Discuss parts and function of pressure monitoring kit focusing on function of transducer.

Arterial Monitoring 

It is very easy to understand this concept. I have made it simple and concise.

System-

1)Intravenous catheter

2)Electromechanic monitoring system 

3)Monitor 

•    The catheter in the artery is connected externally to a tubing which has fluid and is connected to a transducer 

•    This transducer is a device that converts energy from one form to another, here it is converting pressure signal to electrical signal

•    Now,the pulsations and the pressure from these pulsationsis propagated through this fluid to the transducer 

•    Transducer has a diaphragm,this diaphragm is displaced each time the pressure from the pulsation is transmitted by the fluid

•    An electrical cable connects the transducer to the monitor 

•    A flush system is used to keep the catheter from clotting and to test the accurateness of system

•    This flush bag should be pressurised to 200-300 mmHg

•    Zeroing of system-system becomes devoid of atmospheric or hydrostatic pressure influence and it provides a reference level to measure pressures 

•    This reference point is taken as right atrium which is 4th ICS

•    The stopcock is opened to air to zero the system until monitor displays 0

What is dynamic response ?

The ability of the system to reproduce patients hemodynamicwaveform accurately is called dynamic response.Its determinants are –

Resonant Frequency- 

is the frequency at which it oscillates when stimulated 

It should be more than the frequency of the incoming pulsatile signalotherwise the components of the waveform will be exaggerated 

Damping Coefficient- is how quickly the oscillating system comes to rest.

High damping coefficient- causes waveform to decrease

Low damping coefficient- overshoots the signals and give exaggerated waveforms 

What is fast flush test ?

It tests the dynamic response 

Pull the rubber string to do this fast flush means you actually open and close it briefly

This gives a square wave followed by 1 or 2 rapid small oscillations before returning to the baseline 

What is overdamping ?

Blunting of the waveform is overdamping 

It occurs due to- air bubbles,kinks or clots in the tubing

Loose connections 

Soft tubing- has low compliance leading to decrease in natural frequency of the system such that it falls below the limit needed to record all the elements of the waveform 

Underinflatedpressure bag

What is underdamping ?

Exaggerated waveform is underdamping 

Overshoot of systolic pressure and vibrations can be seen 

Longer tubings, hyperdynamiccirculation, tachycardia may cause underdamping