pulmonary functions test powerpoint.pptx
- 2. INTRODUCTION Pulmonary Function Tests help in the evaluation of the mechanical function of the lungs. They are based on researched norms taking into account sex, height and age. e.g. There are predicted values for a male of 65 year age,6 feet tall. When patient performs the tests, the actual results will be compared with the predicted value of a person of a particular(sex, height, age) to see if he falls within normal ranges or has a restrictive or obstructive component based tests.
- 3. Obstructive and restrictive lung diseases RESTRICTIVE LUNG DISEASE – Any abnormal respiratory condition, which makes it difficult to get air into the lungs - inspiration is affected expiration is not OBSTRUCTIVE LUNG DISEASE – Any abnormal respiratory condition, which makes it difficult to push air outside the lungs Mixed: less common.
- 7. CHARACTERISTI CS OBSTRUCTIVE DISEASE RESTRICTIVE DISEASE ANATOMY AFFECTED Airways Lung parenchyma BREATHING PHASE DIFFICULTY Expiration Inspiration PATHOPHYSIOLOG Y Increase in airway resistance Decrease in lung or thoracic compliance USEFUL MEASUREMENTS Flow rates Volumes and Capacities COMPARISON BETWEEN OBSTRUCTIVE AND RESTRICTIVE LUNG DISEASES
- 8. PURPOSE OF THE PFTs 1. To identify and quantify changes in pulmonary function 2. To help define more clearly the type of functional disorder 3. To know whether its obstructive or restrictive lung disease 4. Epidemiological surveillance for pulmonary disease 5. Assessment of post operative pulmonary risk 6. To aid in determination of pulmonary disability 7. To evaluate and quantify therapeutic effectiveness
- 9. Indications of pfts 1. Initial and segmental evaluation of patient with exertional / paroxysmal dyspnea 2. Initial and segmental evaluation of case of known respiratory disorder 3. Differential diagnosis of lung disorders 4. Objective assessment of patients with chest problems. E.g. cough, chest pain. if average FEV1 < 50%, then associated risks are higher after surgery 5. Fitness for surgery, particular heart/lung 6. Guidelines for therapy in respiratory disorders and drug evaluation. E.g. bronchodilator 7. Degree of disability and association of occupational lung disease 8. Research purposes 9. Effect of training and selection of athletes
- 10. PULMONARY FUNCTION TESTS MEASURES 1. LUNG VOLUMES AND CAPACITIES 2. FLOW RATES OF GASES THROUGH AIRWAYS 3. ABILITY OF THE LUNGS TO DIFFUSE GASES( diffusion) PFTs do not dispose specific pulmonary disease, but identifies the presence and degree of pulmonary impairments as well as type of pulmonary disease present.
- 11. ORGANIZATION To measure each component, variety of technique and equipments are used. Common regimen of PFT in laboratory is to evaluate the effectiveness of bronchodilator therapy. Pulmonary mechanics especially the FEV1 (FORCED EXPIRATORY VOLUME IN 1 SECOND) are measured as a baseline. Then patient uses bronchodilator by inhalation of a diluted aerosol or by metered-dose inhaler. Measurements of pulmonary mechanics are updated and the present change is calculated according to following equation: % change=(posttest FEV1 -pretest FEV1)/pretest FEV 1*100 An increase in FEV1 more than 15% indicates beneficial effects of medication.
- 12. EQUIPMENTS Instruments used are: A. Devices that measure gas volume i. Water-sealed spirometers ii. Bellow-spirometers iii. Dry rolling seal spirometers B. Devices that measures gas flow i. Pneumotachometers ii. Thermistors iii. Turbinometers iv. Sonic devices v. Peak flow meters Each instrument has – CAPACITY,ACCURACY,ERROR,PRECISION,LINEARITY AND OUTPUT. Pulmonary function testing is safe, but a possibility of cross contamination exists, either from patients or from technologists.
