title: Sensitized central controller of ventilation in rats with chronic heart failure contributes to hyperpnea little at rest but more during exercise.
abstract: BACKGROUND
  To understand the pathophysiologic basis of exercise hyperpnea in chronic heart failure (CHF), we have developed an experimental method quantitatively characterizing ventilatory regulation system in rats. An equilibrium diagram illustrates the characteristics of two subsystems, i.e., the central controller (arterial CO2 tension [Pa(CO2)] to minute ventilation [V(E)] relationship) and peripheral plant (V(E) to Pa(CO2) relationship). In this study, we compared these between normal and CHF rats at rest.
  
  
  METHODS
  In anesthetized 6 postinfarction CHF rats and 6 normal rats, we induced hypercapnia by changing inspiratory CO2 fraction and measured the steady-state Pa(CO2) to V(E) relation. We altered V(E) by varying the level of artificial ventilation and measured the V(E) to Pa(CO2) relation.
  
  
  RESULTS
  Central controller gain S was significantly lager in CHF rats, confirming clinical observation. The V(E) at rest (operating point) in CHF was 24% larger; central hypersensitivity, however, contributed little (6%) to this increase.
  
  
  CONCLUSIONS
  Central hypersensitivity alone would not explain hyperpnea at rest in CHF rats. Considering the right and upward shift of V(E) to Pa(CO2) relation, central hypersensitivity contributes more to hyperpnea during exercise. The potential difference between normal and CHF rats in exercise-induced changes in controller and plant should be examined to fully understand the mechanism of exercise hyperpnea and to develop a method to attenuate this.
authors.affiliation: National Cardiovascular Center Res. Inst., Suita, Osaka, Japan.
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Miyamoto
authors.forename: Masashi
authors.initials: M
authors.lastname: Inagaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takaki
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kamiya
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Shishido
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugimachi
authors.forename: Kenji
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D000818:Animals; D001698:Biomedical Engineering / Q000379:methods; D004867:Equipment Design; D015444:Exercise; D005080:Exercise Test; D005246:Feedback; D006333:Heart Failure / Q000175:diagnosis* / Q000628:therapy; D006801:Humans; D006985:Hyperventilation; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D051381:Rats; D012119:Respiration; D012146:Rest