Simple Interpretation of Pulmonary Function tests

Spirometry of Obstructive

Lung Diseases

Gamal Rabie Agmy, MD, FCCP Professor of Chest Diseases, Assiut University

Pulmonary Disorders Effects on

Pulmonary Function Obstructive:

Any process that interferes with air flow either into or out of the lungs.

Large or small airways.

Restrictive:

Any process that interferes with the bellows action of the lungs or chest wall.

Reduced lung volumes.

Differential Diagnosis:

COPD and Asthma COPD Onset In mid-life

Symptoms slowly progressive

Long smoking history

Dyspnea during exercise

Largely Irreversible airflow limitation

Asthma Onset early in life (often

childhood)

Symptoms vary from day to day

Symptoms at night/early morning

Allergy, rhinitis, and/or eczema also present

Family history of asthma

Largely reversible airflow limitation

Inflammatory Cascade in

COPD & Asthma

Measures of Assessment and

Monitoring of Asthma

Asthma diagnosis criteria:

Repeated variability in well-performed spirometic values (increase in FEV1 or FVC).

Positive bronchodilator (BD) responses (increase in FEV1 or FVC ⩾12% and 200 mL from baseline).

Positive methacholine challenge (20% fall in FEV1 at a dose ⩽8 μg/mL).

Objective lung function

measurements in Asthma

Spirometry:

▫ Forced Expiratory Maneuvers.

Exhaled Nitric Oxide.

Peak Flows.

GOLD 2013: Diagnosis of COPD

SPIROMETRY REQUIRED TO DIAGNOSE COPD Presence of a post-bronchodilator FEV1/FVC < 0.70 confirms the presence of persistent airflow

limitation and thus of COPD.

Key Indicators to Consider COPD Diagnosis:

1

• SYMPTOMS • Dyspnea-progressive (worsens over time and with exercise) • Chronic cough • Sputum

2

• HISTORY OF EXPOSURE TO RISK FACTORS

• Tobacco smoke • Smoke from home cooking/heating fuels • Occupational dusts and chemical

3 • FAMILY HISTORY OF COPD

Adapted from GOLD 2013

Simple Interpretation of

Pulmonary Function Tests

Gamal Rabie Agmy, MD, FCCP Professor of Chest Diseases, Assiut University

Anatomy

Lungs comprised of

Airways

Alveoli

http://www.aduk.org.uk/gfx/lungs.jpg

Weibel ER: Morphometry of the Human

Lung. Berlin and New York: Springer-

Verlag, 1963

The Airways

Conducting zone: no

gas exchange occurs

Anatomic dead

space

Transitional zone:

alveoli appear, but are

not great in number

Respiratory zone:

contain the alveolar

sacs

The Alveoli

Approximately 300

million alveoli

1/3 mm diameter

Total surface area if

they were complete

spheres 80 sq.

meters (size of a

tennis court)

Murray & Nadel: Textbook of Respiratory

Medicine, 3rd ed., Copyright © 2000 W. B.

Saunders Company

Mechanics of Breathing

Inspiration

Active process

Expiration

Quiet breathing: passive

Can become active


Airway function

Simple spirometry

Forced vital capacity

maneuver

Maximal voluntary

ventilation

Maximal

inspiratory/expiratory

pressures

Airway resistance

Lung volumes and

ventilation

Functional residual

capacity

Total lung capacity,

residual volume

Minute ventilation,

alveolar ventilation,

dead space

Distribution of

ventilation


Diffusing capacity

tests

Blood gases and gas

exchange tests

Blood gas analysis

Pulse oximetry

Capnography

Cardiopulmonary

exercise tests

Metabolic

measurements

Resting energy

expenditure

Substrate utilization

Chemical analysis of

exhaled breath

Terminology

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

Measured in liters (L)

FVC

Interpretation of % predicted:

80-120% Normal

70-79% Mild reduction

50%-69% Moderate reduction

<50% Severe reduction

FVC

Terminology

Forced expiratory volume in 1 second: (FEV1) Volume of air forcefully

expired from full inflation (TLC) in the first second

Measured in liters (L)

Normal people can exhale more than 75-80% of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease

FEV1


>75% Normal

Mild 70-75%

Mod 50-69 %

Severe 35-49%

Very severe < 35%

FEV1 FVC

Terminology

Forced expiratory flow 25-

75% (FEF25-75)

Mean forced expiratory flow

during middle half of FVC

Measured in L/sec

May reflect effort

independent expiration and

the status of the small

airways

Highly variable

Depends heavily on FVC

FEF25-75


>60% Normal

40-60% Mild obstruction

20-40% Moderate obstruction

<20% Severe obstruction

Acceptability Criteria

Good start of test

No coughing

No variable flow

No early termination

Reproducibility

Changes in Lung Volumes in

Various Disease States

Ruppel GL. Manual of Pulmonary Function Testing, 8th ed., Mosby 2003

TLC

TLC < 80% of predicted value = restriction.

