Pulmonary Function Test (PFT) PDF

PULMONARY FUNCTION TEST RINALIZA FADCHAL PATTING – BOGSULEN, RTRP SPIROMETER the primary instrument used in pulmonary function testing designed to measure changes in volume can only measure lung volume compartments that exchange gas with the atmosphere SPIROGRAPH a device that is usually attache...

PULMONARY FUNCTION TEST RINALIZA FADCHAL PATTING – BOGSULEN, RTRP SPIROMETER the primary instrument used in pulmonary function testing designed to measure changes in volume can only measure lung volume compartments that exchange gas with the atmosphere SPIROGRAPH a device that is usually attached to spirometer which measures the movement of gas in and out of the chest. The resulting tracing is called SPIROGRAM.  Classifications of Spirometers 1. Primary Volume Measuring Spirometers ( PVMS ) A) Volume Collecting or Volume Displacement a.1 Water Sealed Spirometer a 1.1 Chain- Compensated Type a 1.2 Stead- Wells Type a.2 Dry- Sealed Spirometer a.3 Bellows Spirometer a.3.1 Fully Expanding Bellows a.3.2 Wedged- Shaped Bellows B) Flow-Through Device b.1 Rotor Spirometer  Primary Volume Measuring Spirometers Directly measure the volume of air moving in and out of the lungs Flow rates is indirectly measured: Flow rate (l/sec) = Volume (L) / Time (sec) 2. Primary Flow Measuring Spirometers ( PFMS ) a. Differential Pressure Pneumotachometer b. Thermal Anemometers c. Ultrasonic Sensor Spirometer d. Dedicated Peak Flow Meter Indications Medical Diagnosis – Determination of the presence of a disorder – Assessment of the degree of impairment due injury or disease – Determination of the pathologic nature of the disease – Planning of therapy – Evaluation of the therapeutic effectiveness – Monitoring progression of a disease Indications Surgery related evaluation – Preoperative and post operative assessment – Disability evaluation Assess effect of rehabilitation program Insurance purposes Legal documentation (Social Security, lawsuit) Public health / research – Epidemiologic survey – General or specific data accumulation Contraindications: Hemoptysis of unknown origin Pneumothorax Unstable cardiovascular status, recent MI, pulmo -nary embolus Thoracic, abdominal, or cerebral aneurysms Recent eye surgery Presence of an acute disease process that might interfere with test performance (nausea, vomiting) Recent surgery of thorax or abdomen Hazards and Complications: Pneumothorax Increased ICP Syncope, dizziness, light-headedness Chest pain Paroxysmal coughing Contraction of nosocomial infection Oxygen desaturation resulting from interruption of OT Bronchospasm Patient Assessment for PFT 1. Basic Information - Name of the patient - Age - Gender - Standing height - Weight - Race - Current diagnosis  Height is the primary factor that affects the predicted normal values more than the age  In children – age becomes a factor in predicting normal values if it reaches more than 60 inches  Weight – increasing weight decrease lung volumes which is attributed to obesity  Age- after the age of 25, ↑age –↓ lung volumes ( except RV and FRC), expiratory flow rates, diffusing capacity  Gender – male - greater lung volumes, FEF, DLCO; however, if with the same predicted normal FVC values, female will have greater values for expiratory flow  Race/ ethnic origin – black / oriental – smaller Patient Assessment for PFT 2. History Taking a. Personal History - allergies - hay fever - asthma - chest injury or surgery - recurring colds - pneumonia/ recurrent lung infections - lung abcess - plerurisy - TB - Ca - pulmonary fibrosis - bronchiectasis - emphysema - chronic bronchitis Patient Assessment for PFT b. Medications for Lung or Heart Problems - types of medications - for what is the medication - dose of medications - schedule of intake (time of last dose) Patient Assessment for PFT c. Smoking History - ex smoker - currently smoking - type of tobacco / substance smoked - age smoking began - date and reason of quitting **pack year history Patient Assessment for PFT d. Hobbies - involves use of chemicals, art supplies, irritating or poisonous substances e. Pets - types and numbers of pets - indoor / outdoor f. Places of residence - includes chronologic history of localities Patient Assessment for PFT g. Occupational history - chronological history of patient’s occupation with description of actual job performed Patient Assessment for PFT 3. History of Symptoms Associated with Pulmo Disorders: a. cough b. dyspnea c. wheezing