3258155__Cheyne_Stokes_Respiration_

3258155__Cheyne_Stokes_Respiration_ - Cheyne-Stokes...

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Cheyne-Stokes Respiration 1 Running head: CHEYNE-STOKES RESPIRATION Cheyne-Stokes Respiration [Author’s Name] [Institution’s Name]
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Cheyne-Stokes Respiration 2 Cheyne-Stokes Respiration Cheyne-Stokes respiration (also known as periodic breathing) is a regularly recurring waxing and waning of tidal volume due to oscillations in central respiratory drive. It is a sign of respiratory control system instability. Under normal conditions, the respiratory and circulatory systems work in concert to deliver O 2 according to metabolic demands, and to excrete CO 2 to maintain acid-base homeostasis. As a result, arterial PO 2 (PaO 2 ), PCO 2 (PaCO 2 ) and pH are held within narrow limits. To accomplish this precise matching of ventilation with metabolic demands, respiration is regulated by a rapidly responsive negative feedback system consisting of a central controller and a peripheral plant. (D.D. Sin, A.G. Logan, F.S. Fitzgerald, P.P. Liu, T.D. Bradley, 2002) The central controller is comprised of the peripheral and central chemoreceptors, which detect alterations in PaO 2 , PaCO 2 , and pH, and the brainstem respiratory motor neurons, which generate a central respiratory drive proportional to the degree of chemoreceptor stimulation. The plant, consisting of the respiratory muscles, rib cage, and lungs, alters ventilation in response to changes in central respiratory drive. These alterations in ventilation in turn provoke changes in arterial blood gas tensions. Several factors stabilize this respiratory control system. First, alterations in arterial blood gas tensions in the lung
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Cheyne-Stokes Respiration 3 are fed back rapidly to the chemoreceptors, owing to a short lung to chemoreceptor circulation time. This damps fluctuations in ventilation, just as a rapidly responsive thermostat will damp fluctuations in room temperature. Second, normal chemoreceptor gain is just sufficient to rapidly correct deviations in PaCO 2 and PaO 2 from their set points, but not to overcorrect. (P. Solin, P. Bergin, M. Richardson, D.M. Kaye, E.H. Walters, M.T. Naughton, 1999) Together, these two factors prevent overshooting of ventilation in response to small increases in chemostimulation. Third, normally the set point for a ventilatory response to CO 2 is well above the apneic threshold. Because PaCO 2 is normally the primary stimulus to breathe, maintaining PaCO 2 well above this threshold facilitates stability of ventilation and arterial blood gas tensions. In general, Cheyne-Stokes respiration is a manifestation of underdamping of the respiratory control system with recurrent over- and undershooting of ventilation. Factors that predispose to respiratory control system instability include prolonged lung to chemoreceptor circulatory delay, increased chemoreceptor gain and arousals from sleep that trigger hyperventilation, and a low PaCO 2 close to the apneic threshold. The critical factor causing very low frequency fluctuations in ventilation in most forms of Cheyne-Stokes respiration is an increased amplitude of oscillations in PaCO 2 . (G. Lorenzi-Filho, E.R. Azevedo, J.D.
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This note was uploaded on 11/29/2010 for the course MANAGEMENT EM-14793 taught by Professor Lindaryaan during the Spring '08 term at Windsor.

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3258155__Cheyne_Stokes_Respiration_ - Cheyne-Stokes...

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