- 15. PRINCIPLES OF MEASUREMENT 1.LUNG VOLUMES Lung has four volumes: TIDAL VOLUME – The volume of air breathed in and out in a single normal quiet breath is Tidal Volume. Normal value – 500ml INSPIRATORY RESERVE VOLUME – Maximal amount of air that can be inhaled from end normal INSPIRATION. Normal Value – 3100 ml EXPIRATORY RESERVE VOLUME – Maximal amount of air that can be exhaled after a normal exhalation. Normal Value – 1200ml RESIDUAL VOLUME – Volume of air that remains in the lungs at the end of maximum expiration. Normal Value – 1200ml
- 16. 2. LUNG CAPACITIES Two or more lung volumes are together called Lung Capacities. The four lung capacities are: INSPIRATORY CAPACITY – It is the maximum volume of air that can be inspired from end expiratory position. IC =TV + IRV =500 +3100 = 3600 ml VITAL CAPACITY – It is the maximum amount of air that can be expelled out forcefully after maximal deep inspiration. VC =IRV + TV + ERV =3100 +500 +1200 =4800 ml FUNCTIONAL RESIDUAL CAPACITY – It is the volume of air remaining in the lungs after normal expiration. FRC = ERV + RV =1200 +1200 = 2400 ml
- 17. TOTAL LUNG CAPACITY – It is the amount of air present in the lungs after a maximal deep inspiration. TLC = (IRV + TV + ERV) + RV = VC + RV = 4800 + 1200 =6000 ml
- 18. MEASUREMENTS OF LUNG VOLUMES AND CAPACITIES Lung Volumes and capacities are measured by instrument called SPIROMETER. Modified spirometer is called respirometer. SPIROMETER Upward curve of graph shows inspiration and downward deflection denotes expiration in spirogram. It can be used only for a single breath. Repeated cycles of respiration cannot be recorded by using this because ,CO2 accumulated in the spirometer cannot be removed and the O2 or fresh air cannot be provided to the subject. RESPIROMETER It is modified spirometer. It has provision for removal of CO2 and supply of O2. CO2 is removed by placing soda lime inside the instrument. O2 is supplied to the instrument from O2 cylinder.
- 19. SPIROGRAM Recording of lung volumes and capacities using spirometer or respirometer is called SPIROGRAM.
- 20. SPIROGRAM Four levels are noted in spirogram: The normal end expiratory level The normal end inspiratory level Maximum expiratory level Maximum inspiratory level COMPUTARISED SPIROMETER It is an electronic equipment, which does not contain a drum or water chamber. Subject has to respire into a sophisticated transducer, which is connected to the instrument by means of a cable. DISADVANTAGES OF SPIROMETRY Residual volume cannot be measured by this. FRC & TLC also can not be measured.
- 21. MEASUREMENT OF FRC,RV AND TLC Volume and capacities which cannot be measured by spirometry can be measured by the following methods: 1) HELIUM DILUTION TECHNIQUE 2) NITROGEN WASHOUT METHOD 3) PLETHYSMOGRAPHY
- 22. HELIUM DILUTION METHOD It is a procedure to measure FRC Respirometer is filled with air containing a known quantity of helium Subject breathes normally. After end of expiration, subject breathes from Respirometer. Helium from Respirometer enters lungs and starts mixing with air in the lungs After few minutes of breathing, the concentration of helium in the Respirometer becomes equal to the concentration of helium in the lungs of subject. This is called as EQUILIBRIUM OF HELIUM After equilibrium of helium in Respirometer and lungs, the concentration of helium in Respirometer is determined
- 23. HELIUM DILUTION METHOD It takes about 5 min for equilibrium of Helium between patient and spirometer to occur. In obstructive disease, it can take up to 30 min. FRC = V(C1 – C2) / C2 C1= initial concentration of helium in the respirometer C2= final concentration of helium in the respirometer V= initial volume of air in the respirometer
- 24. NITROGEN WASHOUT METHOD Concentration of nitrogen in air is 80%.So, if the total quantity of nitrogen in the lungs can be measured, the amount of air present in the lungs can be calculated. PROCEDURE TO MEASURE FRC Subject is asked to breath normally At the end of normal expiration, subject inspires pure O2 through a valve and expires into Douglas bag This procedure is repeated for 6-7 min, until the nitrogen in lungs is displaced by O2 Nitrogen comes to the Douglas bag Following factors are measured to calculate FRC I. Volume of air collected in the Douglas bag II. Concentration of nitrogen in Douglas bag FRC=C1 * V/C 2 V=VOLUME OF AIR COLLECTED C1=CONCENTRATION OF NITROGEN IN THE COLLECTED AIR C =NORMAL CONCENTRATION OF NITROGEN IN AIR
