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Pulmonary Function

Tests

Farah Madhani-Lovely

Pulmonary/Critical Care Division

December 13th 2005

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Indications and contraindications

Spirometry

Lung volumes

Differentiating obstructive and restrictive lung

disease

Diffusion capacity2

Indications

To evaluate symptoms and signs of lung disease

To assess the progression of lung disease

To monitor the effectiveness of therapy

To evaluate preoperative patients

Screen people at risk of pulmonary disease

To monitor for potentially toxic effects of

certain drugs/chemicals

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Contraindications

Patient in respiratory isolation

Inability to cooperate or sit up straight

Acute illness Acute coronary syndrome

Pneumonia

Chest pain

Current tracheostomy

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Spirometry

Measurement of air movement in and out of

the lung during different respiratory maneuvers.

Values measured are:

FVC: Forced Vital Capacity

FEV1: The forced expiratory volume in one second

MVV: Maximum Voluntary Ventilation

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FEV1 & FVC

• Forced expiratory volume in 1 second

– 4.0 L

• Forced vital capacity

– 5.0 L

– usually less than during a slower exhalation

• FEV1/FVC = 80%

FEV1

FVC

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Spirometry

Bronchodilator response is a change in FEV1 or

FVC

200 ml

AND

12% change in initial value

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Maximal Voluntary Ventilation

Fast and hard for 10-15 seconds

Normal estimated FEV1 x 40

Disproportional reduction in MVV

Poor effort

Variable exrathoracic obstruction

Respiratory muscle weakness

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LUNG VOLUMES

• Values obtained by simple spirometry

• For the others parameters additional measurements needed11

FUNCTIONAL RESIDUAL CAPACITY

• Measured by

– body plethysmography

– helium dilution

• Body plethysmography

– mouthpiece obstructed

– rapid panting

By applying Boyle’s law (P · V = constant) lung volume obtained

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FUNCTIONAL RESIDUAL CAPACITY

• Helium dilution

• Spirometer of known volume

and helium concentration connected to the patient

• Closed circuit

• Law of conservation of mass

At beginning After several minutes

Unknown lung volume can be calculated

[He] initial · Vs = [He] final · (Vs + VL)

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LUNG VOLUMES

• Values obtained by simple spirometry

• For the others parameters additional measurements needed14

INTERPRETATION of RESULTS

• In patients with obstructive diseases

– Higher resistance to airflow

FEV1 (Forced expiratory volume)

RV (residual volume)

• Patients with restrictive disease i.e. reduced lung

compliance (e.g., diffuse interstitial fibrosis)

– stiffness of the lungs + recoil of the lungs to a smaller resting volume

TLC (Total lung capacity)

RV (residual volume)

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in respiratory patients

FVC FEV1

• Restrictive disease

– expansion of the lung

– e.g., interstitial fibrosis

• Obstructive disease

– resistance to

airflow

– e.g., COPD, asthma

FLOW-VOLUME CURVE

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Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease

(COPD)

Asthma

Bronchiectasis

Cystic fibrosis

Bronchiolitis obliterans

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Obstructive Airway Disease

Obstruction

FEV1 < 80% predicted

FEV1/FVC < 70%

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Extrathoracic airway obstruction

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Extrathoracic airway obstruction

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Intrathoracic airway obstruction

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Intrathoracic airway obstruction

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Fixed airway obstruction

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Extraparenchymal Disease

Chest wall deformity (kyphoscoliosis)

Neurological disorder (myasthenia gravis)

Muscular disease (myopathy)

Abdominal pressure (ascites, obesity)

Pleural Disease (effusion, fibrothorax)

Restrictive Pulmonary Disease

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Pulmonary parenchymal disease

Pulmonary fibrosis

Pneumoconiosis

Granulomatous dz(Sarcoidosis)

Vasculitis

Restrictive Pulmonary Disease

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Restrictive Lung Disease

VC, FRC, TLC < 80%

FEV1/FVC = Normal

Pseudorestriction

NMDz

Obesity

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in respiratory patients

FVC FEV1

• Restrictive disease

– expansion of the lung

– e.g., interstitial fibrosis

• Obstructive disease

– resistance to

airflow

– e.g., COPD, asthma

FLOW-VOLUME CURVE

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Summary of Obstructive and

Restrictive PFTS

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Diffusion Capacity

Dependent on:

Alveolar capillary membrane

Hemoglobin level

Pulmonary capillary volume

Single breath technique CO

Need to hold your breath for 10 seconds

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Diffusing capacity of the lung for CO

(DLCO)

Detection and evaluation of restrictive disease

Distinction of emphysema from other obstructive

lung disorders

Diagnosis of pulmonary hemorrhage

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Restrictive Lung Disease

VC, FRC, TLC < 80%

FEV1/FVC > 80%

Pulmonary-Parenchymal

(Interstitial)

DLCO < 80%

Extra-pulmonary

DLCO > 80%

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Increased Diffusion Capacity

Supine position

Exercise

Asthma

Obesity

Polycythemia

Intra-alveolar hemorrhage

L-R shunt

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Decreased Diffusion Capacity

Conditions that decrease surface area Emphysema, lung resection, bronchial obstruction, PE, anemia

Conditions that increase capillary or alveolar wall

thickness IPF, CHF, Asbestosis, Sarcoidosis, Collagen vascular disease, drug

induced alveolitis, hypersensitivity pnemonitis

Miscellaneous causes Heavy smokers, Pregnancy

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