Hemodynamics Management

The pressure-volume loop begins with contraction and the isovolumic phase of the cardiac cycle. Ventricular ejection begins once ventricular pressure rises above aortic pressure. Peak LV pressure is similar to peak aortic pressure or systolic blood pressure, which is followed by the end-systolic pressure (Pes). This is followed by the isovolumic relaxation phase and then ventricular filling phase of the cardiac cycle once atrial pressure exceeds ventricular pressure. The difference between end-systolic volume (ESV) and end-diastolic volume (EDV) is stroke volume (SV).

The EDPRV is established by altering ventricular loading conditions, generating a series of PVLs, and connecting the end-diastolic pressure–volume points of each loop. The EDPVR is curvilinear in nature and is indicative of ventricular passive viscoelastic properties or stiffness at the point of complete myofilament inactivation. Chamber stiffness, or its reciprocal, chamber compliance, relates changes in ventricular volume in response to changes in diastolic transmural pressure. An increase…

The use of mechanical ventilation in hypovolemic conditions leads to various physiologic effects. The right ventricular preload decreases due to the compression of the superior vena cava and an increase in intramural right atrial pressure, causing a decrease in transmural right atrial pressure. In West zones I and II, pulmonary capillaries are compressed, leading to an increase in right ventricular afterload. In West zone III, the increase in alveolar pressure pushes blood from the capillaries towards the left side of the heart. Additionally, there is a decrease in left ventricular afterload due to an increase in pleural pressure. The abbreviations used in the text include LA for left atrium, LV for left ventricle, Palv for alveolar pressure, Ppl for pleural pressure, RA for right atrium, and RV for right ventricle.