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CLINICAL MEASUREMENT topics CLINICAL MEASUREMENT topics

CLINICAL MEASUREMENT topics - PowerPoint Presentation

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CLINICAL MEASUREMENT topics - PPT Presentation

Prof Şerban Bubenek MD 1 st Cardiovascular Anesthesia amp Intensive Care Dept  CCIliescu  Institute for Cardiovascular Diseases Bucharest ROMANIA TODAY we speak about ID: 785000

measurement pressure indicator arterial pressure measurement arterial indicator method pac pulse invasive blood measurements dilution monitoring artery temperature flow

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Slide1

CLINICAL MEASUREMENT topics

Prof. Şerban Bubenek MD1-st. Cardiovascular Anesthesia & Intensive Care Dept« C.C.Iliescu » Institute for Cardiovascular DiseasesBucharest - ROMANIA

Slide2

TODAY we speak about :Arterial Pressure Measurement

Cardiac Output Measurement

Slide3

.

Every patient receiving general anesthesia shall have, in addition to the above, circulatory function continually evaluated by at least one of the following: - palpation of a pulse - auscultation of heart sounds - monitoring of a tracing of intra-arterial pressure - ultrasound peripheral pulse monitoring - pulse plethysmography or oximetry !

Slide4

no universal ‘target blood pressure value’ to define intra-operative hypotension

but: - decreases >20% in MAP or for cumulative durations of > 30 minutes - MAP < 60 mmHg ↑ risk of post-op.: MI, stroke, and death. (104,245,246) IIb B Efforts should be made to prevent intra-operative arterial hypotension and inadequately deep anaesthesia.

Slide5

Essential requiremets for CLINICAL MEASUREMENT

ACCURACYis the difference between: the measurements and the real biological signal - in practice, is Δ between: a certain technique vs. a superior 'gold standard‘ techniquePRECISION =

reproducibility

of repeated measurements of the same biological signal.

-

calibration is important

( against predetermined signals or for absolute measurements to zero)

Slide6

.

MEASUREMENT of ARTERIAL PRESSURE a wide range of instruments are used to measure pressure :liquid column manometers : height, zero point, fluid densitymechanical pressure gauges : aneroid manometerdiafragm gauges (coupled to transducers)

Slide7

MEASUREMENT OF ARTERIAL PRESSURE

INDIRECT measurement (non-invasive & not-continous ) - signals generated by the occlusion of a major artery using a cuff - gives not continous but intermittent measurements a. palpation method ( Riva Rocci)

b. auscultation of the Korotkoff

sounds

c.

oscilometry

method

DIRECT measurement (invasive and continuous)

Slide8

Indirect Methods of BP measurement (1)

1. Riva Rocci: simplest method of BP measurement, estimating only the SBP, is by palpating the return of arterial pulse as cuff is deflated.2. Auscultation of the Korotkoff sounds : both SBP and DBPon deflation created by the turbulent blood flow in the artery

Mean Arterial Pressure (MAP) = (SBP + 2 DBP) / 3

Slide9

Indirect Methods of BP measurement (2)

3. OSCCILOMETRY - a microprocessor controlled oscillometer: DINAMAP- a pressure transducer that digitalizes signals ( microprocesor). - rapid, accurate, measurements of SBP, DBP, MAP and HR - SAP = the onset of rapidly increasing oscillations

-

MAP

=

the

maximal oscillation

at the lowest cuff pressure

-

DAP

corresponds to

the onset of rapidly decreasing oscillations

LIMITATIONS:

tendency to:

overestimate at low pressures and underestimate at high pressures

errors :

movements, arrhythmias or rapid BP fluctuations

-

compressive peripheral nerve injuries

(repeated measurements )

Slide10

Cuff Size !

Too small cuff will result in false high blood pressure readingToo large cuff will result in false low

blood pressure reading

Slide11

DIRECT Measurement of the BP

invasive : a catheter into the artery METHODS 1. open Liquid column method : it is obsolete and it measures only MAP! 13.4 cm. H2O = 10 mm.Hg. !

