Spirometry

PFT, INDICES, INDICATION, CONTRAINDICATIONS

1. SPIROMETRY zikrullah

2. CONTENTS Definition Indications of spirometry Contraindications Types of spirometry Spirometry indices How to perform spirometry Stepwise interpretation Side effects Common problems

3. What is spirometry ? Spirometry is a measure of airflow and lung volumes during a forced expiratory maneuver from full inspiration. How to do it ?? Stand or sit up straight (The patient places a clip over the nose ) Inhale maximally Get a good seal around mouthpiece of the spirometer Blow out as hard as fast and forcefully as possible and count for at least 4- 6 seconds ( reliability criteria ) - Record the best of three trial ( REPEATABILITY CRITERIA )

4. INDICATIONS DIAGNOSTICS :- to evaluate symptoms, signs or aBNormal laboratory tests To measure the effect of disease on pulmOnarY functions To screen individuals at risk of having pulmonary diseases To assess preop - risk To assess diagnosis To assess health status before beginning the strenous physical activity

5. M ONITORINGS :- TO ASSESS THERAPEUTIC INTERVENTION TO DESCRIBE THE COURSE OF DISEASE THAT AFFECT LUNG FUNCTONS TO MONITOR PEOPLE EXPOSED TO INJURIOS AGENTS TO MONITOR THE ADVERSE REAXTIONS TO DRUGS WITH KNOWN PULMONARY TOXICITY

6. CONTRAINDICATIONS Hemoptysis of unknown origin Pneumothorax Unstable angina pectoris Recent myocardial infarction Thoracic aneurysms Abdominal aneurysms Cerebral aneurysms Recent eye surgery (increased intraocular pressure during forced expiration) Recent abdominal or thoracic surgical procedures History of syncope associated with forced exhalation

7. PATIENT PREPARATION :- BEFORE THE TEST AVOID ALCOHOL – 4 hr LARGE MEAL – 2hr SMOKING – 1hr VIGOROUS EXERCISE – 30 min

8. For bronchodilator reversibility testing withhold bronchodilators prior to the test : Short-acting inhaled β2 agonists for 2–4h. Short acting inhaled anticholinergics for 4–6 h. Long-acting inhaled or oral β2 agonists for 12–24 h Long-acting inhaled anticholinergics for 24–36 h. Theophyllines for 12 h. Sustained release theophyllines for 24 h.

9. PFT DONE USING SPIROMETERS There are 2 primary kind of spirometers : Primary volume measuring spirometers (PVM) Primary flow measuring spirometers (PFM) Procedure: Generally, the patient is asked to take the deepest breath they can, and then exhale into the sensor as hard as possible, for as long as possible. It is sometimes directly followed by a rapid inhalation (inspiration), in particular when assessing possible upper airway obstruction.

10. Sometimes, the test will be preceded by a period of quiet breathing in and out from the sensor (tidal volume), or the rapid breath in (forced inspiratory part) will come before the forced exhalation. During the test, soft nose clips may be used to prevent air escaping through the nose. Filter mouthpieces may be used to prevent the spread of microorganisms, particularly for inspiratory maneuvers.

11. Primary volume measuring spirometers A volume-time curve is generated , showing volume (liters) along the Y-axis and time (seconds) along the X-axis Flow is measured indirectly: Flow = volume (lit.) / time(sec) They work by displacing or collecting volume of air in a chamber of some kind. Examples: Water sealed spirometers Dry seal spirometers Bellows spirometers Rotor spirometer .

12. Volume Time Graph ( spirogram ) The volume is plotted against the time, it displays the expiration.

13. Primary Flow Measuring Spirometers A flow-volume loop is generated , which graphically depicts the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axis. PFMs measure flow directly by using a pneumotachometer . Volume=flow rate (L/sec)*time (sec) 3 primary types of pneumotachometer Differential pressure pneumotachometer Thermal anemometers Ultrasonic sensor spirometers

14. Flow volume loop showing successful FVC manuever . Positive values represent expiration, negative values represent inspiration. The trace moves clockwise for expiration followed by inspiration. .

15. INDICES OF SPIROMETRY FVC(forced vital capacity) FEV1(forced expiratory volume in 1 sec) FEV1/FVC FEV6(forced expiratory volume in 6 sec) FEF25-75(maximum mid expiratory flow) PEF(peak expiratory flow)

16. Forced Vital Capacity (FVC): It is the maximum volume of gas that can be expired, when the subject tries to expire as forcefully and rapidly as possible after a maximal inspiration to total lung capacity. FVC is the most basic maneuver in spirometry tests. FEV1 (forced expiratory volume in 1 sec) This is the amount of air that you can forcibly blow out in one second, measured in liters. Along with FVC , it is considered one of the primary indicators of lung function.

17. FEV1/FVC or FEV1% or Tiffeneau index :- This is the ratio of FEV 1 to FVC. In healthy adults this should be approximately 75–80%. This value is critically important in the diagnosis of obstructive and restrictive diseases Peak Expiratory Flow: Maximum flow during the FVC test, should be attained within 100 milliseconds after the start of the FVC test

18. FEF 25-75% (forced expiratory flow 25 – 75%): This is the average flow of air coming out of the lung during the middle portion of the expiration. Earliest indicator to get severity & detect derangement in obstructive airway disease. Unlike FEV1 which is dependent on patient’s efforts, it is independent of patients efforts . It represents flow through the small (<2 mm) airways . FEV 6 – Forced expired volume in six seconds: Often approximates the FVC. Easier to perform in older and COPD patients but role in COPD diagnosis remains under investigation.

