WORKSHOP OF LUNG FUNCTION TEST Dr. Lo Iek Long, Department of Respiratory Medicine, CHCSJ, Macau
Big three in Respiratory Medicine Lung Function Test Chest imaging Bronchoscopy
Table of Content Section 1 What is lung function? What is being tested? What is the Indications of lung function test? Section 2 How to interpret lung function test result? Case discussion
Lung function test application form Spirometry Lung volumes Diffusion
Lung function laboratory
Lung function testing result
What is lung function?
Sites at which may cause respiratory disturbance Lung problems Pump problems
Respiratory disorders Restrictive Diffusing capacity Lung problems Airway disease COPD Asthma Alveolar disease Emphysema Interstitial disease ILD, Tb sequela Pulmonary circulation Pulmonary hypertension Pump problems Pleural disease Pleural thickening Chest cage Kyphosis/scoliosis Obesity-hypoventilation NMD ALS Asthenia Gravis CNS Intoxication/stroke
Ventilatory defects & gas exchange Obstructive ventilatory defects (OVD) Airway disease Restrictive ventilatory defects (RVD) Interstitial disease Pleural disease Chest cage disease Neuromuscular disease Gas exchange Airspace disease Interstitial disease Vascular disease
Three key elements of LFT
INDICATIONS OF LFT
ATS/ERS 2005
Indications of LFT To establish a presumed diagnosis (e.g. COPD, asthma, ILD) To investigate a symptom (e.g. cough, SOB, low exercise tolerance) To determine the severity, progression and prognosis of a respiratory illness To evaluate functional impairment/disability (e.g. silicosis and other occupational lung diseases) To assess the peri-operative risk for cardio-thoracic surgery
Preparation of LFT Stopped medications before LFT that may affect bronchial responsiveness: Leukotriene modifier (Singulair): 24 hours Theophylline (Euphylong): 24 hours LABA (Ventolin): 8 hours SAMA (Atrovent): 8 hours (24 hours) LABA (Seretide/Symbicort): 12 hours (48 hours) LAMA (Spiriva): 24 hours (1 week) For follow-up cases, you may not need to stop the medication Guideline for methacholine and exercise challenge test. AJRCCM 2000;161:309-329
SPIROMETRY
Spirometry - Terminology FVC: the volume of air forcefully exhaled from a maximal inspiration FEV1: the volume of air exhaled during the first second of a FVC maneuver FEV1/FVC (%): <70% suggested airflow limitation
The measurement of FVC Volume against time Spirogram Flow against volume Flow-volume curve
Flow volume curve Adequacy of expiratory effort Artifacts Small airway obstruction (long, upwardly concave tail) Central airway obstruction
Patterns of central airway obstruction Fixed obstruction (Box shape) Variable extrathoracic obstruction (truncated inspiratory limb) Variable intrathoracic obstruction (truncated expiratory limb)
Mechanism Vocal cord dysfunction Tracheal mass
Peak expiratory flow (PEF)
Peak expiratory flow Asthmatic patients Record twice daily Diurnal variation > 15% Suggestive of asthma Monitoring
Window of opportunity as an exacerbation begins to develop Exacerbations of Asthma. A Descriptive Study of 425 Severe Exacerbations. Am J Respir Crit Care Med 1999;160:594 599.
FEF25-75 (Measurement of small airway) The average forced expiratory flow during the middle half of the FVC maneuver.
LUNG VOLUMES
Basic Concepts Volume TV Tidal Volume IRV Inspiratory Reserve Volume ERV Expiratory Reserve Volume RV Residual Volume Capacity IC Inspiratory Capacity FRC Functional Residual Capacity VC Vital Capacity TLC Total Lung Capacity
Lung volume and capacity Albert RK, Spiro SG, Jett JR (eds): Comprehensive Respiratory Medicine. St Louis: Mosby, 1999, p 43.
