GE Healthcare IntelliRate Technology for Patient Monitoring - Manual (Page 3)

3
Alarm Accuracy – Problem Background
Patient monitors routinely process parametric signals
acquired from patients to provide clinicians with information
extracted from those signals. For example, information
extracted from ECG signals usually includes heart rate and
the detection of various cardiac arrhythmias (disturbances in
the normal cardiac rhythm).
Providing alarm mechanisms when the patient’s ECG heart
rate is outside of prescribed limits, or when certain cardiac
arrhythmias occur, is an important function of patient
monitors. The presence of artifact or low signal amplitude in
acquired ECG signals often results in signifi cant false positive
alarm rates during the aforementioned conditions. Similarly,
artifact and poor signal conditions cause false positive
alarms when pulse oximetry and invasive blood pressure
are monitored. For example, one study
1 concluded that
during 298 monitored ICU hours, 86% of 2,942 alarms were
classifi ed as false positive. It can be surmised that the high
percentage of false positive alarms can decrease clinician
productivity and satisfaction, and can decrease the validity
and effi cacy of clinical alarm mechanisms.
Information management is an essential technology for
hospitals with programs to increase effi ciency. Clinical
Information Systems (CIS), as well as other automated
systems utilizing physiologic data from patient monitors,
are more prevalent as hospitals seek to streamline costs
associated with patient care. In many hospitals, pager
systems are used to transmit data from patient monitoring
devices directly to the clinician. For such systems to provide
maximum benefi t for the user, it is imperative that the
physiologic parameter data and associated alarms from
patient monitors be as accurate as possible.
Introducing IntelliRate Technology
A GE Healthcare software algorithm called IntelliRate ™ is able
to reduce the number of false heart rate alarms generated by
multi-parameter patient monitors. By improving the accuracy
and reliability of heart rate measurements, this technology
can help reduce needless clinician interruptions, can help
improve patient care workfl ow, and can help reduce risks
associated with high false alarm rates.
IntelliRate Heart Rate Calculation
Monitoring the ECG signal provides clinicians with information
that is critical for patient care. This information includes
an estimate of heart rate that is inferred by detecting the
electrical depolarization of the ventricles. However, as with
any monitored parameter, the heart rate derived from the
ECG signal can frequently be in error due to noise, pacemaker
artifact, or low amplitude QRS complexes in the ECG signal.
A common result is that these inaccurate heart rate readings
can trigger false limit violation alarms.
The IntelliRate algorithm utilizes information contained in
multiple physiologic signals (e.g., ECG, arterial blood pressure,
and pulse oximetry) to help improve the accuracy of the
heart rate calculation. Since all three of the aforementioned
parameters provide their own estimate of heart rate, it is
highly probable that one of the parameters will off er a correct
rate during those times that the ECG heart rate accuracy
is compromised. After assessing the information extracted
from each of the physiologic signals, the IntelliRate algorithm
applies rule-based logic to determine which heart rate source
has the highest likelihood of being accurate. By reporting
rate with the highest likelihood of accuracy, the false limit
violation alarms are minimized.
IntelliRate Alarm Qualifi cation
As a simple example, consider a relatively common scenario
where the amplitude of a patient’s ECG tracing drops below
the monitor’s QRS detection threshold. With traditional ECG
monitoring, QRS complexes are no longer detected, the
measured heart rate errantly drops to zero, and false Asystole
alarm usually occurs. IntelliRate software may recognize that
the patient’s arterial pulse rate and mean arterial pressure
are relatively unchanged.
This would indicate that a more accurate heart rate (the
arterial pulse rate) has been identifi ed, and the false Asystole
alarm can be prevented.
In general terms, the IntelliRate software brings three basic
benefi ts to alarm processing:
• By supplying the heart rate with the highest likelihood of
accuracy to the monitor’s limit alarm processing logic,
the frequency of false heart rate limit violation alarms can
be greatly reduced compared to when the heart rate is
obtained from the ECG signal only.
• The same more accurate rate can be used to help
eliminate certain false arrhythmia alarms, which might
otherwise be asserted by an automated ECG arrhythmia
analysis algorithm.
• It is known that patient monitors can continue to count
pacemaker artifact as beats and report a heart rate, even
though a patient’s heart may have stopped responding to
an electronic pacing device. IntelliRate software helps to
enhance safety as it uses the pulse rate indicators and/or
blood pressure readings to help to identify this situation.