mclintic w23 measurement and monitoring
TRANSCRIPT
Simple approaches to difficult topics
Measurement and Monitoring
Dr Alan McLintic
Middlemore Hospital
Q: How do you measure Cardiac output using thermodilution?
Q: How do you measure Cardiac output using thermodilution?
• Summary– Thermodilution principle is a modification of the Fick principle
flow blood differenceation AVconcentrorganby up taken substance Amt.
Q: How do you measure Cardiac output using thermodilution?
• Summary– Thermodilution principle is a modification of the Fick principle
1.
1-
1.
l.min5
10ml.dl1520
ml.min250
Q
Q
differenceation AVconcentrorganby upen Amount takorgan through flow Blood
Q: How do you measure Cardiac output using thermodilution?
• Summary– Pulmonary artery catheter (‘Swan-Ganz’ catheter)
Thermistor
Balloon
Proximal lumen
Distal lumen
Connection for thermistor
Q: How do you measure Cardiac output using thermodilution?
• Summary– Inserted through large neck vein
Q: How do you measure Cardiac output using thermodilution?
• Summary– Floated through heart until the tip is in the pulmonary artery
Q: How do you measure Cardiac output using thermodilution?
10 ml dextrose (21ºC)
Dilution of ‘coldness’ measured here
Q: How do you measure Cardiac output using thermodilution?
Col
der
Time
Recirculation
Body temperature
Q: How do you measure Cardiac output using thermodilution?
Col
der
Time
The greater the cardiac output, faster the dilution, the smaller the Area Under the Curve (AUC)
Col
der
Time
High cardiac output
Lower cardiac output
Q: How do you measure Cardiac output using thermodilution?
Dye dilution:
(g/l)ion concentratMean (g) added dye MassVolume Mass of dye (g)
Mean concentration dye (g)
Q: How do you measure Cardiac output using thermodilution?
Con
cent
ratio
n dy
e (g
/l)
Time
Dyes:
(g/l.min) AUC(g) added dye Mass.
Q
Q: How do you measure Cardiac output using thermodilution?
Col
der
Time
Thermodilution
AUC added cold Mass.
Q
Body temperature
Q: How do you measure Cardiac output using thermodilution?
Col
der
Time
Thermodilution
AUC
.TT Volume. AUC
added cold Mass InjectateBody. kQ
Body temperature
Q: How do you measure Cardiac output using thermodilution?
Col
der
Time
Thermodilution
0B
InjectateBody.
)(T
.TT Volume. AUC
added cold Mass
dtt
kQ
Body temperature
Modified Stewart-Hamilton equation
Q: How do you measure Cardiac output using thermodilution?
Col
der
Time
Thermodilution
AUC added cold Mass.
Q
Body temperature
Q: How do you measure FRC using a Body Plethysmograph?
Q: How do you measure FRC using a Body Plethysmograph?
• The Body Plethysmograph is a method to measure lung volumes by the application of Boyle’s Law
Q: How do you measure FRC using a Body Plethysmograph?
Box pressure
Shutter
Mouth pressure
Calibrating syringe
• Step1. – Calibrate changes in
box pressure as changes in volume of air in the box
Q: How do you measure FRC using a Body Plethysmograph?
Box volume
Q: How do you measure FRC using a Body Plethysmograph?
• Step2. – Apply Boyle’s Law to
lung air….– …while panting against
closed shutter
Box volume
Q: How do you measure FRC using a Body Plethysmograph?
• Step2.– Apply Boyle’s Law to
lung air….
Box volume
PBar. VFRC = (PBar- P). (VFRC + V)
Q: How do you measure FRC using a Body Plethysmograph?
• Step2.
Atmospheric pressure: 100 kPa
FRC? Mouth pressure when shutter closed
FRC? Box volume
PBar. VFRC = (PBar- P). (VFRC + V)
Box volume
Q: How do you measure FRC using a Body Plethysmograph?
• Summary– Method of measuring lung volumes by the application of Boyle’s
law– Briefly explain set up and calibration of box pressure for box air
volume– Write equation
Atmospheric pressure: 100 kPa
FRC? Mouth pressure when shutter closed
FRC? Box volume
Summary:
PBar. VFRC = (PBar- P). (VFRC + V)
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
• Full answer regarding accuracy– Practical aspects
• Prevention clot, kinking, choice of artery, cannulae• Zeroing
– Static accuracy– Dynamic accuracy
Natural frequency (FN)
Damping
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Tendency for a system to resist oscillation through friction
Frequency at which a system oscillates most freely
Natural frequency (FN)
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Frequency at which a system oscillates most freely
The FN is the same frequency as the upstroke of trace resonance and overshoot
Natural frequency
High as possible
Prevents resonance from biological signals
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
4HRF
N
Short, stiff, short, wide tubing
Small stiff transducer
Low density fluid
Natural frequency
Damping
High as possible
Optimal
Prevents resonance from biological signals
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
7% overshoot in fast flush test
Natural frequency
Damping
High as possible
Optimal
Prevents resonance from biological signals
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
D = 0.64
Short, stiff, short, wide tubing
Small stiff transducer
High density fluid
Natural frequency
Damping
High as possible
Optimal
Prevents resonance from biological signals
To produce flat frequency response
Prevent phase distortion
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Prevents amplitude distortion of high frequency waveforms
All elements of the waveform are delayed by the same time interval
To produce flat frequency response
Arterial waveforms are made up of several different sine waves of different frequencies
Fourier analysis
To produce flat frequency response
Frequency of sine waves
Am
plitu
de re
lativ
e to
cor
rect
am
plitu
de
1.0 Ideal
Very under-damped (0.1)
FN
Optimal damping (0.64)
Flat frequency response to 2/3 FN
All but the very fastest waveforms will be reproduced without amplitude distortion
Too
big
Too
smal
l
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Natural frequency
Damping
High as possible
Optimal
Prevents resonance from biological signals
To produce flat frequency response
Prevent phase distortion
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
Prevents amplitude distortion of high frequency waveforms
All elements of the waveform are delayed by the same time interval
Prevent phase distortion
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
All elements of the waveform are delayed by the same time interval
Natural frequency
Damping
High as possible
Optimal
Prevents resonance from biological signals
To produce flat frequency response
Prevent phase distortion
Q: What are the important physical principles in the design of an invasive pressure monitoring system?
D = 0.64
4HRF
N
Q: How does BIS analyse EEG?
Clinical levels of anaesthesia scored
Statistically determine
EEG patterns commonest at each level of
anaesthesia?
EEG analysed from 2000 healthy adultsundergoing different levels of anaesthesia
Step 1 Step 2
Step 3
Q: How does BIS analyse EEG?How the algorithm was determined
Q: How does BIS analyse EEG?
EEG patterns compared with algorithm
Score determined
from 0 – 100Anaesthesia
recommended 40-60
Patient’s EEG analysed
How the real time analysis works on patients
Burst suppression
Power spectral analysis
Bispectral:
Phase coupling
Q: How does BIS analyse EEG?Bispectral:
Degree of EEG synchronisation
Q: How does BIS analyse EEG?
Q: How does BIS analyse EEG?
Q: How does BIS analyse EEG?