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Updated: Aug 19, 2026
Quantitative and Temporal Control of Oxygen Microenvironment at the Single Islet Level
Published on: November 17, 2013
FIx controller: an instrument to automatically adjust inspired oxygen fraction using feedback control from a pulse
D B Raemer1, X B Ji, G P Topulos
1Department of Anesthesia, Massachusetts General Hospital, Boston 02114, USA.
Objective:
To develop an instrument to help prevent pulmonary O2 toxicity, a syndrome that manifests itself in adult intensive care patients.
Methods:
We designed, built, and tested a device that controls FIO2 exposure using oxygen saturation measured with a pulse oximeter (SpO2) in a negative feedback control system. A target SpO2 is designated by the clinician and the system adjusts the FIO2 from a mechanical ventilator so as to minimize the difference between the measured SpO2 and the target. Important elements of the system include a conservative artifact rejection algorithm, a gainscheduled sampled-data proportional-integral-derivative (PID) controller, and a safety system to prevent inspired mixtures with undesirably low FIO2 due to device failure.
Results:
The control system was tuned in a series of animal experiments. Acceptable clinical response of the system was obtained using a gain-scheduled controller algorithm whereby the gain of the proportional term of a PID controller was adjusted based on the error signal and measured minute ventilation. Also, the artifact rejection algorithm and safety systems were successfully tested using simulation.
Conclusions:
Testing the effectiveness of this instrument will require comparison with manual control of FIO2 in an appropriately designed trial.
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