Pressure, Flow, and Resistance Understanding the relationship among pressure, flow and resistance can help you understand how cardiac output and vascular resistance relate to blood pressure These are relationships that are often manipulated in the acutely ill patient The relationship among flow, resistance and pressure can be mathematically expressed Flow x Resistance = Pressure

Pressure, Flow, and Resistance Flow and resistance can be adjusted to keep pressure steady The flow in the cardiovascular system is the CO, the resistance is the afterload and the pressure is the blood pressure

Normal Pressures When a catheter is passed through the venous system into the heart and pulmonary artery, certain pressure readings and wave forms are measurable During each individual section to follow, we will be looking at normal waveforms displayed depending on type of hemodynamic monitoring being used eg. arterial waveforms, CVP waveforms and PA waveforms To end this section I will leave you with the normal values. We will revisit them again during the sections to follow

Hemodynamic Pressures Central Venous Pressure (CVP)  0 – 6 mm Hg Right Arterial Pressures (RAP)  0 – 6 mm Hg Right Ventricular Pressures (RVP)  Systolic 20 – 30 mm Hg  Diastolic 2 – 8 mm Hg  RV End Diastolic 2 – 6 mm Hg Pulmonary Artery Pressures (PAP)  Systolic 20 – 30 mm Hg  End diastolic 8 – 15 mm Hg Pulmonary Artery Wedge Pressures  (PAWP) ~ (PAOP) ~ (PCWP) = 5 – 12 mm Hg

Hemodynamic Monitoring The high acuity patient has complex nursing needs The nurse requires a working knowledge of the determinants of cardiac output, preload, afterload, and contractility These determinants of cardiac output will be linked to the data available through hemodynamic monitoring with a pulmonary artery line This knowledge, coupled with astute observation and sharp assessment skills, can guide critical thinking at the bedside and provide a higher level of nursing care for the high acuity patient