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Carl D. Mottram, RRT RPFT FAARC Technical Director - Pulmonary Function Labs and Rehabilitation

Associate Professor of Medicine - Mayo Clinic College of Medicine

“Understanding the Basics of Spirometry

It’s not just about yelling “blow””

Prevalence of COPD and Heart Disease in Smokers

Lancet Vol 370, p765–773, 1 September 2007

Centers for Disease Control

Measuring and Monitoring Lung Function

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John Hutchinson MD Surgeon and Master Violinist

Coined the term

“Vital Breath” later

changed to “Vital

Capacity” based on

his observations that

it accurately

predicted the

capacity to live

Hutchinson J. On the capacity of the lungs and on the respiratory function with a view of establishing a

precise and easy method of detecting disease by the spirometer. Med Chir Tr (London) 1846; 29: 137.

Spirometers

Spirometers

Single

component of a

complex PFT

testing system

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“How to” Guidelines and Standards

American Thoracic Society/European Respiratory Society

• 2005 ATS/ERS Spirometry Standards

• 2007 ATS/ERS PFT Testing in Preschool Children

• ATS Pulmonary Function Laboratory Management and Procedure Manual

• 3rd Edition 2016

“Clinical Practice” Guidelines

• National Asthma Education and Prevention Program

Spirometry required to establish the diagnosis of COPD

“Clinical Practice” Guidelines

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Clinical Indications

• Diagnostic

• To evaluate symptoms, signs, or abnormal laboratory tests

• Symptoms: dyspnea, wheezing, orthopnea, cough, phlegm production, chest pain

• Signs: diminished breath sounds, hyperinflation, expiratory slowing, cyanosis, chest deformity, unexplained crackles

• Abnormal laboratory tests: hypoxemia, hypercapnia, polycythemia, abnormal CXR

Clinical Indications

• Monitoring

• To assess therapeutic interventions

• Bronchodilator therapy

• Steroid treatment for asthma, interstitial lung disease, etc.

• Other (antibiotics in cystic fibrosis

etc.)

• Surgical intervention

Spirometry Measurements

• FVC - the volume of air expired forcefully after a maximal inspiration

• FEV1 - the maximal volume of air exhaled with maximally forced effort in 1 second

• FEV1/FVC – “ratio”

• Alphabet soup

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Volume-Time Curve

Spirometry graphs

Flow-Volume Loop

Spirometry graphs

ATS/ERS Standards General Considerations

• Pre-test instructions

Medications

Eating

Exercise

Smoking

• Questionnaire

• Height* and weight

• Equipment quality assurance program

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ATS/ERS Standards General Considerations

• Height and weight

•Measured in indoor clothes without shoes

•Patients with deformities of the thoracic cage should have their arm span measured

•Regression equations

•Ht = arm span/1.06 2005 ATS/ERS Standards

General Laboratory

ATS/ERS Standards General Considerations

• Personnel qualifications •Minimum requirements include sufficient education and training to assure that the testing staff are competent

•Mayo PFL Quality Assurance Program •NIOSH spirometry training

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ATS/ERS Standards Standardization of Spirometry

•Test Procedure

•There are three distinct phases to the FVC maneuver:

1. maximal inspiration

2. a “blast” of exhalation

3. continued complete exhalation to the end of test (EOT)

ATS/ERS Standards Standardization of Spirometry

Maximizing Effort

Use words like: “Blast it out!”, “Snap it out!”

Coaching

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ATS/ERS Standards

Standardization of Spirometry

ATS/ERS Acceptability “Unacceptable”

Cough in the First Second

← ←

ATS/ERS Acceptability “Unacceptable”

Hesitation/Back Extrapolation

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ATS/ERS Acceptability “Unacceptable”

Suboptimal Blast

ATS/ERS Acceptability “Unacceptable

Early Termination or Glottis Closure

ATS/ERS Acceptability “Unacceptable”

Negative Sensor Drift

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ATS/ERS Acceptability “Unacceptable”

Positive Sensor Drift

ATS/ERS Acceptability “Unacceptable”

Sneak Breath

ATS/ERS Acceptability Spirometry Test Results

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ATS/ERS Standards Standardization of Spirometry

Between Maneuver Evaluation

• Minimum of 3 maneuvers

• Acceptable repeatability is achieved when the difference between the largest and the next largest FVC is 0.150 L or less AND the difference between the largest and next largest FEV1 is 0.150 L or less.

