Cardio IV Flashcards
Describe the pattern of pressures within pulmonary and systemic circulation and how they are similar or differ from one another.
Systemic pressures always < pulmonary pressures
Both follow the same pattern of large oscillations (systolic to diastolic) that damp out as you move from arteries to capillaries to veins.
How does the difference in pulmonary vs systemic circulation pressure affect the structure of the heart?
Because the systemic pressure is always higher than the pulmonary pressure, the left ventricle (which feeds into the systemic circulation) is larger than the right ventricle.
What is hydrostatic pressure?
The pressure exerted by a fluid at equilibrium at a given point within the fluid due to the force of gravity.
What is the formula for hydrostatic pressure? Describe each variable.
P = rho x g x h
Where rho is the density of the fluid
g is gravitational force
h is the height of the fluid at the point of interest
What is the conversion between cm H2O and pascals?
1 cm H2O = 90 Pa
What is the conversion between cm H2O and mm Hg?
1 cm Hg = 14 cm H2O
What is the difference between a direct and an indirect method of blood pressure measurement?
A direct method involves puncturing the arteries, while an indirect method does not.
What was the first indirect blood pressure measurement? How did it work?
The mercury sphygmomanometer. It involved wrapping a cuff around the arm and pumping, which would pump a column of mercury.
Convert 1 mm Hg into kPa.
1 mm Hg = 14 mm H2O = 1.4 cm H2O = 0.13 kPa
How was central venous pressure/right atrial pressure originally measured?
Place tip of catheter into right atrium and release saline into the heart. The pressure will be measured with a manometer and will stop moving when the pressure of the saline = central venous pressure.
What is the typical central venous pressure/right atrial pressure?
5-10 cm H2O
What is perfusion pressure?
Perfusion pressure is the pressure of the blood that flows through an organ or through a vessel. It is the pressure that governs blood flow.
What is the formula for perfusion pressure?
Perfusion pressure = arterial pressure - venous pressure
However, since arterial pressure»_space; venous pressure (100 mm Hg to 5 mm Hg), we ignore venous pressure.
What happens if there is no perfusion pressure? When might this occur?
If there is no perfusion pressure, there is no pressure gradient and thus no blood flow. This occurs when the individual is dead.
What are the two factors that affect blood flow? Write the formula expressing their relationship.
Flow = perfusion pressure / resistance