Physical Assessment for PFT General survey of the patient Vital signs Auscultation results Chest X-ray results TEST FOR PULMONARY VOLUMES AND VENTILATION DIRECT SPIROMETRY LUNG VOLUMES AND CAPACITIES Lung Volumes 4 Volumes 4 Capacities IRV IC – Sum of 2 or VC more lung TV TLC volumes ERV FRC RV RV Tidal Volume (TV) Volume of air inspired IRV and IC expired TV VC during TLC normal quiet ERV FRC breathing RV RV 500mL Inspiratory Reserve Volume (IRV) The maximum IRV amount of IC air that can TV VC be TLC inhaled after ERV FRC a normal RV RV inspiration Should be Expiratory Reserve Volume (ERV) Maximum amount of air IRV that can be IC exhaled after TV VC a normal TLC exhalation ERV FRC 1200 mL RV RV 20 – 25% of VC Residual Volume (RV) Volume of air IRV remaining in IC the lungs TV VC after a TLC maximal ERV FRC expi - ration RV RV 1200 mL Vital Capacity (VC) Volume of air that can be exhaled after a maximum IRV inspiration IC FVC: when VC VC exhaled TV TLC forcefully SVC: when VC ERV is exhaled FRC slowly RV RV VC = IRV + TV + ERV 4800 mL Inspiratory Capacity (IC) Maximum amount of air IRV that can be IC inhaled after a TV VC normal TLC inhalation ERV FRC IC = IRV + TV RV RV 3600 mL 75 – 85% of VC Functional Residual Capacity (FRC) Volume of air remaining in the lungs at the end IRV of a TV expiration IC The elastic force VC of the chest wall TV TLC is exactly ERV balanced by the FRC elastic force of RV RV the lungs FRC = ERV + RV 2400 mL Total Lung Capacity (TLC) Volume of air in the lungs IRV after a IC maximum TV VC inspiration TLC TLC = IRV + ERV FRC TV + ERV + RV RV RV 6000 mL RV/TLC Ratio Percentage of the TLC that remains in the lungs after a maximal exhalation Measured by dividing the RV by TLC and multiplying by 100 Decreased in RLD and increased in OLD Normal value is 20% - 35% Acceptability Criteria No coughing No variable effort demonstrated by the subject during the maneuver. No volume loss from a leak in the system No obstruction of the mouthpiece Maximal expiratory and inspiratory efforts are demonstrated with an observable volume plateau Reproducibility Criteria The largest VC and second largest VC values are within 0.2 liter of each other. – If this criterium is not met after two tests, testing must continue until: 1. The criterium is met with additional acceptable test 2. total of four test have been performed 3. patient cannot continue Mdama, VA. Pulmonary Function Testing, 2nd ed INDIRECT SPIROMETRY Nitrogen Washout Open circuit method Patient breathes 100% oxygen while the nitrogen washed out of the lungs is measured Assumes 79% of lung volume is nitrogen Several “problems” with this test PROBLEMS WITH N2 WASH OUT Test Atelectasis may result from washout of nitrogen from poorly ventilated lung zones (obstructed areas) Elimination of hypoxic drive in CO2 retainers is possible Underestimates FRC due to under ventilation of areas with trapped gas Criteria for Ending a Nitrogen Washout Test A nitrogen washout test is successfully completed when the following criterion is met: The exhaled nitro en levels decrease to become less than 1.0% (1.2%-3.% in some references)for subjects without obstructive dis- orders. The test may have to be prematurely discontinued if the following occurs: A system leak(a sudden increase in the expired nitrogen concentration) The patient is not able to continue the test. The Tissot spirometer used, become full.  FRC = expired volume x N2 N1 Where: N1 = nitrogen percentage in lungs at start of the test N2 = nitrogen percentage in spirometer at end of the test Helium Dilution Closed circuit method Known volume and concentration of He added and it will be diluted in pro-portion to the size of the lung volume Criteria for Ending a Helium Dilution Test A helium dilution test is successfully completed when the following criterion is met: – The helium concentration in the system stabilizes and fluctuates no more than 0.02% during a 30-secperiod. The test may have to be prematurely discontinued if the following occurs: – A system leak(sudden decrease in the system helium) – The patient is not able to continue the test.  