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Spirometry Interpretation

Spirometry Interpretation. Debbie Terry- Respiratory Team Leader. Aims and Objectives. Aim of the session To gain an advanced understanding of spirometry interpretation Objectives Gain understanding of spirometry parameters Understand required standards for performing spirometry

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Spirometry Interpretation

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  1. Spirometry Interpretation Debbie Terry- Respiratory Team Leader

  2. Aims and Objectives Aim of the session To gain an advanced understanding of spirometry interpretation Objectives • Gain understanding of spirometry parameters • Understand required standards for performing spirometry • Identify obstructive and restrictive patterns • Use spirometry tracing to help diagnose obstructive/restrictive disorders • Understand NICE guidance in relation to determining COPD severity

  3. What is spirometry? • Conventionally, a spirometer is a device used to measure timed expired and inspired volumes of air. • From these measurements we can calculate how effectively and how quickly the lungs can be emptied and filled

  4. Objectives of Spirometry Diagnosis • Screening for persons at risk of having pulmonary disease. • Measure airflow obstruction to help make a definitive diagnosis of COPD • Detect airflow obstruction in smokers who may have few or no symptoms • Assess severity of airflow obstruction in COPD • Pre-op assessment • Pre-employment screening • Distinguish between obstruction and restriction as causes of breathlessness

  5. Objectives cont.. Monitoring • Occ Health: monitor those exposed to hazardous agents • Determine effectiveness of medication • Follow the course of disease – helps predict mortality and morbidity.

  6. Spirometry cannot.... • Be used in isolation to make a differential diagnosis of lung disease • Define the full extent of a disease • Monitor the response to therapy • Interpret the extent of disability the patient experiences.. • It CAN only classify diseases into “obstructive” or “restrictive” or “mixed” ventilatory disorders

  7. Measures of Lung Volume • Total lung volume is measured in two ways:- Dynamic lung volumes- during FORCED expiration and inspiration Static lung volumes- during RELAXED breathing • Dynamic lung volumes most commonly measured including: FVC, FEV1, FEV1/FVC Ratio • Static lung volumes measured = VC

  8. What are we measuring? • Forced Vital Capacity (FVC)- maximum volume of air expired from the lungs during a forced and complete expiration from full inspiration • Vital Capacity (VC) – maximum volume of air expired during a relaxed but complete expiration

  9. Forced Expiratory Volume in the first second (FEV1)- maximum volume of air expired from the lungs in the first second of a forced expiration FEV1/FVC% (ratio)- amount of air blown out in the first second of a FORCED manuovre, expressed as a percentage of the total amount expired

  10. Predicted Values • These values are derived from statistical analysis of population studies of healthy individuals. • Predicted equations for Spirometry are based on age, sex, height, and in some cases weight. • Weight and ethnicity should be noted on any report as they may influence interpretation • Spirometers should be set to correct ethnicity

  11. Summary of Standards • A minimum of 3 technically satisfactory tests. • A maximum of 8 attempts. • The two best FVC and FEV1’s should have a variance of less than 100mls. • Exhaled for at least 6 seconds (adults) or reached a plateau on the volume-time graph. (No change of volume for at least two seconds.) • Graph traces are smooth and free from irregularity • Smooth take-off without hesitation

  12. Performing the test • Calibrate spirometer • Prepare the pt- written/verbal instructions • Check contra-indications • Check accuracy of pt details, including height • Have patient seated • Record any medications • Repeat blows until 3 of good, reproducible standard e.g 100mils between blows

  13. Potential Technique errors

  14. Criteria for Normal Post-bronchodilator Spirometry • FVC: % predicted > 80% • FEV1: % predicted > 80% • FEV1/FVC: > 0.7

  15. It is important to be able to view the graphs in real-time as the patient performs each test. If you can only view one graph in real time, then you would choose the Flow/Volume graph. But both graphs should be printed on any reports. Volume/Time Curve

  16. Flow/Volume Curve

  17. Interpreting the test • FVC, FEV1, and FEV1 / FVC ratio form the basis for interpretation. Obstructive • Indicative of airways disease, affecting the AIRWAYS, e.g COPD, asthma, bronchiectasis, lung cancer (greater risk in COPD), CF Restrictive • The inability of the lungs to expand. The lungs are small because of: Fibrosis or scarring Full inflation is not possible Inspiratory respiratory muscles are weak

  18. Patterns of Spirometry • Abnormal spirometry may be divided into 3 main groups of ventilatory disorders:- • Obstructive • Restrictive • Mixed/Combined

  19. Obstuctive Ventilatory Disorders • Reduced airflow, causing airflow limitation • Characterised by:- • A reduced FEV1<80% pred • A normal or reduced FVC • A reduction in the FEV1/FVC ratio (<0.70) • A relative concavity (scooping) on a flow volume curve

  20. Obstructive pattern

  21. Diagnose COPD: Spirometry • Perform spirometry if COPD seems likely [2004] • The presence of airflow obstruction should be confirmed by performing post-bronchodilator spirometry [new 2010] • Consider alternative diagnoses or investigations in: older people without typical symptoms of COPD where the FEV1/FVC ratio is < 0.7 • - younger people with symptoms of COPD where the FEV1/FVC ratio is ≥ 0.7 [new 2010] • All health professionals involved in the care of people with COPD should have access to spirometry and be competent in the interpretation of the results [2004] • NICE Guidelines (2010)

  22. Assessment of Severity in COPD • Assess severity of airflow obstruction using reduction in FEV1 * Symptoms should be present to diagnose COPD in people with mild airflow obstruction ** Or FEV1 < 50% with respiratory failure

  23. Restrictive Ventilatory Disorders • Reduced lung size or increased lung stiffness, decreasing the maximum volume of air that is able to be moved in and out of the lungs • Characterised by:- • A reduction to a similar extent in the volume of FEV1 and FVC, normal or high FEV1/FVC • A normal shape pattern, but small volume

  24. For example; Fibrosing lung diseases, extrinsic alveolitis, pneumoconiosis, pulmonary oedema, lobectomy, obesity, pregnancy, neuromuscular disorders, thoracic cage deformity Mixed obstructive/restrictive • When both airways and lung tissue are affected. • When FEV1 / FVC ratio is reduced, FVC and FEV1 or reduced in relation to each other • E.G a person with gas trapping and hyperinflation • An obese person with asthma may show a mixed pattern

  25. Restrictive Pattern

  26. Criteria: Restrictive Disease • FVC: % predicted < 80% • FEV1: % predicted < 80% • FEV1/FVC: > 0.7

  27. Criteria: Mixed patterns • FEV1: % predicted < 80% • FVC: % predicted < 80% • FEV1/FVC: < 0.7

  28. Summary

  29. Any Questions? Debbie Terry Deborah.terry@nottshc-chp.nhs.uk 01636 652616

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