
Oxygen saturation is the percentage of
haemoglobin that is saturated with oxygen

CO2 produces carbonic acid and the acid
dissociates H+ ions in plasma, and this is the
basis of measurement of Co2 concentration
in blood.
Can be measured
Invasively- by removal of blood sample
from the patient

Non-invasively- with no removal of blood
Technology
How it Works
The Conditions It Is Used
Pulse

Measures O2
oximeter

Device like a peg sits on
oxygen saturation of the
the finger and measures
blood in patients
the transmission of light
undergoing any procedure
through tissues
that requires anaesthesia
Measures the amount of
or sedation or those whose
oxygen in arterial blood
breathing or circulation is
There is a large
abnormal


difference between red
light absorbed by
haemoglobin compared
to oxyhaemoglobin

Used to measure the
PULSE OXIMETER and CONDITIONS WHERE IT IS
USED
 The pulse oximeter is a non – invasive technique which
measures the concentration of oxygen in the body.
 The device is either attached to the finger or ear lobe of
the patient, which measures oxygen saturation with
haemoglobin and pulse rate.
 The oximeter works in the following way: a light source
passes through the blood. Different amounts of light are
absorbed depending on the degree of saturation of
oxygen to haemoglobin. A processor then calculates the
light absorption rate and converts this to saturation of
haemoglobin.
• Oximeters are used in many hospital situations even
though they do not measure carbon dioxide levels.
• They are used as monitoring units during anaesthesia.
• They are very efficient because they can be used during
surgery or after surgery to monitor oxygen saturation, pulse
rate and blood flow.
• Oximeters can be used in the success of ventilation
procedures, to see if the administration of oxygen is
successful for the patient.
• Oximeters can also be used in intensive care units or after
surgery to monitor unconscious patients and to notify
nurses/doctors of any changes in oxygen levels.
• Therefore, oximeters are an efficient monitoring system for
oxygen, pulse and blood flow levels.
Technology How it Works
The Conditions It Is Used
Arterial blood

Measures O2 and CO2

gas (ABG)

Uses electrochemical methods
dangerously low oxygen or high
analysis

Measures partial pressure (or
carbon dioxide levels
the concentration) of O2 and

CO2 in the blood



Measures saturation of oxygen
Used when there are signs of
Helps for diagnosing as well as
monitoring patients

Helpful for monitoring patients
(which is the amount of oxygen
under anaesthesia, in intensive
combined to haemoglobin
care, in accident or emergency
compared to the maximum)
facilities and for premature babies
Measures levels of bicarbonate

Eg, a patient in a coma can have
and pH (which show CO2
their blood gases regularly
levels)
monitored
This analysis evaluates how
effectively the lungs are
delivering oxygen and
removing carbon dioxide
BLOOD GAS ANALYSER and CONDITIONS WHERE IT IS USED
• Invasive technique. (Goes inside the body)
 Takes small samples of arterial blood.
 The analyser measures the oxygen using two
electrodes.
 Oxygen diffuses through a membrane between the
two electrodes.
 This produces a small electric current.
 This current is proportional to the amount of oxygen.
e.g. certain values equal certain amounts of oxygen.
• Carbon dioxide levels are also measured by placing the blood specimen
in one chamber and the other chamber a hydrogen electrode.
• Dissolved carbon dioxide diffuses into the hydrogen ion chamber. The
pH is then measured. The hydrogen ion concentration is proportional to
carbon dioxide levels. E.G. certain values equal certain amounts of
carbon dioxide.
• Alternatively instead of taking a blood sample an arterial probe, which is
inserted into the body, may take these measurements.
• Blood gas analysers are commonly used in intensive care units
especially baby care units and labour wards. This is due to the fact that
slight changes in carbon dioxide levels can affect the development of
newly born babies. Excess carbon dioxide and poor oxygen saturation
levels can have detrimental affects on the child.
• The analyser is used as a measuring tool to ensure the patient is looked
after and if oxygen/carbon dioxide levels change a nurse/doctor can
take necessary action to return oxygen/carbon dioxide levels to their
optimum values.