Dräger Cicero EM Instructions For Use Manual page 173

Tips to avoid artefacts during SpO
measurement
Nellcor sensors must be used exclusively and positioned
correctly in order to avoid the risk of measuring errors
and tissue damage.
Damaged sensors with exposed electric wires must not
be used – risk of electric shock.
Adhesive strips must not be reused: they may not adhere
properly. The strips must not be stretched unduly and
never use two together, as this may lead to venous
pulsation and failure of the pulse signal.
High intrathoracic pressure, pressure on the thorax and
other consecutive impairments of the venous flow can
lead to venous pulsation with failure of the pulse signal.
The pulse signal may fail in the presence of shock, low
blood pressure, severe vasoconstriction, major anaemia,
hypothermia, arterial occlusion proximal to the sensor
and asystolia.
The sensor must be covered in bright light (e.g. surgical
lamps and direct sunlight), otherwise the pulse signal
may fail or inaccurate results may be obtained.
The sensor should not be positioned on limbs together
with an arterial catheter, sphygmomanometer cuff or
intravascular venous infusion: pulse signal may fail and
measurement becomes inaccurate.
Major concentrations of dyshaemoglobins, such as
carboxyhaemoglobin or methaemoglobin, as well as of
intravascular dyes, such as methylene blue, can also
make the measurement inaccurate.
Electrocautery (HF surgery devices) can impair the
measuring accuracy; the leads and sensor should
therefore be positioned as far away as possible from the
electrocautery and its neutral electrode.
Sensor performance may be impaired if the patient
moves violently, thus leading to inaccurate results. The
sensor should be applied to a different site in such cases
in order to reduce the risk of artefacts due to movement.
Coupling with non-invasive pressure
2
measurement
The interlock function should be activated for simulta-
neous measurement of SpO
pressure on an arm. This prevents unnecessary alarms
due to failure to detect a pulse during NiBP measurement
(see page 171).
Definitions and instructions
Functional saturation compared with fractional
saturation
The functional saturation is calculated as follows:
% SpO
2
The functional oxygen saturation is defined as the
percentage of oxygen-laden haemoglobin capable of
carrying oxygen in relation to the total haemoglobin.
The oxygenated and reduced haemoglobin values
are measured. Substantial amounts of dysfunctinal
haemoglobins, such as carboxyhaemoglobin and
methaemoglobin, are disregarded. The fractional
saturation can be measured in a variety of ways.
The percentage indicates the ratio of oxyhaemoglobin
to total haemoglobin, regardless of whether or not the
haemoglobin is available for oxygen transport. The
measured dysfunctional haemoglobin is included.
It is important to know the method applied in each case
when comparing the results obtained by different module
manufacturers. The functional saturation can be
calculated from the fractional saturation as follows:
Funct. sat. =
Measured saturation in relation to calculated
saturation
The oxygen saturation calculated from the partial
pressure of the arterial oxygen (PaO
measurements may differ from the values actually
measured. This may be due to the fact that such
parameters as temperature, pH value, PaCO
value and concentration of foetal haemoglobin were not
corrected when calculating the blood gas value.
Functional oxygen saturation (SpO
and non-invasive blood
2
100 x HbO
2
(func) =
HbO + Hb
2
Fract. sat. x 100
100 - (% CO haemoglobin + % methaemoglobin)
Description
)
2
%
) in blood pressure
2
, 2,3-DPG
2
173