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Computer‐aided measurement techniques

Department of Medical Informatics Faculty of MedicineUniversity of SzegedUniversity of Szeged

ComputerComputerComputer‐‐‐aided measurement techniquesaided measurement techniquesaided measurement techniques

Contents

course outlineaimsaimsstructurelecture outlinelecture outlinelaboratory practicals

measurement designelectromyographyelectrocardiographybl dblood pressure measurementrespiratory function


Course outline

aimsaims

To track the link between the world of the continuous analogue signals and the digital processing methods.

To address the main components of this link via the examples of typical non‐link via the examples of typical non‐invasive medical measurements.


Course outlinestructure

Lecture: basic module (4 hrs):Lecture: basic module (4 hrs):fundamentals and tools of measurement techniques and signal processing

Laboratory practicals (4x2 hrs):measurement task • physiological background • jointmeasurement task • physiological background • joint measurements & data acquisition

I di id l k (4 2 h )Individual work (4x2 hrs):off‐line processing of recorded data • report preparation

Seminar (2 hrs):discussion of findings • conclusions


Course outlineL t f d t l d t l f tLecture: fundamentals and tools of measurement techniques and signal processing

basic concepts: signals vs dataclassification of signalstransducerssignal conditioninga lisamplinganalog‐to‐digital conversion

pre‐processing in the time domainh f dpre‐processing in the frequency domain


LECTURE OUTLINE


Discrete (digital) data vs. continuous (analog) signals

SIGNALS:

Physical quantities changing (continuously) in time. They carry dynamic information.time. They carry dynamic information.

Examples: blood pressure recordings, ECG, EEG,Examples: blood pressure recordings, ECG, EEG, EMG, respiratory airflow and pressures.


Discrete (digital) data vs. continuous (analog) signals

DATA:

• Measured (numerical) values; they can be d i h i h llentered in the computer either manually or

from an “intelligent” measuring device di ldirectly.

Examples: blood gas concentrations determined from bloodExamples: blood gas concentrations determined from blood samples, readings of systolic and diastolic blood pressure valuesa ue

• Sample sequences from a (continuous) signal.p q g


DETERMINISTIC SIGNALS

Any future value can be predicted on the basis of past values

HARMONIC

PERIODIC

QUASI‐PERIODIC

TRANSIENT


NON‐DETERMINISTIC SIGNALS(random or stochastic processes)

The temporal change of the signal cannot be predicted by exact mathematical methods There are statistical means of characterizationmethods. There are statistical means of characterization.

STATIONARY

NON‐ STATIONARY(CHANGING POWER)

NON‐ STATIONARY(CHANGING MEAN)


CLASSIFICATION OF ANALOG SIGNALS

ANALOG

DETERMINISTIC NON-DETERMINISTIC

PERIODIC NON- STATIONARY NON-PERIODIC PERIODIC STATIONARY STATIONARY

HARMONIC QUASI-PERIODIC

GENERAL PERIODIC TRANSIENT


SIGNAL ACQUISITION AND PRE‐PROCESSING

CONDITIONED

ANALOGSIGNAL

TRANS‐ AMPLI‐ ANALOGA‐D DIGITALTRANS

DUCERAMPLIFIER

ANALOGFILTER

CONVER‐TER

PROCES‐SOR

ANALOGPHYSICAL DIGITALANALOGELECTRICAL

SIGNAL

PHYSICALSIGNAL

DIGITALVALUES


TRANSDUCERS (SENSORS)

transducer• temperature voltage

input (x) output (y)

t ti

temperature• force• pressure• velocity

voltage

y saturatione o i y• acceleration• voltageetc.

