Cardio-Spirometry PDF

Pulmonary Function Tests Ms. Sammi CHAU Senior Lecturer  Intended Learning Outcomes After this lecture, students should be able to: Recognize and distinguish different pulmonary function tests Understand how to conduct an accurate spirometry test Interpret numeric...

Pulmonary Function Tests Ms. Sammi CHAU Senior Lecturer  Intended Learning Outcomes After this lecture, students should be able to: Recognize and distinguish different pulmonary function tests Understand how to conduct an accurate spirometry test Interpret numerical and graphical spirometry data Recognize the various spirometry patterns associated with restrictive and obstructive pulmonary disease Appreciate the American Thoracic Society recommendations for presenting spirometry test data Appropriately use spirometry data as an outcome measure to evaluate a physiotherapy intervention  Pulmonary Function Tests Pulmonary function tests (PFTs), also called lung function tests are investigations that provide information about the integrity of the airways, the function of respiratory musculature, and the condition of the lung tissues. PFTs measures lung volumes and capacities, gas flow rates, gas diffusion, and gas distribution. One of the diagnostic tools to classify pulmonary diseases into 3 basic categories: Obstructive Restrictive Mixed  Pulmonary Function Tests Function / exercise capacity CPET Exercise test/field test Airways patency & air flow Spirometry Reversibility test Lung volumes & capacities Spirometry Gas diffusion Diffusion capacity test Respiratory muscle strength Maximal expiratory pressure Maximal inspiratory pressure Cough peak flow  Common Pulmonary Function Tests Function / exercise capacity CPET  Exercise test/field test  Airways patency & air flow Spirometry  Reversibility test  Gas diffusion Diffusion capacity test  Lung volume and capacity Body plethysmography Nitrogen washout Respiratory muscle strength Maximal expiratory pressure Maximal inspiratory pressure To be taught Cough peak flow  What is Lung Diffusion Capacity Test (DLCO)? Measurement to assess the lung’s ability to transfer gas from inspired air to the bloodstream Called diffusing capacity of the lungs for carbon monoxide (DLCO) Inhaled carbon monoxide (CO) is used as it has a higher affinity for hemoglobin than O2 by 200-250 times The test will require the patient to perform a 10-second breath hold to measure the uptake of CO (cc of CO/sec/mm of Hg)  Factors that affect the gas diffusion across the alveolar membrane include: 𝐾 ∗ 𝐴 ∆𝑃 Fick’s Equation: 𝑉𝑔 = 𝑇 Surface area of membrane (A) Thickness of the membrane (T) Solubility of the gas (K) Driving pressure/pressure gradient across the capillary membrane (∆P) Surface area of membrane Surface area of membrane Diffusion Alveolar pressure gradient Alveolar pressure gradient decreases Diffusion Solubility of the gas Solubility of the gas increases Membrane thickness Membrane thickness  DLCO Indicated in the evaluation of parenchymal and non-parenchymal lung diseases Obstructive lung diseases (asthma, COPD, emphysema, bronchitis) Restrictive lung diseases (interstitial lung disease, disorders of the chest wall or pleura, neuromuscular disease) Pulmonary vascular disease (thromboembolic disease or pulmonary arterial hypertension) Usually in conjunction of spirometry, with total lung capacity (TLC), it would give an interpretation if restrictive pattern exists. Results: Normal DLCO: >75% of predicted, up to 140% Mild: 60% to LLM Moderate: 40% - 60% Suggestive of parenchymal disease e.g. ILD Severe: 10% of predicted value in FEV1 or FVC as compared to baseline Reversible airways disease Bronchichdilator Diagnostic criteria for asthma > - More sensitivity to Distinguish asthma from COPD (5-6% improvement only)  Reversibility Test Post FEV1 − Post FEV1 𝐑𝐞𝐯𝐞𝐫𝐬𝐢𝐛𝐢𝐥𝐢𝐭𝐲 = x 100 Post FEV1 Bronchodilator Effect on FEV1 FVC Normal FEV1 Post bronchodilator Volume Flow Post bronchodilator Pre bronchodilator Pre bronchodilator Time Volume  Difference in Flow-Volume Patterns 10.0 10.0 COPD Asthma 7.5 7.5 5.0 5.0 2.5 2.5 6 5 4 3 2 6 5 4 3 2 Bronchodilator Effect: Bronchodilator Effect: FEV1 or FVC increase by > 10% FEV1 increase by < 5-6% only ATS (2021)  Restrictive Lung Disease Refers to a group of diseases with various causes: Intrinsic lung disease Interstitial lung disease Sarcoidosis Pneumonitis Pleural tissue: pleural effusion, pleuritis Extrinsic pulmonary disease Neuromuscular disease (e.g. muscular dystrophy, amyotrophic lateral sclerosis) Scoliosis Ascites, obesity, abdominal tumour Characteristics: Decrease elasticity (or compliance) of lung tissue  Restrictive Lung Disease In restrictive lung diseases, the lungs are prevented from fully expanding due to restrictions in the lung tissue, pleurae, muscles or bones. Characterized: Deceased total lung capacity Reduced lung compliance Restrictive Lung Disease Restriction IRV FVC IRV decreased VT VT TLC ERV decreased ERV FRC RV decreased RV Normal Restrictive  Forced Expiratory Time-Volume Graph FVC Normal FEV3 Restrictive lung disease FEV1 The pattern of expiratory Expired volume (L) pattern is similar to normal Restrictive The FVC is reduced FEV1 / FVC ratio is normal Time (s)  Flow-Volume Loop Driving Pressure Flow = Resistance In patients with restrictive pattern Loss in lung volume (loop is narrowed) 10.0 Airflow is greater than normal because of increased elastic recoil Flow (L/s) Characterized by: 7.5 Reduced FVC Normal or increased FEV1/FVC ratio 5.0 Normal looking shape of spirometry Flow-volume loop tends to be narrow and tall and narrow with steep end expiratory phase 2.5 Relatively high PEF Assessment Spirometry may be inconclusive (FEV1/FVC ≥ LLN) 6 5 4 3 2 Lung volume (TLC < LLN)  Forced Expiratory Time-Volume Curve Normal FVC FEV1 Normal Obstructive Restrictive FVC Normal Decreased or Decreased normal Obstructive FEV1 Normal Decreased Decreased or normal Restrictive FEV1/FVC Normal Decreased Normal (70-80%) ( 80%) TLC Normal Normal or Decreased (5-6L) increased  Normal Expiration Restrictive TLC RV Trapped air Obstructive Inspiration  Monitoring of Disease Progression In obstructive diseases A weekly change in FEV1 for normal subjects for ≥ 12% in normal subjects or ≥ 20% for patients with COPD is considered significant Yearly changes in FEV1 should not exceed 15% In restrictive diseases ≥ 10% reduction in FVC in reflective of disease progression In neuromuscular diseases Declining FVC is a strong indicator of disease progression The ATS/ERS interpretative recommendations Gratham et al 2019 1 Pellergrino et al 2005 2 Raghu et al 2011 3 Clavelou et al 2013 How to interpret the results of a spirometry test? What should be used to make reference to?  Classification of Severity of Airflow Limitation in COPD 0 8 Normal =. Global Initiative for COPD (GOLD) criterion A post-bronchodilator FEV1/FVC ratio of < 0.7 is considered diagnostic for airflow obstruction American Thoracic Society (2005) FEV1 1 – Mild FEV1 > 70% 2 – Moderate FEV1 60-69% predicted 3 – Moderate to severe FEV1 50-59% predicted 4 –Severe FEV1 35-49% predicted 5 – Very severe FEV1 < 35% predicted  Classification of Severity of Airflow Limitation in COPD Global Initiative for COPD (GOLD) criterion A post-bronchodilator FEV1/FVC ratio of < 0.7 is considered diagnostic for airflow obstruction American Thoracic Society (2005) FEV1 1 – Mild FEV1 ≥ 70% 2 – Moderate FEV1 60-69% predicted 3 – Moderate to severe FEV1 50-59% predicted 4 –Severe FEV1 35-49% predicted 5 – Very severe FEV1 < 35% predicted  2021 ATS/ERS Technical Standard Not recommended Fixed ratio FEV1/FVC < 0.7 80% predicted to define normal Healthy lung size and function are dependent on: Age, Gender, Height, Weight, Ethics Data from healthy subjects are normally distributed Mean or median is located at the center of bell curve Also referred to as the “predicted value” Compare the measured data to the predicted data from reference equations used Limitations Unable to account for variability across a range of ages Fixed cutoff may cause a risk of age-related bias Mean  Limitation of Using Cuff-off Unable to tell the variations and lead to FEV1/FVC false positive interpretation Under-diagnosis of abnormalities in younger and taller individuals Over-diagnosis in those older or shorter 