- 26. PLETHYSMOGRAPHY Plethysmography is a technique to study the variation in size or volume of a part of the body such as a limb Whole body plethysmography is the instrument used to measure the lung volumes including RV It is based on Boyles’ law of gas, which states that the volume of a sample of a gas is inversely proportional to the pressure of that gas at constant temperature. METHOD Subject sits in an airtight chamber of the whole body plethysmography and breathes normally through a mouthpiece connected to a flow transducer called PNEUMOTACHOGRAPH It detects the volume changes during different phases of respiration After normal breathing for few minutes, the subject breathes rapidly with maximum force During maximum expiration, lung volume decreases very much But volume of gas in chamber increases within pressure
- 27. By measuring the volume and pressure changes inside the chamber, the volume of lungs can be calculated by using the formula P1 * V = P2(V- V) V = P2(V- V)/P1 P1 and P2 = pressure changes V=FRC
- 29. Pulmonary mechanics Tests of pulmonary mechanics include measurement of : 1. FEV – Forced Expiratory Volumes 2. FIF – Forced Inspiratory Flow rates 3. FEF – Forced Expiratory Flow rates 4. MVV – Maximum Voluntary Ventilation Measuring pulmonary mechanics is assessing the ability of lungs to move large volume of air quickly to identify airway obstruction Some measurements aimed at large intrathoracic airways, some at small airways and some assess obstruction throughout the lungs
- 30. Forced expiratory volume (fev) / timed vital capacity Amount of air, which can be expired forcefully in a given unit of time(after a deep inspiration) is called FEV FEV1 – Amount of air expired forcefully in 1 sec FEV2 – Amount of air expired forcefully in 2 sec FEV3 – Amount of air expired forcefully in 3 sec NORMAL VALUES FEV1 – 83% Of TVC FEV2 – 94% of TVC FEV3 – 97% of TVC After 3rd sec = 100% of TVC
- 31. SIGNIFICANCE OF FEV Vital capacity may be normal in some of the respiratory diseases FEV has greater diagnostic value as it is decreased significantly in some respiratory disorders FEV decreases much in obstructive diseases like – ASTHMA & EMPHYSEMA In some restrictive diseases like fibrosis FEV is slightly increased
- 32. Significance of fev1 Reflects the airflow in larger airways The utility of the FEV1 measurement is exemplified by the simple relationship between it and the associated degree of obstruction Normally, 75% of the FVC should be exhaled within I second. An FEV1 % of more than 80% or 90% indicates restrictive condition, while reduced FEV1 % indicates airway obstruction. SADOWSKY Little or no obstruction FEV1 above 2.0 L to normal Mild to moderate obstruction FEV1 between 1.0 L to 2.0 L Severe obstruction FEV1 less than 1.0 L
- 33. Respiratory minute volume(RMV) Amount of air breathed in and out of lungs every minute is called RESPIRATORY MINUTE VOLUME. It is the product of Tidal Volume (TV) and Respiratory Rate (RR) RMV = TV * RR = 500 * 12 = 6000 ml NORMAL RMV = 6 liters VARIATIONS RMV increases in physiological condition like voluntary hyperventilation, exercises and emotional conditions It decreases in respiratory disorders
- 35. Maximum breathing capacity(mbc) / MAXIMUM VOLUNTARY VENTILATION (MVV) Maximum amount of air which can be breathed in and out of lungs by means of forceful respiration (hyperventilation increase in rate and force of respiration) per minute is called MAXIMUM BREATHING CAPACITY or MAXIMUM VOLUNTARY VENTILATION NORMAL VALUE Males – 150-170 l/min Females – 80-100 l/min MEASUREMENT Subject is asked to breathe forcefully and rapidly with respirometer for 12 secs Amount of air inspired and expired is measured from spirogram From this, MBC is calculated from one minute MBC per min = n/12 * 60 liters(e.g. MBC in 12 sec =n liters) MBC is reduced in respiratory diseases.