TLC and RV Full inspiration Full expiration
How to measure? Gas dilution technique Nitrogen washout Helium dilution Body Plethysmography Radiographic planimetry
Nitrogen washout
Body plethysmography Bolye s Law PV=P (V+V )
CXR Accurate measurement as long as the film is obtained at maximal inspiration (TLC)
DIFFUSING CAPACITY
Diffusing capacity of the lung to CO Methods: Single breath Steady state
Diffusing Capacity of CO (DLCO) DLCO = KCO x Va KCO (DLCO/Va): transfer factor Index of alveolar integrity Low: ILD, emphysema Va: alveolar volume DL Adj (adjusted for Hb)
MAXIMAL RESPIRATORY PRESSURE
Maximal inspiratory pressure (PImax) Measured by a pressure transducer at the mouth when a subject makes a maximal inspiratory effect from RV. Early detection of respiratory muscle strength MIP: primarily diaphragm (-60cmH2O) MEP: diaphragm plus abdominal muscles (80cmH2O) Decreased in neuromuscular disease (NMD) Amyotrophic lateral sclerosis (ALS) Guillain-Barre syndrome Myasthenia gravis
INTERPRETATION OF LUNG FUNCTION TEST
Acceptability and Reproducibility Criteria Acceptability Reproducibility ATS/ERS 2005
Normal LFT Technical one Acceptability (Flow-volume loop) Free from artifacts Good starts Satisfactory expiratory time (>6s) Reproducibility Two largest FVC and FEV1 measurements must be within 150ml of each other ATS/ERS 2005
Acceptability
Acceptability and repeatability criteria
Normal LFT - Practical one Normal Spirometry Normal shaped flow-volume loop FEV1/FVC > 70% FVC and FEV1 > 80% of predicted value Normal Lung Volumes TLC and RV between 80-120% of predicted DLCO DLCO > 80% of predicted value
Age Height Gender Race
Normal spirogram
VENTILATORY DEFECTS
Ventilatory Defects Obstructive Ventilatory Defect (OVD) Restrictive Ventilatory Defect (RVD) Diffusion Defect
Obstructive Ventilatory Defects (OVD) FEV1/FVC < 70% is an indicator of airflow limitation OVD may be due to: Asthma Bronchiectasis COPD (bronchitis vs emphysema predominant) Other airway disease (bronchiolitis obliterans)
Mild and severe airflow obstruction
Three More Things to do 1. Assessing the reversibility of the obstruction (BD response, 12% and 200ml increase in FEV1or FVC) 2. Quantifying the severity of OVD (COPD - FEV1% 80%, 50%, 30% of predicted) 3. Determining whether there is hyperinflation or air trapping
Hyperinflation vs Air trapping Hyperinflation TLC > 120% predicted At maximum inspiration, lung volumes are larger than expected Air trapping SVC>FVC by both 12% and 200ml RV>120% predicted During forced expiration, there is dynamic collapse of airway with resultant incomplete expiration of air
Hyperinflation vs Air trapping
Restrictive Ventilatory Defects (RVD) Restriction of outward movement of the lungs and/or chest wall TLC < 80% predicted Mild: 65-80% predicted Moderate: 50-65% predicted Severe: <50% predicted Pulmonary function testing. Textbook of respiratory medicine, 1995
Causes of Restrictive Ventilatory Defects Interpretation of pulmonary function tests A practical guide, 2 nd ed.
