Clinical standardization of two controlled allergen challenge facilities: The Environmental Exposure Unit and the Biogenics Research Chamber.

BACKGROUND: Controlled allergen challenge facilities (CACF), in disparate geographic regions with dissimilar engineering and base populations, have historically functioned as single, independent sites in clinical allergy trials. We aimed to demonstrate "between-unit reproducibility" to allow controlled challenge trials of participants using 2 CACFs. OBJECTIVE: To compare and standardize 2 CACFs located in Kingston, Ontario, Canada, and San Antonio, Texas, by examining participant-reported symptom severity during qualifying and treatment visits and evaluating response to treatment, while using the same allergen. METHODS: At 2 different CACFs, participants were enrolled in a double-blind, placebo-controlled, crossover intervention trial with cetirizine 10 mg. Different distribution devices delivered common short ragweed pollen via laminar air flow and maintained an airborne concentration of 3500 ± 700 grains/m3 in both facilities. A 1-hour "sham" run with no pollen release preceded a priming exposure of 3 hours and was followed 3 days later by a qualifying/treatment 5-hour exposure. At least 14 days later, another priming exposure was followed by the crossover exposure and treatment. RESULTS: Forty-eight and 43 subjects completed the study at Kingston and San Antonio, respectively. Demographics were similar. Fewer than 10% exhibited symptoms with sham exposure. No significant differences were found between the 2 facilities in maximal total rhinoconjunctivitis symptom score, total nasal symptom score, and total ocular symptom score, nor in areas under the curve. In both facilities, no significant effects of cetirizine 10 mg over placebo were detected. CONCLUSION: The results were equivalent, demonstrating that the 2 CACFs can be used together in dual-center clinical trials and show the possibility of multicenter trials involving multiple CACFs.

Environmental exposure chambers in allergen immunotherapy trials: Current status and clinical validation needs.

As required by the European Medicines Agency and the US Food and Drug Administration for pivotal trials involving allergen immunotherapy (AIT) products, clinical efficacy assessment is currently based on double-blind, placebo-controlled field studies with natural allergen exposure during the allergen season. However, this study design is associated with several drawbacks, such as the high variability of allergen exposure in different trial sites or seasons and the presence of confounding environmental factors. On the contrary, environmental exposure chambers (EECs) aim to operate with a stable and reproducible allergen exposure under highly standardized environmental conditions. Technical validation parameters for different EECs worldwide have been published by several groups. However, full clinical validation of EEC study outcomes is required for their classification as an appropriate alternative to natural allergen exposure for AIT product efficacy assessment. Some clinical validation parameters have already been addressed for EEC units. The reliability of provoked symptoms in repeated EEC sessions is high, but the predictive power of EEC settings for the clinical response on natural exposure and the impact of seasonal priming on test results still have to be validated systematically, as does the inter-EEC variability. Thus the authors recommend a continued in-depth validation of EECs to exploit the potential of this technology for future AIT product development.

The Air Pollution Exposure Laboratory (APEL) for controlled human exposure to diesel exhaust and other inhalants: characterization and comparison to existing facilities.

OBJECTIVE: The Air Pollution Exposure Laboratory (APEL) was designed for the controlled inhalation of human subjects to aged and diluted diesel exhaust (DE) to mimic "real-world" occupational and environmental conditions. METHODS: An EPA Tier 3-compliant, 6.0 kW diesel generator is operated under discrete cyclic loads to simulate diesel on-road emissions. The engine accepts standard ultra-low sulfur diesel or a variety of alternative fuels (such as biodiesel) via a partitioned tank. A portion of raw exhaust is drawn into the primary dilution system and is diluted 9:1 with compressed air at standard temperature (20°C) and humidity (40%) levels. The exhaust is further diluted approximately 25:1 by high efficiency particulate air (HEPA)-filtered air (FA) and then aged for 4 min before entering the 4 × 6 × 7-foot exposure booth. An optional HEPA filter path immediately proximal to the booth can generate a particle-reduced (gas-enriched) exposure. In-booth particulate is read by a nephelometer to provide an instantaneous light scattering coefficient for closed-loop system control. A Scanning Mobility Particle Sizer and multi-stage impactor measures particle size distribution. Filter sampling allows determination of sessional average concentrations of size-fractionated and unfractionated particulate oxidative potential, elemental carbon, organic carbon and trace elements. RESULTS: Approximately 300 µg/m(3) PM(2.5) is routinely achievable at APEL and is well characterized in terms of oxidative potential and elemental components. CONCLUSION: APEL efficiently creates fresh DE, appropriately aged and diluted for human experimentation at safe yet realistic concentrations. Description of exposure characteristics allows comparison to other international efforts to deepen the current evidence base regarding the health effects of DE.