TLC > 120% of predicted value =

hyperinflation.

Lung Volumes

Spirometry

Spirometry should be performed after the

administration of an adequate dose of a short acting inhaled bronchodilator (e.g. 400 ᶙg salbutamol) to minimize variability.

A post-bronchodilator FEV 1/FVC <0.70 confirms the presence of airflow limitation that is not fully reversible.

Where possible, values should be compared to age-related normal values to avoid over- diagnosis of COPD In the elderly.

Why Do We Need Spirometry

in COPD?

Spirometry is useful for:

Screen individuals at risk for pulmonary disease.

Confirmation of COPD diagnosis.

Assessing severity of pulmonary dysfunction.

Guiding selection of treatment.

Assessing the effects of therapeutic interventions.

Who Should Be Screened for

COPD?

Consider COPD, and perform spirometry, if any of these indicators are present in an individual over age 40.

▫ Dyspnea that is progressive, usually worse with exercise, and persistent.

▫ Chronic cough (may be intermittent and unproductive).

▫ Chronic sputum.

▫ History of tobacco smoke exposure.

▫ Exposure to occupational dusts and chemicals.

▫ Risk factors.

▫ Exposure to smoke from home cooking and heating fuels.

Spirometry Origin

Most basic of Pulmonary Function Tests

Clinical Tools Origin - Mid 1800' s

▫ John Hutchinson.

▫ Water-sealed spirometry to measure vital capacity (VC).

Reasons for Performing

Spirometry

Diagnostic Purposes.

Monitoring Lung Disease.

Assessing Disability.

Spirometry

Spirometry with flow volume loops assesses the

mechanical properties of the respiratory system by measuring expiratory volumes and flow rates.

▫ Maximal inspiratory and expiratory effort.

▫ At least 3 tests of acceptable effort are performed to ensure reproducibility.

21st Century Spirometry

Measurements of:

Forced Vital Capacity (FVC).

Forced Expiratory Volume in one second (FEV1).

Forced Expiratory Volume in six seconds (FEV6).

Forced Expiratory Flow over various Intervals (FEFx).

Peak Expiratory Flow (PEF).

Definitions and Terms

FEV1 - forced expiratory volume 1 - the volume of

air that is forcefully exhaled in one second.

FEV6 - forced expiratory volume 6 - the volume of

air that Is forcefully exhaled in six seconds.

FVC- forced vital capacity- the volume of air that

can be maximally forcefully exhaled.

FEV1/FVC- ratio of FEV1 to FVC, expressed as a percentage.

Definitions and Terms

FEV/FVC- ratio of FEV6 to FVC, expressed as a percentage.

FEF25 -75 - forced expiratory flow - the average

forced expiratory flow during the mid (25 - 75%) portion of the FVC.

PEF- peak expiratory flow rate - the peak flow rate

during expiration.

Spirometry

Flow volume loops provide a graphic illustration

of a patient's spirometric efforts.

Flow is plotted against volume to display a continuous loop from inspiration to expiration.

The volume versus time curve is a an alternative way of plotting spirometric results.

The overall shape of the flow volume loop is important in Interpreting spirometric results.

Acceptability & Repeatability

Acceptability

At least three (3) acceptable maneuvers

Good start to the test.

No hesitation or coughing for the 1st second.

FVC lasts at least 6 seconds with a plateau of at least 1 second.

No valsalva maneuver or obstruction of the mouthpiece.

FIVC shows apparent maximal effort.

Repeatability

Repeatability criteria act as guideline to

determine need for additional efforts.

▫ Largest and 2nd largest FVC must be within 150 mL.

▫ Largest and 2nd largest FEV 1 must be 150 mL.

▫ PEF values may be variable (within 15%).

If three acceptable reproducible maneuvers are not recorded, up to B attempts may be recorded.

Spirometry Value

Spirometry is typically reported in both absolute values and as a predicted percentage of normal.

Normal values vary and are dependent on:

▫ Gender,

▫ Race,

▫ Age, and

▫ Height.

