User's Manual

Radius-7 Chapter 1- Technology Overview
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rainbow Acoustic Monitoring™ (RAM™)
rainbow Acoustic Monitoring (RAM) continuously measures a patient’s respiration rate based
on airflow sounds generated in the upper airway. The Acoustic Sensor, which is applied on the
patient's neck, translates airflow sounds generated in the upper airway to an electrical signal
that can be processed to produce a respiration rate, measured as breaths per minute.
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 Acquisition
System
Respiratory airflow to sound Sound to
electrical signal
Electrical signal to
digital signal
Signal
Processing
Envelope
Detection
RRa Estimation
Digital signal to respiratory
measurement
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 contribute
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].