Spirometry

Spirometry and PFT

1. SPIROMETRY Dr. Navin Adhikari IM Resident

2. INTRODUCTION Spirometry is one of the pulmonary function test that measure volume or change in volume versus time . water-sealed spirometer and dry, rolling-seal spirometer were used previously Now, most pulmonary function laboratories utilize flow type spirometers using pneumotachographs or rotating turbines to determine airflow. Two types of pneumotachographs are in general use: hot wire and flow resistive. Fishman's Pulmonary Diseases and Disorders 5 th ed.

3. Fishman's Pulmonary Diseases and Disorders 5 th ed.

4. Fishman's Pulmonary Diseases and Disorders 5 th ed.

5. TEXTBOOK OF MEDICAL PHYSIOLOGY (GUYTON _ HALL ) 11TH EDITION

6. PULMONARY VOLUMES Tidal volume: Volume of air inspired or expired with each normal breath – about 500 milliliters . Inspiratory reserve volume : Extra volume of air that can be inspired over and above the normal tidal volume when the person inspires with full force – about 3000 milliliters . Expiratory reserve volume : Maximum extra volume of air that can be expired by forceful expiration after the end of a normal tidal expiration – about 1100 milliliters . Residual volume : Volume of air remaining in the lungs after the most forceful expiration – 1200 milliliters . TEXTBOOK OF MEDICAL PHYSIOLOGY (GUYTON _ HALL ) 11TH EDITION

7. PULMONARY CAPACITIES Inspiratory capacity : Amount of air that can breathe in, beginning at the normal expiratory level and distending the lungs to the maximum amount-equals the tidal volume plus the inspiratory reserve volume- is about 3500 milliliters . The functional residual capacity -This is the amount of air that remains in the lungs at the end of normal expiration , equals the expiratory reserve volume plus the residual volume- ( about 2300 milliliters ). TEXTBOOK OF MEDICAL PHYSIOLOGY (GUYTON _ HALL ) 11TH EDITION

8. Vital capacity - maximum amount of air a person can expel from the lungs after first filling the lungs to their maximum extent and then expiring to the maximum extent equals the inspiratory reserve volume plus the tidal volume plus the expiratory reserve volume - (about 4600 milliliters ). Total lung capacity - maximum volume to which the lungs can be expanded with the greatest possible effort - equal to the vital capacity plus the residual volume- (about 5800 milliliters ) TEXTBOOK OF MEDICAL PHYSIOLOGY (GUYTON _ HALL ) 11TH EDITION

9. FLOW - VOLUME LOO P During the maximal expiration, the rate of airflow peaks at a lung volume that is close to the TLC; as the lung volume decreases and intrathoracic airways narrow, airway resistance increases, and the rate of airflow decreases progressively. During maximal inspiration, the pattern of airflow is different. Because of the markedly negative pleural pressure and large transmural airway pressure, the bronchi are wide, and their calibers increase further as lung volume increases. Consequently, inspiratory flow becomes high while the lung volume is still low and remains high over much of the vital capacity, even though the force generated by the inspiratory muscles decreases as they shorten. MURRAY & NADEL’S TEXTBOOK OF RESPIRATORY MEDICINE, 6 TH ED.

10. FLOW - VOLUME LOO P MURRAY & NADEL’S TEXTBOOK OF RESPIRATORY MEDICINE, 6 TH ED.

11. FEV 1 is the maximal volume of air exhaled in the first second of a forced exhalation that follows a full inspiration. reflects the average flow rate during the first second of the FVC maneuver . most important spirometric variable for assessment of the severity of airflow obstruction . The highest FEV 1 from the three acceptable forced expiratory maneuvers is used for interpretation, even if it does not come from the maneuver with the highest FVC .   FEV1% predicted , which is defined as FEV1% of the patient divided by the average FEV1% in the population for any person of similar age, sex, and body composition 2021 UPTODATE®

