BACKGROUND:The interaction between nebulizer technology and mechanical ventilation can be confusing. Mesh technology has recently been quantified using the mass balance, a technique that measures all aerosol delivered and lost in ventilator circuits. Data for jet nebulizers are limited, and ventilator technology has changed over time. The present study was designed to better define aerosol behavior during jet nebulization by testing device position, gas source, humidification, inspiratory time (TI), and circuit compliance. METHODS:Using radiolabeled particles, mass balance and output rate were measured for the AeroTech nebulizer placed close to the ventilator (IP), Y-piece (YP), and proximal to ETT (DY) in aerosol HME or humidified settings. The nebulizer was driven continuously (8 L/m, 50 PSIG) or by breath actuation (BA) during volume control ventilation at two inspiratory times (TI 0.7 and 0.55 s). Five ventilators and two circuits with different tubing compliance were tested. Radiolabeled saline (3 mL, Tc99m) was nebulized. A well counter measured filters inhaled and expiratory mass (IM, EM), and nebulizer residual (NR). Tubing deposition was measured with a gamma camera. A shielded ratemeter measured output rate and treatment time. RESULTS:Mass balance ranged from 96 to 104% (no. = 66). IM obtained with IP, HME circuit, continuous nebulization (29.8 ± 5%), IP, and BA (26.8 ± 4%); with humidification, continuous (15 ± 1%), BA (27.1 ± 4). Lowest IM at YP position, HME (8.8 ± .6%). Circuit losses ≤20%. EM was lowest for IP (19.2 ± 2%) and highest for YP and DY (46 ± 3%). NR was higher with BA (43.1 ± 6 vs 37.1 ± 3, P = .002). Higher tubing compliance lowered IM (21.8 ± .7% vs 28.3 ± 3% [no. = 9], P = .01). Treatment time for IP, continuous, HME circuit (10 min), and BA circuit (50 min). Changing TI (0.55 s) reduced IM and further increased treatment time. CONCLUSIONS:Optimal conditions for jet nebulization were IP position, HME circuit, continuous nebulization, and stiff tubing. Humidification should be supplied with an aerosol HME. If active humidification, IP breath-actuated was most efficient but with marked increase in treatment time.

Introduction: In normal subjects, during tidal breathing, aerosols deposit by settling in small airways. With obstructive lung disease (OLD), collapse of airways during expiration causes turbulence and increased deposition in central airways. High-flow nasal cannula (HFNC) therapy, washing out dead space, may affect deposition mechanisms and drug delivery. This study compared aerosol deposition and airway responsiveness in OLD after traditional and HFNC nebulization therapy. Methods: Twelve subjects with moderate to severe OLD participated in a two-day study. Spirometry was measured pre- and post-aerosol inhalation. On Day 1 (D1) subjects tidally inhaled radiolabeled albuterol (99mTc DTPA) by mouth via AeroTech II, (Biodex. Shirley, NY). Day 2 (D2) inhalation was via HFNC using i-AIRE (InspiRx, Inc. Somerset, NJ). The HFNC system (60 L/m) was infused by syringe pump at 50 mL/h. D2 lung deposition was monitored in real time by gamma camera to match D1. Pre and post heart rate, O2 sat, and nasopharyngeal deposition (NP) were measured. Mechanistic contributions were modeled using multiple linear regression (MLR) of deposition rate (DR µg/m) as a function of breathing frequency, airway geometry (FEV1), and parenchymal integrity (DLCO). Results: Albuterol lung depositions were matched (p = 0.13) with D1 central/peripheral (sC/P) ratios 1.99 ± 0.98. Following HFNC, peripheral deposition increased (31% ± 33%, sC/P = 1.51 ± 0.43, p = 0.01). D2/D1% change FVC increased by 16.1 ± 16.7% (p = 0.003). NP deposition averaged 333% of lung. Heart rate and O2 sat were unaffected (p = 0.31, p = 0.63 respectively). DR analysis was markedly different between D1 (R2 = 0.82) and D2 (R2 = 0.12). Conclusion: In subjects with OLD, HFNC nebulization at 60 L/min was well tolerated and increased peripheral drug delivery. Spirometry significantly improved. Systemic effects were undetected indicating limited nasal absorption. MLR demonstrated that different mechanisms of deposition govern traditional vs HFNC aerosol delivery. Breath-enhanced nebulization via HFNC may provide controllable and effective aerosol therapy in OLD.