Diffusion DLCO < 80% predicted Mild: 60-80% predicted Moderate: 40-60% predicted Severe: < 40% predicted DLCO = KCO x Va Decreased KCO (DLCO/Va) (transfer factor) Decreased Va (alveolar volume) Both
DLCO = KCO (DLCO/Va) x Va KCO = The rate constant for alveolar uptake of CO Alveolar-capillary membrane
Low DLCO (KCO x Va) Low KCO Alveolar damage ILD Fibrosis Emphysema CHF Pulmonary vascular disease Low Va Normal or high KCO Extra-pulmonary restriction Loss of aerated units Pneumonectomy Consolidation Atelectasis Palange P, Simonds A. ERS handbook 2010
Washington Manual Pulmonary Medicine Subspecialty Consult
PITFALLS IN INTERPRETING LUNG FUNCTION TESTING
Pitfalls in LFT interpretation Grade the severity of OVD based on FEV1/FVC% FEV1/FVC% < 70% = the presence of airflow limitation FEV1% of predicted value = Severity Diagnose RVD based on spirometry Reduced FEV1 or FVC is only suggestive of RVD TLC < 80% predicted is the gold standard for RVD Preclude non-cardiothoracic surgery based on lung function testing
Spirometry alone Spirometry FEV1/FVC >70% <70% FEV1 and >80% predicted normal OVD FVC <80% predicted RVD Mixed
TLC < 80% predicted is the gold standard for RVD Spirometry and lung volume FEV1/FVC >70% <70% FEV1 and FVC < 80% predicted TLC < 80% predicted TLC > 80% predicted RVD Non-specific pattern Mixed Air trapping RVD must be confirmed with TLC<80% predicted!
Adapted from Miller WF, Scacci R, Gast LR: Laboratory Evaluation of Pulmonary Function. Philadelphia: JB Lippincott, 1987
Non-specific Pattern Low FEV1 and FVC, normal FEV1/FVC ratio and TLC. If Raw is increased, we consider it an obstructive disorder and grade severity based on FEV1. If Raw is normal, we call it a nonspecific pattern. The most common associated conditions are asthma, obesity, CHF, and chest wall-limiting conditions. An additional option is to perform methacholine challenge because airways hyperresponsiveness is often associated. Interpretation of pulmonary function tests A practical guide, 2 nd ed.
Preoperative assessment Non-cardiothoracic surgery Cardiothoracic surgery Preoperative Evaluation of the Patient With Pulmonary Disease. CHEST 2007; 132:1637 1645
Non-cardiothoracic surgery Preoperative Pulmonary Risk Stratification for Noncardiothoracic Surgery: Systematic Review for the American College of Physicians. Ann Intern Med. 2006;144:581-595.
In specific situation http://www.mpsmacau.org/publication.html
Lung resection surgery Standard testing Standard LFT (FEV1 and DLCO) Cardiopulmonary exercise testing (VO2) Stair climbing Split lung function studies to predict postoperative values Anatomical calculation Post FEV1 = Pre PEV1 x (18-segments/18) Quantitative CT scans V/Q scans
SUMMARY OF LFT
Summary of lung function testing Lung function test Spirometry Flow volume curve FEV1, FVC, ratio Lung volumes TLC, RV Gas exchange DLCO Major results Major airway obstruction Obstructive ventilatory defects (OVD) Restrictive ventilatory defects (RVD) Impaired gas exchange
Summary lung function test Do not make pathologic diagnoses Provide physiologic measurements Identifying obstructive or restrictive ventilatory defects (OVD vs RVD) Provide support for the existence of the relevant disease process
Methacholine challenge testing Suspected asthma with normal LFT PC20: the concentration of methacholine to cause a 20% decrease in FEV1 PC20 cutoff point 8-16 mg/dl Contraindicated in: Severe airflow limitation Recent (3 months) MI or stroke Uncontrolled hypertension Aortic aneurysm
Cardiopulmonary exercise testing To distinguish between cardiac and pulmonary causes of dyspnea in complex cases To determine whether the patient's symptoms are due to deconditioning To detect the malingering patient To provide disability evaluation in problem cases To determine whether the subject can meet the work requirements of a given occupation Jones NL, Killian KJ. Exercise limitation in health and disease. N Engl J Med 343:632-641, 2000
ATS/ACCP Statement on Cardiopulmonary Exercise Testing
Impulse Oscillometry (IOS) Effortless Differentiating the following conditions: Airway (central vs peripheral) resistance Lung and chest wall resistance Good for children and the elderly Current problems No normal reference for Asian until now Not easy to interpret the result Not very well correlated with standard lung function test
Suggested readings: ATS/ERS TASK FORCE: STANDARDISATION OF LFT http://www.thoracic.org/statements/
LUNG FUNCTION CASES
Case 54/F, never smoker Hx of asthma since childhood, no regular FU No regular treatment Episodic cough, SOB and wheeze in recent 10 years CXR on 15 Jun 2010: unremarkable
Hx of asthma since childhood
Case 69/M, Current smoker FU in health center Chronic cough with exertional SOB for 10 years No data on personal and family history allergic diseases.
