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PULMONARY FUNCTION TESTING
Danish Thameem M.D.Pulmonary and Critical Care Medicine
Indications for Pulmonary Functions
Evaluation of a pulmonary symptom Evaluation of smokers without
symptoms Evaluation of workers exposed to
hazards Quantification of impairment Evaluate response to therapy Preoperative assessment Disability evaluation
Timeline of cigarette smokers that develop obstructive lung disease.
Types of Pulmonary Function Tests Spirometry Lung Volumes Diffusion Capacity Maximal Respiratory Pressures Maximum Voluntary Ventilation
(MVV) Arterial Blood Gases Pulse Oximetry Bronchoprovocation
Lung Volumes Diagram
Lung Volumes and Capacities
Four Volumes VT
IRV ERV RV
Four Capacities VC IC FRC TLC
General Approach to Interpretation
Is the test interpretable? Are the results normal? Or
abnormal? What is the pattern? What is the severity? What does this mean for the patient?
Acceptability Criteria for Spirograms
Free from artifacts Cough or glottis closure during the first second of exhalation Early termination or cutoff Variable effort Leak Obstructed mouthpiece
Satisfactory exhalation 6 sec of exhalation and/or a plateau in the volume-time
curve or Reasonable duration or a plateau in the volume-time curve
or The subject cannot or should not continue to exhale
Are the two largest FVCs within 0.2 L of each other?
Are the two largest FEV1s within 0.2 L of each other?
If both of these criteria are met, the test session may be concluded. If both of these criteria are not met, continue testing until: Both of the criteria are met with analysis of additional acceptable spirograms or
A total of eight tests have been performed or Save a minimum of three best maneuvers
Repeatability Criteria
After three acceptable spirograms have been obtained, apply the following tests
Spirometry
FVC (forced vital capacity): maximum volume of air that can be exhaled during a forced maneuver (after maximal forced inspiration, TLC)
FEV1 (forced expired volume in one second): volume expired in the first second of maximal expiration after a maximal inspiration
FEV1/FVC: FEV1 expressed as a % of FVC, a clinically useful index of airflow limitation
Spirogram
Predicting Normal Values
Depend on patient’s Height Age Gender Racial & ethnic background Weight & BMI (to a lesser degree)
Reference Standards
Percent Predicted as Normal Range Results are expressed as % Predicted
of a predicted normal value of a person the same age, sex, and height. (FVC and FEV1)
Normal Ranges FVC 80-120% FEV1 80-120%
FEV1/FVC >0.70 of predicted ratio
Obstruction vs. Restriction If the FVC and / or FEV1 is below
normal The distinction between obstruction
& restriction is based on the FEV1/FVC ratio
NIH/WHO - GOLD guidelines recommends using ratio below 0.70 for the diagnosis of COPD
Obstructive Lung Disease
Emphysema & Chronic Bronchitis Cystic Fibrosis Asthma Bronchiectasis Some Interstitial Lung Disease:
(combined)
Restrictive Pattern
Normal or elevated FEV1/FVC ratio
With a low FEV1 or FVC suggests restriction
Lung Volumes are needed to confirm Some patients with Asthma or COPD
may have this pattern (“pseudorestriction”)
Restrictive Lung Disease
Rating of Severity
May be based on statements such as from the American Thoracic Society (ATS)
Obstructive Pattern - FEV1
Restrictive Pattern – TLC (lung volumes) If lung volumes not obtained - FVC
ATS/ERS Standardization of Lung Function Testing: Interpretative Strategies for lung function tests - 2005
Classification of COPD by SeverityGOLD Guidelines - 2009
I: Mild FEV1/FVC < 70%; FEV1 > 80% predicted
II: Moderate FEV1/FVC < 70%; 50% < FEV1 < 80%
III: Severe FEV1/FVC < 70%; 30% < FEV1 <50%
IV: Very FEV1/FVC < 70%; FEV1 < 30% predicted Severe or FEV1 < 50% predicted plus chronic
respiratory failure
Bronchodilator Response
Must use bronchodilator with rapid onset
• Albuterol• Levalbuterol
Increase FEV1 or FVC from baseline• By at least 12% • By at least 200 mL
Both values must be met
FLOW VOLUME LOOPS
Normal
Upper Airway Obstruction Patterns Detect obstructive lesions in the major
airways.