characteristics:linearity

offsetnon‐linearity

ysensitivityinput range(zero) stability

x

price


Shannon’s Sampling Theorem:Sampling frequency ≥ 2(max frequency)

original signal

Sampling frequency ≥ 2(max. frequency)

fs>2fmax

fs<2fmax


ANALOG‐DIGITAL CONVERSION

digitalvalues

sampling holding quantitizing codingq g g

011010

conditionedanalogi l

A‐D converter

signal


MULTICHANNEL CONVERSION

a li holdisampling holdingmultiplexeru1

A‐D converteru2

•

2

••

un


ANALOG‐DIGITAL CONVERSION

analog input

u>yu

y

clockinput

1 …101010…

&y

counterzeroing

digital‐analog digital…

digital analogconverter values

Uref


VALUES: CONTINUOUSTIME CONTINUOUSTIME: CONTINUOUS

X(t)X(t)

tt


VALUES: CONTINUOUSTIME DISCRETETIME: DISCRETE


VALUES: DISCRETETIME CONTINUOUSTIME: CONTINUOUS


VALUES: DISCRETETIME DISCRETETIME: DISCRETE


QUANTITATION ERROR


RESOLUTION OF THE A‐D CONVERSION

word length (bit) No of ranges resolution (%)word length (bit) No. of ranges resolution (%)

1 2 502 4 253 8 12.5… … …8 256 0.39110 1024 0.09812 4096 0.02416 65536 0.0015


LOW‐PASS FILTERING

itude

ampli

frequency (Hz)

time (s)


HIGH‐PASS FILTERING

ude

amplitu

frequency (Hz)

time (s)


BAND‐PASS FILTERING

ude

ampl

itu

frequency (Hz)

time (s)


Characterization of stochastic signals: amplitude distribution

200

300

200

300

(t) 0

100

rték

0

100

f

-200

-100

ér

-200

-100

t (s)

37.15 37.20 37.25 37.30 37.35-300

200

szám

0 5 10 15 20 25 30-300

200

t (s) szám


LABORATORY PRACTICALS


Course outlinestructure

Lecture: basic module (4 hrs):Lecture: basic module (4 hrs):fundamentals and tools of measurement techniques and signal processing

Laboratory practicals (4x2 hrs):measurement task • physiological background • jointmeasurement task • physiological background • joint measurements & data acquisition

I di id l k (4 2 h )Individual work (4x2 hrs):off‐line processing of recorded data • report preparation

Seminar (2 hrs):discussion of findings • conclusions


Course outlined f

1 electromyography (EMG)

topics and infrastructure

BIOPAC®

STUDENT LAB SYSTEM

1. electromyography (EMG)2. electrocardiography (ECG) 3 non invasive blood pressure (BP)SYSTEM 3. non‐invasive blood pressure (BP)

4 respiratory mechanics (RM)PISTON® 4. respiratory mechanics (RM)5. electroencephalography (EEG)*6. reaction time*

PISTON®

spirometry system

Wi L 7. skin galvanic response*8. respiratory cycle*9. polygraphy*

WinLung forced oscillation laboratory system p yg p y

* practicals ready for course extension


BIOPAC STUDENT LAB SYSTEM

Aoners

AD ‐DA

al con

diti

sensors:sign

aevaluation:

pre‐processingelectrodespressure transducersswitches

p p gtime intervalsfrequency contentcorrelation

.

.etc.

.

.etc.



setting‐up



setting‐up: sensors



setting‐up: channels



setting‐up: recording length & sampling



setting‐up: channel parameters


channel measurement boxes

channel # measurement type result

Biopac SL SYSTEMscreen

menu commands

lesson buttons

channel # measurement type resultscreen

lesson buttons

channel boxes measurement region

append markersmarker label

event markersmarker tools

lesson buttonsvertical scales

horizontal scalevertical scroll bar

horiz. scroll bar

journal tools

j l

zoom toolI‐beam cursorl ti t ljournal selection tool


electromyographyelectromyographyelectromyographyy g p yy g p yy g p y

electromyography

basics


electromyographyelectromyographyelectromyographybackground

y g p yy g p yy g p y

Skeletal muscle performs mechanicalwork.It is stimulated to contract when thebrain or spinal cord activates motor units.An action potential in the motoneuroncauses activation of muscle fibers.The activation of motor units by actionpotentials generates a stochastic voltagesignal in the muscle.gThe amount of work is proportional tothe number of activated motor units.Surface electromyography is measuresSurface electromyography is measures total muscle electrical activity via skin electrodes