Aims Intubated patients with methicillin‐resistant Staphylococcus aureus pneumonia, fail optimized treatment with intravenous (IV) vancomycin (serum trough 15–20 μg/mL) in 38–79% of cases. Airway blood flow is diminished compared to alveoli and we hypothesized that vancomycin concentrations achieved in airway secretions are suboptimal and nonbactericidal. Targeted therapy by inhalation may overcome this deficit. Methods Airway pharmacokinetics of optimized IV and inhaled vancomycin in infected clinically stable prolonged mechanically ventilated patients were measured. First, IV vancomycin was given until optimized concentrations were achieved (15–20 μg/mL), and, at the same time point, sputum vancomycin concentrations were measured. Then, sputum concentrations were re‐assessed after 4 treatments of inhaled vancomycin (120 mg/2 mL) via a previously characterized nebulizing system that deposited 18 ± 2 mg in the lungs. Vancomycin post‐distribution phase serum peak and trough concentrations were also obtained. Serum albumin was measured to assess binding to vancomycin. Results Mean serum trough concentration was 18.4 ± 6.5 μg/mL. Sputum concentrations were affected by serum albumin. Only patients with severe hypoalbuminaemia had penetration of drug leading to therapeutic (15.7–17 μg/mL) sputum concentrations. Following inhaled vancomycin, sputum concentrations increased significantly to 199 ± 37.0 μg/mL ( P = .002) exceeding minimum inhibitory concentration by 2 orders of magnitude. Conclusion Despite optimized serum concentrations, patients with albumin near normal had suboptimal concentrations of vancomycin in their sputum. Inhaled therapy may be clinically important for successful treatment of ventilator‐associated methicillin‐resistant Staphylococcus aureus infection. Further studies of inhaled therapy are needed to define their role as adjunctive therapy in ventilator‐associated pneumonia and as single therapy in tracheobronchitis.

Background: During invasive ventilation, external flow jet nebulization results in increases in displayed exhaled tidal volumes (V-T). We hypothesized that the magnitude of the increase is inaccurate. An ASL 5000 simulator measured ventilatory parameters over a wide range of adult settings: actual V-T, peak inspiratory pressure (PIP), and time to minimum pressure. Methods: Ventilators with internal and external flow sensors were tested by using a variety of volume and pressure control modes (the target V-T was 420 mL). Patient conditions (normal, COPD, ARDS) defined on the ASL 5000 were assessed at baseline and with 3.5 or 8 L/min of added external flow. Patient-triggering was assessed by reducing muscle effort to the level that resulted in backup ventilation and by changing ventilator sensitivity to the point of auto-triggering. RESULTS: Results are reported as percentage change from baseline after addition of 3.5 or 8 L/min external flow. For ventilators with internal flow sensors, changes in displayed exhaled V-T ranged from 10% to 118%, however, when using volume control, actual increases in actual V-T and PIP were only 4%-21% (P = .063, .031) and 6%-24% (P = .25, .031), respectively. Changes in actual V-T correlated closely with changes in PIP (P < .001; R-2 = 0.68). For pressure control, actual V-T decreased by 3%-5% (P = .031) and 4%-9% (P = .031) with 3.5 and 8 L/min respectively, PIP was unchanged. With external flow sensors at the distal Y-piece junction, volume and pressure changes were statistically insignificant. The time to minimum pressure increased at most by 8% (P = .02) across all modes and ventilators. The effects on muscle pressure were minimal (similar to 1 cm H2O), and ventilator sensitivity effects were nearly undetectable. CONCLUSIONS: External flow jet nebulization resulted in much smaller changes in volume than indicated by the ventilator display. Statistically significant effects were confined primarily to machines with internal flow sensors. Differences approached the manufacturer-reported variation in ventilator baseline performance. During nebulizer therapy, effects on V-T can be estimated at the bedside by monitoring PIP.

