Pulmonary Function Tests Dr Tasaduk Khan. MD. FRCP(UK). FCCP(USA) Consultant Internist & Pulmonologist. Security Forces Hospital, Riyadh. 9/16/2018

Pulmonary Function Testing Uses a variety of maneuvers to measure and record the properties of four(4) lung components. 1) Airways( large & small) 2) Lung parenchyma( alveoli, interstitium) 3) Pulmonary vasculature. 4) Bellows- pump mechanism. 9/16/2018

Basic concepts of normal pulmonary physiology that are involved in pulmonary function testing include. 1) Mechanics( air flows and lung volumes) 2) V/Q interrelationship. 3) Diffusion & gas exchange. 4) Respiratory muscle or bellows strength. 9/16/2018

Types of PFT Peak flow meter 2. Spirometry 3. Measurement of lung volumes-Plethismography 4. Gas transfer factor 5. Exercise test- 6 min walk test, ergometer test 6. ABG 9/16/2018

PFT Indications Evaluation of symptoms such as chronic persistent cough, wheezing, dyspnea, and exertional cough or chest pain. Objective assessment of bronchodilator therapy. Assessing the presence of disease in a patient with known risk factors, such as smoking. Evaluation of effects of exposure to dusts or chemicals at work. Risk evaluation of patients prior to thoracic or upper abdominal surgery. Objective assessment of impairment or disability. 9/16/2018

3. Measurement of lung volumes-Plethismography 4. Gas transfer factor Peak flow meter 2. Spirometry 3. Measurement of lung volumes-Plethismography 4. Gas transfer factor 5. Exercise test- walk test, ergometer test 6. ABG 9/16/2018

PEFR The peak expiratory flow rate (PEFR, also known as peak flow) is the maximal rate that a person can exhale during a short maximal expiratory effort after a full inspiration. Monitoring the PEFR is useful for detecting changes or trends in a patient’s asthma control. An individual patient's normal PEFR range is defined as 80 and 100 percent of their personal best. The personal best is generally the highest PEFR achieved during 2 wks post-treatment monitoring period. 9/16/2018

Peak Flow Meter Cheapest and easy 2. Home management of asthma 3. In absence of spirometer, establish, assess and monitor Bronchial asthma 4. PEF variability= (Max PEFR-Min PEFR)x100/Max PEFR; >20% is suggestive of Bronchial Asthma 9/16/2018

Types of PFT Peak flow meter 2. Spirometry 3. Measurement of lung volumes-Plethismography 4. Gas transfer factor 5. Exercise test- 6 min walk test, ergometer test 6. ABG 9/16/2018

Spirometry Spirometry, in which a maximal inhalation is followed by a rapid and forceful complete exhalation into a spirometer, includes measurement of FEV1 and FVC. Spirometry is used to measure forced expiratory flow rates and volumes. The results of spirometry can be used to determine the following: Determine whether baseline airflow limitation (obstruction) is present (reduced FEV1/FVC ratio) Assess the reversibility of the obstructive abnormality Characterize the severity of airflow limitation For patients with normal airflow (normal FEV1/FVC ratio), identify a restrictive pattern as an alternate explanation for dyspnea (eg, FVC <80 percent predicted) 9/16/2018

Spirometry - Forced expiratory volume in one second (FEV1) Simple, office-based Measures flow, volumes Volume vs. Time Can determine: - Forced expiratory volume in one second (FEV1) - Forced vital capacity (FVC) - FEV1/FVC - Forced expiratory flow 25%-75% (FEF25-75)

Terminology Forced expiratory volume in 1 second: (FEV1) Volume of air forcefully expired from full inflation (TLC) in the first second Measured in liters (L) Normal people can exhale more than 75-80% of their FVC in the first second; thus the FEV1/FVC can be utilized to characterize lung disease

FEV1 Interpretation of % predicted: >75% Normal 60%-75% Mild obstruction 50-59% Moderate obstruction <49% Severe obstruction FEV1 FVC

Terminology Forced vital capacity (FVC): Total volume of air that can be exhaled forcefully from TLC The majority of FVC can be exhaled in <3 seconds in normal people, but often is much more prolonged in obstructive diseases Measured in liters (L)