The pathobiology of blast injuries and blast-induced neurotrauma as identified using a new experimental model of injury in mice.

Current experimental models of blast injuries used to study blast-induced neurotrauma (BINT) vary widely, which makes the comparison of the experimental results extremely challenging. Most of the blast injury models replicate the ideal Friedländer type of blast wave, without the capability to generate blast signatures with multiple shock fronts and refraction waves as seen in real-life conditions; this significantly reduces their clinical and military relevance. Here, we describe the pathophysiological consequences of graded blast injuries and BINT generated by a newly developed, highly controlled, and reproducible model using a modular, multi-chamber shock tube capable of tailoring pressure wave signatures and reproducing complex shock wave signatures seen in theater. While functional deficits due to blast exposure represent the principal health problem for today's warfighters, the majority of available blast models induces tissue destruction rather than mimic functional deficits. Thus, the main goal of our model is to reliably reproduce long-term neurological impairments caused by blast. Physiological parameters, functional (motor, cognitive, and behavioral) outcomes, and underlying molecular mechanisms involved in inflammation measured in the brain over the 30 day post-blast period showed this model is capable of reproducing major neurological changes of clinical BINT.

Evaluation of precision and accuracy of the Borgwaldt RM20S(®) smoking machine designed for in vitro exposure.

The Borgwaldt RM20S(®) smoking machine enables the generation, dilution, and transfer of fresh cigarette smoke to cell exposure chambers, for in vitro analyses. We present a study confirming the precision (repeatability r, reproducibility R) and accuracy of smoke dose generated by the Borgwaldt RM20S(®) system and delivery to exposure chambers. Due to the aerosol nature of cigarette smoke, the repeatability of the dilution of the vapor phase in air was assessed by quantifying two reference standard gases: methane (CH(4), r between 29.0 and 37.0 and RSD between 2.2% and 4.5%) and carbon monoxide (CO, r between 166.8 and 235.8 and RSD between 0.7% and 3.7%). The accuracy of dilution (percent error) for CH(4) and CO was between 6.4% and 19.5% and between 5.8% and 6.4%, respectively, over a 10-1000-fold dilution range. To corroborate our findings, a small inter-laboratory study was carried out for CH(4) measurements. The combined dilution repeatability had an r between 21.3 and 46.4, R between 52.9 and 88.4, RSD between 6.3% and 17.3%, and error between 4.3% and 13.1%. Based on the particulate component of cigarette smoke (3R4F), the repeatability (RSD = 12%) of the undiluted smoke generated by the Borgwaldt RM20S(®) was assessed by quantifying solanesol using high-performance liquid chromatography with ultraviolet detection (HPLC/UV). Finally, the repeatability (r between 0.98 and 4.53 and RSD between 8.8% and 12%) of the dilution of generated smoke particulate phase was assessed by quantifying solanesol following various dilutions of cigarette smoke. The findings in this study suggest the Borgwaldt RM20S(®) smoking machine is a reliable tool to generate and deliver repeatable and reproducible doses of whole smoke to in vitro cultures.

A controlled inhalation diesel exhaust exposure facility with dynamic feedback control of PM concentration.

