ACUSON Cypress™ Operator’s Manual
10-29
Measurement Accuracies
Heart Rate
Informa-
tion
Several calculations in the Cypress system employ the heart rate.
It is important that the heart rate number used in calculations be
accurate and derived from an
ECG
source that is free of artifact.
The Cypress system heart rate display is an average value that is
extracted continuously from previous R-R intervals. The heart
rate filtering function is a time-weighted average of R-R intervals
with the highest weight assigned to the most recent interval. Suc-
cessively older R-R intervals are assigned successively lower
weights. For the purposes of characterizing this filter function, it
can be considered an average of the last 5 heart cycles. For the
6th and older R-R intervals, a 20% variation in that interval will
result in a 1% or less variation in the heart rate display, with each
successively older interval contributing successively less to the
average.
Manually
Entered
Patient
Informa-
tion
Some calculations in the system employ manually entered
patient information. The Body Surface Area is obtained using
height and weight information. It is assumed that the values
entered for these indices are accurate.
TABLE 57.
Potential Sources of Error
Source
Explanation of Error(s)