12. FVC also known as the forced expiratory volume . is the maximal volume of air exhaled with a maximally forced effort from a position of full inspiration . The FVC may be reduced by suboptimal patient effort, airflow limitation, restriction ( eg , from lung parenchymal , pleural, or thoracic cage disease), or a combination of these. 2021 UPTODATE®

13. MURRAY & NADEL’S TEXTBOOK OF RESPIRATORY MEDICINE, 6 TH ED.

14. INDICATIONS DIAGNOSTIC INDICATIONS Evaluation of the signs and symptoms of a patient or their abnormal investigations and lab tests Evaluation of the effect a certain disease has on pulmonary function Screening and early detection of individuals who are at risk of pulmonary disease Assessing surgical patients for preoperative risk Assessing the severity and the prognosis of a pulmonary disease. HTTP://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK560526/

15. MONITORING INDICATIONS Assessment of the efficiency of a therapeutic intervention such as bronchodilator therapy Describing the course and progression of a disease that is affecting pulmonary function such as interstitial lung disease or obstructive lung disease Monitoring pulmonary function in individuals with high-risk jobs HTTP://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK560526/

16. CONTRAINDICATION ABSOLUTE CONTRAINDICATIONS Hemodynamic instability Recent myocardial infarction or acute coronary syndrome Respiratory infection, a recent pneumothorax or a pulmonary embolism A growing or large (>6 cm) aneurysm of the thoracic, abdominal aorta Hemoptysis of acute onset Intracranial hypertension Retinal detachment HTTP://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK560526/

17. RELATIVE CONTRAINDICATIONS Patients who cannot be instructed to use the device properly and are at risk of using the device inappropriately such as children and patients with dementia Conditions that make it difficult to hold the mouthpiece such as facial pain Recent abdominal, thoracic, brain, eye, ear, nose or throat surgeries Hypertensive crisis HTTP://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK560526/

18. PROCEDURE Three phases Phase 1: Coach the patient to take as deep a breath as possible Phase 2: Strongly prompt the patient to blast out the air into the spirometer without hesitation after reaching a full inspiration Phase 3 : Encourage the patient to continue exhaling until a plateau in exhaled volume or 15 seconds is reached, unless just measuring FEV 6 in which case the exhalation should last at least six seconds (three seconds for children) 2021 UPTODATE®

19. 2021 UPTODATE®

20. ADEQUACY OF TEST requires three acceptable and repeatable forced vital capacity (FVC) maneuvers . Detection of poorly performed maneuvers by direct inspection of both flow-volume curves and volume-time spirograms . An acceptable maneuver requires a sharp peak in the flow curve and an expiratory duration that reaches a plateau of exhaled volume . At least three acceptable maneuvers should be available . Repeatability is determined by comparing the FVC and FEV 1 values of the maneuvers . The two highest values for FVC and for FEV 1 should be within 0.15 L of each other (for adults; the limit is 0.10 L for children). 2021 UPTODATE®

21. 2021 UPTODATE®

22. INTERPRETATION Step 1: Determine If the FEV1/FVC Ratio Is Low Step 2: Determine If the FVC Is Low Step 3: Confirm the Restrictive Pattern Step 4: Grade the Severity of the Abnormality Step 5: Determine Reversibility of the Obstructive Defect Step 6: Bronchoprovocation Step 7: Establish the Differential Diagnosis Step 8: Compare Current and Prior Results   Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

23. FEV 1 /FVC RATIO The FEV 1 /FVC ratio is the fraction of the forced vital capacity that can be exhaled in the first second. important parameter for detecting airflow limitation in diseases like asthma and COPD ratio is not useful for gauging severity of disease, since the FVC also tends to decrease with increasing obstruction . Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

24. (FEV 1 /FVC) ratio is low, indicating an obstructive defect GOLD criteria, which use a cutoff of less than 70 % the ATS criteria, which use the lower limit of normal (LLN) as the cutoff for adults.The LLN is a measurement less than the fifth percentile of spirometry data obtained from the Third National Health and Nutrition Examination Survey (NHANES III) Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

