Engineering of a Low-Cost Open-Source Hypoxia Chamber for Rodent Models of Obstructive Sleep Apnea

Introduction: Reproducible intermittent hypoxia (IH) exposure is essential for investigating the pathophysiology of obstructive sleep apnea (OSA) and its cardiopulmonary consequences. However, commercially available IH systems are often prohibitively expensive, technically restrictive, and reliant on proprietary architectures. This study aimed to develop and validate a low-cost, open-source IH chamber capable of automated oxygen cycling, real-time environmental monitoring, and multi-animal capacity for translational sleep-apnea research. Methods An open-source IH system was constructed using a Raspberry Pi–based control unit, solenoid-valve gas switching, and custom Python software for automated hypoxia–normoxia cycling and data logging. Chamber-level oxygen concentration (FiO₂) was continuously monitored using a galvanic O₂ sensor, alongside temperature and humidity sensors; a carbon monoxide sensor was included solely as a qualitative safety indicator. Two validated IH regimens were tested: moderate IH (10–12% O₂; 20–30 cycles·h⁻¹) and severe IH (5–7% O₂; 30–60 cycles·h⁻¹). Precision, reproducibility, and environmental stability were assessed using coefficient of variation analysis and one-way ANOVA (p < 0.05). Results The chamber reliably achieved rapid and reproducible FiO₂ oscillations between normoxia (21%) and target hypoxic nadirs (10–12% or 5–7%) within 20–25 s, with cycle-to-cycle variability < 5%. Environmental conditions remained stable during prolonged exposures (22–24°C; 55–80% relative humidity), and effective chamber ventilation prevented abnormal gas accumulation. The total system cost was approximately SAR 2,990 (≈ US$800), representing < 5% of the cost of a commercial OxyCycler while delivering comparable desaturation dynamics. Conclusion This validated, low-cost, open-source IH chamber provides a scalable and reproducible platform for modeling OSA-related intermittent hypoxia in rodents. Its affordability, transparency, and multi-animal capacity support broader adoption and standardization of IH research across laboratories worldwide.