Scientists at Health Canada

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Scientists at Health Canada’s Bureau of Chemical Hazards have developed a nose-only inhalation manifold for concurrent exposure to different doses of a test compound.

The manifold comprises 8 exposure ports which make use of standard CH Technologies animal tubes. Each inhalation port is supplied by two distinct inlets for the introduction, above and below the animal’s head, of independently regulated substances. A single centrally located outlet duct allows for the removal of exhalate and spent test atmosphere. The total internal volume of the manifold, from inlet to exhaust outlet, is approximately 100 cm 3 ; the individual port breathing zone volume is less than 15 cm 3 . At an air flow of 10 li/min, air velocity in the breathing zone was estimated at below 60 cm/sec (2 km/h).
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The manifold is small in size, less than 6" in diameter, and can be operated in a standard size fumehood. Its lightweight and sturdy construction allows for easy transportation. According to the application, it can be machined from various types of plastics, allowing for exposures to bioaerosols and subsequent autoclaving, as well as exposures to non-biological aerosols, reactive gases and vapours. Rare substances or products available in limited amounts can be introduced by natural means in the respiratory tract under minimal protocols.
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The technology provides the capability of modifying the ratio of a test compound to the dilution air at individual inhalation ports, such that a gradient of doses can be created. Thus a dose-response can be performed on a single system with a single exposure.
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The independent inlets can be used to bring into contact, immediately before inhalation, substances that would otherwise be incompatible or unstable if mixed upstream prior to delivery to the inhalation device.
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Furthermore, while a continuous flow of conditioned air is fed through one inlet, the second inlet can be used to introduce, within the breathing zone, pulses of a substance at critical points of the breathing cycle. New patterns of exposure are made possible, such as creating complex sequences of test atmospheres.
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