electromyographyelectromyographyelectromyographymeasurement tasks


t f EMG d i t i h imeasurement of EMG during stepwise changes in grip force

i f EMG i icomputation of EMG intensitycorrelation analysis between grip force and EMG activityrelationship between grip force and EMG intensity during maximum effort


electromyographyelectromyographyelectromyographymeasurement protocol



electromyographyelectromyographyelectromyographypreprocessing


raw EMG power smoothed EMG powerraw EMG power smoothed EMG power


electromyographyelectromyographyelectromyographyevaluation: plateau responses



electromyographyelectromyographyelectromyographyevaluation: muscle fatigue


tt0.50.5


electromyographyelectromyographyelectromyographypoints of discussion

0 7

0.8

y g p yy g p yy g p yV.s) 0.6

0.7•• submaximal effort: linear submaximal effort: linear

relationshipsrelationshipsi l ffi l ff

Eva ‐ right armEva ‐ left arm

ower (m

V

0.4

0.5 •• maximal effort: maximal effort: dysproportional EMG dysproportional EMG powerpower

EMG po

0.2

0.3•• asymmetryasymmetry•• shifted relationshipsshifted relationships

E

0 0

0.1

0.2

grip force (N)

0 10 20 30 40 50 600.0

grip force (N)


electromyographyelectromyographyelectromyography0.8 points of discussion

y g p yy g p yy g p yV.s) 0.6

0.7Vladim ir ‐ right armVladim ir ‐ left arm

•• submaximal effort: linear submaximal effort: linear relationshipsrelationships

wer (m

V

0.4

0.5relationshipsrelationships

•• maximal effort: maximal effort: dysproportional EMG dysproportional EMG powerpower

EMG pow

0 2

0.3

powerpower•• asymmetryasymmetry•• different slopesdifferent slopes

E

0.1

0.2

i f (N)

0 10 20 30 40 500.0

grip force (N)


electromyographyelectromyographyelectromyography0.6 points of discussion

y g p yy g p yy g p ymV.s)

0.4

0.5B. A. ‐ right armB. A ‐ left arm

•• nearly linear nearly linear relationshipsrelationshipsk dk d

ower (m

0.3

0.4 •• marked asymmetrymarked asymmetry•• small intersmall inter‐‐observer observer

variabilityvariability

EMG po

0.2

0 0

0.1

grip force (N)

0 10 20 30 40 50 600.0

g p ( )


electrocardiographyelectrocardiographyelectrocardiographyg p yg p yg p y

l d helectrocardiography

basics


electrocardiographyelectrocardiographyelectrocardiographyBackground Action potentials

g p yg p yg p y

Specialized pacemaker cells start the electrical sequence ofsequence of depolarization and repolarization

The electrical signal is generated by the sinoatrial (SA) node and spreads to the ventricular muscle

The electrical activities of the heart can be detected on the body surface via

f l dsurface electrodes


electrocardiographyelectrocardiographyelectrocardiographyBackground:

g p yg p yg p y

rhythm generator:rhythm generator:sinus node

rhythm generator: rhythm generator: polarisation polarisation ‐‐depolarisationdepolarisation

atrioventricular (AV) node conducting conducting

systemsystemHis bundle

right and left contractile cellscontractile cells

systemsystem

Tawara bundle

Purkinje fibers


<ECG_principle_slow.gif>Computer‐aided measurement techniques

electrocardiographyelectrocardiographyelectrocardiographyR‐R

the ECG waves

g p yg p yg p y

1.1. baselinebaseline22 P: atrialP: atrial2.2. P: atrial P: atrial

repolarisationrepolarisation3.3. QRS: ventricular QRS: ventricular

depolarisationdepolarisationdepolarisationdepolarisation4.4. SS‐‐T: ventricular T: ventricular

contractioncontraction55 T: ventricularT: ventricular

P Q

5.5. T: ventricular T: ventricular repolarisationrepolarisation

P‐QQRS

Q‐TQ‐T


electrocardiographyelectrocardiographyelectrocardiographyWillem Einthoven (1860 –1927)

g p yg p yg p y

( )