• For those with an FVC of 1.0 L or less both these values are 0.100 L.

What is Your Predicted Normal?

Factors Affecting Lung Volumes & Flow Rates

• Height

• Age

• Sex

• Race

These measurements are very critical since the

predicted normal values (reference values) are based

on these.

Weight does NOT affect predicted normals!

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Men have larger lung volumes than women.

Blacks & Asians have lower predicted

values than Caucasians.

What is considered abnormal?

What reference values are you using?

• Knudson (1976)

• Knudson (1983)

• Morris

• Crapo

• NHANES III (Hankinson, et. al., 1999)

• Global Lung “All Age” (3-95yrs)

• Quanjer, Stocks, et al., 2012

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What is Considered Abnormal?

• Lower Limit of Normal (LLN)

• Threshold below which a value is considered abnormal (Of a Normal population--95% will be above and 5% will be below the LLN)

• “Rules of thumb”:

• 80% of predicted for FVC & FEV1

• 70% for actual FEV1/FVC ratio

Global Initiative for Obstructive Lung Disease (GOLD)

• Recommends FEV1/FVC < 70% (after bronchodilator) as diagnostic of COPD obstruction

• 70% cut-off results in increased false negatives and false positives with potential for misclassification

GOLD Misclassification

Mottram CD Ruppel’s Manual of Pulm Func 11th 2017

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Interpretation Guidelines

• Official Statements of the American Thoracic Society and the European Respiratory Society

Obstructive Pattern “COPD/Asthma”

Restrictive Pattern “osis”, chest wall, weakness

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Basic Spirometry Interpretation Algorithm

FEV₁/FVC%

Normal?

No (<LLN) Yes FVC

Normal? Obstruction

Yes No

(< LLN)

Normal Restriction

Example #1

Pred LLN Actual %Pred

FVC 4.97 ( 4.12 ) 6.00 120.7%

FEV1 4.08 (3.36 ) 4.80 117.6%

FEV1/FVC 81.9% (72.2%) 80.0% 97.7%

A. Normal

B. Obstruction

C. Restriction

A. Normal

B. Obstruction

C. Restriction

Example #2

Pred LLN Actual %Pred

FVC 4.97 (4.12) 3.00 60.4%

FEV1 4.08 (3.36) 3.00 73.5%

FEV1/FVC 81.9% (72.2%) 100.0% 122.1%

A. Normal

B. Obstruction

C. Restriction

D. Unacceptable

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Example #3

Pred LLN Actual %Pred

FVC 4.97 (4.12) 1.80 36.2% FEV₁ 4.08 (3.36) 1.78 43.6%

FEV₁/FVC 81.9% (72.2%) 99.0% 120.9%

A. Normal

B. Obstruction

C. Restriction

A. Normal

B. Obstruction

C. Restriction

Example #4

Pred (LLN) Actual %Pred

FVC 4.97 (4.12) 3.20 64.4%

FEV1 4.08 (3.36) 0.89 21.8%

FEV1/FVC 81.9% (72.2%) 27.8% 33.9%

A. Normal

B. Obstruction

C. Restriction

A. Normal

B. Obstruction

C. Restriction

Example #5

Pred (LLN) Actual %Pred

FVC 4.97 (4.12) 4.45 89.5%

FEV1 4.08 (3.36) 3.00 73.5%

FEV1/FVC 81.9% (72.2%) 67.4% 82.2%

A. Normal

B. Obstruction

C. Restriction

D. Neuromuscular weakness

or suboptimal blast

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