A facility has been assembled that provides a controlled inhalation exposure to freshly diluted and mixed diesel exhaust using a diesel engine under load and a two-stage exhaust dilution system with dynamic feedback control. The concentrations of particulate matter less than 2.5 microm in diameter (PM(2.5)), particulate carbon, and gaseous pollutants including carbon monoxide and oxides of nitrogen (NOx) have been characterized and the exposure conditions have been found to be both stable and reproducible. Control of the PM(2.5) concentration at intended levels relies on the relatively linear relationship between particle light scattering and exhaust particle mass concentration. While the exposure system does not entirely replicate diesel exhaust conditions in the atmosphere due to the relatively low ratio of nitrogen dioxide to total NOx, the fine particulate matter size distributions are quite similar to those of aged diesel exhaust. The facility enables study of the relationship between diesel exhaust and cardiovascular and respiratory health effects in human and animal models.

Delayed hyperbaric oxygenation is more effective than early prolonged normobaric hyperoxia in experimental focal cerebral ischemia.

Hyperbaric (HBO) and normobaric (NBO) oxygen therapy have been shown to be neuroprotective in focal cerebral ischemia. In previous comparative studies, NBO appeared to be less effective than HBO. However, the experimental protocols did not account for important advantages of NBO in the clinical setting such as earlier initiation and prolonged administration. Therefore, we compared the effects of early prolonged NBO to delayed HBO on infarct size and functional outcome. We also examined whether combining NBO and HBO is of additional benefit. Wistar rats underwent filament-induced middle cerebral artery occlusion (MCAO) for 150 min. Animals breathed either air, 100% O(2) at ambient pressure (NBO; initiated 30 min after MCAO) 100% O(2) at 3 atm absolute (HBO; initiated 90 min after MCAO), or a sequence of NBO and HBO. Infarct volumes and neurological outcome (Garcia score) were examined 7d after MCAO. HBO (174+/-65 mm(3)) significantly reduced mean infarct volume by 31% compared to air (251+/-59 mm(3)) and by 23% compared to NBO treated animals (225+/-63 mm(3)). In contrast, NBO failed to decrease infarct volume significantly. Treatment with NBO+HBO (185+/-101 mm(3)) added no additional benefit to HBO alone. Neurological deficit was significantly smaller in HBO treated animals (Garcia score: 13.3+/-1.2) than in animals treated with air (12.1+/-1.4), but did not differ significantly from NBO (12.4+/-0.9) and NBO+HBO (12.8+/-1.1). In conclusion, HBO is a more effective therapy than NBO in transient experimental ischemia even when accounting for delayed treatment-onset of HBO. The combination of NBO and HBO results in no additional benefit.

Methods for building an olfactometer with known concentration outcomes.

We provide detailed instructions and part selections for construction of a five-channel air dilution olfactometer capable of generating neat odorants and binary mixtures at a range of known concentrations. At the heart of the olfactometer is an odorant canister that is (1) cheap and readily available, (2) safe and durable, (3) has minimal odor adherence, (4) is easily incorporated into any olfactometer, and critically (5) produces a highly consistent stimulus. By flowing a given carrier gas at a given flowrate through a given odorant in this canister, the same end-vapor is achieved. Flow/concentration outcomes are provided for several odorants routinely used in olfactometry. This tool will enable researchers to generate known concentrations without expensive analytical machinery.

Single-pass environmental chamber for quantifying human responses to airborne chemicals.

Despite increasing interest in the short-term effects of airborne environmental contaminants, experimental findings are generated at a very slow pace. This is due in part to the expense and complexity of most environmental chambers, which are needed for quantifying effects of wholebody exposures. We lessened this obstacle by designing, constructing, and testing a single-pass, 10-m3 stainless-steel chamber. Compressed air is purified before being sent to an air dilution olfactometer, which supplies 1000 L (1 m3) per minute (referenced to STP) while maintaining 40% relative humidity (RH) and 22.6 degrees C. Precise control of all stimulus parameters is greatly simplified since air is not recirculated. Vapor-phase odorant concentrations are achieved by varying the proportion of total airflow passing through one or more saturators, and are verified in real time by an infrared (IR) spectrometer. An adjoining 5-m3 anteroom is used for introducing known intensities of more chemically complex vapor and/or particulate stimuli into the chamber. Prior to the point that air is exhausted from the chamber, all components are made of stainless steel, Teflon, or glass. A LabView program contains feedback loops that achieve document chamber conditions and document performance. Additional instrumentation and computer systems provide for the automated collection of perceptual, respiratory, eye blink, heart rate, blood pressure, psychological state, and cognitive data. These endpoints are now being recorded, using this facility, in response to ranges of concentrations of propionic acid and environmental tobacco smoke.

