Pulmonary Function Tests

Spirometry

Learning Objectives

Understand the meaning of FEV1, FVC,

FEV1/FVC ratio, and the flow-volume loop

Be able to use these values during diagnostic

evaluations.

Understand how FEV1 can be used to grade

severity of disease.

How is Spirometry Performed?

How is Spirometry Performed?

Lung Volumes

Volume

Time

Vital

CapacityTidal

Volume

Expiratory

Reserve

Volume

Inspiratory

Reserve

Volume

Residual

Volume

Inspiratory

Capacity

Functional

Residual

Capacity

Total Lung

Capacity

Lung Volumes

Volume

Time

Vital

Capacity

Called “Forced Vital

Capacity” (FVC) when

performed as rapidly

as possible.

1 second

Forced

Expiratory

Volume in

1 Second

(FEV1)

FVC Maneuver

Time(seconds)

Volume(Liters)

0 1 2 3 4 5 6

1

2

3

4

5

6

FEV1

FVC

Flow = ∆Volume / ∆Time

Maximum slope of curve = Peak expiratory flow rate

Flow-Volume Loop

Time

Flow(L/sec)

Volume(Liters)

024

8

4

0

-4

Expiration

Inspiration

Volume

Peak Expiratory

Flow Rate (PEFR)

RV

TLCFEV1

FVC

PEFR

FVC

Values Measured by Spirometry

Major

FEV1

FVC

FEV1 / FVC ratio

Flow volume loop

Minor

Peak expiratory flow rate (PEFR)

FEF25-75%

Maximal voluntary ventilation (MVV)

Response to bronchodilators

Interpretation of FEV1, FVC, and FEV1/FVC Ratio

FEV1 FVC FEV1 / FVC Ratio(Tiffeneau Index)

Obstructive Lung

Disease

Normal (very mild obstruction)

or

Decreased (mod/severe obstruction)

Normal (mild/mod obstruction)

or

Decreased (severe obstruction)

Decreased

(< 70%)

Restrictive Lung

Disease

Normal or

DecreasedDecreased

Normal or

Increased

(≥ 70%)

Assess

FEV1 / FVC

Low

Normal / High

Possible

Restriction

LowNormal

LowAssess

FVC

Assess

FVC

Normal /

High

ObstructionObstruction

or Mixed

Normal Lung

Mechanics

Where is pulmonary vascular disease?

Interpretation of Spirometry

Mild

ObstructionRestrictionNormal

Flow

Volume

Volume

Time

Volume

Time

Volume

Time

Severe

Obstruction

Volume

Time

Late plateau

FVC preserved

Coving

PEFR mildly

reduced

PEFR severely

reduced

No plateau

FVC reducedNormal plateau

FVC reduced

PEFR normal or

mildly reduced

Coving No coving

PEFR

FVC

Expiration

Inspiration

Variable Extrathoracic

Airway Obstruction

Fixed Airway

Obstruction

Flow

Volume

Variable Intrathoracic

Airway Obstruction

Normal

Examples

Tracheal stenosis

Goiter

Airway tumor

Examples

Tracheomalacia

Airway tumor

Examples

Vocal cord paralysis

Tracheomalacia

Airway tumor

PEFR

Expiration

Inspiration

Staging of COPD Based on FEV1

The Global Initiative for Chronic Obstructive Lung Disease (GOLD)

classifies COPD severity based on post-bronchodilator FEV1.

FEV1 compared to predicted for

age/gender/height

GOLD Stage I FEV1 ≥ 80%

GOLD Stage II 50% ≤ FEV1 < 80%

GOLD Stage III 30% ≤ FEV1 < 50%

GOLD Stage IV FEV1 < 30%

Staging of COPD Based on FEV1

IIIIIIIV

Adapted from: Jones PW.

Health status and the spiral

of decline. COPD. 2009; 6:

59-63.

There is only a weak correlation between FEV1 and quality of life.

SQRQ = St. George Respiratory Questionnaire – a disease-specific instrument designed to measure impact on overall health,

daily life, and perceived well-being in patients with obstructive airways disease. (Higher numbers more limitations)

Assessing Response to Bronchodilators

Among patients with obstructive

lung disease, > 12-15% increase

in FEV1 after administration of a

bronchodilator is considered

significant.

However, a lack of such an

increase should not preclude a

trial of bronchodilators.

Copyright © 2014 by Eric Strong

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