Post on 12-Sep-2021
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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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