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CrossTalk proposal: Elevated loop gain is a consequence of obstructive sleep apnoea
Author(s) -
Younes Magdy
Publication year - 2014
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2014.271833
Subject(s) - control theory (sociology) , overshoot (microwave communication) , feedback loop , perturbation (astronomy) , loop gain , crosstalk , respiration , rise time , respiratory system , closed loop , chemistry , mechanics , physics , medicine , computer science , anatomy , engineering , voltage , quantum mechanics , optics , telecommunications , control (management) , computer security , artificial intelligence , control engineering
Before addressing this question it is necessary to define loop gain (LG) in the context of obstructive sleep apnoea (OSA). In a closed loop system, such as the breathing system, a perturbation in the controlled loop component (the respiratory apparatus, or ‘plant’) elicits changes in the feedback (blood gas tensions) received by the controller (respiratory centres), which in turn effects a compensatory response in the plant. The initial response may partially correct the blood gas changes, with the residual changes being gradually corrected later. This is a stable response. However, the initial response may result in over-correction of the gas changes (‘overshoot’) such that they are better than what existed before the perturbation. The ventilatory apparatus is then inhibited through the same changes in blood gas tensions that resulted in the initial response, and a second hypopnoea results. If the second hypopnoea is less severe than the original one, the disturbance in gas tensions will also be less severe, eliciting a lesser response and a less severe hypopnoea results, and so on. Ultimately, the system stabilizes. If the overshoot results in such improvement in gas tensions that the second hypopnoea is more severe than the initial one, the cycle can perpetuate indefinitely. LG is the ratio of the initial response to the initial perturbation. A LG of <1.0 is