspiratory time of 0.5 seconds was used. Budesonide was assayed using an ultraviolet spectrophotometric assay.

RESULTS

Thirty percent of the nominal dose passed through the endotracheal tube and was collected in the multistage liquid impinger. Mean drug delivery to the filter in the ventilator circuit was 20%.

CONCLUSIONS

This in vitro study indicates that drugs from dry powder inhalers (in this case the Turbohaler) can be satisfactorily delivered through endotracheal tubes and that clinical evaluation of this technique is now indicated.

The delivery of aerosolized steroids from MDIs with nozzle extensions: quantitative laboratory evaluation of a method to improve aerosol delivery to intubated patients

OBJECTIVE

Pulmonary deposition of aerosolized drug from a metered dose inhaler (MDI) is low with intubated patients. In the laboratory, extension of the MDI nozzle to the endotracheal tube tip has been shown to increase the delivered dose of albuterol. The objectives of this study were to determine the dose of aerosolized steroid (beclomethasone and triamcinolone) delivered through a MDI nozzle extension, the effect of nozzle extension length and number of actuations on the delivered dose, and particle size delivered through the nozzle extension.

DESIGN

A 19-G catheter was used as the MDI nozzle extension. The nozzle extension was attached to a 60-ml syringe via the Luer-Lok connection, and the distal end was directed through a hole drilled into a 15-ml capped tube. The MDI was placed into the syringe and actuated by pressing the syringe plunger. Drug delivered through the nozzle extension into the tube was dissolved in methanol (beclomethasone) or ethanol (triamcinolone). Nozzle extension lengths of 10 cm, 20 cm and 30 cm were studied. For each nozzle extension length, delivery was assessed using one, two, three and five actuations of each drug. Drug remaining in the nozzle extension was recovered by rinsing with the appropriate solvent. Aerosol particle size leaving the nozzle extension was determined using a seven-stage cascade impactor. Beclomethasone and triamcinolone concentrations were determined by spectrophotometry at 239 nm.

SETTING

Respiratory care laboratory of a university teaching hospital.

RESULTS

For the pooled results, 70.2 +/- 14.1% of the dose was delivered through the nozzle extension, with no difference between beclomethasone and triamcinolone (p = 0.838). The proportion of drug delivered through the 10-cm extension (76.7 +/- 8.4%) was greater than that from the 20-cm (66.1 +/- 16.5%) and 30-cm (67.7 +/- 13.9%) extensions (p = 0.001). Less drug was delivered through the extension with one actuation (54.1 +/- 17.7%) than with two (71.2 +/- 7.7%), three (77.2 +/- 5.5%), or five actuations (78.2 +/- 4.3%) (p < 0.001). There was a decrease in MMAD with increasing nozzle extension length (3.14 +/- 0.61 microns for 10 cm, 2.97 +/- 0.28 microns for 20 cm, 2.37 +/- 0.27 microns for 30 cm; p = 0.005).

CONCLUSIONS

A high proportion of aerosolized steroid was delivered with a MDI actuated through a nozzle extension. The proportion delivered through the nozzle extension was significantly less with longer nozzle extensions and with fewer actuations, but this may not be clinically important. Although particle sizes were smaller from longer nozzle extensions, all were within the respirable range. These results suggest that steroids can be delivered efficiently using a MDI nozzle extension.

Efficiency of bronchodilator aerosol delivery to the lungs from the metered dose inhaler in mechanically ventilated patients. A study comparing four different actuator devices

STUDY OBJECTIVE

To compare aerosol delivery to the lungs in ventilated patients from two devices with holding chamber and two devices without holding chamber.

DESIGN

A controlled clinical trial with randomization to one of four delivery devices.

SETTING

An academic university-affiliated Canadian ICU.

PATIENTS

Forty-eight patients undergoing mechanically assisted ventilation for a variety of clinical reasons and each judged to require inhaled bronchodilator therapy by the attending physician.

INTERVENTIONS

Patients received 4 puffs of fenoterol labeled with technetium 99m pertechnetate delivered by metered-dose inhaler via 1 of the following: A, a 167-ml chamber device; B, a 700-ml chamber device; C, a nonchamber device (A, B, and C, all in the ventilator inspiratory line); and D, a nonchamber device on the end of the endotracheal tube.

MEASUREMENTS AND RESULTS

One-minute images of the thorax were made by a portable gamma camera at the bedside. Deposition of radioactivity in the lungs (uncorrected for tissue absorption and calculated as a percentage of the radioactivity delivered from 4 puffs) was 5.53 +/- 0.72 (mean +/- 1 SEM), 6.33 +/- 1.16, 1.67 +/- 0.43, and 3.89 +/- 0.52 percent for devices A, B, C, and D, respectively (p = 0.004). Subgroup analysis showed a statistically significant difference in delivery between devices A and C and between devices B and C only.

CONCLUSION

There were statistically significant differences between delivery from both chamber devices and the inline nonchamber device, but not between delivery from other devices. Further work will be necessary to determine the effect of device position in the ventilator circuit on aerosol delivery.

Metered-dose inhaler versus nebulized albuterol in mechanically ventilated patients

In nonintubated patients, beta 2-agonist bronchodilators are equally effective when delivered by metered-dose inhalers (MDI) or nebulizers (NEB). The delivery of these drugs by MDI to intubated, mechanically ventilated patients has become a widespread practice. To compare the efficacy of the two delivery systems and establish optimal dosing, we prospectively randomized 10 mechanically ventilated patients, with increased airways resistance, to receive albuterol by either MDI or nebulizer in incrementally higher doses. After a 4-hr washout, patients were crossed-over to receive the drug by the alternative route of administration. Albuterol delivered by NEB to a total dose of 2.5 mg reduced the inspiratory flow-resistive pressure (peak-pause airway pressures) from 21.5 +/- 5.7 to 17.6 +/- 5.4 cm H2O (p < 0.01). Nebulized albuterol at cumulative doses of 7.5 mg led to further reductions in 8 of 10 patients (p < 0.1), but led to toxic side effects in 4 of them; in the remaining 6 patients toxicity occurred at a cumulative dose of 15.0 mg. By contrast, albuterol in cumulative doses reaching 100 puffs (9 mg) from an MDI administered into an endotracheal tube adapter did not significantly reduce resistive pressures, and produced no toxicity. We conclude that nebulized albuterol provides objective physiologic improvement, while albuterol administered by MDI through an endotracheal tube adapter has no effect in mechanically ventilated patients with airflow obstruction. Nebulizer treatments can and should be titrated to higher-than-conventional doses, using toxic side-effects and physiologic response to guide therapy.