14-11-2012, 11:34 AM
MEASUREMENT OF BLOOD PRESSURE
MEASUREMENT OF BLOOD.ppt (Size: 629 KB / Downloads: 110)
Stethoscope - Principle
When the cuff is placed on the upper arm and inflated, the pressure compresses the brachial artery underlying. So blood flow is stopped in the vessel. No sounds are heard.
When the cuff pressure is reduced, pressure drops below systolic pressure. Small amounts of blood travel past the cuff with some crashing, snapping sound called Korotkoff sound. Pressure of the cuff that is indicated on the manometer when the first Korotmoff sound is heard is recorded as SYSTOLIC BLOOD PRESSURE
As the pressure in cuf continues to drop, Korotkoff sounds, continue until the cuff pressure no logner is suffient to construct the vessel. The sound disappers at one point. This pressure value on manometer is DIASTOLIC BLOOD PRESSURE.
Phenomena of disappearance of Korotkoff sound is
Catheter Tip Method
Transducer is placed through catheter at the actual site of measurement in bloodstream or mounted on the tip of catheter
Using catheter tip probe, blood is taken from the vessel
Pressure from vessel is exerted to the pressure transducer which converts the pressure into electrical signals.
IMPLANTATION TECHNIQUES
Transducer: Body made of Titanium- 4 S.G bonded to inner surface of diaphragm. Stand size 4.5 mm diameter and 1.2 mm thickness. When B.P increases on diaphragm, inner surface is stressed. When the bridge is excited, o/p voltage proportional to the blood pressure can be obtained.
Defibrillators
A defibrillator, is a fairly simple device that delivers a
large amount of energy across a patient’s chest when the heart is
not beating properly. When the heart is not beating with a
pattern, all cells are contracting at different times; this is known
as fibrillation. is a fairly simple device that delivers a
large amount of energy across a patient’s chest when the heart is
not beating properly. When the heart is not beating with a
pattern, all cells are contracting at different times; this is known
as fibrillation.
This
large amount of energy causes all cells in the heart to depolarize
at once. This action may allow the SA node to resume function
and generate a normal electrical pattern. Sometimes the SA node
can recover, but sometimes it cannot. The shape of the energy
waveform has evolved with experience.
AEDs – automated external defibs
these devices are including in planes, in police cars, and with security personnel. AEDs are the same as defibs,
but they generally have no waveform display, use stick-on
patient pads rather than paddles, and calculate the power to be
delivered automatically. An important feature of AEDs is the
patient pads that check for ECG signals so that a patient who is
not in fibrillation will not be shocked. Many of these units
provide audible instructions so that they can be operated by
someone without medical training. In addition, the devices have
memory that stores the ECG waveforms of the patient and
makes them available to medical staff when the patient is transported
to a hospital. improve the survivability of cardiac fibrillation victims by
decreasing the time until defibrillation can be applied. The
AEDs themselves must be self-diagnostic since testing is
expected to be performed by untrained people without test
equipment.
Pacemakers
Pacemakers can support the proper function of the heart to keep
regular electrical rhythm, or they can stimulate the heart only
when it does not beat properly. An example of a pacemaker is
shown in Figure 6.3. In general, only BMETs with specialized
training are involved in supporting pacemakers. There are several
types of pacemakers.