# 3 - Ventilation.pdf

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Published on 17 Apr 2013
School
Department
Course
IV. Ventilation
West – Chapter 2
sept 26th
Spirometers --> measures lung volume
- sit down in front of machine with nose clip
- directs all air through mouth --> all air going through regulator tube
- drum connected to a pulley, connected to a pen which traces to a graph
- volume inc = drum goes up = pen goes down = tracing :. up on graph (inspiration), down on graph (expiration)
- x-axis: time, y-axis: change in volume
...see next slide
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Volume (L)
Spirogram and subdivision of
the lung volumes
**
**inspiration
*
* expiration
X
X : breathe in as much as you can
Y
__
| Tidal volume
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Inspiratory Pressure Volume
Vt
Expiratory Pressure Volume
Residual Volume
- air left in lungs
- cant be measured with a spirometer
[1]
[2]
[3]
[4]
smallest unit measured
in the lungs
Inspiratory
capacity
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Expiratory
capacity
Measuring Total Lung Capacity
O
Functional
reserved capacity
(FRC)
- vol. in lungs at
end of normal expiration
- equal & opposite forces
- put more work in to expand lungs
- always want to come back to FRC
-
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Measurement of RV by Helium
********
VALVE
LUNG
MACHINE
[C1]=6%
measures 6% v
Valve = 4L
He
Equilibrium
[C] = 3%
Vtotal = V
C1V1 = C2V2
(6%)(4L) = (3% He) (V total)
L + (VM / 4L)
Assumption
----------------
Solubility of He is low
=========
cardiac output & exchange
(residual
volume)
- spirometer filled with helium
- The amount of He in the
spirometer is known at the
beginning of the test
(concentration x volume = amt)
- patient is then asked to
breathe (normal
breaths) in the mixture
starting from FRC (Functional
Residual Capacity), which is the
gas volume in the lung after a
normal breath.
- spirometer measures [helium]
- helium spreads into the lungs of the
patient, settles at a new concentration
(C2)
- Because there is no leak of substances
in the system, the amount of helium remains
constant during the test, and the FRC is
calculated by using the following equation:
C1×V1 = C2×V2
(START HERE)
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