0.7 Both individuals with healthy lungs and obstructed airways would fall into a fixed cutoff (zone of uncertainty)  Range of expected values Varies with the type of test, the age, height, gender of the individual and other factors Spread of values around the mean is expressed as coefficient of variation Standard deviation (SD) divided by the mean (in %) These ranges for each test are described by: Z-scores Percentiles Lower limit of normal (LLN) LLN = mean predicted value (based on the patient’s gender, age and height) minus 1.64 times the standard error of the estimate (SEE) from the population reference 5th percentile of a healthy, non smoking population Recognize the change with age of the measured value from the age specific FEV1/FVC predicted for any individual Minimize the bias  2021 ATS/ERS Technical Standard To define normal range Use percentile Lower limit of normal = 5th percentile Upper limit of normal = 95th percentile To define severity of function impairment Use Z-score Mild: -1.65 to -2.5 Moderate: -2.51 to -4.0 Severe: < -4.1 Classification on Severity of Airflow Obstruction GOLD 2023 ATS/ERS 2021 When FEV1/FVC < 0.7 Use Z-Score Post-bronchodilator FEV1 value Z-Score GOLD Criteria Normal Z-score ≥ -1.64 1 – Mild FEV1 ≥ 80% predicted Mild Z-score -1.65 to -2.5 2 – Moderate 50% ≤ FEV1 < 80% Moderate Z-score -2.51 to -4 3 – Severe 30% ≤ FEV1 < 50% Severe Z-score < -4.1 4 – Very severe FEV1 < 30% predicted LLN & Z-Score Z-Score Z-Score Z-Score -4 -2.5 -1.645 Z-Score Normal Z-score ≥ -1.64 Mild Z-score -1.65 to -2.5 Moderate Z-score -2.51 to -4 Severe Z-score < -4.1  Classification of Severity in Restriction Total lung capacity (TLC) is reduced Use TLC (% predicted) TLC (% Predicted) Normal ≥ 80% predicted Mild 70 – 79% predicted Moderate 50 – 69% predicted Severe < 50% predicted Use 5th percentile TLC < 5th percentile Diffusing capacity of the lungs for carbon monoxide (DLCO) Assess the lungs’ ability to transfer gas from inspired air to the bloodstream If DLCO is normal (>70% of predicted), it suggests non-parenchymal disease. If DLCO is impaired, it implies interstitial lung disease  Summary Spirometry To identify obstructive and restrictive pattern lung disease To diagnose and monitor progress of respiratory disease To assess pre-operative risk A physiotherapist must know how: To conduct a proper spirometry assessment To interpret spirometry data and expiratory curves To use spirometry data as an appropriate outcome measure  References Hillegass E.A. (2011) Essentials of Cardiopulmonary Physical Therapy (3rd Ed). Saunders. Cooper et al. The Global Lung Function Initiative (GLI) network: bridging the worlds’ respiratory reference values together. Breathe. 2017; 13:e56-e64 Graham et al. Standardization of Spirometry 2019 update. Am J Respir Crit Care Med 200; 8: e70-e88 doi:10.1164/rccm.201908-1590ST Culver et al. (2017). Recommendations for a Standardized Pulmonary Function Report. An Official American Thoracic Society Technical Statement. American Journal of Respiratory and Critical Care Medicine, 196, 1463–1472. Janson C, Malinovschi A, Amaral AFS, et al. (2019) Bronchodilator reversibility in asthma and COPD: findings from three large population studies. Eur Respir J 2019; 54: 1900561 Andrello AC et al. (2021) Maximum Voluntary Ventilation and Its Relationship With Clinical Outcomes in Subjects With COPD. Respiratory Care January 2021, 66 (1) 79-86  References Haynes JM et al. (2020) Pulmonary Function Reference Equations: A brief history to explain all the confusion. Respiratory Care July 2020, 65 (7) 1030-1038 Stanojevic S, Wade A, Stocks J (2010) Reference values for lung function: past, present and future. Eur Respir J. 2020 Jul;36 (1):12-9 Global Initiative for Chronic Obstructive Lung Disease (GOLD). Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2023 report Stanojevic S. et al. ERS/ATS technical standard on interpretive strategies for routine lung function test. Eur Respir J 2022; 60:21012499  Acknowledgement Professor Alice Jones Honorary Professor at the University of Queensland Fellow of Australian College of Physiotherapy in Cardiopulmonary Physiotherapy