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89
I
160 / 40
ECG
bpm
97
---
90
SpO2
SpO2
%
III
15.07.1999
09:05:00
QRSPulse
SpO2
ECG
Tone
etCO2
OFF
Figure 9-1.
SpO
value and plethysmogram
2
Warning
False Parameter Readings — Pulse oximetry is
not suitable for oxygen monitoring of fetuses
(ante-partum or sub-partu). Also this method is
not suitable for patients with carbon monoxide
poisoning.
Elevated levels of carboxyhemoglobin (CO-Hb)
and methemoglobin (Met-Hb) may affect the
measured values. Also dyes injected in the blood
stream (such as Cardiogreen) may impair meas-
urement accuracy.
Warning
No Alarm — Under certain conditions the device
may not be able to identify a signal disturbance
when monitoring the patient. In this situation
artifacts are capable of simulating a plausible
parameter reading, so that the monitor fails to
sound an alarm. In order to ensure reliable patient
monitoring the proper application of the probe
and the signal quality must be checked at regular
intervals.
227 490 02-C
Pulse Oximetry
9 Pulse Oximetry (SpO
Some Basic Facts
SpO
percentage of functional hemoglobin saturated
with oxygen in the patient's arterial blood. Alarm
limits can be set for monitoring of the SpO
The plethysmogram waveform can be displayed on
the screen (Figure 9-1).
The device measures arterial oxygen saturation by
a method called pulse oximetry. This method is
based on the measurement of the different
semiautom.
absorption spectra of reduced hemoglobin and
Next
oxyhemoglobin.
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Therefore the probes consist of a light source (two
LEDs in most cases) and a photodetector on the
opposite side which collects the incident light.
After interaction with the blood and tissue, the red
and infrared light (range between 660 nm and 940
nm) from the LEDs hits the photodetector which
converts it into an electrical signal. The pulsatile
component of the signal is used to build the
plethysmogram.
Literature
W
UKITSCH
D.R.;P
Theory, Technology, and Practice, J. Clin. Monit. 4:
290–301 (1988)
C
ECIL
A Clinical Evaluation of the Accuracy of the Nellcor N-
100 and Ohmeda 3700 Pulse Oximeters, J. Clin. Monit.
4: 31–36 (1988)
Marquette Responder® 3000
measurement is used to determine the
2
, M.W.; P
, M.T.; T
ETTERSON
, J.A.: Pulse Oximetry: Analysis of
OLOGE
, W.T.; T
, K.J.; F
HORPE
IBUCH
)
2
value.
2
,
OBLER
E.E.; T
, G.F.:
UOHY
49
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