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Pulmonary Function Tests

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1 Pulmonary Function Tests
Wanida Paoin

2 Objectives Review basic pulmonary anatomy and lung volume.
Indication for PFTs. Technique and basic interpretation of spirometry. Difference between obstructive and restrictive lung disease. Clinically application

3 Conducting Airways Air travels via laminar flow through the conducting airways: trachea, lobar bronchi, segmental bronchi, subsegmental bronchi, small bronchi, bronchioles, and terminal bronchioles.

4 From Netter Atlas of Human Anatomy, 1989

5 Gas Exchange Capillaries are wrapped around alveoli.
Approximately 300 million alveoli Alveolar-capillary barrier: 0.3 μm in some places, surface area of square meters! (size of a tennis court) Murray & Nadel: Textbook of Respiratory Medicine, 3rd ed., Copyright © 2000 W. B. Saunders Company

6 Lung Volumes 4 Volumes 4 Capacities Sum of 2 or more lung volumes IRV

7 Pulmonary Function Tests
Pulse oximetry Blood gases End tidal CO2 Spirometry Peak expiratory flow rate Bronchial challenge testing Exercise tests Respiratory muscle pressure measurement Lung volumes by helium dilution or body plethysmography Diffusing capacity

8 Pulmonary Function Tests
Evaluates 1 or more major aspects of the respiratory system Lung volumes Airway function Gas exchange

9 Indications Detect disease
Evaluate extent and monitor course of disease Evaluate treatment Measure effects of exposures Assess risk for surgical procedures Assess bronchial hyperreactivity

10 Evaluate extent and monitor course of disease
Obstructive disease - asthma - FB - subglottic, tracheal stenosis - tracheomalacia - vascular ring - vocal cord paralysis

11 Evaluate extent and monitor course of disease
Restictive disease - external compression: thoracic cage abnormality, pleural effusion, pneumothorax, obesity, scoliosis - unexpanded lung: interstitial fibrosis, pulmonary edema - neuromuscular disease: poliomyelitis, myasthenia grevis

12 Importance Patients and physicians have inaccurate perceptions of severity of airflow obstruction and/or severity of lung disease by physical exam Provides objective evidence in identifying patterns of disease

13 Spirometry Measurement of the pattern of air movement into and out of the lungs during controlled ventilatory maneuvers. หายใจเข้าเต็มที่ หายใจออกแรงเต็มที่ ส่วนใหญ่ทำได้ในเด็ก > 6 ปี Silhouette of Hutchinson Performing Spirometry, From Chest, 2002

14 Limitation They do not act alone.
They act only to support or exclude a diagnosis.

15 Mechanical Properties
Compliance Describes the stiffness of the lungs volume / pressure Elastic recoil The tendency of the lung to return to it’s resting state A lung that is fully stretched has more elastic recoil and thus larger maximal flows

16 Resistive Properties Determined by airway caliber Affected by
Lung volume Bronchial smooth muscles Airway collapsibility

17 Factors That Affect Lung Volumes
Age Sex Height Weight Race Disease

18 Special Considerations
Ability to perform spirometry dependent on developmental age of child, personality, and interest of the child. Patients need a calm, relaxed environment and good coaching. Patience is key. Even with the best of environments and coaching, a child may not be able to perform spirometry.

19 Parameter from spirometer
PEFR Spirogram FVC FEV1 FEF25-75 Flow-Volume Curve

20 Technique Give instructions and demonstrate
Acceptable criteria < 10 y: > 3 min > 10 y: > 6 min or no more volume > 1 min Not inhale No air leak No pause Give instructions and demonstrate Patient performs the maneuver Sit / Stand direct Puts nose clip on Inhales maximally Puts mouthpiece on mouth and closes lips around mouthpiece Exhales as hard and fast and long as possible Repeat minimum of three times (check for reproducibility.) Use the best value for interpretation as %predicted of control (age, height, sex, race) 2 maximum FVC different < 10% (adapted from ATS, 1994)

21 FVC Forced vital capacity (FVC):
Total volume of air that can be exhaled forcefully from TLC The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases

22 FEV1 Forced expiratory volume in 1 second: (FEV1)
Volume of air forcefully expired from full inflation (TLC) in the first second Normal people can exhale more than 80% of their FVC in the first second (FEV1/FVC)

23 FEF25-75 Forced expiratory flow 25-75% (FEF25-75)
Mean forced expiratory flow during middle half of FVC May reflect effort independent expiration and the status of the small airways Highly variable Depends heavily on FVC


25 PEFR Peak flow meter device Technique Sit/Stand direct
Inhales maximally Puts mouthpiece on mouth and closes lips around mouthpiece Blow out as hard and fast as possible Repeat minimum of three times Use the best value for interpretation as %predicted / personal best Clinical application: monitor severity, daily variability, pre and post bronchodilator Green : > 80% Yellow : 50-79% Red : < 50% Normal < 20% Normal < 12%