19. Functional residual capacity: It is the remaining lung volume at the end of a normal quiet respiration. FRC= RV+ ERV. It is reduced by approx. 20% with spontaneous breathing and by approx. 16% with artificial ventilation. This is due to change in the chest wall shape and cephalad movement of diaphragm. FRC cannot be measured by spirometry . Methods to measure FRC are: Helium dilution method. Nitrogen washout method. Body plethysmography .

20. Importance of FRC: First, when FRC < Closing capacity, airways close in the dependent parts of the lung during certain periods of normal tidal ventilation. Second, blood o xygenatio n during the expiratory phase is mainly dependent on the remaining lung volume , which is FRC.

21. STEP-WISE INTERPRETATION Step 1: Look at the forced vital capacity (FVC) to see if it is within normal limits. Step 2: Look at the forced expiratory volume in one second ( FEV 1 ) and determine if it is within normal limits. Step 3: If both FVC and FEV 1 are normal, then you do not have to go any further - the patient has a normal PFT test. Step 4: If FVC and/or FEV 1 are low, then the presence of disease is highly likely.

22. Step 5: If Step 4 indicates that there is disease then you need to go to FEV 1 /FVC. If 85%-90% or higher , then the patient has a restrictive lung disease. If 69% or lower , then the patient has an obstructed lung ds Step 6: Take a look at the TLC % predicted. If below Lower Limit Normal/LLN ( 80% ) confirms restrictive defect. If above LLN (120% ) confirms obstruction and qualifies for hyperinflation.

23. Step 7: Take a look at RV% predicted. If above LLN ( 120% ) confirms air trapping or airway closure ( Obstruction) Step 8: Compare Pre& Post Bronchodilator measurements. An increase in FEV1 and/or FVC greater than 12% and ≥ 200mls is a positive response.

24. BRONCHODILATOR REVERSIBILITY TESTING Administer salbutamol in four separate doses of 100 μg through a spacer FEV1 /FVC should be measured before and 15-20 minutes after bronchodilator An increase in FEV1 and/or FVC > 12% of control and >200 mL constitutes a positive bronchodilator response, indicates asthma It is important to determine whether fixed airway narrowing is present. In patients with COPD, post-bronchodilator FEV1/FVC remains < 0.7 or 70%.

25. The contour of the loop assists in the diagnosis and localization of airway obstruction as different lung disorders produce distinct ,easily recognized pattern.

26. Obstructive disorders Restrictive disorders FVC normal or ↓ FEV1 ↓ FEF25-75% ↓ FEV1/FVC ↓ TLC normal or ↑ FVC ↓ FEV1 ↓ FEF 25-75% N to ↓ FEV1/FVC N to ↑ TLC ↓

27. Obstructive vs restrictive disease

28. EMPHYSEMA :- Airways may collapse during forced expiration because of destruction of the supporting lung tissue causing very reduced flow at low lung volume and a characteristic (STEEPLE pattern /dog-leg) appearance to the flow volume curve Example of SEVERE obstructive disorder.

29. ASTHMA :- Peak expiratory flow/PEF reduced so maximum height of the loop is reduced Airflow reduces rapidly with the reduction in the lung volumes because the airways narrow and the loop becomes co ncave/Coning. Concavity may be the indicator of airflow obstruction and may present before the change in FEV1 or FEV1/FVC

30. Flow volume loop in Restrictive lung disease : Full lung expansion is prevented by fibrotic tissue in the lung parenchyma and the FVC & TLC are reduced . Elastic recoil may be increased by fibrotic tissue leading to increase in the airflow FEV1 ,FVC may be reduced with reduced RV because the lungs are small and stiff ,but the peak expiratory flow may be preserved or even higher than predicted leads to tall,narrow and steep flow volume loop in expiratory phase.

31. Fixed obstruction 1. Post intubation stenosis 2. Goiter 3. Endotracheal neoplasms 4. Bronchial stenosis Maximum airflow is limited to a similar extent in both insp iration and exp iration

32. Variable extrathoracic Obstruction 1. Bilateral and unilateral vocal cord paralysis 2. Vocal cord constriction 3. Reduced pharyngeal cross-sectional area 4. Airway burns The obstruction worsens in inspiration because the negative pressure narrows the trachea and inspiratory flow is reduced to a greater extent than expiratory flow

33. variable intrathoracic obstruction 1. Tracheomalacia 2. Polychondritis 3. Tumors of the lower trachea or main bronchus. The narrowing is maximal in expiration because of increased intrathoracic pressure compressing the airway. The flow volume loop shows a greater reduction in the expiratory phase

34. Effect of Smoking : Smoking in patients with COPD is associated with decline in FEV1 of 90-150 mL/year Smoking cessation is (associated with increase in FEV1 for first year) followed with a decline of only 30 mL/year

35. COMMON PROBLEMS Inadequate or incomplete blow Lack of blast effort durind exhalation Slow start to maximal effort Lips not sealed around mouthpiece Coughing during the blow Extra breath during the blow Glottic closure or obstruction of mouthpiece by tongue or teeth Poor posture-leaning forwards

36. POSSIBLE SIDE EFFECTS Feeling light headed Headache Fainting:reduced venous return or vasovagal attack(reflex) Transient urinary incontinence

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