FVC Interpretation of % predicted: 80-120% Normal 70-79% Mild reduction 50%-69% Moderate reduction <50% Severe reduction FVC

Terminology Forced expiratory flow 25-75% (FEF25-75) Mean forced expiratory flow during middle half of FVC Measured in L/sec May reflect effort independent expiration and the status of the small airways Highly variable Depends heavily on FVC

FEF25-75 Interpretation of % predicted: >60% Normal 40-60% Mild obstruction 20-40% Moderate obstruction <10% Severe obstruction

Flow Volume Curve Illustrates maximum expiratory and inspiratory flow-volume curves Useful to help characterize disease states (e.g. obstructive vs. restrictive) Maximum expiratory flow (PEF) Expiratory flow rate L/sec FVC RV TLC Inspiratory flow rate L/sec 9/16/2018 Volume (L)

Categories of Disease Obstructive Restrictive Mixed

Obstructive Disorders Characterized by a limitation of expiratory airflow Examples: asthma, COPD Decreased: FEV1, FEF25-75, FEV1/FVC ratio (<0.8) Increased or Normal: TLC

Spirometry in Obstructive Disease Slow rise in upstroke May not reach plateau

Restrictive Lung Disease Characterized by diminished lung volume due to: change in alteration in lung parenchyma (interstitial lung disease) disease of pleura, chest wall (e.g. scoliosis), or neuromuscular apparatus (e.g. muscular dystrophy) Decreased TLC, FVC Normal or increased: FEV1/FVC ratio

Restrictive Disease Rapid upstroke as in normal spirometry Plateau volume is low

Large Airway Obstruction Characterized by a truncated inspiratory or expiratory loop

Normal Spirometry Image source: http://www.spirxpert.com/index.html

Obstructive Pattern Decreased FEV1 Decreased FVC Decreased FEV1/FVC - <70% predicted FEV1 used to follow severity in COPD Image source: http://www.spirxpert.com/index.html FEV1 is decreased out of proportion to FVC, which causes the ratio to decrease as well.

Obstructive Lung Disease — Differential Diagnosis Asthma COPD - chronic bronchitis - emphysema Bronchiectasis Bronchiolitis Upper airway obstruction This is not a complete list, just some of the most common diseases that should be on your differential for obstructive lung disease.

Restrictive Pattern Decreased FEV1 Decreased FVC FEV1/FVC normal or increased Image source: http://www.spirxpert.com/index.html FEV1 decreases in proportion to decrease in FVC, so ratio remains normal or even slightly increased

Restrictive Lung Disease —Differential Diagnosis Pleural Parenchymal Chest wall Neuromuscular Restrictive lung disease is made up of intrinsic lung disease (causes inflammation and scarring (interstitial lung diseases) or fill the airspaces w/ debris, inflammation (exudate); extrinsic causes are chest wall or pleural diseases that mechanically compress the lung and prevent expansion. Neuromuscular causes decreases ability of respiratory muscles to inflate and deflate the lungs.

Flow Volume Curve Patterns Obstructive and Restrictive Severe obstructive Restrictive Expiratory flow rate Expiratory flow rate Expiratory flow rate Volume (L) Volume (L) Volume (L) Reduced peak flow, scooped out mid-curve Steeple pattern, reduced peak flow, rapid fall off Normal shape, normal peak flow, reduced volume 9/16/2018

Bronchodilator Reversibility Testing Provides the best achievable FEV1 (and FVC) Helps to differentiate COPD from asthma Must be interpreted with clinical history - neither asthma nor COPD are diagnosed on spirometry alone 9/16/2018

Bronchodilator Reversibility Testing in COPD Spirometry (continued) Possible dosage protocols: 400 µg β2-agonist, or 80-160 µg anticholinergic, or the two combined FEV1 should be measured again: 10-15 minutes after a short-acting b2-agonist 30-45 minutes after the combination 9/16/2018

Bronchodilator Reversibility Testing An increase in FEV1 that is both greater than 200 ml and 12% above the pre-bronchodilator FEV1 (baseline value) is considered positive response. 9/16/2018

Bronchoprovocation Test-Indications Diagnosis of asthma: typical symptoms but normal spirometry and no response to BD; atypical symptoms eg nocturnal awakening, cough; evaluate occupational asthma, reactive airways dysfunction syndrome, or irritant-induced asthma; screening test for asthma, such as scuba divers, military personnel. Assesssment of asthma therapy. Identification of specific asthma triggers  9/16/2018

