Applanation Arterial Tonometry
The instrument is based on the principle of "Applanation Tonometry". With this
method, the sensor is placed on the skin in correspondence with the arterial pulse,
exerting a moderate pressure: in such a way the artery is slightly compressed
(applanation tonometry) and a balance of the circumferential forces inside the
vessel is obtained. The sensor records the pressure inside the compressed artery.
Intermediate layers between sensor and vessel, with their thickness and rigidity that
vary for each individual, influence the pressure measured by the sensor in a not, a
priori, quantifiable manner. For this reason, it is necessary to calibrate the
tonometric signals using the systolic and diastolic pressures obtained from an
external sphygmomanometer (supplied by the operator). The calibration process is
based on the assumption that diastolic and mean pressure substantially don’t
change along the arterial tree.
The pulse wave velocity is defined as the
propagation velocity of the pressure wave
(not of the blood) from the center to the
periphery and is therefore obtained by
dividing the distance between two examined
points (for example Carotid and Femoral) by
the related sphygmic wave transit time
(DeltaT).
PWV = Distance (B-A) / DeltaT
PWV it is conventionally expressed in m / s
(meters / second).
The transit time of the sphygmic wave can be assessed in two different ways:
I. Using the wEc1 unit together with the wTn1 unit to measure the delay time between the R peak of the
ECG wave and the “foot” of the tonometric waves, first for the Carotid Artery (R-cW) and then for the
Peripheral Artery (e.g. the Femoral Artery in the figure, R-fW ), obtaining DeltaT, the difference
between time A and B.
II. Using two wTn1 units to contemporarily capture two tonometric signals, one of the Carotid Artery and
the other of the selected Peripheral Artery, to obtain the time interval DeltaT between the two “feet”
of the waves.
The DeltaT interval in any case is calculated automatically by the WPP001-ETT Software.
As for the distance measurement, refer to the next paragraph.
⚠
The ECG lead captured must only be used for the PWV estimation and must never be used for any
kind of diagnosis on the patient!
5
User Manual
PulsePen
- V. 5.0_b
