Pulmonary Function Tests

Question 1

What is Pulmonary function testings?

Answer 1

PFT is an important part of clinical medicine and serves a number of purposes – Establish the diagnosis of pulmonary disease and assess its severity – document the effectiveness of therapy for various pulmonary disorders – Chart the course of a disease through serial testing – Educate patients and, perhaps, facilitate alterations in lifestyle

Question 2

What are all of the Pulmonary function tests available?

Answer 2

• Spirometry – Bronchodilator • Flow Volume Loop • Lung volumes – Gas analysis • Helium dilution • Nitrogen washout – Body plethysmography •D LCO diffusing capacity • Maximum inspiratory and expiratory pressure • Inhalation challenge – Methacholine – Cold air • Maximum Voluntary Ventilation (MVV) • Cardiopulmonary exercise testing • Arterial Blood Gas • Oximetry • Six minute walk • FeN

Question 3

Normal values for lung volume and flow rate are based on?

Answer 3

• Normal values for lung volume and flow rate measurements (spirometry) are based on: – Age – Sex – Height – Race

Question 4

What lung variables does spirometry show?

Answer 4

Question 5

What is the procedure for spirometry?

Answer 5

1. Patient’s mouth is placed on a mouthpiece attached to machine that has flow sensors. Nose is occluded with a nasal clip.
2. The test starts with quiet breathing.
3. Generally, the patient is asked to take the deepest breath they can, and then exhale into the sensor as hard as possible, for as long as possible, preferably at least 6 seconds.
4. It is sometimes directly followed by a rapid inhalation (inspiration)

Question 6

What does a normal forced expiratory spirogam plotted against time look like/

Answer 6

Question 7

Explain the spirograms for Obstructive lung disease and restrictive disease?

Answer 7

Question 8

What is Forced Expiratory Vital capacity (FVC)? Sensitive to? Parameter tested? Patterns in disease? Decreases seen in?

Answer 8

The most important pulmonary function test for a given individual during expiration. There is a unique limit to the maximal flow that can be reached at any lung volume.
• The FVC test is very sensitive to diseases that alter the lung’s mechanical properties

• Parameter tested: – Expansion of chest wall and lungs
• Patterns in disease: – Reduced (below 80% of predicted) in restrictive disease – May be decrease in obstructive lung disease with air trapping
• Decreases seen in: – Restrictive disease: interstitial lung disease, pulmonary fibrosis, chest burn scars, ascites, pregnancy, obesity, and may be seen in obstructive diseases with air trapping: COPD, asthma

Question 9

What is forced expiratory volume in one second (FEV1)? Parameter tested? Patterns in disease? Decreases seen in?

Answer 9

The most reproducible spirometric value, the most commonly obtained, and possibly the most useful measurement. The FEV1 is easily identified directly from the spirogram.

• Parameter tested: – Potency of large airways
• Patterns in disease: – Reduced in obstructive disease – May be low in restrictive disease when FVC is low and the FEV1/FVC ratio is normal
• Decreases seen in: – Chronic bronchitis, emphysema, asthma

Question 10

What does the FEV1/FEV ratio tell us? Explain this number? what will tell us obstruction? restriction? Key to confirming a restriction?

Answer 10

• Generally expressed as a percentage
• The amount exhaled during the 1st second is a fairly constant fraction of the FVC irrespective of lung size
• In the normal adults, depending upon age, the rates range from 75 to 85% but it decreases somewhat with aging
• The American Thoracic Society takes a value less than 70% as indicative of obstrcution
• Aids in quickly identifying persons with airway obstruction in whom the FVC is reduced
• The ratio is valuable for identifying the cause of the low FEV1
• Decreased FEV1, questioned airway obstruction or restriction check the FEV1/FVC ratio
• Decreased FEV1 with normal FEV1/FVC usually indicates restriction
• Decreased FEV1 and a decreased FEV1/FVC ratio signifies a predominant obstructive process
• The key to confirming restriction is a lung volume study with a reduced TLC

Question 11

Obstruction will show what with FVC, FEV1, and FEV1/FCV?

Answer 11

FVC Normal or decreased

FEV1 Decreased

FEV1/FVC Decreased

Question 12

Restriction will show what with FCV, FEV1, and FEV1/FCV?

Answer 12

FVC Decreased

FEV1 Decreased

FEV1/FVC Normal

Question 13

What are major lung diseases that have a reduced FEV1/FCV ratio and reduced FEV1?

Answer 13

• COPD – Chronic bronchitis – Emphysema
• Asthma
• Bronchiectasis

Question 14

Explain the GOLD classification for COPD?

Answer 14

Question 15

Explain the findings of spirometry and what diseases they could mean?

Answer 15

Question 16

What methods can we use to determine total lung capacity?

