title: Impact of baroreflex on venous return surface.
abstract: BACKGROUND
  Although Guyton's concept of venous return (VR) revolutionized circulatory physiology, the pulmonary circulation is invisible in its original framework. Since the pulmonary circulation is critical in left heart failure, we characterized the VR as a surface described by right (P(RA)) and left atrial (P(LA)) pressures and demonstrated that the VR surface was capable of representing mechanics of pulmonary as well as systemic circulation. However how baroreflex impacts the VR surface remains unknown.
  
  
  RESULTS
  In 8 dogs, we isolated the carotid sinuses and replaced both ventricles with pumps. We varied cardiac output, shifted blood distribution between the systemic and pulmonary circulation at carotid sinus pressures (CSP) of 100 or 140 mmHg. The coefficient of determination of the VR surface ranged 0.96-0.99 indicating how flat the surface is. Increasing CSP decreased maximum VR (233 ± 27 vs. 216 ± 33 ml/kg/min, p<0.05), whereas did not change the slopes of VR along P(RA) or P(LA) axes.
  
  
  CONCLUSIONS
  Baroreflex parallel shifts the VR surface, thereby stressed volume, without changing its slopes.
authors.affiliation: Kyushu University, Fukuoka 8128582, Japan. tsaka@cardiol.med.kyushu-u.ac.jp
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Murayama
authors.forename: Atsushi
authors.initials: A
authors.lastname: Tanaka
authors.forename: Kazuo
authors.initials: K
authors.lastname: Sakamoto
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Tobushi
authors.forename: Keita
authors.initials: K
authors.lastname: Saku
authors.forename: Kazuya
authors.initials: K
authors.lastname: Hosokawa
authors.forename: Ken
authors.initials: K
authors.lastname: Onitsuka
authors.forename: Takeo
authors.initials: T
authors.lastname: Fujino
authors.forename: Kenji
authors.initials: K
authors.lastname: Sunagawa
mesh_terms: D000818:Animals; D017704:Baroreflex; D004285:Dogs; D014680:Veins / Q000502:physiology*