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MEDICAL
INSTRUMENTATION
8th 2005200444 정진웅
Chapter. 9
Respiratory System Measurement
Respiratory System Measurement
From now on,
we focus on two subject
- PFT : pulmonary function test
- Patient monitoring(Respiration monitoring)
Respiratory System Measurement
( Architecture )
trachea
UT  AT
velocit
y
Q  UT  AT  U A  AA
bronchi
a
airflo
w
U A  AA
alveolar
cross
section
area
(l / min )or (ml / s)
U A  UT
O2 and CO2
diffusion at alveolar
AT
AA
Respiratory System Measurement
◎ physiological function
- O2 transport into blood stream
- CO2 removed from blood stream
- Homeostasis of ph, partial pressure of O2, partial pressure of
CO2
Ventilatory mechanics
⇒ RC equivalent circuit model
◎ Respiration
Gas transport
⇒ Mass balance equation
(Diffusion process)
Respiratory System Measurement
◎ Pressure measurement
① Differential Pressure transducer
Diaphragm
P2
P1
x1
Strain gage
x2
C
A
C1
B
C2
Respiratory System Measurement
② Balloon sensor
hole
gas
pressure sensor
(balloon)
5V
force pressure (P)
metal switch
0V : switch on P > Pi
or,
5V : switch off P < Pi
resistor
V1
P
air pump
force pressure (P)
control
Respiratory System Measurement
◎ Flow measurement
① Rotating vane
② Ultrasound flow-meter
③ Thermal convection flow-meter
④ Prieumotachometer
Respiratory System Measurement
P1
P2
Diff pressure
sensor
Q(flow)
mesh
screen
measurement
using with a injector
P1  P2  RQ
resistance(fixed)
P1  P2
Q
R
mouth
Respiratory System Measurement
◎ Volume measurement (plethysmography)
Respiratory System Measurement
① water spirometer
air
water
mouth
CO2absorber
Respiratory System Measurement
② dry spirometer
mouth
expiratory
gas
piston
Inspiratory
gas
valve
Respiratory System Measurement
◎ FRC measurement
① Helium dilution technique
- Patient at FRC
- Prepare a spirometer of volume VSP and
initial He concentration of fIHE
- Patient brethes helium the spirometer
- Find helium contradiction of expiration gas fFHE
Respiratory System Measurement
VSP  FIHE  (VSP  FRC )  FFHE
“ Equation of mass balance ”
FIHE  FFHE
 FRC 
 VSP
FFHE
Respiratory System Measurement
② N2 washout technique
- Patient at FRC
- Prepare a spirometer with VSP , O2
- Patient brethes to the spirometer
- Measure N2 concentration in the expiratory gas
0.8  FRC  ( FRC  VSP )  FFN2
Respiratory System Measurement
◎ Gas concentration measurement
① Mass spectroswophy
② Gas chromatography
③ Infrared spectroswophy
④ Raman spectroswophy
⑤ Emission spectroswophy
⑥ Paramagnetic O2 analyzer
Respiratory System Measurement
◎ Gas transport measurement
① Gas distribution test
⇒ single N2 breathe washout
- RC → TLC O2 inspiration
- Pause (Hold breath)
- Expiration and measure FN2
Respiratory System Measurement
② Diffusion
⇒ CO diffusion capacity
- Inspire CO, He, in air to TLC ( FICO , FIHe )
- Hold breath for 10sec.
- Expire to measure FFCO and FFHe
f ICO FFHe
60V
 DCO 
ln(

):
t
(
P

47
)
F
f
fCO
IHe
CO diffusion
capacity
THANKS!