25. GOLD VS. ATS CRITERIA Studies has shown that the GOLD criteria is better to diagnose obstructive lung disease in patients 65 years and older with respiratory symptoms who are at risk of COPD (i.e., current or previous smoker). And the ATS criteria is better in diagnosing obstructive lung disease in patients younger than 65 years regardless of smoking status, and in nonsmokers who are 65 years and older. Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

26. DETERMINE FVC less than the LLN for adults or less than 80% of predicted for those five to 18 years of age, indicates a restrictive pattern. restrictive pattern can indicate restrictive lung disease, a mixed pattern (if a patient has an obstructive defect and a restrictive pattern), or pure obstructive lung disease with air trapping.  Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

27. . Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

28. Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

29. Confirm the Restrictive Pattern F ull PFTs with DLCO testing The restrictive pattern is confirmed as a true restrictive defect if the total lung capacity is less than 80% of predicted in patients five to 18 years of age, or less than the LLN in adults. If full PFTs cannot be obtained, the FVC can be used to infer a restrictive defect; however, FVC has a poor positive predictive value Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

30. GRADING THE SEVERITY Fishman's Pulmonary Diseases and Disorders 5 th ed.

31. Determine Reversibility of the Obstructive Defect If obstructive defect, determine if it is reversible based on the increase in FEV 1  or FVC after bronchodilator treatment (i.e., increase of more than 12% in patients five to 18 years of age, or more than 12% and more than 200 mL in adult. If spirometry returns to within normal limits (FEV1/(F)VC, FEV1 and (F)VC within the normal range), then there is complete reversibility of airflow limitation. If obstruction remains apparent after inhaled bronchodilator, then there is incomplete reversibility of airflow limitation. Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

32. Bronchoprovocation If Spirometry results are normal but there is still suspicion of exercise- or allergen-induced asthma, the next step is bronchoprovocation , such as a methacholine challenge, a mannitol inhalation challenge, exercise testing. A positive methacholine challenge result is defined as a greater than 20% reduction in FEV1 at or before administration of 4 mg per mL of inhaled methacholine .15 The result is considered borderline if the FEV1 drops by 20% at a dose between 4 and 16 mg per mL. Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

33. Establish the Differential Diagnosis Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

34. Stepwise Approach to the Interpretation of Pulmonary Function Tests, www.aafp.org

35. Compare Current and Prior PFT Results If prior spirometry results are available, they should be compared with the current results to determine the course of the disease or effects of treatment.

36. FLOW-VOLUME LOOP DISORDERS

37. CLINICAL USE OF FLOW-VOLUME LOOP detection of obstruction of the upper airway Three distinct patterns: variable extrathoracic obstruction, variable intrathoracic obstruction, and fixed obstruction the contour of the flow-volume loop can provide additional information about the location of airway constriction, the sensitivity is low for mild obstruction and interpretation can be hampered by overlapping diseases ( eg , chronic obstructive pulmonary disease [COPD] and tracheal stenosis ). Thus, positive and negative findings should be confirmed with imaging and/or direct visualization. 2021 UPTODATE®

38. 2021 UPTODATE®

39. 2021 UPTODATE®

40. 2021 UPTODATE®

41. EXAMPLES

42. Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

43. Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

44. Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

45. Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

46. Interpreting Lung Function Tests: A Step-by Step Guide 1 st ed.

47. REFERENCES 2021 UPTODATE® FISHMAN'S PULMONARY DISEASES AND DISORDERS 5 TH ED. MURRAY & NADEL’S TEXTBOOK OF RESPIRATORY MEDICINE, 6 TH ED. STEPWISE APPROACH TO THE INTERPRETATION OF PULMONARY FUNCTION TESTS, WWW.AAFP.ORG HTTP://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK560526/ TEXTBOOK OF MEDICAL PHYSIOLOGY (GUYTON _ HALL ) 11TH EDITION INTERPRETING LUNG FUNCTION TESTS: A STEP-BY STEP GUIDE 1 ST ED.

48. THANK YOU