Respiratory Function Test Department of internal medicine Chen Yu

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

Lung Volume and Subdivisions VT IRV ERV RV IC FRC VC RV TLC Normal respiration basal line Forced respiration basal line 500ml

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

Basal Lung Capacity F IC (inspiratory capacity): VT+ IRV F FRC (functional residual capacity): ERV + RV F VC (vital capacity) : IC + ERV normal men: 4217ml women: 3105ml F TLC (total lung capacity): VC + RV

Some Explanatory Points F Lung volume is to describe the changes of the lung volume during one breathing at static conditions, also called static lung volume. F 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 F VC depends on sex, age and height. F VC% < 80% is abnormal. F VC : restrictive ventilation disorder severe obstructive ventilation disorder

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

Ventilation Function Test F It is called as dynamic lung volumes. F Fast spirometric trace to illustrate timed ventilation tests (air volume and air flow during breathing).

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

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

F MVV ( maximal voluntary ventilation): ventilated volume at the most rate and most breathing deep during a minute Normal : 80—100L abnormal: < 70L F MVV%=(MVV—VE)/MVV % Normal: >95% ventilation storage : <86%

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

F FEV1 (forced expiratory volume in the first second) F FEV1/FVC% ( the first rate) FEV1/FVC%: 83% FEV2/FVC%: 96% FEV3/FVC%: 99% Normal: > 80% FEV1/FVC% <70%: obstructive ventilation disorder FEV1/Pridict value <80%: obstructive ventilation disorder

FVC Curve 83% Normal 96%99% FVC

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

F VA (alveolar ventilation) The air volume entered respiratory bronchioli and the alveoli during a minute. F VD (dead space )=150ml F VA = (VT –VD) ×RR/min F Normal VD/VT= VD/VT : effective ventilation increased VD/VT : effective ventilation decreased

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

Degrees of Lung Disfunction VC or MVV act/pre% FEV1% Normal >80 >70 Mild reduce Mediate reduce Severe reduce <=40 Respiratory failure <=20

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

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

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

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

Bronchial Provocation Test F Method : to inhale histamine from low to high concentration till the FEV1 decrease ≥20%. Calculate drug volume (PD 20 FEV1). F Positive: PD 20 FEV1<7.8umol indicate airway hyperresponsiveness asthma

Gas Exchange Test F Gas distribution: Nitrogen concentration method normal < 2.5% F Ventilation/perfusion ratio (V/Q) : 0.8 P (A-a)O2 : 5-15mmHg F Diffusion capacity (D L ): CO method Normal: D L CO =20 ～ 25 ml/min/mmHg D L CO ≥80%Predict D L CO ＜ 80%Predict---Diffusion capacity ··

Small Airway Function Test F Small airway: diameter ≤2mm F Closing volume (CV): N 2 or He method F Maximum expiratory flow-volume curve (MEFV): Flow-Volume Curve （ V-V Curve ） indicate disease from the curve shape ·

Lung disease normal Flow L/s Vmax 75% Vmax 50% Vmax 25% Flow-Volume Curve （ V-V Curve ） Volume

V-V curve when different diseases

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