2. Liquid manometers

(obsolete)

3.

Electromechanical transducers

:

-

conversion of mechanic signal into an electric signal

-

and then electronically converted and displayed as :

SAP, DAP, MAP

Slide12

Electromechanical

transducersThe diaphragm : - is moved by arterial pulsations which push the saline columnshould be thin, small and rigid !Transducer : - based upon strain gauge principle : stretching (by PRESSURE ) a wire or a silicone crystal changes its electrical resistance

- connected to a wheatstone

bridge circuit

the voltage output is proportionate to the pressure applied it

!

Slide13

The 3 major problems may occur:

1. Improper zeroing and zero drift2. Improper transducer / monitor calibration 3. Inadequate dynamic response of system : a. RF ( resonant or natural frequency) b. damping

RF =

frequency at which a system oscillates when stimulated

- if the frequency of an input signal (

i.e.,

pressure waveform

) approaches the RF of a system : progressive amplification of the output signal occurs,

a phenomenon known as

ringing.

Slide14

The ARTERIAL PRESSURE Waveform

ARTERIAL WAVEFORM is a complex sine-wave The fundamental frequency (FF) or the 1-st harmonic is equal to the HR ( ex: for HR 60 b/min = 1 beat / sec = 1 cycle/sec = 1Hz.)physiologic peripheral arterial waveforms have a FF = 3 to 5 Hz ( 180 – 300 beats / min)The MONITORING SYSTEM ( catheter + transducer + lines)

- RF of the monitoring system should be at least at least 5 times higher than the highest frequency in the input signal or better : approx.10 times the FF

at least RF > 20 – 25 Hz to avoid ringing and systolic overshoot

Slide15

The ARTERIAL PRESSURE Waveform

,Damping Coefficient (DC): is a measure of how quickly an oscillating system comes to rest Testing DC: the fast-flush test (“square wave” test)

optimal damping

overdamping

= underestimates SAP and overestimates DAP

-

underdamping

= overestimates SAP and underestimates DAP

- in

both cases however,

MAP is relatively accurate !!!

Slide16

REDUCING ARTIFACTS IN A-LINES

Lines free of kinks and clots avoid Air Bubbles : small amount may augment systolic pressure reading, while large amount cause an over-damped systemonly one stopcock per lineHeparinized saline flushed maintaining patency

Transducer should be electronically balanced or

re-zeroed

because the zero point may drift if

the room temperature changes

to have an adequate damping =

flushing TEST !

The catheter and lines

:

short and rigid

Slide17

MEASUREMENT OF BLOOD FLOW:

CARDIAC OUTPUT

Slide18

Potential Methods able to measure the

Cardiac Output Fick method Indicator dilution Pulse waveform (“pulse contour”) methods Ultrasounds ( 2D-Echo and Doppler techique) BioimpedanceANGIOGRAPHYMRI

Slide19

Ideal Cardiac Output Monitoring Technique

Precise and No biasNon-invasiveContinous and instantaneousAutomaticOperator independentCheapEasy available in OR the ICULeads to treatment changes / improvement in outcome IT DOES NOT EXIST !

Use the Best Compromise : feasibility – precision – patient !

Slide20

The FICK principle

defines flow by: the ratio of the uptake or clearance of a tracer within an organ to the arterio-venous difference in concentration CO = VO2 / ( CaO2 – CvO2)

VO2 is measured by: a

spirometer

+ a Douglas bag

CvO2 is taken from the pulmonary artery

CaO2 is taken from a catheter in a peripheral artery

Slide21

The FICK method

considered to be the most accurate method for CO but : - invasive, time consuming - accurate VO2 samples are difficult to acquire discontinous CO : Deltatrac (Datex)

continous CO : possible, but no integrated system available

modified

Fick

equation :

continous

CO by NICO2 apparatus !

