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Radical-7R Pulse CO-Oximeter Operator’s Manual
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SPCO, SPMET, AND SPHB MEASUREMENTS DURING PATIENT MOTION
The Radical-7R displays measurements of SpCO, SpMet and SpHb during patient motion. However,
because of the changes in the physiological parameters such as blood volume, arterial-venous
coupling, etc., that occur during patient motion, the accuracy of such measurements may not be
reliable during excessive motion. The measurements for SpCO, SpMet and SpHb display “---” and a
message, “LOW SpCO SIQ”, “LOW SpMet SIQ” or “LOW SpHb SIQ”, displays to alert the clinician
that the instrument does not have confidence in the value due to poor signal quality caused by
excessive motion or other signal interference.
RAINBOW ACOUSTIC MONITORING
Rainbow Acoustic Monitoring is a real time, continuous, non-invasive method for measuring
respiration rate based on respiratory sounds. Respiratory sounds include sounds related to
respiration such as breath sounds (during inspiration and expiration), adventitious sounds,
cough sounds, snoring sounds, sneezing sounds, and sounds from the respiratory muscles
[1]. These respiratory sounds often have different characteristics depending on the location
of recording [2] and they originate in the large airways where air velocity and air turbulence
induce vibration in the airway wall. These vibrations are transmitted, for example, through
the lung tissue, thoracic wall and trachea to the surface where they may be heard with the
aid of a stethoscope, a microphone or more sophisticated devices.
Rainbow Acoustic Monitoring Architecture
The following figure illustrates how a respiratory sound produced by a patient can be turned
into a numerical measurement that corresponds to a respiratory parameter.
Patient
Sensor
Acquisiton
System
Signal
Processing
Respiratory
Airflow to
Sound
Sound to
Electrical
Signal
Electrical
Signal to
Digital Signal
Digital Signal
to Respiratory
Measurement
Envelope Detection
RRa Estimation
Patient
The generation of respiratory sounds is primarily related to turbulent respiratory airflow in
upper airways. Sound pressure waves within the airway gas and airway wall motion contrib-
ute to the vibrations that reach the body surface and are recorded as respiratory sounds.
Although the spectral shape of respiratory sounds varies widely from person to person, it is
often reproducible within the same person, likely reflecting the strong influence of individual
airway anatomy [2-6].
Sensor
The sensor captures and transmits respiratory sounds (and other biological sounds) much
like a microphone does. When subjected to a mechanical strain, (i.e., surface vibrations
generated during breathing), the sensor becomes electrically polarized. The degree of
polarization is proportional to the applied strain. This is known as the ‘Piezoelectric effect’ in
this manual. The output of the sensor is an electric signal that includes a sound signal that
is modulated by inspiratory and expiratory phases of the respiratory cycle.
O v e r v i e w