Reporting Standards

Largest FVC obtained from all acceptable efforts

should be reported.

Largest FEV1 obtained from all acceptable trials should be reported.

May or may not come from largest FVC effort.

All other flows, should come from the effort with the largest sum of FEV 1 & FVC.

PEF should be the largest value obtained from at least 3 acceptable maneuvers.

Results Reporting

Example

Report Format

Report should also include:

▫ Age on testing day.

▫ Height (standing without shoes).

▫ Weight (without shoes).

▫ Gender.

▫ Race or ethnic origin.

▫ Technologist comment section.

FEV1 Results for Asthma

FEV 1 Severity Results for Asthma

At Risk for COPD

Spirometric classification of airflow limitation (in patients with FEV1/FVC<0.70).

▫ GOLD 1 (Mild; FEV1 ≥80% predicted).

▫ GOLD 2 (Moderate; 50% ≤FEV1 <80% predicted).

▫ GOLD 3 (Severe; 30% ≤FEV1 <50% predicted).

▫ GOLD 4 (Very severe; FEV1 <30% predicted).

Adapted from GOLD 2013

Pre & Post Bronchodilator

Studies

B-Adrenergic aerosols are most common form

for testing.

Standardize.

▫ Drug.

▫ Dosage.

▫ Delivery Device.

Minimum of 15 minutes between pre and post tests.


Studies: Withholding Medications


Studies: Interpretations

Determined based on improvement of FEV1.

Commonly expressed as Percent Change.

% Change = Post FEV 1 - Pre FEV1 x 100

Pre FEV1

Reversibility

Reversibility of airways obstruction can be

assessed with the use of bronchodilators.

> 12% increase in the FEV1 and 200 ml

improvement in FEV1

OR

> 12% increase in the FVC and 200 ml

improvement in FVC.

Spirometry

Asthma Challenge Testing

Spirometry can be used to detect the bronchial

hyperreactivity that characterizes asthma.

Increasing concentrations of histamine or methacholine.

Patients with asthma will demonstrate symptoms and produce spirometric results consistent with airways obstruction at much lower threshold concentration than normals.

Bronchial Provocation for Asthma

Spirometry

Indications — Diagnosis

Evaluation of signs and symptoms

- SOB, exertional dyspnea, chronic cough

Screening at-risk populations

Monitoring pulmonary drug toxicity

Abnormal study

- CXR, EKG, ABG, hemoglobin

Preoperative assessment

Spirometry






Abnormal study



Smokers > 45yo

(former & current)

Spirometry





Evaluation of occupational symptoms


Abnormal study



Spirometry

Indications — Prognostic

■ Assess severity

■ Follow response to therapy

■ Determine further treatment goals

■ Referral for surgery

■ Disability

1-First Step, Check quality of the test

1- Start:

*Good start: Extrapolated volume (EV) < 5% of FVC or 0.15 L

*Poor start: Extrapolated volume (EV) ≥5% of FVC or ≥ 0.15 L

2- Termination:

*No early termination :Tex ≥ 6 s

*Early termination : Tex < 6 s

2- Look at …………FEV1/FVC

< N(70%)

Obstructive or Mixed

≥ N(70%)

Restrictive or Normal

3- Look at FEV1 To detect degree Mild > 70% Mod 50-69 % Severe 35-49% Very severe < 35%

4- Postbronchodilator FEV1/FVC

> 70% asthma

< 70% COPD

5- Reversibility test of FEV1

> 12%, 200 ml Reversible (asthma)

< 12% ,200 ml Ireversible (COPD)

6- Look at TLC

≥ 80-120% Pure obstruction

< 80% Mixed

2- Look at …………FEV1/FVC

< N(70%)

Obstructive or Mixed

≥ N(70%)

Restrictive or Normal

3- Look at FVC

≥ N(80%) < N(80%) Normal or SAWD

4-Look at FEF25/75

> 50% Normal < 50% SAWD

Restrictive

Patterns of Abnormality

Restriction low FEV1 & FVC, high FEV1%FVC

Recorded Predicted SR %Pred

FEV 1 1.49 2.52 -2.0 59

FVC 1.97 3.32 -2.2 59

FEV 1 %FVC 76 74 0.3 103

PEF 8.42 7.19 1.0 117

Obstructive low FEV1 relative to FVC, low PEF, low FEV1%FVC


FEV 1 0.56 3.25 -5.3 17

FVC 1.65 4.04 -3.9 41

FEV 1 %FVC 34 78 -6.1 44

PEF 2.5 8.28 -4.8 30

high PEF early ILD

low PEF late ILD

Patterns of Abnormality

Upper Airway Obstruction low PEF relative to FEV1


FEV 1 2.17 2.27 -0.3 96

FVC 2.68 2.70 0.0 99

FEV 1 %FVC 81 76 0.7 106

PEF 2.95 5.99 -3.4 49

FEV 1 /PEF 12.3

Discordant PEF and FEV1

High PEF versus FEV1 = early interstitial lung disease (ILD)

