Transonic HT331-FT - Page 47

AU-OPR-AureFloFT-EN,
Rev H
41
D/S RATIO CALCULATION PREREQUISITES
In order to clearly delineate systolic and diastolic phases of a ow waveform, FlowTrace
®
relies on a signal
analysis of the ECG trace. FlowTrace
®
only performs the calculation of the D/S Ratio with associated ow
waveform coloring when it:
● Is connected to the HT300-Series Compatible Flowmeter
● Has a stable ECG signal that can be analyzed by FlowTrace
®
software to identify systolic and diastolic
phase demarcations.
For most accurate results, rely on D/S ratio readings only during snapshot mode.
NOTE: Connecting pressure only will not color waveforms with systolic and diastolic phases.
ECG/PRESSURE SIGNAL SPECIFICATIONS
Transonic
®
Flowmeters have a back-panel ECG and Pressure analog input terminals for signal transmission
from a patient-connected ECG/Pressure capable device in the OR, most often the anesthesia patient
monitor (Fig. 2.5, page 7). A qualied biomedical service engineer should be consulted to connect
the Flowmeter to an existing ECG/Pressure signal device. The ECG/Pressure signal is automatically scaled
to standard levels, and is displayed on a standard grid so users may directly read it in “millivolts” and
“milliseconds” (Fig. C.1, page 39).
The presence of blue/red colored signals indicates good ECG signal connection and waveform. If an ECG
appears, but doesn’t colorize, a different cardiac lead should be selected. This is an easy adjustment that
can be made by anesthesia.
SYSTOLIC & DIASTOLIC PHASE COLORING
FlowTrace
®
colorizes both the ECG and ow waveform in real time with systolic phases colored red and
diastolic phases colored blue, so that the surgeon can see, at a glance, the electrical and mechanical
functions of the heart. Therefore, the D/S ratio can be dened as: “The ratio between systolic and diastolic
areas in the ow waveforms, where the systolic phase and the diastolic phase coincide with the heart’s
contraction and relaxation as derived from the ECG signal leads connected to a compatible HT300-Series
Flowmeter.” These areas under the waveform are used to calculate the D/S ratio or DF%.
FlowTrace’s Snapshot mode will also color the systolic and diastolic waveform phases (in the presence of
a valid ECG signal). Coloring and D/S-Ratio calculation of the Snapshot can be performed with a more
accurate algorithm that uses retrospective analysis of a larger number of ECG cycles, and ow averaging
over the full retrospective Snapshot.
FLOWTRACE
®
SYSTOLE & DIASTOLE IDENTIFICATION
FlowTrace
®
identies the systolic and diastolic phases of the heart’s electrical activity on the ECG. HT300-
Series Flowmeters utilize mean ow, Flowsound
®
, and a strip-chart recorder to analyze and record the
effects of the heart’s contraction and relaxation. Because electrical evidence of contraction and relaxation
precede the mechanical effect, there is a slight time delay noted between the colorization points on the
ECG and the corresponding points on an AureFlo
®
ow waveform. During isovolumetric contraction, there
is no initial systolic effect on coronary ow. Comparably, during isovolumetric relaxation, coronary ow
continues to perfuse the myocardium. These time lags result in coronary ow overlapping into the next
mechanical phase of the heart’s cycle, and the delays are reected on the ow waveform.
SUMMARY
The D/S ratio and DF% both represent comparisons of diastolic volume ow to systolic ow or total ow to
determine whether a patient’s graft ow has diastolic or systolic dominance.
ECG Signal, D/S Ratio & DF