Aerosol delivery using conventional nebulizers with fixed maximal output rates is limited and unpredictable under high-flow conditions. This study measured regulated aerosol delivery to the lungs of normal volunteers using a nebulizer designed to overcome the limitations of HFNC therapy (i-AIRE (InspiRx, Inc., Somerset, NJ, USA)). This breath-enhanced jet nebulizer, in series with the high-flow catheter, utilizes the high flow to increase aerosol output beyond those of conventional devices. Nine normal subjects breathing tidally via the nose received humidified air at 60 L/min. The nebulizer was connected to the HFNC system upstream to the humidifier and received radio-labeled saline as a marker for drug delivery (99mTc DTPA) infused by a syringe pump (mCi/min). The dose to the subject was regulated at 12, 20 and 50 mL/h. Rates of aerosol deposition in the lungs (µCi/min) were measured via a gamma camera for each infusion rate and converted to µg NaCl/min. The deposition rate, as expressed as µg of NaCl/min, was closely related to the infusion rate: 7.84 ± 3.2 at 12 mL/h, 43.0 ± 12 at 20 mL/h and 136 ± 45 at 50 mL/h. The deposition efficiency ranged from 0.44 to 1.82% of infused saline, with 6% deposited in the nose. A regional analysis indicated peripheral deposition of aerosol (central/peripheral ratio 0.99 ± 0.27). The data were independent of breathing frequency. Breath-enhanced nebulization via HFNC reliably delivered aerosol to the lungs at the highest nasal airflows. The rate of delivery was controlled simply by regulating the infusion rate, indicating that lung deposition in the critically ill can be titrated clinically at the bedside.

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BACKGROUND: Aerosolized drug delivery via high-flow nasal cannula (HFNC) decreases as gas flow is increased. To improve aerosol delivery, breath-enhanced jet nebulizer may increase aerosol output. This study tested that hypothesis and compared breath-enhanced jet nebulizer to vibrating mesh nebulizer technology. METHODS: First, in an isolated circuit, breath-enhanced jet nebulizer and vibrating mesh nebulizer aerosol outputs were measured during simulated HFNC by using infused saline solution at rates of 5–60 mL/h. Limits were defined when nebulizer filling was detected. The devices were then tested by using 99mTc/saline solution to measure maximum rates of aerosol production. After the output experiments, drug delivery was measured in vitro by using a model that consisted of an HFNC circuit interfaced to a realistic 3-dimensional printed head. The 99mTc/saline solution was infused at rates of 5 to 60 mL/h for the breath-enhanced jet nebulizer and 5 to 20 mL/h for the vibrating mesh nebulizer with HFNC gas flows of 10 to 60 L/min. Aerosol delivery to the trachea was measured by using a shielded ratemeter, which defined the rate of drug delivery (µg NaCl/min). RESULTS: With increasing gas flow, breath-enhanced jet nebulizer output increased to a maximum of 50 mL/h, the vibrating mesh nebulizer maximum was 12 mL/h. At HFNC gas flow of 60 L/min, breath-enhanced jet nebulizer delivered 3.16 to 316.8 µg NaCl/min, the vibrating mesh nebulizer delivered 23.5 to 61.7 µg NaCl/min. For infusion pump flows of 5 to 12 mL/h, the rate of drug delivery was independent of nebulizer type (P = .19) and dependent on infusion pump flow (P < .001) and gas flow (P < .001). CONCLUSIONS: Increasing gas flow increased breath-enhanced jet nebulizer output, which demonstrated the effects of breath enhancement. At 60 L/min, breath enhanced jet nebulizer delivered up to 5 times more aerosol compared with conventional vibrating mesh nebulizer technology. Breath-enhanced jet nebulizer delivered a wide range of dose rates at all high flows. In patients who are critically ill, breath-enhanced jet nebulizer technology may allow titration of bedside dosing based on clinical response by simple adjustment of the infusion rate.

