title: Effect of PEEP, blood volume, and inspiratory hold maneuvers on venous return.
abstract: According to Guyton's model of circulation, mean systemic filling pressure (MSFP), right atrial pressure (RAP), and resistance to venous return (RVR) determine venous return. MSFP has been estimated from inspiratory hold-induced changes in RAP and blood flow. We studied the effect of positive end-expiratory pressure (PEEP) and blood volume on venous return and MSFP in pigs. MSFP was measured by balloon occlusion of the right atrium (MSFPRAO), and the MSFP obtained via extrapolation of pressure-flow relationships with airway occlusion (MSFPinsp_hold) was extrapolated from RAP/pulmonary artery flow (QPA) relationships during inspiratory holds at PEEP 5 and 10 cmH2O, after bleeding, and in hypervolemia. MSFPRAO increased with PEEP [PEEP 5, 12.9 (SD 2.5) mmHg; PEEP 10, 14.0 (SD 2.6) mmHg, P = 0.002] without change in QPA [2.75 (SD 0.43) vs. 2.56 (SD 0.45) l/min, P = 0.094]. MSFPRAO decreased after bleeding and increased in hypervolemia [10.8 (SD 2.2) and 16.4 (SD 3.0) mmHg, respectively, P < 0.001], with parallel changes in QPA Neither PEEP nor volume state altered RVR (P = 0.489). MSFPinsp_hold overestimated MSFPRAO [16.5 (SD 5.8) vs. 13.6 (SD 3.2) mmHg, P = 0.001; mean difference 3.0 (SD 5.1) mmHg]. Inspiratory holds shifted the RAP/QPA relationship rightward in euvolemia because inferior vena cava flow (QIVC) recovered early after an inspiratory hold nadir. The QIVC nadir was lowest after bleeding [36% (SD 24%) of preinspiratory hold at 15 cmH2O inspiratory pressure], and the QIVC recovery was most complete at the lowest inspiratory pressures independent of volume state [range from 80% (SD 7%) after bleeding to 103% (SD 8%) at PEEP 10 cmH2O of QIVC before inspiratory hold]. The QIVC recovery thus defends venous return, possibly via hepatosplanchnic vascular waterfall.
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland;
authors.forename: David
authors.initials: D
authors.lastname: Berger
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; Department of Anaesthesiology and Intensive Care Medicine, Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden;
authors.forename: Per W
authors.initials: PW
authors.lastname: Moller
authors.affiliation: Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland;
authors.forename: Alberto
authors.initials: A
authors.lastname: Weber
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland;
authors.forename: Andreas
authors.initials: A
authors.lastname: Bloch
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; Department of Cardiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; and.
authors.forename: Stefan
authors.initials: S
authors.lastname: Bloechlinger
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland;
authors.forename: Matthias
authors.initials: M
authors.lastname: Haenggi
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, Institute of Clinical Sciences at the Sahlgrenska Academy, University of Gothenburg, Sahlgrenska University Hospital, Gothenburg, Sweden;
authors.forename: Soren
authors.initials: S
authors.lastname: Sondergaard
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland;
authors.forename: Stephan M
authors.initials: SM
authors.lastname: Jakob
authors.affiliation: Department of Critical Care, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Sheldon
authors.initials: S
authors.lastname: Magder
authors.affiliation: Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland; jukka.takala@insel.ch.
authors.forename: Jukka
authors.initials: J
authors.lastname: Takala
mesh_terms: D000818:Animals; D016280:Atrial Function, Right; D001794:Blood Pressure; D001810:Blood Volume / Q000502:physiology*; D062485:Breath Holding; D002302:Cardiac Output / Q000502:physiology; D006325:Heart Atria; D020896:Hypovolemia / Q000503:physiopathology*; D008297:Male; D011175:Positive-Pressure Respiration; D011312:Pressure; D034421:Sus scrofa; D013552:Swine; D014682:Vena Cava, Inferior / Q000502:physiology*
keywords: blood volume; cardiac output; mean systemic filling pressure; mechanical ventilation; positive end-expiratory pressure; right atrial pressure