title: Analysis of left ventricular systolic function during elevated external cardiac pressures: an examination of measured transmural left ventricular pressure during pressure-volume analysis.
abstract: BACKGROUND
  Variations or disturbances in intrathoracic and extracardiac pressures (ECP) occur in critically ill and anaesthetised patients. There are uncertainties concerning the analysis of left ventricular pressure-volume relationship (LVPVR) and the calculation of systolic function parameters when conducted without reference to transmural left ventricular pressure (LVPtm) in the setting of elevated ECP.
  
  
  METHODS
  In 7 anaesthetised adult pigs, we measured LVPVR using conductance volumetry and tip manometry along with measurement of pericardial and other intrathoracic pressures. Experimental pericardial infusion and pleural insufflation were performed. Transient controlled preload reductions were accomplished using balloon occlusion of the inferior vena cava. Preload recruitable stroke work (PRSW) was calculated using both intracavitary left ventricular pressure (LVPic) and LVPtm, and differences were tested for using a paired t-test.
  
  
  RESULTS
  The pericardial and pleural interventions produced significant elevations in ECP. No difference in PRSW calculated using LVPic and LVPtm was detected.
  
  
  CONCLUSIONS
  These results suggest that LVPtm need not be measured and included in LVPVR analysis of systolic function when there is significant external cardiac pressure. To be able to employ LVPVR analysis of systolic function without reference to LVPtm is important for simplified application in the clinical setting, particularly when elevated extracardiac pressures are suspected, or have been therapeutically induced, as with continuous positive pressure ventilation.
authors.affiliation: Surgical and Perioperative Sciences, Section for Anaesthesiology and Intensive Care Medicine, Umeå University, Umeå, Sweden. michael.haney.us@vll.se
authors.forename: M F
authors.initials: MF
authors.lastname: Haney
authors.forename: G
authors.initials: G
authors.lastname: Johansson
authors.forename: S
authors.initials: S
authors.lastname: Häggmark
authors.forename: B
authors.initials: B
authors.lastname: Biber
mesh_terms: D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D006321:Heart / Q000502:physiology*; D010496:Pericardium / Q000502:physiology; D010994:Pleura / Q000502:physiology; D015203:Reproducibility of Results; D013552:Swine; D016277:Ventricular Function, Left / Q000502:physiology*