Bubbler System Design for Regulating Media Oxygen Levels in an Open Testing Environment

Many biological processes are affected by hypoxia. For example, hypoxia has been suggested to be a driver of tendon degeneration especially in conjunction with mechanical stimulation. To better study the effects of both factors on tendon degeneration, tendon explant studies can be useful. However, such explant models are complicated by the need of an incubator to control the oxygen levels, limiting the types of experiments that can be done. In this paper, we describe the design of a bubbler system to alter oxygen levels for experiments conducted in an open environment. The basin volume, basin surface area-to-volume ratio, total system volume, and pump flow rate were optimized to obtain the lowest possible oxygen level. Oxygen levels were most sensitive to the total system volume and pump flow rates with higher values for both parameters leading to lower oxygen readings. This bubbler system was able to reach and maintain hypoxic levels sufficient to conduct future tendon explant experiments to understand the mechanism driving tendinopathy.