Optimized Open-Source Setting for Subjecting Rodents to Chronic Normobaric Hypoxia in Facilities with Minimal...

Very prevalent respiratory and cardiovascular diseases result in chronic hypoxia, promoting metabolic, kidney, heart, and other malignant diseases. Hypoxia research employs animal models based on chronically breathing hypoxic air (O₂ < 21%), usually by injecting N₂ into the animal's chamber. However, continuous high-flow N₂ supply is available only in limited facilities, reducing the capability for hypoxia research to be widely conducted. Here, we describe an optimized setting for subjecting rodents to chronic normobaric hypoxia by requiring minimal N₂ supply. The primary aim of this study was the technical development and optimization of a system for chronic normobaric hypoxia exposure rather than testing a specific biological hypothesis The setting is based on providing the O₂ consumed by the animals and eliminating the exhaled CO₂ and water vapor. O₂, CO₂, temperature, and humidity in the hypoxic chamber are controlled by an Arduino-based unit activating a pump that introduces room air to restore the metabolized O₂. Another pump continuously recirculates the chamber air through a Peltier-based dryer and CO₂-absorbing soda lime. To correct any deviation in the actual value of hypoxia within the chamber, the control unit allows the injection of N₂ into the chamber from a gas source. The setting performance was successfully tested in vivo when subjecting mice to 11%-O₂ chronic hypoxia. This device, requiring a low N₂ supply, may facilitate in vivo experimental research on hypoxia-related diseases.