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. Author manuscript; available in PMC: 2015 Sep 15.
Published in final edited form as: Respir Physiol Neurobiol. 2014 Jul 17;201:84–92. doi: 10.1016/j.resp.2014.07.002

Fig. 4.

Fig. 4

Adaptive estimation of controller, plant, and loop gain with and without the SQICO2. Starting around 400 s, PAV was progressively increased (panel A). Our derived breath-by-breath index of PETCO2 quality (SQICO2) is shown in panel B. Adaptive estimation of the controller, plant, and loop gain of the system before and after including the SQICO2 are presented in panels C and D, respectively (the confidence bounds associated with individual estimates are omitted for clarity). Inclusion of the SQICO2 in panel D resulted in a better estimate of the plant gain and the loop gain around the 430 s mark (note that the controller gain drops to zero in panel C due to artifactual measurements of end-tidal CO2 around the 430 s time mark). Note how the adaptive algorithm detected a progressively larger value of the controller gain, which resulted in progressive increase in system loop gain. This example lends strong credibility to the value of incorporating a signal quality index into the parameter estimation algorithm.