- 36. It reflects strengths and endurance of the respiratory muscles Maximum voluntary ventilation (MVV) is the maximal volume of gas a patient can move during 1 minute. However normal values can vary as much as 25% t0 30%: therefore, only major reductions in the values are clinically significant. As a rule of thumb MVV is typically described as being about 35 times greater than the FEV1. sadowsky
- 38. Slow vital capacity(svc) The slow vital capacity (SVC) – also called the vital capacity (VC) – is similar to the FVC, but the exhalation is slow rather than being as rapid as possible as in the FVC. In a normal subject, the SVC usually equals the FVC, while in patients with an obstructive lung disorder ,the SVC is usually larger than the FVC. The reason for this is that, in obstructive lung disorders, the airways tend to collapse and close prematurely because of the increased positive intrathoracic pressure during a forceful expiration. This increased pressure leads to air trapping. Accordingly, a significantly higher SVC compared with FVC suggests air- trapping
- 39. Peak expiratory flow rate (PEFR) Maximum rate at which the air can be expired after a deep inspiration is known as PEFR NORMAL VALUE- 400 L/min MEASUREMENT Determined by using – WRIGHT’S PEAK FLOWMETER / MINI PEAK FLOWMETER From a position of full inspiration, air is forcibly expired across a pivoted vane or a lightweight piston. The displacement of vane or piston is proportional to maximum flow rate. cash
- 40. SIGNIFICANCE OF PEFR It is useful for assessing respiratory diseases especially to differentiate obstructive and restrictive diseases. PEFR is decreased in any type of respiratory disease It is more significant on obstructive (100 L/min) than in restrictive (200 L/min) www.docstock.com-Clement Clarke
- 42. FLOW VOLUME CURVE The flow volume procedure simply reports flow against volume on X-Y recorder Helps in diagnosing lung disease, since it is independent of effort. Curve below demonstrates that flow rises to a high value and then declines over most of expiration In restrictive lung diseases – the maximum flow rate is decreased, as it is the total volume exhaled In obstructive lung disease – the flow rate is low in relation to the lung volume and a scooped out graph is seen
- 43. Following a period of normal quiet breathing' patient is instructed to perform a maximal inspiration to hold the breath for I or 2 secand then expire fully sadowsky
- 45. FLOW VOLUME LOOP It is a diagnostic test that uses forced expiration It is a graphical analysis of the flow generated during a forced expiratory volume maneuver followed by a forced inspiratory volume maneuver Shape of graph helps to diagnose disease Obstructive disease- scooped out appearance
- 46. AIRWAY DIVISION
- 47. CLASSIFICATION OF OLD OLD Small airway obstruction Asthma COPD Emphysem a/Bronchiti s Large airway Obstruction Predominant Bronchitis Asthma Upper airway obstruction Variable Extrathorac ic UAO Variable Intrathoracic UAO Fixed UAO
- 48. Upper airway obstruction Flow Volume loop MUST be recorded to diagnose UAO. It can be …. 1) FIXED – UAO remains unchanged during inspiration and expiration 2) VARIABLE (Extrathoracic & Intrathoracic) UAO degree changed during inspiration and expiration Empley’s index helps to CONFIRM presence and Identify type of UAO.
