Pulmonary Function Tests

1. Pulmonary Function Tests Mike Poullis

2. Overview • Lung Volumes • FVC and FEV1 • Ratios FVC/FEV1 • Obstruction, restriction and mixed pictures • Flow Volume loops • Upper airway obstruction • Dead space • V/Q scanning • DLCO • Zones of West • Predicting post op FEV1 and DLCO • BTS Guidelines

3. Lung Volumes TLC = RV + ERV + TV + IRV. VC = ERV + TV + IRV. FRC = RV + ERV. TV

5. TLC • TLC < 80% of predicted value = restriction. • TLC > 120% of predicted value = hyperinflation.

6. FVC/FEV1

7. Definitions • FEV1 - forced expiratory volume 1 - the volume of air that is forcefully exhaled in one second. • FVC - forced vital capacity - the volume of air that can be maximally forcefully exhaled • FEV1/FVC - ratio of FEV1 to FVC, expressed as a percentage • PEF - peak expiratory flow rate - the peak flow rate during expiration

8. Comparison

9. FVC FEV1 ratios

11. Normal

12. Obstruction Severity

13. Mild Obstruction

14. Mild and severe obstruction

15. Restrictive Lung Disease

16. Restrictive Lung Disease

17. Obstruction, Restriction, Mixed

18. Upper Airway Obstruction • Variable extrathoracic obstructions • vocal cord paralysis, • thyromegaly, • tracheomalacia, or • Neoplasm • Large airways variable intrathoracic obstructions • tracheomalacia or • neoplasm • Fixed obstruction • tracheal stenosis, • foreign body, or • neoplasm.

19. Variable Extrathoracic Upper Airway Obstruction

20. Fixed Upper Airway Obstruction

21. Anatomical verses physiological dead space • In physiology, dead space is air that is inhaled by the body in breathing, but does not partake in gas exchange. • Anatomical dead space - the gas in the conducting areas of the respiratory system, such as the mouth and trachea, where the air doesn't come to the alveoli of the lungs. • Alveolar dead space - the area in the alveoli that does get air to be exchanged, but there is not enough blood flowing through the capillaries for exchange to be effective.

23. Quantitative VQ scans

24. Diffusion Capacity • This is a test of the ability of inhaled carbon monoxide to diffuse into the pulmonary circulation. • It is dependent on functional alveolar capillary membrane surface area and red blood cells within the circulation. • It is reduced when ever there is a loss of functional alveolar capillary membrane surface area or decrease in hemoglobin. • The diffusion capacity is "corrected" for lung volume by dividing by VA (alveolar volume). This gives an estimate of the diffusion capacity of the lung volume that is present.

25. VQ mismatch Zones of West

26. Predicting post operative FEV1 and DLCO • epoFEV1 = preFEV1 * (19 - segs. to be removed) • If any segments obstructed use: • epoFEV1 = preFEV1 ´*(19 - a) - b)/(19 – a) • a = no. of obstructed segments • b = no. of unobstructed segments to be resected • Right upper lobe 3, left upper lobe 3 • middle lobe 2, lingula 2 • right lower lobe 5 • left lower lobe 4

27. % verses Actual FEV1 • 2 L for pneumonectomy • 1.5 L for lobectomy • Risk model based on % • Think patient size

28. BTS Guidelines • PART I: FITNESS FOR SURGERY • Age • Pulmonary function • Cardiovascular fitness • Weight loss, performance status and nutrition • Multiple risk factors • PART II: OPERABILITY • Diagnosis and staging • Operability and adjuvant therapy • Operations available • Locally advanced disease • Small cell lung cancer

29. BTS Bottom Line • Pred FEV1, DLCO • 40 % magic numbers • Exercise test if not sure

30. 250metres