26 Categories of Disease Obstructive Restrictive Mixed

27 FVC Interpretation of % predicted: 80 % Normal 70-79% Mild reduction
50%-69% Moderate reduction <50% Severe reduction

28 FEV1 Interpretation of % predicted: >80% Normal
65-79% Mild obstruction 50-64% Moderate obstruction <49% Severe obstruction

29 Spirometry Interpretation:
% predicted FVC > 80% FEV1 FEF25-75% > 70% PEFR FEV1/FVC > 80% absolute value

30 Spirometry in Obstructive Disease
Slow rise in upstroke May not reach plateau

31 Restrictive Disease Rapid upstroke as in normal spirometry
Plateau volume is low

32 Spirometry Interpretation: Obstructive vs. Restrictive Defect
What parameter is the most sensitive in airway obstruction? Parameter Obstructive Disorders Restrictive Disorders FVC FEV1 FEF25-75% FEV1/FVC PEFR N or ↓ ↓ ↓ ↓ ↓ N to ↓ ↓ N or ↑ ↓ N to ↓

33 Spirometry Interpretation:
Obstructive Disorders Characterized by a limitation of expiratory airflow Examples: Asthma Bronchiectasis COPD Cystic Fibrosis Restrictive Disorders Characterized by reduced lung volumes/decreased lung compliance Examples: Interstitial Fibrosis Kyphoscoliosis Obesity Lung Resection Neuromuscular diseases Cystic Fibrosis Improve FEV1 เมื่อ asthma ดีขึ้น

34 Flow-Volume Loop PEFR Do FVC maneuver and then inhale as rapidly and as much as able. The expiratory and inspiratory flow volume curves put together make a flow volume loop. flow expiration volume inspiration TLC RV Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

35 Restrictive Lung Disease
Characterized by diminished lung volume Decreased TLC, FVC Normal or increased: FEV1/FVC ratio

36 Obstructive Lung Disease
Characterized by a limitation of expiratory airflow Examples: asthma, COPD

37 Large Airway Obstruction
Characterized by a truncated inspiratory or expiratory loop

38 Incomplete exhalation Variable extrathoracic ob
Flow-Volume Loops L1 R1 L2 R2 L3 R3 Incomplete exhalation Variable extrathoracic ob L4 Variable intrathoracic ob Fixed central or up aw ob Inadq effort Restrictive lung disease (Rudolph and Rudolph, 2003)

39 Spirometry: Pre and Post Bronchodilator
Obtain spirogram and flow-volume loop. Pre and 15 minutes after administration of the bronchodilator Salbutamol MDI 4 puffs via valve spacer Slow inhale Breath hold 5-10 sec. 5-10 sec pause between each puff. Reversibility: FEV1 / PEFR > 12% Improve flow-volume loop.

40 PEFR Inhales maximally Exhales as hard and fast and short as possible
Repeat minimum of three times Use the best value for interpretation as %predicted of control / personal best Highly effort dependent Diurnal variation (normal < 20%) Different value in each devices

41 Exercise challenge test
Perform spirometry Exercise 6-8 min (tread mill) till HR /min Repeat spirometry at 5, 10, 15, 20, 30 min EIB: FEV %, or wheezing

42 Respiratory muscle testing
Measure maximum inspiratory P. (PImax, MIP) or negative inspiratory force (NIF) Maximum inhale via pressure manometer Normal < -60 cmH2O Useful for evaluation neuromuscular dis: myasthenia grevis, Guillian-Barre syndrome, diaphragmatic paralysis, pre-extubation Other parameter: FVC, PEFR

43 Clinical Applications

44 Case #1 Case #1 Parameter Actual %Predicted FVC (L) 4.11 116 FEV1 (L)
3.28 108 FEV1/FVC (%) 80 93 FEF25-75% (L/s) 6.94 88 PEFR (L/s) 3.15 107

45 Case #2 Parameter Actual (best) Predicted %Predicted FVC (L) 4.31 4.44
97 FEV1 (L) 2.15 3.83 56 FEV1/FVC (%) 50 86 58 FEF25-75% (L/s) 0.93 4.27 22 PEFR (L/s) 5.23 8.01 65

46 Case #3 Parameter Actual (best) Predicted %Predicted FVC (L) 1.24 3.60
34 FEV1 (L) 1.19 3.09 38 FEV1/FVC (%) 95.65 86.00 111 FEF25-75% (L/s) 1.69 3.48 48 PEFR (L/s) 4.37 6.70 65

47 Case #4 Parameter Actual (best) Predicted %Predicted FVC (L) 3.40 4.93
69 FEV1 (L) 2.17 4.25 51 FEV1/FVC (%) 63.72 84.68 75 FEF25-75% (L/s) 1.09 4.75 23 PEFR (L/s) 6.65 9.00 73

48 Case #5 Parameter Pre %Pred Post FVC (L) 1.58 84 1.91 102 21.07
%Change FVC (L) 1.58 84 1.91 102 21.07 FEV1 (L) 1.04 63 1.44 87 38.62 FEV1/FVC 66.05 77 75.63 88 14.50 FEF25-75% 0.55 27 1.10 55 101.64 PEFR (L/s) 2.39 73 3.42 104 42.85

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