Limitations of the open loop gain concept in studies of respiratory control

1990 ◽  
Vol 18 (5) ◽  
pp. 533-547
Author(s):  
Frederick M. Bennett
Keyword(s):  
Respiratory Control ◽  
Open Loop ◽  
Loop Gain

Analog computer simulation of abnormal periodic breathing

SIMULATION ◽  
1966 ◽  
Vol 6 (4) ◽  
pp. 266-271
Author(s):  
Howard T. Milhorn ◽  
Arthur C. Guyton
Keyword(s):  
Control System ◽  
Respiratory System ◽  
Respiratory Control ◽  
Periodic Breathing ◽  
Analog Computer ◽  
Open Loop ◽  
Feedback Control System ◽  
Loop Gain ◽  
Computer Study ◽  
Human Respiration

The human respiratory system is compared to a techno logical feedback control system. Oscillation of the tech nological system is discussed and related to abnormal oscillation of human respiration (Cheyne-Stokes breath ing). A mathematical model of the human respiratory control system, utilizing CO 2 control of respiration only, is derived and programmed on an analog computer. The resulting computer study has shown that, as in the tech nological system, an increase of open-loop gain and/or delay time around the open loop can cause the respiratory system to become unstable and oscillate in an abnormal manner.

scholarly journals P019 Obstructive sleep apnoea endotypes in people with multiple sclerosis

2021 ◽  
Vol 2 (Supplement_1) ◽  
pp. A27-A28
Author(s):  
S Carter ◽  
H Hensen ◽  
A Krishnan ◽  
A Chiang ◽  
J Carberry ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Obstructive Sleep Apnoea ◽  
Group Analysis ◽  
Respiratory Control ◽  
Upper Airway ◽  
Sleep Apnoea ◽  
Loop Gain ◽  
Male Predominance ◽  
Arousal Threshold ◽  
Obstructive Sleep

Abstract Purpose Obstructive sleep apnoea (OSA) is common in people with multiple sclerosis (MS) despite a lack of typical risk factors for OSA in people with MS such as obesity and male predominance. Therefore, underlying factors other than sex and obesity may be particularly important in the pathogenesis of OSA in people with MS. Thus, the primary aim of this study was to determine the relative contributions of OSA endotypes in people with MS and compare this to matched controls with OSA only. Methods Eleven people with MS and OSA (MS-OSA group) (apnoea-hypopnoea index [AHI]>5events/h) and eleven controls matched for OSA severity, age and sex without MS (OSA group) were studied. Participants underwent a detailed overnight polysomnography with an epiglottic pressure catheter and genioglossus intramuscular electrodes to allow for quantification of pathophysiological contributors to OSA. This included the respiratory arousal threshold, genioglossus muscle responsiveness, respiratory loop gain and upper airway collapsibility. Results Measures of the four primary OSA endotypes were not different between the MS-OSA and OSA groups (e.g. NREM respiratory arousal threshold -27±15 vs. -23±8 cmH2O respectively, p=0.24). Within group analysis indicated higher loop gain in non-obese MS-OSA participants compared to obese MS-OSA participants (0.53±0.11 vs. 0.37±0.11, p=0.04). Conclusions Overall, OSA endotypes are similar between MS-OSA participants and matched OSA controls. However, within the MS-OSA group, non-obese participants have higher loop gain (unstable respiratory control) compared to obese participants. Thus, unstable respiratory control may play an important role in OSA pathogenesis in many people with MS.

Development of a 300°C capable SiC based operational amplifier

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000305-000309 ◽  
Author(s):  
Vinayak Tilak ◽  
Cheng-Po Chen ◽  
Peter Losee ◽  
Emad Andarawis ◽  
Zachary Stum
Keyword(s):  
Silicon Carbide ◽  
High Temperature ◽  
Operational Amplifier ◽  
Room Temperature ◽  
Open Loop ◽  
Common Source ◽  
Loop Gain ◽  
Long Term Stability ◽  
Silicon Silicon

Silicon carbide based ICs have the potential to operate at temperatures exceeding that of conventional semiconductors such as silicon. Silicon carbide (SiC) based MOSFETs and ICs were fabricated and measured at room temperature and 300°C. A common source amplifier was fabricated and tested at room temperature and high temperature. The gain at room temperature and high temperature was 7.6 and 6.8 respectively. A SiC MOSFET based operational amplifier was also fabricated and tested at room temperature and 300°C. The small signal open loop gain at 1kHz was 60 dB at room temperature and 57 dB at 300°C. Long term stability testing at 300°C of the MOSFET and common source amplifiers showed very little drift.

Possible mechanisms of periodic breathing during sleep

1988 ◽  
Vol 64 (3) ◽  
pp. 1000-1008 ◽  
Author(s):  
K. R. Chapman ◽  
E. N. Bruce ◽  
B. Gothe ◽  
N. S. Cherniack
Keyword(s):  
Control System ◽  
Respiratory Control ◽  
Periodic Breathing ◽  
Nrem Sleep ◽  
Loop Gain ◽  
Hypoxic Conditions ◽  
Spontaneous Oscillations ◽  
End Tidal ◽  
Arterial O2 Saturation ◽  
Stage 1

