Loop Gain of Respiratory Control upon Reduced Activity of Carbonic Anhydrase or Na+/H+ Exchange



Considerations from control theory revealed that an elevated gain of the feedback loop may lead to instability of the respiratory system, e.g. during sleep [Longobardo et al.,1982; Honda et al., 1983; Khoo, 2000; Dempsey et al., 2004]. In respiratory medicine, the carbonic anhydrase (CA) inhibitor acetazolamide is known to reduce the incidence of apneas in mountain sickness [Swenson et al., 1991]or sleep disordered breathing [Tojima et al., 1988; Verbraecken et al., 1998]. Other clinical studies revealed that patients prone to sleep apnea showed an increased sodium/proton exchange activity in their lymphocytes [Tepel et al., 2000]. To predict possible protective effects of substances inhibiting either carbonic anhydrase activity or sodium/proton exchange, we evaluated steady state feedback loop characteristics of the respiratory control system from previous studies in anaesthetized rabbits [Kiwull-Schöne et al., 2001a,b]. Steady state loop gain (G) was assessed as ratio of the slope of the CO2 response (S) and that of the metabolic hyperbola (SL ) [Honda et al., 1983; Khoo, 2000] at the intersection of both curves, by which also the arterial set point PCO2 (PspCO2) is determined.


Obstructive Sleep Apnea Sleep Apnea Carbonic Anhydrase Central Sleep Apnea Carbonic Anhydrase Activity 
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© Springer 2006

Authors and Affiliations

    • 1
    • 2
    • 3
    • 1
  1. 1.Dept. of PhysiologyRuhr-UniversityBochumGermany
  2. 2.Dept. of AnesthesiologyLeiden UniversityThe Netherlands
  3. 3.Dept. of PhysiologyUniversity of Duisburg-EssenGermany

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