Methacholine challenge test Generally, a methacholine PC20 of 8 mg/mL (<4 mg/mL, for SGaw) or less is considered a positive test. A PC20 greater than 16 mg/mL is considered a negative test. Positive test indicates AHR, which is present mostly in Asthma. False positive MCT can occur in allergic rhinitis, cystic fibrosis, heart failure, COPD, and bronchitis. 9/16/2018

Examples - Unacceptable Traces Troubleshooting Examples - Unacceptable Traces

Unacceptable Trace – Slow Start Normal Volume, liters Time, seconds 9/16/2018

Unacceptable Trace - Coughing Normal Volume, liters Time, seconds 9/16/2018

Unacceptable Trace – Extra Breath Normal Volume, liters Time, seconds 9/16/2018

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Lung function Tests Peak flow meter 2. Spirometry 3. Measurement of lung volumes-Plethismography 4. Gas transfer factor 5. Exercise test- walk test, ergometer test 6. ABG 9/16/2018

Lung Volumes 4 Volumes 4 Capacities Sum of 2 or more lung volumes IRV IC VC TLC TV ERV FRC RV RV

Because spirometry is an expiratory maneuver, it Lung volumes. Because spirometry is an expiratory maneuver, it measures exhaled volumes or vital capacity but doesn`t measure RV, FRC or TLC. TLC is measured from FRC+ IC IC is measured by spirometry. FRC is measured by gas dilution technique. 9/16/2018

3. Measurement of lung volumes-Plethismography 4. Gas transfer factor Peak flow meter 2. Spirometry 3. Measurement of lung volumes-Plethismography 4. Gas transfer factor 5. Exercise test- walk test, ergometer test 6. ABG 9/16/2018

DLCO DLCO measures the ability of the lungs to transfer gas from inhaled air to the red blood cells in pulmonary capillaries. The DLCO is low in ILD,but normal in disorders of pleura, chest and neuromuscular disorder causing restrictive lung function. DLCO is also useful for following the course of or response to therapy in ILD. 9/16/2018

3. Measurement of lung volumes-Plethismography 4. Gas transfer factor Peak flow meter 2. Spirometry 3. Measurement of lung volumes-Plethismography 4. Gas transfer factor 5. Exercise test- walk test, ergometer test 6. ABG 9/16/2018

Exercise Tests uses Exercise testing with spirometry: EIB 6 MWT: provide simple, repeatable assessments of disability and response to treatment. Finally, cardiopulmonary exercise testing using cycle or treadmill exercise with measurement of metabolic gas exchange, ventilation and cardiac responses is useful in distinguishing cardiac limitation from respiratory limitation in the breathless patient. 9/16/2018

ABG Arterial blood gases (ABGs) may be a helpful adjunct to pulmonary function testing in selected patients. The primary role of measuring ABGs in stable outpatients is to confirm hypoventilation when it is suspected on the basis of clinical history (eg, respiratory muscle weakness, advanced COPD), an elevated serum bicarbonate level, and/or chronic hypoxemia. ABGs also provide a more accurate assessment of the severity of hypoxemia in patients who have low normal oxyhemoglobin saturation 9/16/2018

Question 1 Q. Spirometry is indicated for all except? Unexplained cough. Unexplained shortness of breath. Follow up of Asthma treatment. Hemoptysis. Follow up of Interstitial lung disease. 9/16/2018

Question 2 Q. Spirometry measures all except. Total lung capacity(TLC). FEV1. FVC. FEV1/FVC. FEF 25-75%. 9/16/2018

Question 3 Q. In obstructive airway disease all are true except. FEV1 is low. FVC is low. FEV1/ FVC is low. FEV1 is high. FVC can be normal. 9/16/2018

Question 4 Q. Pulmonary function testing includes all except. PEFR. Spirometry. Echocardiography. Timed six minute walk test.T6MWT. ABG. 9/16/2018

Question5 Q. In restrictive defect all are correct except? FEV1/ FVC is high/ N. TLC is low or normal. FEV1 can be normal. DLCO is always low. FEF 25-75% is normal. 9/16/2018