- 49. Fixed UA obstruction 1. Post intubation tracheal stricture 2. Large Goiter 3. Endotracheal neoplasms 4. Tracheal stenosis Maximum airflow is limited to a similar extent in both inspiration and expiration so it give “BOX ” like look on FV loop. In Large goiter FV loop is Normal when sitting so its better to do Spirometry in supine position
- 50. Variable extrathoracic obstruction Causes : 1. Bilateral and unilateral vocal cord paralysis 2. Vocal cord constriction 3. Hypertrophied tonsils and Adenoids 4. Airway burns 5.Pharyngeal and Laryngeal growth The obstruction worsens in inspiration because the negative pressure narrows the trachea and inspiratory flow is reduced to a greater extent than expiratory flow so it show FLATTNING of the inspiratory curve of FV loop
- 51. Variable intrathoracic obstruction Causes: 1. Tracheomalacia 2. Polychondritis 3. Tumors of the lower trachea or main bronchus. 4. Excessive mucus plugging 5. Mediastinal mass compressing trachea 6. Aortic aneurysm The narrowing is maximal in expiration because of increased intrathoracic pressure compressing the airway. The flow volume loop shows a FLATTENING of expiratory curve.
- 52. 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 (dog-leg) appearance to the flow volume curve.
- 53. Restrictive lung disease A characteristic pattern in restrictive lung disease is “Normal shaped, Miniature graph” due to reduction of the flow rate along with reduction of FVC.
- 54. Neuromuscular restrictive lung disease 1. Generalized Weakness - malnutrition 2. Paralysis of the diaphragm 3. Myasthenia Gravis 4. Muscular Dystrophy 5. Poliomyelitis 6. Amyotrophic Lateral Sclerosis - Lou Gerig's Disease
- 56. MEASUREM ENT NORMAL OBSTRUCTI VE RESTRICTIV E TIDAL VOLUME 500 ml N / increased N / decreased IRV 3300 ml N / decreased decreased ERV 1200 ml N / decreased decreased RV 1200 ml increased decreased IC N / increased decreased FRC increased decreased TLC 6000 ml N / increased Decreased FVC 4800 ml Decreased Decreased FEV1 4200 ml Decreased N / decreased FEV1/FVC >70% Decreased N / increased
- 58. DIFFUSION CAPACITY OF LUNG Third major category of pulmonary function testing is measuring the ability of the lungs to transfer gases across the alveolar capillary membrane The diffusion capacity of lung or Dlco or sometimes called as TRANSFER FACTOR It is expressed in ml/min/mm Hg under standard temperature and pressure and dry conditions(STPD) Gas normally used to measure the diffusing capacity of lung is CO(carbon monoxide) according to following equation: DLCO= VE(FI CO – FECO)/(PACO – PcCO) DLCO = 25-30 ml/min/mm Hg VE= volume FI CO = concentration of CO in inhaled air FECO = concentration of CO in exhaled air PACO = alveolar partial pressure of CO PcCO = partial pressure of CO in pulmonary capillary plasma
- 59. COMMON METHODS USED ARE: 1. SINGLE BREATH – requires patients co operation and breath holding 2. STEADY STATE TECHNIQUE – uses normal breathing pattern Carbon monoxide (CO) is normally employed as a measure Diffusion of gases because it has an affinity for hemoglobin nearly 210 times greater than that of oxygen. As long as person’s Hb is normal the alveolar CO should bind to the Hb and the partial pressure of CO in plasma is zero The normal diffusing capacity of carbon monoxide is about 25 to 30 mL/min/mm Hg. Although there may be many causes for an abnormal DLCO test, they can be attributed to three key factors: (1) decreased quantity of hemoglobin per unit volume of blood (2) increased thickness of the alveolar-cappillary membrane (3) decreased functional surface area available for diffusion sadowsky
- 60. LIMITATIONS OF PFT 1. Tests cannot reveal patient disease unless the function are sufficiently lower 2. Tests do not provide anatomical diagnosis but can help localizing it to a section of airway/lung 3. Tests fail to localize disease process except when lungs/lobes are tested separately 4. Tests must be multiple since no single test can evaluate total abnormality at one time
- 61. References Principles and practice of cardiopulmonary physical therapy (third edition) – DONNA FROWNFELTER & ELIZABETH DEAN EGAN’s fundamentals of respiratory care (seventh edition) Essentials of Cardiopulmonary physical therapy –ELLEN HILEGASS & STEVEN SADOWSKY CASH’s textbook of chest, heart and vascular disorders for physiotherapists Essentials of medical physiology – K SEMBULINGAM & PREMA SEMBULINGAM