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Left ventricular geometry during positive end-expiratory pressure in dogs
Critical Care Medicine
|August 1, 1985
Summary
Positive end-expiratory pressure (PEEP) alters left ventricular (LV) geometry by reducing dimensions and influencing regional preload and afterload. Lung volume changes, not just ventricular interdependence, significantly affect LV shape during mechanical ventilation.
Area of Science:
- Cardiology
- Pulmonology
- Medical Physiology
Background:
- Mechanical ventilation, particularly intermittent positive-pressure ventilation (IPPV), can impact cardiac function.
- Positive end-expiratory pressure (PEEP) is commonly used to improve oxygenation but may alter hemodynamics.
Purpose of the Study:
- To evaluate the effects of PEEP on left ventricular (LV) geometry during IPPV.
- To differentiate the effects of PEEP from baseline IPPV on LV dimensions and regional function.
Main Methods:
- Ten dogs were studied using IPPV with and without 10 cm H2O PEEP.
- Measurements of LV dimensions in orthogonal axes and right ventricular dimensions were recorded.
- Analysis focused on end-diastolic (ED) and end-systolic (ES) dimensions and regional shortening.
Main Results:
- PEEP decreased LV ED and ES volumes in all three orthogonal axes.
- PEEP altered anterior-posterior (AP) dimensions and regional shortening, suggesting changes in pulmonary venous return.
- Septal-lateral (SL) percent regional shortening decreased with PEEP, with less respiratory variation, indicating a dominant regional preload effect in AP and SL axes and afterload reduction in the long axis.
Conclusions:
- PEEP significantly alters LV geometry beyond simply reducing dimensions.
- Regional preload and afterload effects, alongside lung volume changes influencing LV free wall motion, are key determinants of LV geometry during PEEP.
- Ventricular interdependence does not fully explain the observed changes in LV dimensions with PEEP.