Respiratory Function - China Medical University
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Transcript Respiratory Function - China Medical University
Respiratory Function Test
Department of internal medicine
Chen Yu
Respiratory Function Test
Lung
volumes
Ventilation function
Gas exchange
Blood flow
Respiratory motive force
Lung Volume and Subdivisions
IC
TLC
VC
IRV
VT
ERV
FRC
RV
RV
Basal Lung Volume
VT
(tidal volume): 500ml
IRV (inspiratory reserve volume)
ERV (expiratory reserve volume)
RV (residual volume)
Basal Lung Capacity
IC
(inspiratory capacity): VT+ IRV
FRC (functional residual capacity):
ERV + RV
VC (vital capacity) : IC + ERV
normal men: 4217ml
women: 3105ml
TLC (total lung capacity): VC + RV
Some Explanatory Points
Lung
volume is to describe the changes of
the lung volume during one breathing at
static conditions, also called static lung
volume.
VT, VC, TLC are used at clinical. VT and
VC are determined by Spirometric trace ,
but FRC and RV by indirect method:
Helium or Nitrogen analyses method.
Clinical Significance
VC
depends on sex, age and height.
VC% < 80% is abnormal.
VC : restrictive ventilation disorder
severe obstructive ventilation disorder
Clinical Significance
RV/TLC%
(residual air rate)
normal : < 35%
emphysema: > 40 %
old person can be 50%.
FRC : emphysema
FRC : interstitial pulmonary fibrosis
Ventilation Function Test
It
is called as dynamic lung volumes.
Fast
spirometric trace to illustrate timed
ventilation tests (air volume and air flow
during breathing).
Ventilation Function Test
Lung
ventilation volume
VE and MVV
Forced vital capacity (FVC)
Maximal mid-expiratory flow (MMEF.
MMF)
·
Alveolar ventilation (VA)
VE
( minute ventilation):
= VT×RR/min
normal : 4—6 liter
< 3L : hypoventilation
>10L: hyperventilation
MVV
( maximal voluntary ventilation):
ventilative volume at the most rate and
most breathing deep during a minute
Normal : 80—100L
abnormal: < 70L
MVV%=(MVV—VE)/MVV %
Normal: >95%
ventilation storage : <86%
FVC
(Forced Vital Capacity)
The volume that after full inspiration,
to expire with the most force and the most
rate.
FEV1
(forced expiratory volume in the first
second)
FEV1/FVC% ( the first rate)
FEV1/FVC%: 83%
FEV2/FVC%: 96%
FEV3/FVC%: 99%
Normal: > 80%
<70%: obstructive ventilation disorder
MMEF (maximal
mid-expiratory flow)
The mean flow between 25% and 75%
forced expiration.
Significance: to evaluate the small airway
obstruction in early stage
VA (alveolar ventilation)
The air volume entered respiratory
bronchioli and the alveoli during a
minute.
VD (dead space )=150ml
VA = (VT –VD) ×RR/min
Normal VD/VT=0.3-0.4
VD/VT : effective ventilation increased
VD/VT : effective ventilation decreased
Clinical Values of Ventilation Test
MVV active/predictive%
Air
rate index =
VC active/predictive%
Normal
: =1
Degrees of Lung Disfunction
VC or MVV act/pre%
Normal
>80
Mild reduce
80-71
Mediate reduce
70-51
Severe reduce
50-21
Respiratory failure <=20
FEV1%
>70
70-61
60-41
<=40
Classification of Ventilative Function Disorder
obstruction
FEV1/FVC
MVV
VC
N or
Rate index
<1.0
RV
TLC
N or
restriction
N or
or N
>1.0
N or
mix
=1.0
uncertain
uncertain
Degrees of Obstructive Emphysema
RV/TLC (%)
Normal
<=35%
Mild emphysema
36-45
Mediate emphysema
46-55
Severe emphysema
>=56
Bronchial Dilation Test
Method:
to determine FEV1 and FEV1/FVC%
before and after ß2-agonist inhalation
After-before
× 100%
improved rate= before
Positive: >15%
Reversible limitation:
asthma
>15% and improved volume>200ml
Result:
PEF Variable Rate
PEF
(peak expiratory flow): the most flow
during forced expiration. It indicates the
force of respiratory muscle and airway
obstruction.
PEFmax-PEFmin
× 100%
PEF variability=
1/2 (PEFmax+PEFmin)
PEF
variability≥20% : asthma
Bronchial Provocation Test
Method
: to inhale histamine from low to
high concentration till the FEV1 decrease
≥20%. Calculate drug volume (PD20FEV1).
Positive:
PD20FEV1<7.8umol
indicate airway hyperresponsiveness
asthma
Gas Exchange Test
Gas
distribution: Nitrogen concentration
method
normal < 2.5%
· ·
Ventilation/perfusion ratio (V/Q) : 0.4
P(A-a)O2: 5-15mmHg
Diffusion capacity (DL): CO method
Small Airway Function Test
airway: diameter ≤2mm
Closing volume (CV): N2 or He method
Maximum expiratory flow-volume curve
(MEFV):
indicate disease from the curve shape
Small
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