Pulmonary Function Tests Farah Madhani-Lovely Pulmonary/Critical Care Division December 13th 2005 1

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Indications and contraindications

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Spirometry

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Lung volumes

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Differentiating obstructive and restrictive lung disease

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Diffusion capacity

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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 3

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Contraindications 

Patient in respiratory isolation

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Inability to cooperate or sit up straight

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Acute illness  

Acute coronary syndrome Pneumonia

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Chest pain

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Current tracheostomy 4

Spirometry 

Measurement of air movement in and out of the lung during different respiratory maneuvers.

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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

• FEV1/FVC = 80% 6

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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 

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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 needed 11

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 At beginning

After several minutes

• Helium dilution • Spirometer of known volume and helium concentration connected to the patient • Closed circuit • Law of conservation of mass

[He] initial · Vs = [He] final · (Vs + VL)  Unknown lung volume can be calculated 13

LUNG VOLUMES

• Values obtained by simple spirometry • For the others parameters additional measurements needed 14

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) 15

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FLOW-VOLUME CURVE in respiratory patients • Restrictive disease –  expansion of the lung – e.g., interstitial fibrosis

• Obstructive disease  FEV1

 FVC

–  resistance to airflow – e.g., COPD, asthma

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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
80% Pulmonary-Parenchymal (Interstitial)

Extra-pulmonary

DLCO < 80%

DLCO > 80%

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Increased Diffusion Capacity       

Supine position Exercise Asthma Obesity Polycythemia Intra-alveolar hemorrhage L-R shunt 32

Decreased Diffusion Capacity 

Conditions that decrease surface area 

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Conditions that increase capillary or alveolar wall thickness 

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Emphysema, lung resection, bronchial obstruction, PE, anemia

IPF, CHF, Asbestosis, Sarcoidosis, Collagen vascular disease, drug induced alveolitis, hypersensitivity pnemonitis

Miscellaneous causes 

Heavy smokers, Pregnancy 33

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