System vol = helium added (mL % He (first reading) FRC = (%He1 - %He2) X system vol x BTPS CF He2 Where: H1 = He concentration before patient is connected to the system He2 = final helium concentration when equilibrium has occured BTPS CF = constant to convert vol to BTPS Body Plethysmography Or “body box” Uses the Principle of Boyle’s Law “If the temperature and mass remain constant, the volume of gas varies inversely with its pressure” Unknown lung gas vol = Gas pressure of the box Known box gas vol Gas pressure of the lungs In body plethysmography, the patient sits inside an airtight box, inhales or exhales to a particular volume (usually FRC), and then a shutter drops across their breathing valve. The subject makes respiratory efforts against the closed shutter causing their chest volume to expand and decompressing the air in their lungs. The increase in their chest volume slightly reduces the box volume and thus increases the pressure in the box. This method of measuring FRC actually measures all the conducting pathways including abdominal gas; the actual measurement made is VTG (Volume of Thoracic gas). Acceptability Criteria A test for VTG may be considered acceptable if: The panting by the subject is correct in Volume and rate TEST FOR PULMONARY MECHANICS Forced Vital Capacity Most commonly performed test for pulmonary mechanics Pulmonary mechanics measurement is used to assess the ability of the lungs to move large volume of air in order to identify airway obstruction Effort-dependent maneuver that requires proper patient instruction, understanding, coordi-nation and cooperation Volume Time Curve FVC – the maximum amount of gas that can be force fully exhaled after a maximum inspira-tion FEV1 – the maximum amount of gas that can be exhaled during the first second of a forced vital capacity maneuver - the most effort dependent part of the FVC maneuver FEV1/FVC Ratio calculated by dividing the largest FEV1 by the largest FVC multiplied by 100 50 – 60% of the FVC is exhaled in 0.5 sec 75-85% of the FVC is exhaled in 1 sec 94% of the FVC is exhaled in 2 sec 97% of the FVC is exhaled in 3 sec Forced expiratory flow 25- 75% (FEF25-75) – Mean forced expiratory flow during middle half of exhalation – Can also be referred to as maximal midexpiratory flow rate – Least effort dependent and is useful in assessing the status of the small airways – Normal value: 4-5L/sec FEF200 – 1200 – the forced expiratory flow between the first 200ml of volume and the next 1000ml of volume – the average of the expiratory flow during the early phase of exhala-tion - Effort dependent - Can also be referred as maximum expiratory flow rate - Normal value= 6-7L/ sec (400L/min) Flow Volume Loop PEF – the maximum flow rate during the forced vital capacity - 400-600L/min (6.5 – 10 L/sec) PIF – the fastest flow rate during a maximum inspiratory effort Obstructive Disorders Characterized by a limitation of expiratory airflow – Examples: asthma,COPD Decreased: FEV1, FEF25-75, FEV1/ FVC ratio ( 135, this Parameter Normal indicates air TLC 80 – 120 % trapping FRC 65 – 125 % If TLC and RV are RV 65 – 130 % increased, this VC > 81 % indicates sRAW ≤ 120 hyperinflation If sRAW is > 120, this indicates increased airway resistance TEST FOR PULMONARY GAS DIFFUSION  Test Description Measures the ability of the lungs to permit transfer of an alveolar gas along the alveolo-capillary membrane to combine with hemoglobin Diffusing capacity (DLgas / Dgas - the quantity of a specific gas that can diffuse along the alvelo-capillary pathway in response to a pressure gradient  Other factors affecting the diffusing capacity: – Ventilation / perfusion relationships –Characteristics of gas to be used: 1. gas must be capable of diffusing along the alveolo-capillary pathway 2. gas must be capable of being transported by hemoglobin  Indications: – Evaluation and follow up of parenchymal lung disease associated with dusts (asbestos); drug reaction (amiodarone) or sarcoidosis – Evaluation and follow up of emphysema and CF – Differentiation among CB, emphysema and asthma – Evaluation of pulmonary involvement in systemic disease (rheumatoid arthritis, SLE)  Indications: – Evaluation of cardiovascular diseases (pulmonary HPN, pulmonary edema, thromboembolism) – Prediction of arterial desaturation during exercise in COPD – Evaluation and quantification of disability associated with ILD – Evaluation of the effects of chemotherapy agents and other drugs known to induce pulmonary dysfunction – Evaluation of hemorrhagic disorders  Contraindications: – Mental confusion / incoordination preventing the subject from performing the test – A large meal – Vigorous exercise – Smoking within 24 hours of test administration  Hazards and Complications: – Some patients may perform Valsalva maneuver (high intrathoracic) or Muller