Life Functions: Circulation & Perfusion

The primary purpose of respiration is to inhale enough OXYGEN from the atmosphere to sustain all the cells in your body, and to exhale enough CARBON DIOXIDE  to remain in proper acid/base balance called homeostasis.

VENTILATION: the movement of air in and out of the lungs

OXYGENATION: transporting oxygen to the blood

CIRCULATION: the movement of blood through the body

PERFUSION: getting oxygen to the tissues

They are listed in order of necessity for survival.


Circulation is 3rd, and describes the movement of blood through the body by the heart and blood vessels.


Circulation can be measured by observing the patient’s vital signs:

HEART RATE:  Increase or decrease in beats per minute (normal 60 – 100)

HEART STRENGTH: Strength of the heart’s contractions (remember that the heart wall is muscular)

CARDIAC OUTPUT: How much blood is pumped or ejected from the heart in liters per min (HR times stroke volume)


Perfusion is the 4th critical life function, which exhibits the getting oxygen into the body’s tissues.


Perfusion can be measured by observing the patient’s vital signs:

BLOOD PRESSURE: changes in systemic blood pressure (systolic and diastolic)

HEMODYNAMICS: changes in pressures inside the heart, pulmonary circuit

SENSORIUM: lack of awareness can indicate poor perfusion

TEMPERATURE: changes from normal body temperature of 98.6 F / Cool or clammy skin indicates poor perfusion

URINE OUTPUT: decrease in amount of urine produced (normal 40 ml/hour)