Pulmonary function test

Evaluation of pulmonary function is important in many clinical situations evaluation of a variety of forms of lung disease assessing the presence of disease in a patient with known risk factors

Indications Risk evaluation of patients prior to thoracic or upper abdominal surgery Objective assessment of impairment or disability

Indications Evaluation of symptoms such as chronic persistent cough, wheezing, dyspnea and exertional cough or chest pain Objective assessment of bronchodilator therapy. Evaluation of effects of exposure to dusts or chemicals at work

Contraindications Hemoptysis of unknown origin Pneumothorax Unstable angina pectoris Recent myocardial infarction Thoracic aneurysms

Contraindications Abdominal aneurysms Cerebral aneurysms Recent eye surgery (increased intraocular pressure during forced expiration) Recent abdominal or thoracic surgical procedures History of syncope associated with forced exhalation

The major types of pulmonary function tests spirometry flow-volume loops measurement of lung volumes quantitation of diffusing capacity Measurements of maximal respiratory pressures

The predicted values of Lung volumes and Lung Capacities

Spirometry Evaluate dyspnea Smokers over age 45 to detect COPD Check recovery from exacerbation of asthma, COPD

Spirometry with bronchodilator Chronic cough or chest tightness Suspect asthma or COPD Determine response to specific bronchodilator therapy

What is a spirometry ?? Spirometry is a measure of airflow and lung volumes during a forced expiratory maneuver from full inspiration Spirometry is one of the most widely used lung function tests

How to do it ?? 1. Stand or sit up straight (The patient places a clip over the nose ) 2. Inhale maximally 3. Get a good seal around mouthpiece of the spirometer 4. Blow out as hard as fast as possible and count for at least 6 seconds. 5. Record the best of three trial

The basic values to interpret Spirometry are:The basic values to interpret Spirometry are: 1. FVC 2. FEV 1 3. FEV 1 /FVC ratio 4. FEV1/FEV6 5. FEF25–75%

Forced Vital Capacity (FVC) The FVC is the maximal amount of air that the patient can forcibly exhale after taking a maximal inhalation

FEV1 Volume of air which can be forcibly exhaled from the lungs in the first second of a forced vital capicity maneuver. The FEV 1 is the most important spirometric variable for assessment of airflow obstruction

FEV1 It declines in direct and linear proportion with clinical worsening of airways obstruction It increases with successful treatment of airways obstruction The FEV 1 should be used for determining the degree of obstruction (mild, moderate, or severe) Serial comparisons is important when following patients with asthma or COPD

FEV1/FVC Ratio of FEV1 to FVC : It indicates what percentage of the total FVC was expelled from the lungs during the first second of forced exhalation This value is critically important in the diagnosis of obstructive and restrictive diseases

FEF25% Amount of air that was forcibly expelled in the first 25% of the total forced vital capacity test.

FEF75% The amount of air expelled from the lungs during the first (75%) of the forced vital capacity test.

FEF25%-75% The amount of air expelled from the lungs during the middle half of the forced vital capacity test. More sensitive marker of mild small airway obstruction than the FEV1 But reproducibility is poor

Loops Flow-volume LOOP

Residual Volume (RV) The amount of air left in the lungs after a maximal exhalation The amount of air that is always in the lungs and can never be expired

The contour of the loop assists in the diagnosis and localization of airway obstruction as different lung disorders produce distinct,easily recognized pattern

Interpretation of PFTs Step 1. Look at the Flow-Volume loop to determine acceptability of the test, and look for upper airway obstruction pattern. Step 2. Look at the FEV1 to determine if it is normal (≥ 80% predicted). Step 3. Look at FVC to determine if it is within normal limits (≥ 80%). Step 4. Look at the FEV1/FVC ratio to determine if it is within normal limits (≥ 70%).

Step 5. Look at FEF25-75% (Normal (≥ 60%) If FEV1, FEV1/FVC ratio, and FEF25-75% all are normal, the patient has a normal PFT. If both FEV1 and FEV1/FVC are normal, but FEF25-75% is ≤ 60%,then think about early obstruction or small airways obstruction.

If FEV1 ≤ 80% and FEV1/FVC ≤ 70%, there is obstructive defect, if FVC is normal, it is pure obstruction. If FVC ≤ 80%, possibility of additional restriction is there. If FEV1 ≤ 80%, FVC ≤ 80% and FEV1/FVC ≥ 70%, there is restrictive defect, get lung volumes to confirm.

Obstructive Lung Diseases Asthma COPD (chronic bronchitis, emphysema and the overlap between them). Cystic fibrosis

Airflow is reduced because the airways narrow and the FEV1 is reduced

Flow-volume loops in Obstructive Pulmonary Disease Mild Obstruction ModerateObstruction Moderate Obstruction PIF PEF SevereObstruction Severe Obstruction

Spirometry interpretation flow chart for the detection of obstruction

Restrictive Lung Diseases

A. Intrinsic Restrictive Lung Disorders 1. Sarcoidosis 2. Idiopathic pulmonary fibrosis 3. Interstitial pneumonitis 4. Tuberculosis 5. Pnuemonectomy (loss of lung) 6. Pneumonia

B. Extrinsic Restrictive Lung Disorders 1. Scoliosis, Kyphosis 2. Ankylosing Spondylitis 3. Pleural Effusion 4. Pregnancy 5. Gross Obesity 6. Tumors 7. Ascites 8. Pain on inspiration - pleurisy, rib fractures

C. Neuromuscular Restrictive Lung Disorders 1. Generalized Weakness – malnutrition 2. Paralysis of the diaphragm 3. Myasthenia Gravis 4. Muscular Dystrophy 5. Poliomyelitis 6. Amyotrophic Lateral Sclerosis

Full expantion of the lung is limited and therefore the FVC is reduced FEV1 may be reduced because the stiffness of fibrotic lungs increases the expiratory pressure FEV1/FVC will be Normal or Increased

Flow volume loop in Restrictive lung disease

This is a characteristic pattern of a low FVC and comparatively high expiratory flow The curve will descend in a straight line from the PEF to the X axis

Spirometry interpretation flow chart for the detection of restrictive lung disease 43

Mixed Disorders Restrictive Disorders Obstructive Disorders Measure Decreased Normal or increased DecreasedFEV1/FVC Decreased, normal, or increased DecreasedFEV1 Decreased or normalFVC Decreased Normal or increasedTLC Decreased, normal, or increased Decreased Normal or increasedRV 44

Mixed Disorders Restrictive Disorders Obstructive Disorders Measure Decreased Normal or increased DecreasedFEV1/FVC Decreased Decreased, normal, or increased DecreasedFEV1 DecreasedDecreased Decreased or normal FVC Decreased Normal or increased TLC Decreased, normal, or increased Decreased Normal or increased RV 45

Mixed Disorders Restrictive Disorders Obstructive Disorders Measure Decreased Normal or increased DecreasedFEV1/FVC Decreased Decreased, normal, or increased DecreasedFEV1 DecreasedDecreased Decreased or normal FVC Decreased Normal or increased TLC Decreased, normal, or increased Decreased Normal or increased RV 46

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