title: The impact of inspiratory pressure on stroke volume variation and the evaluation of indexing stroke volume variation to inspiratory pressure under various preload conditions in experimental animals.
abstract: OBJECTIVE
  Stroke volume variation (SVV) measures fluid responsiveness, enabling optimal fluid management under positive pressure ventilation. We aimed to investigate the effect of peak inspiratory pressure (PIP) on SVV under various preload conditions in experimental animals and to ascertain whether SVV indexed to PIP decreases the effect.
  
  
  METHODS
  Mild and moderate hemorrhage models were created in nine anesthetized, mechanically ventilated beagle dogs by sequentially removing 10 and then an additional 10 ml/kg of blood, respectively. In all the animals, PIP was incrementally increased by 4 cmH2O, from 5 to 21 cmH2O. SVV was measured by arterial pulse contour analysis. Stroke volume was derived using a thermodilution method, and central venous pressure and mean arterial pressure were also measured.
  
  
  RESULTS
  SVV increased according to PIP with significant correlation at baseline, with mild hemorrhage and moderate hemorrhage. PIP regression coefficients at baseline and in the mild and moderate hemorrhage models were 0.59, 0.86, and 1.4, respectively. Two-way repeated-measures analysis of variance showed that PIP and the degree of hemorrhage had a significant interaction effect on SVV (p = 0.0016). SVV indexed to PIP reflected the hemorrhage status regardless of PIP changes ≥9 cmH2O.
  
  
  CONCLUSIONS
  PIP is significantly correlated with SVV, even under hypovolemia, and the effect is enhanced with decreasing preload volumes. Compared with SVV, the indexed SVV was less susceptible to higher inspiratory pressures.
authors.affiliation: Department of Emergency and Critical Care Medicine, Wakayama Medical University, 811-1, Kimiidera, Wakayama, 641-8510, Japan, ukz411@gmail.com.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kawazoe
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Nakashima
authors.forename: Toshie
authors.initials: T
authors.lastname: Iseri
authors.forename: Chiaki
authors.initials: C
authors.lastname: Yonetani
authors.forename: Kentaro
authors.initials: K
authors.lastname: Ueda
authors.forename: Yuka
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Seiya
authors.initials: S
authors.lastname: Kato
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002496:Central Venous Pressure / Q000502:physiology*; D004285:Dogs; D006470:Hemorrhage / Q000503:physiopathology*; D020896:Hypovolemia / Q000378:metabolism; D011175:Positive-Pressure Respiration; D011312:Pressure; D013318:Stroke Volume / Q000502:physiology*