Patient Assessment
Assessment of a PatientLife Function
A key life function is getting oxygen from the air to all the cells in the body. This process depends on four connected functions:
Ventilation: Moving air in and out of the lungs.
Oxygenation: Getting oxygen into the blood.
Circulation: Moving blood through the body.
Perfusion: Delivering oxygen from the blood into the tissues.
These functions can be compared to a delivery system: ventilation brings oxygen into the lungs, oxygenation loads it into the blood, circulation transports the blood, and perfusion delivers oxygen to the tissues.
Measuring the Four Life Functions
The four life functions are assessed using different clinical measurements, including vital signs and other observations.
Life function | Assessment measures |
|---|---|
Ventilation | Respiratory rate, tidal volume, chest movement, breath sounds, PaCO2, and ETCO2 |
Oxygenation | Heart rate, skin or body color, sensorium, PaO2, and SpO2 |
Circulation | Heart rate and strength, and cardiac output |
Perfusion | Blood pressure, sensorium, temperature, urine output, and hemodynamics |
Assessment and Treatment Priorities
Assessment and treatment should be based on the patient’s life functions. Almost every part of a patient assessment relates to one of these four functions.
If assessment identifies a problem with one of the life functions, the problem must be treated or corrected immediately. The purpose of assessment is therefore not only to collect information, but also to identify life-threatening problems quickly.
Emergency Situations
If one or more life functions are absent, such as when there is no breathing, no pulse, or no blood pressure, the situation is an emergency and may require resuscitation.
During an emergency, the priorities are:
Ventilation
Oxygenation
Circulation
Perfusion
This sequence represents the order in which the life functions are prioritized during an emergency.
Common Problem
The most common problem identified during patient assessment is related to oxygenation.