Answer 16

– Gas analysis for FRC • Helium dilution technique • Nitrogen washout method

– Body plethysmography – thoracic gas volume # FRC- most common now

– Chest roentgenography – planimeter TLC

Question 17

What are the normal lung volumes for Total lung capacity, vital capacity, residual volume, inspiratory capacity, tidal volume, functional residual capacity

Answer 17

• Total lung capacity 6.0L
• Vital capacity 4.8L
• Residual volume 1.2L
• Inspiratory capacity 3.6L
• Tidal volume 0.7L
• Functional residual capacity 2.4L

Question 18

in obstructive and restrictive lung pathology what will see in the lung variables?

Answer 18

Question 19

Flow Volume loop analysis is part of may spirometers, what is its benefit and use?

Answer 19

• Best indicator of test quality
• Analysis of flow in latter portion of FVC seems to be a more sensitive way of detecting obstructive airway disease than usual spirographic analysis
• Flow-volume loop analysis may lead to detection of large airway lesions such as bilateral vocal cord paralysis, tracheal tumors, and tracheal stricture which would not be suspected from a routine spirogram
• Poor patient effort is easily detected compared to spirometry
• Peak expiratory flow (PEF) and peak inspiratory flow (PIF) are easily determined

Question 20

what is this an example of?

Answer 20

fixed Obstructing Lesions of the Central Airway

Question 21

What are causes of fixed upper airway obstructions?

Answer 21

• Bilateral vocal cord paralysis
• Tracheal stenosis
• Tracheal tumors
• Extrinsic compression from: goiter, lymphadenopathy, or tumor
• Fibrosing mediastinitis

Question 22

What are some causes and what does a variable obstructive intrathoracic lesion look like?

Answer 22

• Tracheal tumors
• Tracheobronchomalacia
• Tracheobronchomegaly

Question 23

what is the curve, and the causes of variable extrathoracic obstruction?

Answer 23

• Vocal cord dysfunction
• Glottic stricture
• Laryngeal tumor

Question 24

What is the Diffusion Capacity DLCO:

Answer 24

DLCO estimates the transfer of oxygen from alveolar gas to the hemoglobin with the red cell. The amount of oxygen transferred is largely determined by three factors:

1. Area (A) of the alveolar-capillary membrane
2. Thickness (T) of the membrane
3. Driving pressure: the difference in oxygen tension between the alveolar gas and the venous blood (change in PO2).

Question 25

What are the indications for Performing a DLCO test?

Answer 25

• Differential diagnosis of airways obstruction
• Screening for mild (early) interstitial lung disease (ILD)
• Differential diagnosis of lung volume restriction
• Detection of pulmonary vascular disease
• Disability/impairment evaluations for ILD or COPD
• Followup for ILD
• Need for oxygen therapy

Question 26

What is the severity classification for DLCO abnormality?

Answer 26

• High > 140 % predicted*
• Normal 81-140%
• Borderline low 76-80%*
• Mild decrease 61-75%
• Moderate decrease 41-60%
• Severe decrease < 40%
• *The upper and lower limits of the normal range should be substituted for the 140% and 76% predicted cut points if available from the reference study.

Question 27

What are factors that cause a reduction in DLCO?

Answer 27

• Thickening of the alveolar-capillary membrane
• Loss of alveolar-capillary area
• Abnormalities of alveolar ventilation, lung perfusion and ventilation/perfusion match-up
• Reduction in red cell mass
• Decreased affinity of hemoglobin for CO

Question 28

Differential for increased DLCO?

Answer 28

• Polycythemia vera • Exercise • Supine position • L to R cardiac shunts • Asthma • Obesity • Pulmonary edema

Question 29

Differential for decreased DLCO?

Answer 29

• Pulmonary vascular disease • CHF • Emphysema • Lung resection • Interstitial lung disease • Bronchial obstruction • Anemia • Pneumoni

Question 30

What is the Fractional Exhaled Nitric Oxide?

Answer 30

FENO: A marker of T-helper cell type 2 mediated eosinophilic airway inflammation

FENO: A test used to assess allergic/eosinophilic asthma status Reflects T-helper 2 driven eosinophilic airway inflammation The concentration of exhaled nitric oxide is used to assess the pressure of potentially corticosteroid responsive airway inflammation

Question 31

How could FENO be used in the office?

Answer 31

Question 32

Pros and Cons of FENO?

Answer 32

FENO is one of two simple tests to assess airway inflammation. The other is induced sputum analysis for eosinophils.
Pros: Simple and safe. Excellent point of care tool. Immediate results. Ideal for monitoring and decision purposes. Helps in decision regarding corticosteroids.
Cons: Expensive. Not covered by all insurers. Limited to a specific asthma phenotype.

Question 33

Schematic of how to used and evaluate PFTs?

Answer 33

Question 34

What is the only true lung function test?

Answer 34

The function of the lung is: 1. To get oxygen 2. To get rid of CO2 3. To help maintain acid base balance

Hence arterial blood gases is the true pulmonary function test. The rest of the tests gives us a reason why the lung is not functioning well.