Slide22

INDICATOR DILUTION

CO measurement by indicator dilution has 3 phases :(a) an indicator is brought into the circulation (injection)(b) the indicator mixes with the bloodstream (mixing and dilution)

(c) the concentration of the indicator is measured

downstream

(detection)

Slide23

INDICATOR DILUTION

Chemical indicator dilution (dye)Thermal indicator dilution ( Thermodilution ) the widest used : PAC = Swan-Ganz

Slide24

Chemical indicator dilution

The Stewart-Hamilton formula (time-concentration curve) using indocyanine green was the conventional indicator dilution method used to measure CO in ICU until the 1970’s.Indocyanine green : - nontoxic, inert, safe - short half-life

- not affected by arterial saturation

Slide25

The Thermodilution

(TD) method Thermodilution = the indicator is the change in blood temperature a known volume of

injectate at low temperature

is injected into the

right atrium

and the cooled blood

traverses

a

thermistor

in a major vessel branch

downstream over a duration of time.

TD Methods :

1.

PULMONARY

Thermodilution

(P-TD) : PAC

2.

TRANSPULMONARY

Thermodiution

(TP-TD)

Slide26

The CLINICAL STANDARD

is the PAC !Pulmonary -TD

Slide27

PAC-Thermodilution

The change of the blood’s temperature in is measured in the pulmonary artery using the PAC thermistor and then,the monitor electronically displays a temperature/time curve.

The CO is inversely proportional to :

-

the temperature change

- the area under the curve

PAC measures the Pulm.CO = Global CO if no intra-cardiac shunt exists!

Slide28

Sources of

error for P-TDLoss of indicator Variation of injectate temperature and volumeRecirculation - IC shunts : false high CO valuesTricuspid regurgitation : false low CO valuesFluctuations in baseline temperature

Slide29

...........................

10 ml.cold saline (4 °- 6° C)optimal < 4 sec.> 4-5 sec. false low CO during the same respiratory phase-at least 3 measurements with ∆ less than < 10 % between them !

Slide30

Advantages of P-TD

the standard method for clinical CO measurementsimple and repeated measurements possibleThe modified PAC may provide CCOthermal indicator : intermitent heating of a resistance44°C for 1-4 sec, each 30-60 secNot really continuous : mean of 3-4 min ! expensive

The PAC provides not only CO, SV, ..

but also PA pressures, PCWP,

SvO2,

and optionally RVEF

and RVEDV.

but: IT IS INVASIVE!

Slide31

TRANSPULMONARY Thermodiution

(TPTD) The TPTD femoral artery curve appears later and has a lower

peak temperature than the

pulmonary artery TD

curve.

The TPTD was shown to be as accurate and precise as P-TD is !

TP-TD is less invasive than P-TD,

but does not offer:

SvO2, PCWP and PAP values

,

TD

TD

Slide32

The Clinical USE of TP-TD

Mainly : as a “ calibration method” for other systems : PiCCO, EV-1000PiCCO and EV-1000 are able after the initial calibration by TPTD, to measure in a continuous manner ( beat by beat ) the C.C.O, using the Pulse Contour method !

Slide33

CCO by the P

ulse contour methodThe area under the systolic part of the AP waveform correlates : - directly with Left Ventricular STROKE VOLUME - inversely with aortic impedance (Z)SV = Systolic Area / Z

Slide34

The Pulse Contour methods

CALIBRATED techniques PiCCO EV-1000 LiDCO – Pulse CO (TP- Lithium dilution)

NON-CALIBRATED techniques

Flow-Track – VIGILEO

Pro-AQT

Nexfin

( Clear-Sight): totally non-invasive

TPTD

C.C.O

.

mini-invasive

Slide35

PiCCO & EV-1000are “calibrated” C.C.O.( mean 5 -15 sec.) with intermittent TP-TD calibration. Enables continuous hemodynamic monitoring using: - a femoral / axilary artery catheter

+

- a central venous catheter (CVC)

Slide36

LiDCO – Pulse CO

the calibration technique is : Lithium indicator Dilutionsafe and minimally invasive : peripheral venous and arterial cathetersthe PulseCO algorithm used by LiDCO is based on pulse power analysis !Continuous, real-time cardiovascular monitoring

Slide37

Pulse Contour NON-CALIBRATED

techniques Flow-Track VIGILEOPulsioFlex- ProAQTLiDCO-rapid - demographics - only an arterial line + a proprietary sensor in line

NEXFIN (Clear-Sight)

- totally non-invasive !