BACKGROUND: To understand the fate of aerosols delivered by high-flow nasal cannula using continuous nebulization, an open-source anatomical model was developed and validated with a modified real-time gamma ratemeter technique. Mass balance defined circuit losses. Responsiveness to infusion rate and device technology were tested. METHODS: A nasal airway cast derived from a computed tomography scan was converted to a 3-dimensional-printed head and face structure connected to a piston ventilator (breathing frequency 30 breaths/min, tidal volume 750 mL, duty cycle 0.50). For mass balance experiments, saline mixed with Technetium-99m was infused for 1 h. Aerosol delivery was measured using a gamma ratemeter oriented to an inhaled mass filter at the hypopharynx of the model. Background and dead-space effects were minimized. All components were imaged by scintigraphy. Continuous nebulization was tested at infusion rates of 10-40 mL/h with gas flow of 60 L/min using a breath-enhanced jet nebulizer (BEJN), and a vibrating mesh nebulizer. Drug delivery rates were defined by the slope of ratemeter counts/min (CPM/min) versus time (min). RESULTS: The major source of aerosol loss was at the nasal interface (similar to 25%). Significant differences in deposition on circuit components were seen between nebulizers. The nebulizer residual was higher for BEJN (P = .006), and circuit losses, including the humidifier, were higher for vibrating mesh nebulizer (P = .006). There were no differences in delivery to the filter and head model. For 60 L/min gas flow, as infusion pump flow was increased, the rate of aerosol delivery (CPM/min) increased, for BEJN from 338 to 8,111; for vibrating mesh nebulizer, maximum delivery was 2,828. CONCLUSIONS: The model defined sites of aerosol losses during continuous nebulization and provided a realistic in vitro system for testing aerosol delivery during continuous nebulization. Real-time analysis can quantify effects of multiple changes in variables (nebulizer technology, infusion rate, gas flow, and ventilation) during a given experiment.

Background: Aerosol delivery via high flow nasal cannula (HFNC 10-60 L/min) is limited by turbulent losses and leaking at the nose. In theory, a jet nebulizer can utilize the high flow passing through the nebulizer chimney to increase drug delivery, e.g., breath enhanced jet nebulization (BEJN). BEJN was applied to a high flow delivery system and tested in an invitro model compared to conventional mesh nebulizer (VMN). Methods: Aerosol outputs were measured during nebulization of infused 99mTc/saline which defined maximum aerosol production. Following the output experiments, drug delivery was measured invitro using a model consisting of a HFNC circuit interfaced to a realistic 3D-printed head. Aerosol delivered to the trachea was measured using a shielded ratemeter which defined the rate of drug delivery (µg NaCl/min). 99mTc/saline was infused at rates of 5 to 60 mL/h for BEJN, 5 to 20 mL/h for VMN with HFNC gas flows of 10 to 60 L/min. Results: BEJN aerosol output increased to a maximum at 50 mL/h, VMN at 12. While 90% of generated particles were lost in the system, maximal drug delivery to the trachea for BEJN was 5 times VMN. BEJN aerosol delivery could be titrated over a wide range of infusion flow rates. At the highest flow of 60 L/min the rate of aerosol delivery ranged over 2 orders of magnitude. Conclusion: Aerosol delivery during HFNC is inefficient. To counteract this effect, BEJN utilizes the high flow in the HFNC to generate increased quantities of aerosol. BEJN delivered a wide range of dose rates at all high flows with delivery tightly controlled by rate of infusion. In the critically ill, BEJN technology may allow titration of bedside dosing by simple adjustment of infusion rate.

TYPE: Abstract TOPIC: Pharmacotherapeutics PURPOSE: The i-NEB-MiniTM is a jet nebulizer designed for controlled delivery of small (< 2 mL) volumes of potent drugs to the deep lung. The purpose of this study was to determine aerosol parameters and post nebulization drug activity of a novel formulation of recombinant Interferon Gamma (rIFNγ), a pluripotent molecule with Th1 helper cell activity. METHODS: rINFγ (200 μg/mL) was aerosolized using i-NEB-MiniTM driven by a portable compressor at 3.5 L/min. Two (2) mL was aerosolized into a Next Generation Impactor (NGI) using a 15 L/min vacuum. Aerosol parameters (MMAD, GSD, Total Respirable Dose) were determined using an HPLC assay (Vectura Ltd., UK). Bioactivity pre-/post-nebulization was determined using an HLADR assay (PBL Assay Sciences, Piscataway, NJ, USA). RESULTS: The MMAD, GSD and Total Respirable dose from a 200 μg/mL formulation (n=6) was 2.5 (± 0.2), 1.6 (± 0.4) and 123.7 (± 19.8) μg respectively. The bioactivity pre- and post-nebulization was consistent with the EP standard suggesting that nebulization did not affect biological activity of the protein. CONCLUSIONS: This study indicates that a clinically relevant and reproducible dose of rINFγ can be delivered with i-NEB-MiniTM. Bioactivity assay indicates that aerosol rINFγ retains protein integrity after nebulization. CLINICAL IMPLICATIONS: rINFγ is an immunomodulatory pleiotropic cytokine with potential for treatment of respiratory diseases such as Pulmonary Fibrosis, MDRTB, COPD and SARS-CoV-2. The results indicate that a clinically relevant dose of rINFγ can be aerosolized using the i-NEB-MiniTM jet nebulizer. DISCLOSURE: Stony Brook and New York University hold patents on the use of inhaled interferon licensed to InspiRx, Inc. Dr. Smaldone consults to InspiRx and is a member of the advisory board. Mr. Shukla and Dr. Toddywala are employees of InspiRx. KEYWORD: immunomodulation

