title: Cardiac power parameters during hypovolemia, induced by the lower body negative pressure technique, in healthy volunteers.
abstract: Changes in cardiac power parameters incorporate changes in both aortic flow and blood pressure. We hypothesized that dynamic and non-dynamic cardiac power parameters would track hypovolemia better than equivalent flow- and pressure parameters, both during spontaneous breathing and non-invasive positive pressure ventilation (NPPV).
  
  
  
  Fourteen healthy volunteers underwent lower body negative pressure (LBNP) of 0, -20, -40, -60 and -80 mmHg to simulate hypovolemia, both during spontaneous breathing and during NPPV. We recorded aortic flow using suprasternal ultrasound Doppler and blood pressure using Finometer, and calculated dynamic and non-dynamic parameters of cardiac power, flow and blood pressure. These were assessed on their association with LBNP-levels.
  
  
  
  Respiratory variation in peak aortic flow was the dynamic parameter most affected during spontaneous breathing increasing 103 % (p < 0.001) from baseline to LBNP -80 mmHg. Respiratory variation in pulse pressure was the most affected dynamic parameter during NPPV, increasing 119 % (p < 0.001) from baseline to LBNP -80 mmHg. The cardiac power integral was the most affected non-dynamic parameter falling 59 % (p < 0.001) from baseline to LBNP -80 mmHg during spontaneous breathing, and 68 % (p < 0.001) during NPPV.
  
  
  
  Dynamic cardiac power parameters were not better than dynamic flow- and pressure parameters at tracking hypovolemia, seemingly due to previously unknown variation in peripheral vascular resistance matching respiratory changes in hemodynamics. Of non-dynamic parameters, the power parameters track hypovolemia slightly better than equivalent flow parameters, and far better than equivalent pressure parameters.
authors.affiliation: Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway. audun.rimehaug@gmail.com.|Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway. audun.rimehaug@gmail.com.|Circulation research group Trondheim (CIRCUT), Trondheim, Norway. audun.rimehaug@gmail.com.
authors.forename: Audun Eskeland
authors.identifier: 0000-0002-4803-6083
authors.initials: AE
authors.lastname: Rimehaug
authors.affiliation: Norwegian Air Ambulance Foundation, Drøbak, Norway.|Department of Anesthesiology, Oslo University Hospital, Oslo, Norway.
authors.forename: Ingrid Elise
authors.initials: IE
authors.lastname: Hoff
authors.affiliation: Department of Anesthesiology, Oslo University Hospital, Oslo, Norway.|Faculty of Medicine, University of Oslo, Oslo, Norway.
authors.forename: Lars Øivind
authors.initials: LØ
authors.lastname: Høiseth
authors.affiliation: Department of Vascular Medicine, Oslo University Hospital, Oslo, Norway.
authors.forename: Jonny
authors.initials: J
authors.lastname: Hisdal
authors.affiliation: Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway.|Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.|Circulation research group Trondheim (CIRCUT), Trondheim, Norway.
authors.forename: Petter
authors.initials: P
authors.lastname: Aadahl
authors.affiliation: Department of Anesthesiology and Intensive care, St Olav Trondheim University Hospital, Trondheim, Norway.|Department of Circulation and Medical Imaging, NTNU, Norwegian University of Science and Technology, Trondheim, Norway.|Circulation research group Trondheim (CIRCUT), Trondheim, Norway.
authors.forename: Idar
authors.initials: I
authors.lastname: Kirkeby-Garstad
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006321:Heart / Q000503:physiopathology*; D006334:Heart Function Tests; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D020896:Hypovolemia / Q000503:physiopathology*; D008150:Lower Body Negative Pressure / Q000009:adverse effects*; D008297:Male; D016544:Patient Simulation; D011175:Positive-Pressure Respiration; D012119:Respiration; D055815:Young Adult
keywords: Cardiac power; Critical care; Hypovolemia; Lower body negative pressure; Vascular impedance