Professor, University of Leiden (1886)of Leiden (1886)

Nobel Prize in Medicine (1924)( )


electrocardiographyelectrocardiographyelectrocardiographyAugustus Desiré Waller (1856–1922)

g p yg p yg p y


electrocardiographyelectrocardiographyelectrocardiography

Measurement tools

g p yg p yg p y



Electrode leads

Bipolar (Einthoven)The standard leads I II and IIIThe standard leads I, II and III form a triangle, from which the electrical axis of the heart can be establishedestablishedUnipolar

aVR: right handa ig aaVL: left handaVF: left leg



l

g p yg p yg p y

Measurement tools

non‐reusable electrodescable

lifiamplifieranti‐aliasing filterAD con erterAD converter



Measurement tools

The virtual ground: th t l t i lthe central terminal


electrocardiographyelectrocardiographyelectrocardiographysignal analysis

g p yg p yg p y

0 . 5 0

P

RT

P

R

0 . 0 0

mV

ECG P

Q

S

P

Q

4 . 4 0 4 . 6 0 4 . 8 0 5 . 0 0 5 . 2 0 5 . 4 0 5 . 6 0 5 . 8 0s e c o n d s

- 0 . 5 0S

QT intervalRR interval

display of the ECG signal at different time scalesdetermination of the characteristic time intervals (RR and QT) és and their ratio (QT/RR) t ki f th i t t h t ttracking of the instantaneous heart rate


electrocardiographyelectrocardiographyelectrocardiographyg p yg p yg p yheart rate dynamicsy

200.00

mean heart rates are similar in supine and sitting positionspost‐exercise heart rate decreases fast initially but does not normalise in 2 min

100.00

120.00

140.00

160.00

180.00

BP

M

Rat

e

0.00

20.00

40.00

60.00

80.00

0.50

1.00

1.50

mV

EC

G

0.00 12.80 25.60 38.40 51.20 64.00 76.80 89.60 102.40 115.20 128.00 140.80 153.60 166.40 179.20 192.00 204.80 217.60 230.40

-1.00

-0.50

0.00


seconds

electrocardiographyelectrocardiographyelectrocardiographysteady periods unaffected, baseline stability recovered

g p yg p yg p yPre‐processing: high‐pass

Deep breathing

0.50

1.00

VCGunfiltered

baseline stability recoveredfiltering

112.60 115.80 119.00 122.20 125.40 128.60 131.80 135.00 138.20 141.40 144.60 147.80 151.00 154.20seconds

-0.50

0.00

mEC

Deep breathing

unfiltered

0.00

0.50

1.00

mV

EC

Gf > 0.5 Hz

112.60 115.80 119.00 122.20 125.40 128.60 131.80 135.00 138.20 141.40 144.60 147.80 151.00 154.20seconds

-0.50

Deep breathing

1.00

112.60 115.80 119.00 122.20 125.40 128.60 131.80 135.00 138.20 141.40 144.60 147.80 151.00 154.20

-0.50

0.00

0.50

mV

EC

Gf > 1 Hz

112.60 115.80 119.00 122.20 125.40 128.60 131.80 135.00 138.20 141.40 144.60 147.80 151.00 154.20seconds



Effect of low‐pass filtering smoothing without shape distortion

g p yg p yg p y

p g g p

EC

Gunfiltered

1 1 1 . 0 0 1 1 1 . 2 0 1 1 1 . 4 0 1 1 1 . 6 0 1 1 1 . 8 0 1 1 2 . 0 0 1 1 2 . 2 0 1 1 2 . 4 0 1 1 2 . 6 0

EC

Gf < 20 Hzf < 20 Hz

1 1 1 . 0 0 1 1 1 . 2 0 1 1 1 . 4 0 1 1 1 . 6 0 1 1 1 . 8 0 1 1 2 . 0 0 1 1 2 . 2 0 1 1 2 . 4 0 1 1 2 . 6 0



