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.

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.

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.