To determine the effect of respiratory control system loop gain on periodic breathing during sleep, 10 volunteers were studied during stage 1-2 non-rapid-eye-movement (NREM) sleep while breathing room air (room air control), while hypoxic (hypoxia control), and while wearing a tight-fitting mask that augmented control system gain by mechanically increasing the effect of ventilation on arterial O2 saturation (SaO2) (hypoxia increased gain). Ventilatory responses to progressive hypoxia at two steady-state end-tidal PCO2 levels and to progressive hypercapnia at two levels of oxygenation were measured during wakefulness as indexes of controller gain. Under increased gain conditions, five male subjects developed periodic breathing with recurrent cycles of hyperventilation and apnea; the remaining subjects had nonperiodic patterns of hyperventilation. Periodic breathers had greater ventilatory response slopes to hypercapnia under either hyperoxic or hypoxic conditions than nonperiodic breathers (2.98 ± 0.72 vs. 1.50 ± 0.39 l.min-1.Torr-1; 4.39 ± 2.05 vs. 1.72 ± 0.86 l.min-1.Torr-1; for both, P less than 0.04) and greater ventilatory responsiveness to hypoxia at a PCO2 of 46.5 Torr (2.07 ± 0.91 vs. 0.87 ± 0.38 l.min-1.% fall in SaO2(-1); P less than 0.04). To assess whether spontaneous oscillations in ventilation contributed to periodic breathing, power spectrum analysis was used to detect significant cyclic patterns in ventilation during NREM sleep. Oscillations occurred more frequently in periodic breathers, and hypercapnic responses were higher in subjects with oscillations than those without. The results suggest that spontaneous oscillations in ventilation are common during sleep and can be converted to periodic breathing with apnea when loop gain is increased.

Stability Determination for Linear Control Systems with Distributed Lags

1972 ◽  
Vol 5 (6) ◽  
pp. 238-241 ◽  
Author(s):  
F L N-Nagy ◽  
M N Al-Tikriti
Keyword(s):  
Control Systems ◽  
Open Loop ◽  
Linear Control ◽  
Linear Control Systems ◽  
Loop Gain ◽  
Variable Parameters ◽  
Distributed Lag ◽  
Distributed Lags ◽  
Loop Transfer Function ◽  
The Stability

The paper outlines a specially adapted stability criterion for linear control systems with distributed lags. The stability is studied with respect to two variable parameters, ie the loop-gain and the distributed lag. The criterion employs an easily constructed chart prepared beforehand and only requires the plotting of two curves derived from the open-loop transfer function. The stability of a simple control system is investigated to illustrate the scheme.

High-cut characteristics of the baroreflex neural arc preserve baroreflex gain against pulsatile pressure

2002 ◽  
Vol 282 (3) ◽  
pp. H1149-H1156 ◽  
Author(s):  
Toru Kawada ◽  
Can Zheng ◽  
Yusuke Yanagiya ◽  
Kazunori Uemura ◽  
Tadayoshi Miyamoto ◽  
...  
Keyword(s):  
Heart Rate ◽  
Transfer Function ◽  
Sympathetic Nerve Activity ◽  
Dynamic Range ◽  
Open Loop ◽  
Loop Gain ◽  
Frequency Range ◽  
Nerve Activity ◽  
Pulsatile Pressure ◽  
Rate Frequency

A transfer function from baroreceptor pressure input to sympathetic nerve activity (SNA) shows derivative characteristics in the frequency range below 0.8 Hz in rabbits. These derivative characteristics contribute to a quick and stable arterial pressure (AP) regulation. However, if the derivative characteristics hold up to heart rate frequency, the pulsatile pressure input will yield a markedly augmented SNA signal. Such a signal would saturate the baroreflex signal transduction, thereby disabling the baroreflex regulation of AP. We hypothesized that the transfer gain at heart rate frequency would be much smaller than that predicted from extrapolating the derivative characteristics. In anesthetized rabbits ( n = 6), we estimated the neural arc transfer function in the frequency range up to 10 Hz. The transfer gain was lost at a rate of −20 dB/decade when the input frequency exceeded 0.8 Hz. A numerical simulation indicated that the high-cut characteristics above 0.8 Hz were effective to attenuate the pulsatile signal and preserve the open-loop gain when the baroreflex dynamic range was finite.

Estimation of open-loop gain of canine arterial pressure control system by a new method

1981 ◽  
Vol 240 (6) ◽  
pp. H832-H836 ◽  
Author(s):  
H. Hosomi ◽  
K. Yokoyama
Keyword(s):  
Control System ◽  
Arterial Pressure ◽  
Pressure Change ◽  
Pressure Control ◽  
Systemic Arterial Pressure ◽  
Open Loop ◽  
Loop Gain ◽  
Reflex Gain ◽  
Pressure Control System ◽  
Arterial Pressure Control System

We developed a method to estimate an overall open-loop gain of the arterial pressure control system without surgically opening the reflex loop. Dogs anesthetized by intravenous injection of Nembutal (35 mg/kg body wt) were bled by 2 ml/kg body wt within 2-3 s through a catheter inserted into the abdominal aorta. Arterial pressure change after the quick hemorrhage was monitored via a catheter placed in the aortic arch for more than 2 min. The overall open-loop gain of the lumped arterial pressure control system was assessed as (delta API/delta APs)-1, where delta API is the immediate fall and delta APs the steady-state fall in mean arterial pressure obtained by a filter with a 2-s time constant. The advantage of this method is that the overall open-loop gain can be estimated under the closed-loop condition in which the baroreceptor reflexes operate naturally around the existing range of systemic arterial pressure. This enables one to study time-varying characteristics of the reflex gain. The disadvantage is that the substantial constituents of the lumped reflex system remain to be confirmed.

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