1. Respiratory Function Test
Department of internal medicine
Chen Yu

2. Respiratory Function Test
Lung volumes
Ventilation function
Gas exchange
Blood flow
Respiratory motive force

3. Lung Volume and Subdivisions
IRV IC VC
TLC VT
ERV
FRC RV RV

4. Basal Lung Volume VT (tidal volume): 500ml
IRV (inspiratory reserve volume)
ERV (expiratory reserve volume)
RV (residual volume)

5. 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

6. 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.

7. Clinical Significance
VC depends on sex, age and height.
VC% < 80% is abnormal.
VC : restrictive ventilation disorder
severe obstructive ventilation disorder

8. Clinical Significance
RV/TLC% (residual air rate)
normal : < 35%
emphysema: > 40 %
old person can be 50%.
FRC : emphysema
FRC : interstitial pulmonary fibrosis

9. 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).

10. Ventilation Function Test
Lung ventilation volume
VE and MVV
Forced vital capacity (FVC)
Maximal mid-expiratory flow (MMEF. MMF)
Alveolar ventilation (VA)

11. VE ( minute ventilation):
= VT×RR/min
normal : 4—6 liter
< 3L : hypoventilation
>10L: hyperventilation

12. 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%

13. FVC (Forced Vital Capacity)
The volume that after full inspiration, to expire with the most force and the most rate.

14. 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

15. MMEF (maximal mid-expiratory flow)
The mean flow between 25% and 75% forced expiration.
Significance: to evaluate the small airway obstruction in early stage

16. 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=
VD/VT : effective ventilation increased
VD/VT : effective ventilation decreased

17. Clinical Values of Ventilation Test
Air rate index =
Normal : =1
MVV active/predictive%
VC active/predictive%

18. Degrees of Lung Disfunction
VC or MVV act/pre% FEV1%
Normal > >70
Mild reduce
Mediate reduce
Severe reduce <=40
Respiratory failure <=20

19. Classification of Ventilative Function Disorder
obstruction restriction mix
FEV1/FVC N or
MVV or N
VC N or
Rate index < > =1.0
RV N or uncertain
TLC N or uncertain

20. Degrees of Obstructive Emphysema
RV/TLC (%)
Normal <=35%
Mild emphysema
Mediate emphysema
Severe emphysema >=56

21. Bronchial Dilation Test
Method: to determine FEV1 and FEV1/FVC% before and after ß2-agonist inhalation
Result: improved rate=
Positive: >15%
Reversible limitation: asthma
>15% and improved volume>200ml
After-before ×
100%
before

22. PEF Variable Rate
PEF (peak expiratory flow): the most flow during forced expiration. It indicates the force of respiratory muscle and airway obstruction.
PEF variability=
PEF variability≥20% : asthma
PEFmax-PEFmin ×
100%
1/2 (PEFmax+PEFmin)

23. 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

24. 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

25. Small Airway Function Test
Small airway: diameter ≤2mm
Closing volume (CV): N2 or He method
Maximum expiratory flow-volume curve (MEFV):
indicate disease from the curve shape

26. Thank you!