ECG amplitude is modulated by respiration

185.00

195.00

Heart rate dynamics

125.00

135.00

145.00

155.00

165.00

175.00

BP

M

Rat

e

85.00

95.00

105.00

115.00

1 50

0.50

1.00

1.50

mV

EC

G

-1.00

-0.50

0.00

E

204.20205.00 205.80 206.60 207.40 208.20 209.00 209.80 210.60 211.40 212.20 213.00 213.80 214.60 215.40 216.20 217.00 217.80 218.60 219.40 220.20 221.00 221.80 222.60 223.40 224.20 225.00 225.80 226.60seconds


electrocardiographyelectrocardiographyelectrocardiographyboth ECG amplitude and heart rate are modulated by breathingHeart rate dynamics

g p yg p yg p y

After sitting u

165.00

175.00

185.00

are modulated by breathingy

115.00

125.00

135.00

145.00

155.00

BP

M

Rat

e

85.00

95.00

105.00

2.00

0.50

1.00

1.50

mV

EC

G

30.40 32.00 33.60 35.20 36.80 38.40 40.00 41.60 43.20 44.80 46.40 48.00 49.60 51.20 52.80 54.40 56.00 57.60 59.20 60.80seconds

-1.00

-0.50

0.00


electrocardiographyelectrocardiographyelectrocardiographyrespiration changes the length of the isoelecticECG h t t d i

g p yg p yg p y

length of the isoelectic intervalECG: heart rate dynamics

0.50

mV

0.00

-0.50

Q ‐ TQ ‐ T

90.80 91.00 91.20 91.40 91.60 91.80 92.00 92.20 92.40 92.60 92.80 93.00 93.20 93.40 93.60dseconds


electrocardiographyelectrocardiographyelectrocardiographyHeart rate dynamics

g p yg p yg p yQ‐T shortening and recovery

Q ‐ T0 . 5 0

1 . 0 0

rest

1 1 2 . 6 0 1 1 2 . 8 0 1 1 3 . 0 0 1 1 3 . 2 0 1 1 3 . 4 0 1 1 3 . 6 0 1 1 3 . 8 0 1 1 4 . 0 0 1 1 4 . 2 0 1 1 4 . 4 0s e c o n d s

- 0 . 5 0

0 . 0 0

mV

EC

G

1 . 0 0

0 . 0 0

0 . 5 0

mV

EC

G10 s

R‐R and Q‐T intervalsshorten

1 4 7 . 8 0 1 4 8 . 0 0 1 4 8 . 2 0 1 4 8 . 4 0 1 4 8 . 6 0 1 4 8 . 8 0 1 4 9 . 0 0 1 4 9 . 2 0 1 4 9 . 4 0 1 4 9 . 6 0s e c o n d s

- 0 . 5 0

0 . 5 0

1 . 0 0

post‐exercise

R‐R interval still elevated

2 2 3 . 4 0 2 2 3 . 6 0 2 2 3 . 8 0 2 2 4 . 0 0 2 2 4 . 2 0 2 2 4 . 4 0 2 2 4 . 6 0 2 2 4 . 8 0 2 2 5 . 0 0 2 2 5 . 2 0

- 0 . 5 0

0 . 0 0

mV

EC

G

100 s

post‐exercises e c o n d s



Poi t of di u ioPoi t of di u io

g p yg p yg p y

Why was the ECG baseline less stable after the exercise than before?

Points of discussion:Points of discussion:

Why was the ECG baseline less stable after the exercise than before?

Heart rate did not return to the resting level in 2 min after the exercise. H l i d hi k ld b d d f l ?How long time do you think would be needed for a complete recovery?