Low PEF versus FEV1 = upper airway obstruction

Concordant PEF and FEV1

Both low in airflow obstruction, myopathy, late ILD

Common FVL Shapes

Volume

Flo

w

Normal Young or quitter Poor effort

Hesitation Knee Coughing

Asthma

0 1 2 3 4 5 60

2

4

6

8

10

12

Flo

w in L

/s

Litres

concave FV curve

intrapulmonary airflow obstruction

Restrictive

0 1 2 3 4 5 6

-8

-6

-4

-2

0

2

4

6

8

10

12 F 19 yrs 1.64m

FVC 2.41 L -3.42 SR

FEV 2.41 L -2.62 SR

FEV% 100 +2.23 SR

PEF 5.55L/s -2.00 SR

F/P 7.2 RT 116 ms

Flo

w in

L/s

Litres

COPD

0 1 2 3 4 5

-6

-4

-2

0

2

4

6

8

10

Flo

w in

L/s

Litres

pressure dependent airways collapse

Poorly co-ordinated start

0 1 2 3 4 5 6

-10

-8

-6

-4

-2

0

2

4

6

8

10

12

Flo

w in

L/s

Litres

EV = large

Rise Time = 496 ms

Irregular shape

Poorly repeatable

Upper Airway Obstruction

0 1 2 3 4 5 6

-6

-4

-2

0

2

4

6 Age 40 yrs

FVC 3.52 L 0.84 SR

FEV1 3.0 L 0.74 SR

PEF 4.57 L/s -2.18 SR

FEV/PEF = 10.9

Inspiratory

Expiratory

Flo

w in

L/s

Volume in Litres

FEV1 in mls

PEF in L/min > 8


0 1 2 3 4 5 6

-6

-4

-2

0

2

4

6

8

10

12

Flo

w in

L/s

Volume in Litres

Male aged 62 Height 1.68m

Recorded Predicted Range SR

FEV 1 2.23 2.94 2.1 to 3.8 -1.4

FV C 3.40 3.71 2.7 to 4.7 -0.5

FEV 1% FV C 66 76 64 to 88 -1.5

PEF 2.85 7.81 5.8 to 9.8 -4.1

FEV 1/PEF 13.1

Inspiration

-ve

-ve

Expiration

+ve

+ve

Extra-thoracic UAO

worse on insp. Intra-thoracic UAO

worse on exp.

Variable UAO

Intra-thoracic UAO

0 1 2 3 4 5 6

-8

-6

-4

-2

0

2

4

6

8

10

12F

low

in

L/s

L ite rs

Age 65 Female

FVC 2.97 L 1.3 SR

FEV1 2.26 L 0.6 SR

FEV1% 76% -0.1 SR

PEF 3.4 L·s-1 -2.5 SR

F/P 11.1 RT 455 ms


• Variable extrathoracic obstructions 1. vocal cord paralysis,

2. thyromegaly,

3. tracheomalacia, or

4. Neoplasm

• Large airways variable intrathoracic obstructions 1. tracheomalacia or

2. neoplasm

• Fixed obstruction 1. tracheal stenosis,

2. foreign body, or

3. neoplasm.

Obstruction, Restriction, Mixed

Variable Extrathoracic Upper Airway Obstruction

Fixed Upper Airway Obstruction

True Restrictive Disorders

Intraparenchymal

Interstitial Infilterative Diffuse alveolar

Chest Wall

Pleural Skeletal Neuromuscular

Reduced TLC.FRC,RV,VC and normal to high FEV1/FVC

DLVA,Dlcoc or both DLVc parynhymal If normal Chest wall or neuromuscular

Pseudorestrictive Disorders

Normally: IC/ERV=2-3/1

True restrictive: IC/ERV=<2/1

Pseudorestrictive: IC/ERV=6/1


Asthma is a disorder characterized by increased reactivity of the

airways. Patients with asthma have recurrent or persistent airflow

obstruction, which is reversible either spontaneously or with

appropriate therapy. An obstructive pattern is most often present,

recognized by reduced forced expiratory volume in 1 s (FEV1), and

FEV1 to forced vital capacity (FEV1/FVC) or FEV1/vital capacity

(VC) ratio. Patients may have normal spirometry between attacks.

