Oximetry feedback flow control simulation for oxygen therapy.
OBJECTIVE
For many with Chronic Obstructive Pulmonary Disease (COPD), arterial oxygen saturation while receiving Long-Term Oxygen Therapy (LTOT) falls below an acceptable threshold (SpO(2) < 90%) for extended periods during routine daily activities. Using a closed-loop controller, we have evaluated a simulated method to automatically regulate the oxygen flow-rate in response to the measured oxygen demand.


METHODS
The closed-loop control scheme was implemented in a computer simulation on Simulink. Feedback from a pulse oximeter was used to maintain a target SpO(2) of 91% by changing the oxygen flow-rate to the patient. The controller was evaluated using a model to approximate the patient's arterial oxygen saturation response, including hypoxic events from artificial disturbances as well as recorded patient oximetry data.


RESULTS
The simulated controller produced improvement in arterial oxygen saturation throughout a wide range of disturbance frequencies. It suppressed disturbances with periods greater than a couple of minutes by more than -10 dB. When evaluated with patient oximetry recordings, the controller on average reduced the time spent with arterial blood saturation below threshold by 76%. Given the same volume of oxygen, the closed-loop controller also produced a 63% improvement compared to fixed flow-rate LTOT.


CONCLUSIONS
The simulation findings indicate an optimized matching between oxygen supply and demand, maintaining SpO(2) above threshold to improve therapeutic efficacy compared to standard LTOT.
Iobbi
Mario G
MG
Department of Bioengineering, South Kensington Campus, Imperial College London, London, SW7 2AZ, UK.
Simonds
Anita K
AK
Dickinson
Robert J
RJ
D000465:Algorithms; D003198:Computer Simulation; D005246:Feedback; D006801:Humans; D008954:Models, Biological; D010092:Oximetry / Q000379:methods*; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood*; D010102:Oxygen Inhalation Therapy / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000175:diagnosis / Q000628:therapy*; D013813:Therapy, Computer-Assisted / Q000379:methods*
D010100:Oxygen