High‐pass filtering can restore the baseline stability of a recording that g p g y gincludes low‐frequency fluctuations, but it must not change the ECG waveform. What (high‐pass) corner frequency (in Hz) would you set if the minimum heart rate in the recording is 70/min?the minimum heart rate in the recording is 70/min?


blood pressure measurementblood pressure measurementblood pressure measurement

non‐invasive measurement of blood pressure

basicsbasics


blood pressure measurementblood pressure measurementblood pressure measurementINDIRECT MEASUREMENT OF SYSTEMIC BLOOD PRESSURE

arrangement of the auscultation method

Riva-Rocci, 1896Korotkoff, 1905


blood pressure measurementblood pressure measurementblood pressure measurementINDIRECT MEASUREMENT OF SYSTEMIC BLOOD PRESSURE

PRINCIPLE: comparison of cuff pressure, Korotkoff sounds and ECG

Nikolai Sergeievich Korotkoff


blood pressure measurementblood pressure measurementblood pressure measurementmechanisms of the Korotkoff sounds

cavitation theory

vessel wall stretch htheory

turbulenceother theoriesother theoriescombinations


blood pressure measurementblood pressure measurementblood pressure measurementIDENTIFICATION OF THE KOROTKOFF SOUNDS

75.00

125.00

175.00

25.00

0.98

1.95

off S

ound

s) first sound last sound

-1.95

-0.98

0.00 mV

Ste

thos

cope

(Kor

otko

0 50artefacts

0 25

0.00

0.25

0.50

mV

EC

G (.

5 - 3

5 H

z)

0.00 10.02 20.03 30.05s econds

-0.50

-0.25



SYSTOLIC, MEAN AND DIASTOLIC PRESSURES

pressure (mmHg)

systolic (SBP)systolic (SBP)

A1mean (MAP)

PP

diastolic (DBP)A2

( )

t i l (MAP)mean arterial pressure (MAP):

MAP=DSP+PP/3pulse pressure (PP):

time (s)(A1≈A2)PP=SBP‐DBP


blood pressure measurementblood pressure measurementblood pressure measurementKOROTKOFF SOUNDS AND THE ECG CYCLE

110.56

113.32

116.08

cuff pressure

107.79

0 98

1.95ds

)

-0.98

0.00

0.98

mV

Ste

thos

cope

(Kor

otko

ff S

ound

sound

-1.95

0.25

0.50

V

35 H

z)

ECG

R

19.18 19.65 20.11seconds

-0.50

-0.25

0.00 mV

EC

G (.

5 - ECG Q

ST


blood pressure measurementblood pressure measurementblood pressure measurementpppstudy arrangement

BIOPAC STUDENT LAB SYSTEMBIOPAC STUDENT LAB SYSTEM

35MP3

Pcuff

micEKG


blood pressure measurementblood pressure measurementblood pressure measurementrecordings: cuff pressure – stethoscope sound ‐ ECG



identification of the Korokoff sounds and artifacts

?? ?



auditory vs visual identification of the Korokoff sounds


blood pressure measurementblood pressure measurementblood pressure measurementthe oscillometric principle maximum pulse pressure=mean arterial pressure

cuff pressure

stethoscope soundsound

ECG

pulse pressureextrapolation? extrapolation?


blood pressure measurementblood pressure measurementblood pressure measurementcomparison of the routine measurements with the computer evaluations: semiautomatic vs BIOPAC

130

140

Right 1Right 2

90

p

mm

Hg 120

130 Right 2Right 3Left 1Left 2Left 3 m

mH

g

70

80

P (s

emia

ut)

100

110Left 3

P (s

emia

ut)

60

70

SBP

80

90 DBP

50

SBP (BIOPAC) mmHg

70 80 90 100 110 120 130 14070

DBP (BIOPAC) mmHg

40 50 60 70 80 9040


blood pressure measurementblood pressure measurementblood pressure measurementcomparison of the routine measurements with the computer evaluations: wrist vs BIOPACp

130

14090

mH

g 120

130

mH

g

70

80

BP (w

rist)

m

100

110

BP (w

rist)

m

60

70

Right 1Ri ht 2SB

80

90 DB

40

50Right 2Right 3Left 1Left 2Left 3

SBP (BIOPAC) mmHg

70 80 90 100 110 120 130 14070

DBP (BIOPAC) mmHg

30 40 50 60 70 80 9030

Left 3


( ) g ( ) g

blood pressure measurementblood pressure measurementblood pressure measurementcomparison of the routine measurements with the computer evaluations: auscultation vs BIOPACp

