Siemens ACUSON Cypress Operator's Manual page 269

Potential Sources of Error
TABLE 57.
Source Explanation of Error(s)
Heart Rate Several calculations in the Cypress system employ the heart rate.
Informa-
It is important that the heart rate number used in calculations be
tion
accurate and derived from an
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 Some calculations in the system employ manually entered
Entered
patient information. The Body Surface Area is obtained using
Patient
height and weight information. It is assumed that the values
Informa-
entered for these indices are accurate.
tion
ACUSON Cypress™ Operator's Manual
Measurement Accuracies
source that is free of artifact.
ECG
10-29