BACKGROUND:Recent observational studies of nebulizers placed on the wet side of the humidifier suggest that, after some time, considerable condensation can form, which triggers an occlusion alarm. In the current study, an inline breath-enhanced jet nebulizer was tested and compared in vitro with a vibrating mesh nebulizer on the humidifier dry-inlet side of the ventilator circuit. METHODS:Two duty cycle breathing patterns were tested during continuous infusion (5 or 10 mL/h) with and without dynamic changes in infusion flow and duty cycle, or bolus delivery (3 or 6 mL) of radiolabeled saline solution. Inhaled mass (IM) was measured by a real-time ratemeter (µCi/min) and analyzed by multiple linear regression. RESULTS:During simple continuous infusion, IM increased linearly for both nebulizer types. IM variability was attributable to the duty cycle (P < .001) (34%) and infusion flow (P < .001) (32%) but independent of nebulizer technology (P = .38) (7%). Dynamic continuous infusion studies that simulate clinical scenarios with ventilator and pump flow changes demonstrated a linear increase in the rate of aerosol that was dependent on pump flow (P < .001) (63%) and minimally dependent on the duty cycle (P = .003) (8%). During bolus treatments, IM increased linearly to plateau. IM variability was attributable to the duty cycle (P < .001) (40%) and residual radioactivity in the nebulizer (P < .001) (20%). Separate analysis revealed that the vibrating mesh nebulizer residual volume contributed 16% of the variability and inline breath-enhanced jet nebulizer contributed 5%. IM variability was independent of bolus volume (P = .82) (1%). System losses were similar (the inline breath-enhanced jet nebulizer: 32% residual in nebulizer; the vibrating mesh nebulizer: 34% in circuitry). CONCLUSIONS:Aerosol delivery during continuous infusion and bolus delivery was comparable between the inline breath-enhanced jet nebulizer and the vibrating mesh nebulizer, and was determined by pump flow and initial ventilator settings. Further adjustments in ventilator settings did not significantly affect drug delivery. Expiratory losses predicted by the duty cycle were reduced with placement of the nebulizer near the ventilator outlet.

TYPE: Abstract TOPIC: Critical Care PURPOSE: This study tests nebulizers configured to deliver multiple medications during continuous nebulization without interruption or circuit disconnection. METHODS: A prototype i-AIRE dual-medication port breath-enhanced jet nebulizer (BEJN) was compared to Aerogen Solo vibrating mesh nebulizers (VMN). VMN were stacked; one for infusion, the second for bolus drug delivery. Radiolabeled saline was infused over 4 hr at 5 & 10 mL/h with 3 mL and 6 mL radiolabeled saline bolus injections into the circuit at 30 and 120 min respectively. Inhaled Mass expressed as % of initial syringe activity (IM%/min) was monitored in real time with a ratemeter. All delivered radioaerosol was collected on a filter at the airway opening. Transients in aerosol delivery were documented. RESULTS: IM %/h during continuous infusion was linear, with BEJN and VMN delivering 3-4 %/hr. BEJN functioned without incident. VMN stopped nebulizing spontaneously 50% of the time but tapping restarted VMN function during 3 of 4 continuous runs and 7 of 9 bolus delivery runs. Bolus delivery IM% (mean ± SD): 22 ± 8%, 14 ± 11 % for BEJN and VMN, respectively. CONCLUSIONS: Simultaneous continuous and bolus nebulization without circuit disconnection is possible for both jet and mesh technology. CLINICAL IMPLICATIONS: Continuous nebulization of pulmonary vasodilators is an off-label therapy for critically ill patients with hypoxemia. This study indicates that additional drugs (bronchodilators/antibiotics) can be given by bolus nebulization without circuit disconnection. Monitoring of VMN devices may be necessary in case of spontaneous interruption of nebulization. DISCLOSURE: Stony Brook University owns patents on inhaled therapy in intubated patients licensed to InspiRx, Inc. Dr. Smaldone consults to InspiRx and is a member of the Advisory Board. Ms Cuccia has served as a consultant to InspiRx. Dr. Lee and Mr. McPeck have no KEYWORD: nebulization