maneuver (low intathoracic) – Transfer of infection (droplet nuclei or body fluids) – patient to patient ; patient to technologist A.Single Breath Method (Modified Krogh) Method - Most common measurement technique - Based on diffusion decay curve described by Forster  Equipment Required: – Sealed spirometer prefilled with test gas – Test gas – 0.3% Co, 10% He, 21%O2 – Five way breathing valve to direct the patient’s inspiratory and expiratory airflows for inspiration, volume measurement and gas sampling – End-tidal gas sampling system for He and CO – Spirometer / recording system  Test Administration – Patient must refrain from smoking for at least 24 hours – record the time the patient consumed a cigarette – Patient must refrain from consuming alcohol at least 4 hours before the test – Patient should refrain from eating at least 2 hours before the test – Patient must refrain from performing strenous exercise – Oxygen-enriched gas mixture should not be breathed immediately before the test – Patient should sit and rest for at least five mins before the test – Supplemental oxygen must be discontinued 5 mins before the test ** there should be 4 mins interval between repeats of procedure  Instruction: – Patient must exhale to RV then inhale maximally to TLC (VC) , breath hold for at least 10 secs (9 – 11 secs) Then exhale back to RV (patient in sitting postion with nose clips) *** bost inspiration from RV to TLC and exhalation back down to RV must be done rapidly *** during breath holding, patient should be instructed to simply relax against a closed glottis)  B. Steady State Method ( Filey) – Allows measurement with the patient performing normal tidal breathing – Uses 0.1% - 0.2% CO. – The patient will breath the gas mixture for 5 – 6mins – During the last 2 mins of breathing, the patient’s exhaled air is collected in a Douglas bag. Concentration of the gas O2, CO and CO2 are measured from the sample – An ABG sample is required  Advantages of DLCOss Disadvantages of – Allow a more DLCOss 1. Allow the natural breathing possibility of COHb maneuver buildup – Allow for 2. more affected by measurements to V/Q abnormalities be made under a because of the variety of clinical smaller lung volumes conditions (exercise, used sleep, anesthesia) C. DLCO rebreathing method (DLCORB) – Like the DLCOss, it allows for normal tidal breathing by the patient – Has two rebreathing techniques : reservoir – sampling and wash out – sampling technique – The gas mixture used: 0.3% CO and 10% He from a bag or balloon like reservoir  Instruction: – Patient will exhale down to RV – Rebreathe from the reservoir bag with an RR as close to 30/min as possible. The nag must be emptied completely with inspiration 1. Reservoir sampling The patient will rebreathe the gas for a period of 30 – 45 secs. A sample from the reservoir is taken for measurement of CO, He and O2 concentrations 2. Wash-out sampling Rebreathing continues until a gas concentration equilibrium is reached between the reservoir and the patient’s lungs  Conditions that produce changes in LCO A.Increased in DLCO 1.L to R CV shunt abnormalities (1) 2.High altitude (1) 3.Exercise (1) 4.Left sided heart failure (1) 5.Supine body position (1) 6.Early polycythemia (2)  1 – increased pulmonary blood volume – unchanged lung volume 2 – increased number of RBC – unchanged lung volume  Decrease DLCO 1.Emphysema (3) 2.Pulmonary resection (4) 3.Asbestosis (4) 4.Chronic hypersensitivity pneumonitis (4) 5.Lymphangitic spread of Ca (4) 6.Chronic interstitial pneumonitis (Hamman- Rich disease) (4)  3 – loss of functional alveolocapillary tissue – increased lung volume 4 – loss of alveolocapillary tisssue – decreased lung volume 7. Histiocytosis (4) 8. Oxygen Toxicity (4) 9. Radiation induced fibrosis (4) 10. Sarcoidosis (4) 11. Scleroderma lung disease (4) 12. SLE (4)  13. Pulmonary Alveolar proteinosis (4) 14. anemia (5) 15. Pulmonary emboli (6) 16. early collagen vascular disorder (6) 17. early miliary TB (6) 18. Early sarcoidosis (6) 5 – reduced number of RBC – unchanged lung volume 6- Loss of pulmonary capillary bed – unchanged lung volume  BronchoProvocation Study (Metacholine Challenge Test) Indications Exclude the diagnosis of airway hyperreactivity Evaluate occupational asthma Assess the severity of hypperesponsiveness Determine the relative risk of developing asthma Assess the response to therapeutic interventions Absolute Contraindications Presence of severe ventilatory impairment (FEV1