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