A fully-automated environmental chamber for examination of long-term effects of intermittent hypoxia on medium-size animals

We describe the design and construction of a fully-automated environmental chamber for the simultaneous exposure of up to four medium- size laboratory animals to long-term intermittent hypoxia. The air-sealed automated environmental chamber consists of a box equipped with a ventilation fan and three electrically-activated solenoid valves. Our system was used to expose four rabbits to 12 h of repetitive episodes of hypoxia (environmental O₂ concentration 12-13%) lasting 45 min followed by breathing room air for 15 min. During environmental hypoxia, the mean arterial Pa(O2) and Pa(CO2) were 41±3.0 and 24±0.7 mmHg (mean±SEM), respectively. In this system, opening and closing of the solenoid valves is fully computerized to allow different settings of the duration and severity of hypoxia. The chamber is safe and fully automated and cost-effective for studying the effects of long- term intermittent hypoxemia in medium-size animals.