Cough etiquette and respiratory hygiene are forms of source control encouraged to prevent the spread of respiratory infection. The use of surgical masks as a means of source control has not been quantified in terms of reducing exposure to others. We designed an in vitro model using various facepieces to assess their contribution to exposure reduction when worn at the infectious source (Source) relative to facepieces worn for primary (Receiver) protection, and the factors that contribute to each. In a chamber with various airflows, radiolabeled aerosols were exhaled via a ventilated soft-face manikin head using tidal breathing and cough (Source). Anothermanikin, containing a filter, quantified recipient exposure (Receiver). The natural fit surgical mask, fitted (SecureFit) surgicalmask and an N95-class filtering facepiece respirator (commonly known as an " N95 respirator") with and without a Vaselineseal were tested. With cough, source control (mask or respirator on Source) was statistically superior to mask or unsealed respirator protection on the Receiver (Receiver protection) in all environments. To equal source control during coughing, the N95 respirator must be Vaseline-sealed. During tidal breathing, source controlwas comparable or superior to mask or respirator protection on the Receiver. Source control via surgical masks may be an important adjunct defense against the spread of respiratory infections. The fit of the mask or respirator, in combination with the airflow patterns in a given setting, are significant contributors to source control efficacy. Future clinical trials should include a surgicalmask source control arm to assess the contribution of source control in overall protection against airborne infection.

Introduction Critically ill mechanically ventilated patients routinely receive aerosol delivery of epoprostenol by continuous infusion of the nebulizer by syringe pump. This procedure is 'off-label' as no FDA approved drug presently exists. Without standardized protocols, therapy is based on prior experience with bronchodilators, limited studies of delivery systems and anecdotal clinical trials. Current protocols based upon patient body weight and drug concentration determines the infusion rate of drug dose delivered to the nebulizer , which is only distantly related to dose delivered to the lung and may be altered by many factors. Areas covered This paper reviews the background of this technique as well as current methods of managing drug delivery, technical challenges, and limitations. A recent advance in aerosol laboratory bench testing, using radiolabeled aerosols, is presented to reveal important factors defining delivery. Expert opinion Off-label use of continuously nebulized prostacyclin in the ICU lacks the support of large clinical trials needed for FDA clearance. However, comprehensive bench studies afford the potential for clinicians to better understand and manage therapy at a level above simple dosing of the nebulizer by body weight. New research techniques are enhancing our basic comprehension of the interaction between aerosol devices and the mechanical ventilator.

Respiratory infection is common in intubated/tracheotomized patients and systemic antibiotic therapy is often unrewarding. In 1967, the difficulty in treating Gram-negative respiratory infections led to the use of inhaled gentamicin, targeting therapy directly to the lungs. Fifty-three years later, the effects of topical therapy in the intubated patient remain undefined. Clinical failures with intravenous antibiotics persist and instrumented patients are now infected by many more multidrug-resistant Gram-negative species as well as methicillin-resistant Staphylococcus aureus. Multiple systematic reviews and meta-analyses suggest that there may be a role for inhaled delivery but "more research is needed." Yet there is still no Food and Drug Administration (FDA) approved inhaled antibiotic for the treatment of ventilator-associated infection, the hallmark of which is the foreign body in the upper airway. Current pulmonary and infectious disease guidelines suggest using aerosols only in the setting of Gram-negative infections that are resistant to all systemic antibiotics or not to use them at all. Recently two seemingly well-designed large randomized placebo-controlled Phase 2 and Phase 3 clinical trials of adjunctive inhaled therapy for the treatment of ventilator-associated pneumonia failed to show more rapid resolution of pneumonia symptoms or effect on mortality. Despite evolving technology of delivery devices and more detailed understanding of the factors affecting delivery, treatment effects were no better than placebo. What is wrong with our approach to ventilator- associated infection? Is there a message from the large meta-analyses and these two large recent multisite trials? This review will suggest why current therapies are unpredictable and have not fulfilled the promise of better outcomes. Data suggest that future studies of inhaled therapy, in the milieu of worsening bacterial resistance, require new approaches with completely different indications and endpoints to determine whether inhaled therapy indeed has an important role in the treatment of ventilated patients.