Enfermería y oxigenoterapia hiperbárica / Nursing and hyperbaric oxygen therapy

Introducción: La Oxigenoterapia Hiperbárica (OHB) consiste en el tratamiento de enfermedades en cámaras hiperbáricas (CH), utilizando Oxígeno al 100 por ciento y a presión superior a la atmosférica. Las técnicas de enfermería no difieren de las realizadas a presión ambiente, aunque debe tenerse en cuenta las diferencias provocadas por los cambios de presión. Objetivos: Conocer las características específicas de las técnicas de Enfermería en el medio hiperbárico. Conclusiones: Se producen efectos fisiológicos. Dependen del aumento de la presión ambiental, y del aumento de la presión parcial del oxígeno. Es necesario conocer las indicaciones, contraindicaciones y efectos secundarios de la OHB. Sondas y catéteres se utilizan igual que en ambiente normobárico, aunque el llenado de anclajes se realiza con líquidos. Se utilizan respiradores adaptados o los habituales con posibilidad de variación de la ventilación. Al realizar gasometrías y otras pruebas en una CH, la muestra puede experimentar un accidente disbárico. Los aparatos utilizados para vigilar constantes no están preparados para funcionar en una CH, se resuelve instalando conectores eléctricos transmurales. La presión ejerce efectos mecánicos sobre los envases, los equipos de perfusión no deben tener burbujas. Los recipientes de medicamentos deben abrirse antes de introducirlos en la CH, o precargarse en el exterior. La administración de medicamentos por vía intramuscular o subcutánea está contraindicada. El personal sanitario debe conocer los factores de riesgo en la OHB y las medidas higiénicas para el control de infecciones nosocomiales (AU)

[Technology of hyperbaric chambers]. / Kammertechnik.

Technical requirements for hyperbaric chambers are subject to permanent change. Medical gas supplies, the chamber hulls, control systems, medical equipment as well as the security check-up modalities have been constantly adapted according to the most recent technical developments. Moreover, different subtypes of hyperbaric chambers such as treatment facilities, chambers used for training purposes or facilities set up for primary experimental use require specific technical outfit. Keeping in mind some recent tragic accidents in hyperbaric facilities, chamber security is of foremost importance. Alarm- as well as technical monitoring systems, fire-fighting equipment, deluge systems and pressure locks are absolute requirements for any hyperbaric chamber. In chambers used for therapeutic purposes the possibility of invasive and noninvasive patient monitoring as well as hygienic standards have to be ensured.

The construction and validation of a high containment nose-only rodent inhalation facility.

A new nose-only inhalation facility for rodents has been designed and built for operation within a high containment glove box facility. All operations using the equipment, whether concerned with aerosol generation or animal handling and exposure are conducted under high containment with total operator protection. The facility has been used to investigate known carcinogenic fibres such as the amphiboles. It has been designed to be resistant to most chemicals, under the conditions of an experiment, and can be used with radioactive material within the limitations which would be imposed for radiological protection. This paper describes the construction and validation of the equipment using titanium dioxide.

A dual-respiration chamber system with automated calibration.

This study characterizes respiration chambers with fully automated calibration. The system consists of two 14-m3 pull-type chambers. Care was taken to provide a friendly environment for the subjects, with the possibility of social contact during the experiment. Gas analysis was automated to correct for analyzer drift and barometric pressure variations and to provide ease of use. Methods used for checking the system's performance are described. The gas-analysis repeatability was within 0.002%. Results of alcohol combustion (50-350 ml/min CO2) show an accuracy of 0.5 +/- 2.0 (SD) % for O2 consumption and -0.3 +/- 1.6% for CO2 production for 2- to 24-h experiments. It is concluded that response time is not the main factor with respect to the smallest practical measurement interval (duration); volume, mixing, gas-analysis accuracy, and levels of O2 consumption and CO2 production are at least equally important. The smallest practical interval was 15-25 min, as also found with most chamber systems described in the literature. We chose to standardize 0.5 h as the minimum measurement interval.