Impact of Increasing Lower Body Negative Pressure and Its Abrupt Release on Left Ventricular Hemodynamics in Anesthetized Pigs

Figures

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  Figure 1. X-ray after invasive instrumentation including pressure volume catheter in the left ventricle (*) and the Swan Ganz catheter with its tip in the left pulmonary artery (**).

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  Figure 2. Position I was 10 cm below the xiphoid process, position III at the anterior iliac spine, position II between I and III. After reaching a steady state baseline recordings were performed, followed by measurements at −15, −30 and −45 mmHg (steps i–iii). At position III LBNP was repeated under dobutamine infusion (IIId).

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  Figure 3. Examples from original pressure–volume loops (x-axis: volume in ml, y-axis: pressure in mmHg) for each sealing position (I–III) and pressure step (i−iii), visually showing the pronounced impact of LBNP-derived preload reduction. A left- and down-ward shift of the loops is more pronounced at sealing position I compared to position II and III.

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  Figure 4. LBNP did not elevate heart rate (HR). Significant LBNP-induced decrease was seen in cardiac output (CO), mean arterial pressure (MAP), mean central venous pressure (mCVP), left ventricular end-diastolic pressure (LV-EDP) and left ventricular end-diastolic volume (LV-EDV). Left ventricular end-systolic volume (LV-ESV) did not change significantly.

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  Figure 5. LBNP negatively impacted maximal left ventricular pressure (LVPmax) (B), maximum rate of pressure increase (LV-dP/dtmax) (C), stroke work (SW) (E) and pressure volume area (PVA) (F). No significant effect ensued in ejection fraction (EF) (A), left ventricular-end-systolic volume at 100 mmHg (LV-VPes100) (D) and cardiac work efficiency (CWE) (G). Data are presented as average with error bars indicating SD. Asterisk (for position I-III) and # (for dobutamine, position IIId) mean p < 0.05 compared to baseline.

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  Figure 6. Full return of cardiac volume load after abrupt release of LBNP demonstrated by the right- and upward shift of the pressure-volume loop (PV loop), more pronounced at position I compared to position II and III. P0 reference marks the reference line at zero pressure.

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  Figure 7. Full return of cardiac volume load after three respiratory cycles after LBNP release (MAP = mean arterial pressure, mean CVP = mean central venous pressure, LV-EDP = left ventricular-end-diastolic pressure, LV-EDV = left ventricular end-diastolic volume, LV-ESV = left ventricular end-systolic volume. Heart rate did not change (as statistic spike it did in position 2).

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  Figure 8. Hemodynamic changes after abrupt release of LBNP: The LV ejection fraction (A), maximum of left ventricular pressure (LVPmax) (B), maximum rate of pressure increase (LV-dP/dtmax) (C) and PVA (E) increased to baseline values. Stroke work (D) and pressure volume area (PVA) did not. Cardiac work efficiency (CWE) (F) was unchanged. Asterisk and # indicate p < 0.05 compared to baseline, ** indicates that at this level all positions are p < 0.05 to baseline.