130

140

Right 1 90

mm

Hg 120

130 Right 2Right 3Left 1Left 2Left 3 m

mH

g

70

80

P (a

uscu

lt) m

100

110Left 3

P (a

uscu

lt) m

60

70

SBP

80

90 DBP

40

50

SBP (BIOPAC) mmHg

70 80 90 100 110 120 130 14070

DBP (BIOPAC) mmHg

30 40 50 60 70 80 9030


( ) g ( ) g


points of discussion:

• effects of atherosclerosis• persistence of sounds below DBP• the mercury columnthe mercury column• aneroid barometers• finger photoplethysmography• finger photoplethysmography• upper arm – wrist ‐ finger• oscillometry• oscillometry


respiratory functionrespiratory functionrespiratory function

spirometry and oscillationspirometry and oscillation mechanics

basicsbasics


respiratory functionrespiratory functionrespiratory functionSpirometer types

Menzies spirometer (1790)

Water seal cylinder spirometer

Bellows spirometer


respiratory functionrespiratory functionrespiratory functionquasistatic lung volumes

a

TV

IRV

TLCVC

max

TVERVRV0

FRC

V

TV tid l lTV: tidal volumeIRV: inspiratory reserve volumeERV: expiratory reserve volumeRV: residual volume

FRC: functional residual capacityVC: vital capacityTLC: total lung capacity


RV: residual volume

respiratory functionrespiratory functionrespiratory functionforced expiratory flow‐volume loop

fl

expiration

flow

task: expiration of

inspiration volume

task: expiration of the maximum possible volume of the forcedof the forced expiratory vital capacity (FVC) in th 1 t dthe 1st second (FEV1)



the pneumotachographthe pneumotachograph

Fl (Vʹ) i d th d•Flow (Vʹ) is measured as the pressure drop across a fine metal or plastic screen

•In the laminar regime, the pressure drop is proportional to flow (Hagen‐Poiseuille law)

•Volume is obtained via integration of the flow signal



the simple model of respiratory mechanics – the resistance

mechanical analoguemechanical analogue

electrical analogueg



the simple model of respiratory mechanics – the inertance

mechanical analogue

electrical analogue



the simple model of respiratory mechanics – the elastance

mechanical analogue

electrical analogue


respiratory functionrespiratory functionrespiratory functionthe simple 3‐parameter model of respiratory mechanics

R (resistance)

di i ti

X (reactance)

energy dissipationresistance

energy storageinertanceelastance

frequency


respiratory functionrespiratory functionrespiratory functionbroad‐band impedance of the respiratory system


respiratory functionrespiratory functionrespiratory function3‐parameter evaluation of respiratory impedance

measured mean and SDmodel fitting

resonance

0.00


respiratory functionrespiratory functionrespiratory function3‐parameter evaluation of respiratory impedance

F%: mean fitting errorRaw: airway resistance (hPa s/l)Raw: airway resistance (hPa.s/l)Iaw: inertance (hPa.s2/l)H: elastance (hPa/l)

resonance frequency:

fRES = (1/2π) √(H/Iaw)


respiratory functionrespiratory functionrespiratory functionuse of reference values for spirometry and mechanicsmechanics

normal values established in a large population

statistical relationships describing the dependence on height a i i a e a io ip e i i g e epe e e o eig(H), age (A) and body weight (W), for both genders

e g the predicted value of Raw (Raw*) for females:e.g. the predicted value of Raw (Raw ) for females:

Raw*[hPa.s/l] = 9,051 – 0,0542∙H[cm] + 0,0105∙A[yr] + 0,0369∙W[kg]

if H=160 cm, A=20 yr and W=55 kg, Raw*=2,62 hPa.s/l



Points of discussion:Points of discussion:

• relationship between quasi‐static and forced expiratory vital capacity

• measures of reproducibility• errors in model fitting• errors in model fitting• interdependence of lung volumes and

mechanical parametersmechanical parameters



spirometry and oscillationspirometry and oscillation mechanics

basicsbasics


INTERREG IIIA Közösségi Kezdeményezés Program HUSER0602/066 Szegedi Tudományegyetem

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