Characterizes the lesion:Location of the lesion:
Intrathoracic Extrathoracic
Behavior of the lesion in rapid inspiration and expiration:
Fixed Variable
Variable Extrathoracic Obstruction
Levitzky MG Pulmonary Physiology, McGraw Hill 4th ed, 1995, p 50
Vocal cord paralysisGoiterTumor
Variable Intrathoracic Obstruction
Levitzky MG Pulmonary Physiology, McGraw Hill 4th ed, 1995, p 50 Tracheomalacia
Intratracheal tumor
Fixed Obstruction
Levitzky MG Pulmonary Physiology, McGraw Hill 4th ed, 1995, p 50
Tracheal stenosis/strictureBilateral vocal cord paralysis
Extrinsic compression
Lung Volumes
Lung Volumes Diagram
Lung Volumes in Lung Diseases
Lung Volumes
Obstructive Lung
Disease
Restrictive Lung
Disease
TLC
Increased
(Hyperinflation)
Decreased
RV
Increased
(Airtrapping)
Decreased
VC
Normal or Decreased
Decreased
RV/TLC
Increased
Normal (30-40)
Diffusion Capacity
Estimates the transfer of oxygen in the alveolar air to the red blood cell.
Factors that influence the diffusion:1) Area of the alveolar-
capillary membrane (A)2) Thickness of the
membrane (T)3) Driving pressure 4) Hemoglobin5) Carboxyhemoglobin
Diffusing Capacity
Single-breath DLCO measures the capacity of the lung to transfer gas
Patient exhales to RV then rapidly inhales gas mixture with minute amount of CO. After, 10 second breath-hold at TLC, the patient rapidly exhales & the exhaled gas is analyzed to measure the amount of CO transferred into the capillary blood during the maneuver
Abnormalities of Diffusing Capacity
Decreased in conditions that disrupt the alveolar-capillary surface for gas transfer Loss of surface area (resection, fibrosis,
emphysema, pneumonia) Reduced lung capillary volume
(vasculitis, thromboembolism, primary pulm htn, ILD)
Increased diffusion distance (PAP, PCP)
Abnormalities of Diffusing Capacity
Increased by conditions that lead to recruitment of pulmonary vascular bed and increase in capillary blood volume (exercise, mild CHF, asthma)
Or by increased amount of hemoglobin which binds CO (pulmonary hemorrhage, erythrocytosis)
CASE 1
54 y/o male smoker PFT
FEV1 : 1.3 L (23%) FVC : 2.3 L (45%) FEV1/FVC : 56 TLC 98% RV : 156% DLCO : 30%
Diagnosis
Very severe obstructive defect Severe reduction in DLCO High RV
Air trapping
COPD
CASE 2
35 y/o F with SLE FEV1 : (56%) FVC : (45%) FEV1/FVC 90 TLC : 48% RV: 45% DLCO : 23%
FEV1 increased by 4% (0.1 L) with bronchodilator testing
Diagnosis
Severe restriction without significant response to bronchodilators
Severe reduction in DLCO
ILD PULMONARY FIBROSIS
CASE 3
45 y/o female with history of allergic rhinitis and dyspnea on exertion
FEV1 - 3.2 (70%) pre, 4.5 (100%) post BD
FVC - 4.9 (70%) pre, 6.0 (85%) post BD
RATIO - 65% pre and 75% post TLC - 6 L (100%) DLCO - 100%
Diagnosis
Mild obstruction with significant response to bronchodilators (normal)
Normal lung volumes and DLCO
ASTHMA
CASE 4
76 y/o male with weight loss and dyspnea
FEV1 - 4 L ( 85%) FVC - 5.1 L (80%) RATIO - 78% TLC - 6 L ( 82%) DLCO - 88%
Diagnosis
Normal spirometry Truncated inspiratory limb of the flow
volume loop
EXTRATHORACIC OBSTRUCTION