In some patients, the FVC may be reduced due to air trapping,

resulting in pseudorestriction on spirometry in the presence of

increased or normal total lung capacity (TLC), increased functional

residual capacity (FRC) and increased residual volume (RV). We

have reported 12 asthmatic patients with reduced VC and no

increase in RV, i.e., a true restrictive impairment [Gill et al. Chest

2012)


Obesity:

*Early airway closure (low ERV & high RV)

*FRC is more reduced than TLC&VC

*Low FEF50% , FEF75%, FEF25-75%,


Neuromuscular Disease:

*FRC normal

*IC&ERV decreased

*Decreased TLC

*Increased RV

*A-aO2 gradient normal

*MIP&MEP decreased


Asthma:

*FRC &TLC increased

*Improvement of FEV1&FVC with bronchodilators

*Positive bronchoprovacation test

*Increased diffusing capacity and DLco/VA

Pseudopseudorestrictive

Patients with obstructive diseases who do not

complete expiratory effort of FVC. This may

lead to a below normal FEV1 and FVC with

pseudonormalization of ratio.

Mixed Disorder

*Sarcoidosis

*Rhematoid

*Advanced IPF

*Bronchiectasis

*BOOP in smokers

Obstructive Pattern

■ Decreased FEV1

■ Decreased FVC

■ Decreased FEV1/FVC

- <70% predicted

■ FEV1 used to follow severity in COPD

Obstructive Lung Disease —

Differential Diagnosis

Asthma

COPD

- chronic bronchitis

- emphysema

Bronchiectasis

Bronchiolitis

Upper airway obstruction

Restrictive Pattern

Decreased FEV1

Decreased FVC

FEV1/FVC normal or increased

Restrictive Lung Disease —

Differential Diagnosis

Pleural

Parenchymal

Chest wall

Neuromuscular

Spirometry Patterns

Bronchodilator Response

Degree to which FEV1 improves with inhaled

bronchodilator

Documents reversible airflow obstruction

Significant response if:

- FEV1 increases by 12% and >200ml

Request if obstructive pattern on spirometry

Flow Volume Loop

“Spirogram”

Measures forced inspiratory and expiratory

flow rate

Augments spirometry results

Indications: evaluation of upper airway

obstruction (stridor, unexplained dyspnea)

Flow Volume Loop


Variable intrathoracic obstruction

Variable extrathoracic obstruction

Fixed obstruction


Lung Volumes

Measurement:

- helium

- nitrogen washout

- body plethsmography

Indications:

- Diagnose restrictive component

- Differentiate chronic bronchitis from emphysema

Lung Volumes – Patterns

Obstructive

- TLC > 120% predicted

- RV > 120% predicted

Restrictive

- TLC < 80% predicted

- RV < 80% predicted

Diffusing Capacity

Diffusing capacity of lungs for CO

Measures ability of lungs to transport inhaled gas

from alveoli to pulmonary capillaries

Depends on:

- alveolar—capillary membrane

- hemoglobin concentration

- cardiac output

Diffusing Capacity

Decreased DLCO

(<80% predicted)

Obstructive lung disease

Parenchymal disease

Pulmonary vascular

disease

Anemia

Increased DLCO (>120-140% predicted)

Asthma (or normal)

Pulmonary hemorrhage

Polycythemia

Left to right shunt

DLCO — Indications

Differentiate asthma from emphysema

Evaluation and severity of restrictive lung disease

Early stages of pulmonary hypertension

Bronchoprovocation

Useful for diagnosis of asthma in the setting of normal pulmonary function tests

Common agents:

- Methacholine, Histamine, others

Diagnostic if: ≥20% decrease in FEV1

PFT Patterns

Emphysema

FEV1/FVC <70%

“Scooped” FV curve

TLC increased

Increased compliance

DLCO decreased

Chronic Bronchitis

FEV1/FVC <70%

“Scooped” FV curve

TLC normal

Normal compliance

DLCO usually normal

PFT Patterns

Asthma

FEV1/FVC normal or decreased

DLCO normal or increased

But PFTs may be normal bronchoprovocation

Health & Medicine

Simple Interpretation of Pulmonary Function tests