lung function tests.pptx

lung function tests

1. SP I RO M E T RY

2. PY 6.8 DEMONSTRATE THE CORRECT TECHNIQUE TO PERFORM & INTERPRET SPIROMETRY. SLOs: After attending lecture & studying the assigned materials, the student will: 1. 2. State the principles of recording of Spirometry. Define & draw different lung volumes & capacities. Explain FEV (TVC) correctly with its clinical significance. Demonstrate the correct procedure of recording

3. RELEVANCE Although many sophisticated tests are available for assessing respiratory functions VC is a simple & useful measurement for assessing the ventilatory functions of the lungs in health & disease.

4. MEASUREMENT VC may be measured either on a Simple Spirometer or Recording Spirometer. Simple Spirometer ( student Spirometer also called vitalograph ) Recording Spirometer (lung volume & capacity) & Wright’s peak flow meter

5. TYPES OF LUNG FUNCTION TESTS Lung function tests are of two types: Static lung function tests Dynamic lung function tests.

6. 1. STATIC LUNG FUNCTION TESTS Static lung function tests are based on volume of air that flows into or out of lungs. These tests do not depend upon the rate at which air flows. Static lung function tests include static lung volumes and static lung capacities.

7. PARAMETERS THAT ASSESS VENTILATION Lung volumes and capacities - the volume of the air in lungs changes considerably during a respiratory cycle. For convenience 4 lung volumes and 4 lung capacities are distinguished: The maximum volume to which a lung can be expanded has been divided into four non-overlapping volumes Tidal volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), & Residual Volume (RV).

8. LUNG CAPACITIES Lung capacities are combination of two or more pulmonary volumes and include; VITAL CAPCITY (VC = TV+ ERV + IRV), FORCED VITAL CAPCITY (FVC), FORCED EXPIRED VOLUME (FEV). INSPIRATORY CAPACITY (IC = TV + IRV) FUNCTIONAL RESIDUAL CAPACITY (FRC = RV + ERV) TOTAL LUNG CAPACITY (TLC = VC + RV)

9. DYNAMIC LUNG FUNCTION TESTS Dynamic lung function tests are based on time, i.e. the rate at which air flows into or out of lungs. These tests include forced vital capacity, forced expiratory volume Dynamic lung function tests are useful in determining the severity of obstructive and restrictive lung diseases.

10. Apparatus Required Recording Spirometer Nose clips Potassium permanganate solution/Spirit to clean mouth piece Graph paper

11. Recording Spirometer The recording spirometer, whi c h i s electri c al l y driven, is used to provide a g r aph i c r e c o r d ( c al l ed spirogram) of various lung volumes and capacities. Pul l e y chain Outer cylinder Pen marker attached to counter weight Kymograph Bi Directional Valve to connect mouthpiece with atmospheric air/ spirometer Control panel for kymograph O2 inlet W at er outlet Corrugated rubber tube with mouthpiece 2 corrugated rubber tube one for inspiration ,other for expiration each with unidirectional valve

12. After familiarizing the subject with the apparatus , start taking the readings as described below Connect the subject to the spirometer and allow her/him to breathe quietly for a short time. Then start the kymograph at the speed of 60 mm/ min and record the excursions of the pen writer for about a minute. Note that the upstrokes are inspirations and down strokes expirations. This record of tidal breathing will be used for calculating the rate of respiration, tidal volume (TV) and minute ventilation (minute volume; MV). TV- Volume of air breathed in or out during quiet respiration. Normal- 500 ml Minute ventilation: Volume of air inspired or expired out of the lungs in one minute. MV = TV x RR = 500 x 12= 6L/min. Upstroke- inspiration Downstroke- expiration TV

13. Recording of Inspiratory reserve volume(IRV) and inspiratory capacity(IC) IRV: It is the maximal volume of air which can be inspired after completing a normal tidal inspiration i.e. inspired from the end inspiratory position . Normal: 2000-3000 ml IC: It is the maximal volume of air which can be inspired after completing tidal expiration i.e. from the end expiratory position . IC= TV+ IRV Normal: 2500-3500 ml To record IRV, ask the subject to breathe in as deeply as possible after a quiet inspiration. IRV + TV will give IC. Record a few tidal breaths afterwards. IC

14. Recording of Expiratory reserve volume(ERV) Expiratory Reserve Volume (ERV). It is the extra amount of air that can be expelled (expired) by forceful expiration from the spontaneous end-expiratory point, i.e. over and above the normal tidal expiration. Normal: 750-1100 ml. To record ERV, ask the subject to breathe out as forcefully as possible after a quiet expiration.

15. Recording of Vital capacity (VC) After few tidal breaths, subject is asked to inspire as deeply and as fully as possible to fill the lungs, then subject is asked to expel all the air that he can with maximum effort into the spirometer.

16. THE LUNG VOLUMES AND CAPACITIES THAT CANNOT BE MEASURED ON A SPIROMETER Residual Volume (RV): It is the amount of air that remains behind in the lungs after a maximum voluntary expiration. It amounts to 1300 ml. The lungs cannot be emptied out completely of air even with maximum effort . So, The lung capacities that have RV as their component , cannot be measured on a spirometer. These include Total lung capacity (TLC): It is the volume of air that is present in the lungs at the end of a deepest possible inspiration. It is a measure of VC + RV , and amounts to 6Litres. Functional residual capacity (FRC): This is the amount of air remaining in the lungs at the end of a normal (quiet) expiration. FRC= ERV + RV It amounts to about 2300-2500ml .

17. P r e c autions Subject should not face the recording spirometer during recording. All lung volume and capacities are measured from the end that is expiratory position. Make sure that there is no leak (of air) from the vitalograph and spirometer.

18. Residual volume and the functional residual capacity cannot be measured by spirometer and can be determined by three methods: Helium dilution technique Nitrogen washout method Plethysmography.

19. TIMED VITAL CAPACITY (TVC) OR FORCED VITAL CAPACITIES (FVC) Forced vital capacity is the volume of the air that can be expired rapidly with a maximum force following a maximum inspiration. The volume of air expired can be timed by recording the vital capacity on a spirograph moving at the known speed.

20. Components of TVC or FVC (i) Forced expiratory volume in 1 s (FEV1). - It represents the volume expired in the first second of a FVC. - Estimation o f F E V 1 is t h e m o s t c o m m o n ly u s ed screening test f o r airway diseases. The FEV1 is actually a flow rate: its unit are L/s. FEV1% is the percent of FVC expired in 1 s (i.e. FEV1% = FEV1/FVC × 100) normally FEV1% is about 80% of the FVC (Fig. 5.2-8A).

21. Clinical application. Useful in distinguishing between restrictive and obstructive lung diseases: Patients with restrictive lung disease (e.g. kyphoscoliosis and ankylosing spondylitis) have a reduced FVC but are able to achieve relatively high flow rates; therefore their FEV1% exceeds 80% (Fig. 5.2-8B). Patients with obstructive lung disease (e.g. bronchial asthma) have low flow rates as a result of high airway resistance therefore their FEV1% is abnormally low (Fig. 5.2-8C).

22. THANK YOU . . .