Incidentally found lung mass, smoker Siprometry only
Complete lung function test
Case 62/M, ex-smoker (30 pack-years, quit 3 year) Hx of HTN Referred from cardiologist for the investigation of exertional SOB CXR on 12 July 2011: No significant finding
Case 26/F, never smoker, No personal and family history of allergic disease Hx of pemphigus in 2007, received steroid and immunosuppressant for several months Presented with progressive SOB since July 2008 PE: left cervical LN enlargement ABG: hypoxemia without CO2 retention Cardiac echo: no pulmonary hypertension or cardiac dysfunction
Chest imaging CXR - hyperinflation CT - mild tubular bronchiectasis
Left cervical LN biopsy showed T-cell lymphoma We searched the literature: T-cell lymphoma and other malignancy may cause pemphigus (called paraneoplastic pemphigus) Paraneoplastic pemphigus associated bronchiolitis obliteran (BO) has been reported She was put on monoclonal antibody to CD52. However, respiratory failure progressed the patient passed away.
Case 76/M, Ex-smoker, quitted for 20 years Worker in textile industry before retirement, retired for more than 10 years. Hx of CHB, HCC in 2011. PE: velcro rales over both lower lungs, no clubbing noted
HRCT
Case 71/M, current smoker (40 pack-years) Retired farmer, no pigeon at home. Received cholecystectomy in 2009 Abdomen CT showed ILD Progressive SOB for 2 years, dry cough for one year
Case 36/F, never smoker, dealer in Casino Hx of recurrent uveitis for 10 years Denied Hx of allergic disease Presented with dry cough for 2 years, exertional SOB for 1 year CXR on Dec 2009 showed multiple lung nodules Sputum negative for AFB and malignant cells
HRCT (Miliary TB? CA?)
LFT on Jan 2010
LFT on Feb 2010
Sarcoidosis FOB: no endobronchial lesion; transbronchial lung biopsy and random endobronchial biopsy showed granuloma without AFB Final diagnosis: sarcoidosis LFT in sarcoidosis Decreased in DLCO: early stage, sensitive OVD: 30-50% patients with sarcoidosis RVD: late stage (fibrosis) Pulmonary Sarcoidosis: Pulmonary Function Tests in Sarcoidosis. Semin Respir Crit Care Med. 2007;28(1):53-74
Case 35/F Right chest pain for more than 1 year. CXR showed right loculated pleural effusion. Thoracentesis showed exudate.
Pre-operative LFT
After VAT-S in Apr 2011
Case 59/M, never smoker PTB 40 years ago Admitted for right pneumothorax in Nov 2010, received pleurodesis HRCT in Nov 2010: tubular bronchiectasis in RUL, spotty calcification scattered in both upper lungs, suggestive of TB sequela
Case 76/M, Portuguese Never smoker, Hx of HTN and DM Presented with low exercise tolerance (SOB and fatigue) for one year CXR on 12 Dec 2010: increased lung marking with poor inspiration CT Thorax on 31 Jan 2011: Minimal fibrotic patches image in right upper lobe ABG: 7.37, PaO2 91.6, PaCO2 44.1, BE -0.4
Case 66/M, current smoker (50 pack-years) Construction site worker for more than 20 years, retired since 2009 Denied PTB and allergic disease Cough with white sputum for 5 years, associated with progressive SOB.
Progressive Massive Fibrosis
LFT in Silicosis 89% silicotic subjects are smokers OVD: silicosis and tobacco smoking RVD: progressive massive fibrosis Reduced DLCO: progressive massive fibrosis HKMJ 2001;7:343-9
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