Critically ill mechanically ventilated patients routinely receive aerosol delivery of epoprostenol by continuous infusion of the nebulizer by syringe pump. This procedure is 'off-label' as no FDA approved drug presently exists. Without standardized protocols, therapy is based on prior experience with bronchodilators, limited studies of delivery systems and anecdotal clinical trials. Current protocols based upon patient body weight and drug concentration determines the infusion rate of drug dose delivered to the nebulizer , which is only distantly related to dose delivered to the lung and may be altered by many factors.This paper reviews the background of this technique as well as current methods of managing drug delivery, technical challenges, and limitations. A recent advance in aerosol laboratory bench testing, using radiolabeled aerosols, is presented to reveal important factors defining delivery.Off-label use of continuously nebulized prostacyclin in the ICU lacks the support of large clinical trials needed for FDA clearance. However, comprehensive bench studies afford the potential for clinicians to better understand and manage therapy at a level above simple dosing of the nebulizer by body weight. New research techniques are enhancing our basic comprehension of the interaction between aerosol devices and the mechanical ventilator.

Background: Previous work measured aerosol delivery for i-AIRE, a prototype inline breath-enhanced jet nebulizer (BEJN) located on the wet/outlet of the humidifier. Recent observations reported that placement of single-patient-use nebulizers in this location results in excess condensation in the inspiratory limb and nebulizer flooding. The present study tested i-AIRE in vitro compared to Solo, a vibrating mesh nebulizer (VMN) on the humidifier dry/inlet side of the ventilator circuit during continuous and bolus treatment nebulization. Methods: Two adult duty cycle (DC) breathing patterns were tested during continuous infusion (5 or 10 mL/h) with and without dynamic changes in infusion rate and DC, or bolus delivery (3 or 6 mL) of radiolabeled saline. Inhaled mass (IM) reported as a function of time was measured in real-time using a gamma ratemeter (µCi/min) and analyzed by multiple linear regression. Expiratory losses (EXP) were measured and reported as the IM:EXP ratio. Results: During simple continuous infusion, IM increased linearly for both nebulizer types. IM variability was attributable to DC (P Conclusions: Aerosol delivery during continuous infusion and bolus delivery is comparable between the BEJN and VMN and determined by pump flow and initial ventilator settings. Once treatment is initiated, further adjustments in ventilator settings did not significantly affect drug delivery. Furthermore, placement of the nebulizer on the humidifier dry-side allows for a greater inhaled mass-to-expiratory loss ratio than predicted by ventilator DC.

Background: A new real-time method for assessing factors determining aerosol delivery is described. Methods: A breath-enhanced jet nebulizer operated in a ventilator/heated humidifier system was tested during bolus and continuous infusion aerosol delivery. 99mTc (technetium)/saline was either injected (3 or 6 mL) or infused over time into the nebulizer. A shielded gamma ratemeter was oriented to count radioaerosol accumulating on an inhaled mass (IM) filter at the airway opening of a test lung. Radioactivity measured at 2–10-minute intervals was expressed as % nebulizer charge (bolus) or % syringe activity per minute infused. All circuit parts were measured and imaged by gamma camera to determine mass balance. Results: Ratemeter activity quantitatively reflected immediate changes in IM: 3 and 6 mL bolus IM% = 16.1 and 18.8% in 6 and 14 minutes, respectively; infusion IM% = 0.64 + 0.13 (run time, min), R2 0.999. Effect of nebulizer priming and system anomalies were readily detected in real time. Mass balance (basis = dose infused in 90 minutes): IM 39.2%, breath-enhanced jet nebulizer residual 35.5%, circuit parts including humidifier 23.4%, and total recovery 98.1%. Visual analysis of circuit component images identified sites of increased deposition. Conclusion: Real-time ratemeter measurement with gamma camera imaging provides operational feedback during in vitro testing procedures and yields a detailed analysis of the parameters influencing drug delivery during mechanical ventilation. This method of analysis facilitates assessment of device function and influence of circuit parameters on drug delivery.