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