Slide38

BIOIMPEDANCEbio tissues (bone,

muscle,blood, etc) have different electric proprietiesblood is the most conductive tissue ( Na+ and Cl-)pulsatile modifications of ITBV → Δ TB Δ TB ~ Δ stroke volume SV = K x (dZ / dt

) / Zo

x TEV

Δ TB is measured by : producing and

transmiting

electricity

( high

υ

= 70 kHz low A = 2,5

mA

) between 2 pairs of electrodes

Slide39

Echocardiography (ultrasounds)

for measuring the CO 2 D – methodDoppler - method

Slide40

UltrasoundsUS techniques can detect :

the shape, size and movement of tissue interfaces, especially soft tissues and blood (RBC)US are defined by : - amplitude of oscillation (dB) - the wavelength (distance between successive peaks) - frequency (inversely proportional to wavelength) nr. of cycles / secondhuman ear can detect frequencies : 20-20,000 Hz.

US have frequencies > 20,000 cycles /sec ( 20 KHz)

diagnostic US uses frequencies in the range of 1-10

MHz.

!!!!!

Slide41

2-D

MethodSV = EDV – ESVLV volumes (Simpson’s method): the summation of the volume of stacked cylinders within the LV at end-diastole and end-systole

SV

= 150 ml - 52 ml = 98 ml

Slide42

Doppler Effect

Doppler effect represented by: V = _ΔF . c _ 2 F0 cos θwhere V = velocity of object

Δ

F = frequency shift

c = speed of sound in medium (body tissue here)

F

0

= frequency of emitted sound

cos

θ

= angle between sound wave and flow (RBC)

cos

90◦ = 0 so the US beam should be parallel to RBC

Maximum angle = 20◦ !

Slide43

Doppler Method for CO measurements

Principle SV =Area x VelocityArea of left ventricular outflow tractObtain LVOT dimension in

parasternal long axis view

Simplified

formula

= (2.1cm)

2

* 0.785

D=2.1

cm

SV = 3.46

cm

2

Flow Velocity at LVOT

PW

Doppler at LVOT in apical 5 chamber view

Velocity time integral 25 cm

25

cm

=

87

cm

3

X

Slide44

OESOPHAGEAL DOPPLER

Measurement of blood flow velocity in the descending aorta at the tip of the flexible probe 4 MHz continuous or 5 MHz pulsed wave DAF FTc (corrected flow time)PV (peak velocity)  MD (minute distance)  HR (heart rate)

Slide45

n

Methods: ESICM invited 12 experts to form a Task Force to update a previous consensus (Antonelli et al.: Intensive Care Med 33:575–590, 2007) Conclusions This consensus provides 44 statements that can be used at the bedside to diagnose, treat and monitor patients with shock.

Slide46

Monitoring - KEY MESSAGES (1) NOT routine for measuring CO 1C

in non-responders to initial therapy

CO or SV should be measured”

to evaluate response to fluid or

inotropes

1 C

Serial measurements of

blood LACTATE

1 C

Not only lactate, but ScvO2 and CO2-gap 2 B

the commonly used preload measures (such as CVP, PAOP or

LVEDAi

or GEDV)

alone should not

be used to guide fluid resuscitation 1 B

use: dynamic over static variables

to predict fluid responsiveness

1B

Slide47

Hemodynamic Monitoring

ECHO is first !In complex pts. we suggest to use additionally to ECHO: PAC or TPTD to determine type of shock 2 CWe suggest PAC in patients with refractory shock + RV dysfunction. 2 C

We suggest the use of PAC or TPTD with in pts

. severe shock especially in the case of associated ARDS

2 C

We recommend that less invasive devices are used, instead of more invasive devices, only when they have been validated in shock pts. UG-BP

We

do NOT recommend the routine use of

PAC

for patients in shock.

1

A

Slide48

THANKS for your attention !

&GOOD LUCK !