PWTT, pulse wave transit time, is a new noninvasive parameter which can indicate sudden change in blood pressure. PWTT is measured by continuous monitoring of ECG and pulse wave. No additional sensors or modules are required.
In many cases, change in PWTT correlates with change in blood pressure. When PWTT change exceeds a threshold, it triggers NIBP measurement to confirm blood pressure.
Periodic NIBP measurement is only measured at specified times so sudden critical blood pressure changes that occur between the periodic measurements may be missed until the next periodic measurement.
Nihon Kohden's innovative PWTT technology could solve this problem. With PWTT, if sudden blood pressure change occurs between periodic NIBP measurements, PWTT can detect it and trigger an NIBP measurement to confirm it.
PWTT has a correlation with blood pressure in most cases. However it cannot catch all instances of blood pressure change. See the "Measurement Limitations" section for more details. With recognition of these limitations, PWTT can be a valuable enhancement to noninvasive blood pressure monitoring.
Applications
PWTT threshold can be set according to the patient situation and hospital area. Higher sensitivity detects smaller changes and triggers more frequent NIBP measurements. Lower sensitivity detects only larger changes and triggers less frequent NIBP measurements.
In the OR, use smaller threshold to trigger more frequent NIBP measurement. In the ICU, CCU or ward, excessive NIBP measurements are a burden on the patient so PWTT threshold can be increased.What is measured?PWTT is calculated for each beat from the ECG and peripheral pulse wave. The peripheral pulse wave is measured by an SpO2 probe on the finger or toe.PEP and a-PWTTPWTT includes PEP (Pre-Ejection Period) and a-PWTT (Pulse Wave Transit Time in the Artery).
PEP
Pre-ejection period
a-PWTT:
Pulse wave transit time at artery
PWTT:
PEP + a-PWTT
a-PWTT is the time it takes the pulse wave to travel from the aorta to a peripheral artery. a-PWTT is directly related to blood pressure. Unfortunately, a-PWTT cannot be measured directly. We can only measure PWTT, which also includes PEP.
PEP is the period just before the blood is pumped into the aorta. In general, PEP change over short periods of time is negligible in most cases so we can assume that PWTT corresponds to a-PWTT and therefore to blood pressure.
However, vasoactive and other drugs can cause significant changes in PEP and affect the correlation between PWTT and blood pressure.
Generally in most cases, we can say that PWTT corresponds to a-PWTT and blood pressure.
Relationship between blood pressure and pulse wave speedWhen the heart pumps blood into the aorta, it also generates a pressure wave that travels along the arteries ahead of the pumped blood. This is the pulse wave.
The speed of the pulse wave depends on the tension of the arterial walls. When the blood pressure is high, the arterial walls are tense and hard and the pulse wave travels faster. When the blood pressure is low, the arterial walls have less tension and the pulse wave travels slower.
This can also be understood by the following example. When a ping-pong ball is thrown against a hard table, the rebound is strong and fast. If the ping-pong ball is thrown against a soft blanket, the blanket absorbs the force and the rebound is weak and slow.
How PWTT detects change in blood pressureAlthough the actual blood pressure itself cannot be determined from the speed of the pulse wave, a change in blood pressure is indicated by change in the speed of the pulse wave. Therefore, PWTT is used to detect change in pressure.
Change in PWTT indicates potential change in blood pressure. PWTT for each beat is compared to the PWTT of the last NIBP measurement. When PWTT change exceeds a threshold, it triggers NIBP measurement to measure the actual blood pressure.
You can increase or decrease the PWTT threshold to respond to larger or smaller blood pressure changes and trigger less frequent or more frequent NIBP measurements.
source: http://www.nihonkohden.com/
In many cases, change in PWTT correlates with change in blood pressure. When PWTT change exceeds a threshold, it triggers NIBP measurement to confirm blood pressure.
Periodic NIBP measurement is only measured at specified times so sudden critical blood pressure changes that occur between the periodic measurements may be missed until the next periodic measurement.
Nihon Kohden's innovative PWTT technology could solve this problem. With PWTT, if sudden blood pressure change occurs between periodic NIBP measurements, PWTT can detect it and trigger an NIBP measurement to confirm it.
PWTT has a correlation with blood pressure in most cases. However it cannot catch all instances of blood pressure change. See the "Measurement Limitations" section for more details. With recognition of these limitations, PWTT can be a valuable enhancement to noninvasive blood pressure monitoring.
Applications
PWTT threshold can be set according to the patient situation and hospital area. Higher sensitivity detects smaller changes and triggers more frequent NIBP measurements. Lower sensitivity detects only larger changes and triggers less frequent NIBP measurements.
In the OR, use smaller threshold to trigger more frequent NIBP measurement. In the ICU, CCU or ward, excessive NIBP measurements are a burden on the patient so PWTT threshold can be increased.What is measured?PWTT is calculated for each beat from the ECG and peripheral pulse wave. The peripheral pulse wave is measured by an SpO2 probe on the finger or toe.PEP and a-PWTTPWTT includes PEP (Pre-Ejection Period) and a-PWTT (Pulse Wave Transit Time in the Artery).
PEP
Pre-ejection period
a-PWTT:
Pulse wave transit time at artery
PWTT:
PEP + a-PWTT
a-PWTT is the time it takes the pulse wave to travel from the aorta to a peripheral artery. a-PWTT is directly related to blood pressure. Unfortunately, a-PWTT cannot be measured directly. We can only measure PWTT, which also includes PEP.
PEP is the period just before the blood is pumped into the aorta. In general, PEP change over short periods of time is negligible in most cases so we can assume that PWTT corresponds to a-PWTT and therefore to blood pressure.
However, vasoactive and other drugs can cause significant changes in PEP and affect the correlation between PWTT and blood pressure.
Generally in most cases, we can say that PWTT corresponds to a-PWTT and blood pressure.
Relationship between blood pressure and pulse wave speedWhen the heart pumps blood into the aorta, it also generates a pressure wave that travels along the arteries ahead of the pumped blood. This is the pulse wave.
The speed of the pulse wave depends on the tension of the arterial walls. When the blood pressure is high, the arterial walls are tense and hard and the pulse wave travels faster. When the blood pressure is low, the arterial walls have less tension and the pulse wave travels slower.
This can also be understood by the following example. When a ping-pong ball is thrown against a hard table, the rebound is strong and fast. If the ping-pong ball is thrown against a soft blanket, the blanket absorbs the force and the rebound is weak and slow.
How PWTT detects change in blood pressureAlthough the actual blood pressure itself cannot be determined from the speed of the pulse wave, a change in blood pressure is indicated by change in the speed of the pulse wave. Therefore, PWTT is used to detect change in pressure.
Change in PWTT indicates potential change in blood pressure. PWTT for each beat is compared to the PWTT of the last NIBP measurement. When PWTT change exceeds a threshold, it triggers NIBP measurement to measure the actual blood pressure.
You can increase or decrease the PWTT threshold to respond to larger or smaller blood pressure changes and trigger less frequent or more frequent NIBP measurements.
source: http://www.nihonkohden.com/
No comments:
Post a Comment