pft6777777777777777777777hddgghjkkkk.pdf
- 2. Definition ā¢ Spirometry is a method of assessing lung function by measuring the volume of air that the patient is able to expel from the lungs after a maximal inspiration. ā¢ It is a reliable method of differentiating between obstructive airways disorders (e.g. COPD, asthma) and restrictive diseases (where the size of the lungs is reduced, e.g. fibrotic lung disease).
- 3. Indications ā¢ To evaluate symptoms and signs of lung disease (eg, cough, dyspnea, cyanosis, wheezing, hyperinflation, hypoxemia, hypercapnia) ā¢ To assess the progression of lung disease ā¢ To monitor the effectiveness of therapy ā¢ To evaluate preoperative patients in selected situations.
- 4. ā¢ To screen people at risk of pulmonary disease such as smokers or people with occupational exposure to toxic substances in occupational surveys. ā¢ To monitor for the potentially toxic effects of certain drugs or chemicals (eg, amiodarone, beryllium) ā¢ Measure airflow obstruction to help make a definitive diagnosis of COPD
- 5. ā¢ Confirm presence of airway obstruction ā¢ Assess severity of airflow obstruction ā¢ Perform pre-employment screening in certain professions. ā¢ Assess the degree of disability.
- 6. NB: Pulmonary function tests are not otherwise indicated in patients without symptoms, and they may be confusing when nonpulmonary diseases that affect the pulmonary system are active (eg, congestive heart failure).
- 7. Contraindications If any of the following have occurred recently, then it may be better to wait until the patient has fully recovered before carrying out spirometry. ā¢ Haemoptysis of unknown origin ā¢ Pneumothorax ā¢ Unstable cardiovascular status, recent myocardial infarction or pulmonary embolism.
- 8. ā¢ Thoracic, abdominal or cerebral aneurysms ā¢ Recent eye surgery ā¢ Acute disorders affecting test performance, such as nausea or vomiting ā¢ Recent thoracic or abdominal surgical procedures ā¢ Current severe pain of the abdomen and chest.
- 11. Definition It is defined as the maximal amount of air that can be exhaled forcefully after a maximal inspiration or the most air a person can blow out after taking the deepest possible breath.
- 12. Most important parameters ā¢ FEV1 ā¢ FVC ā¢ šš¬š½š šš½šŖ ā¢ PEF ā¢ FEF25-75% ā¢ V-T Curve ā¢ F-V loop
- 13. FVC - forced vital capacity ā¢ Defines maximum volume of exchangeable air in lung (vital capacity) during forced expiratory breathing maneuver. (approx. 4 liters) ā¢ It requires muscular effort and some patient training so slowly diminishes with normal aging. ā¢ Significantly reduced FVC suggests damage to lung parenchyma e.g. fibrosis
- 14. FEV1 ā¢ Forced expiratory volume in the 1st sec: ā¢ It is the volume of air exhaled during the first second of a forced expiratory maneuver. ā normal FEV1 about 3 liters
- 15. FEV1/FVC% Definition: ā The value expresses the volume of air the patient exhales in one second as a percent of the total volume of air that is exhaled. ā Calculated by using largest valid FEV1 and largest FVC even if they are not from the same tracing. ā¢ Find largest valid FEV1 ā¢ Find largest valid FVC ā¢ Divide FEV1 by FVC ā¢ Multiply by 100 to obtain percentage.
- 16. PEF - Peak Expiratory Flow rate ā¢ Measures airflow limitations in large (central) airways ā¢ PEF measurements recommended for asthma management ā¢ PEF not recommend to evaluate patients for COPD ā cannot measure small airway airflow limitations ā¢ Advantages of PEF tests ā Measurements within a minute (three short breaths) ā Uses simple, safe, low price, hand-held devices. ā¢ Disadvantages of PEF tests (compared to spirometry) ā Insensitive to obstruction of small airways (mild or early obstruction) ā PEF is very dependent on patient effort (large intra-subject variability) ā Mechanical PEF meters are much less accurate than spirometers
- 17. FEF25-75% ā¢ Definition: āThe mean expiratory flow during the middle half of the FVC ā¢ More sensitive than FEV1. ā¢ Considerably more variability than FVC and FEV1. ā¢ ATS recommends only be considered after determining presence and clinical severity of impairment and should not be used to diagnosis disease in individual patients
- 18. Ideal curve It is characterized by: 1. An immediate vertical rise, 2. A sharp peak, and 3. A fairly smooth descent that returns to zero flow.
- 19. Limitations to Spirometry ā¢ Effort dependant If patient canāt or wonāt follow instructions, the quality of results are poor and interpretation difficult ā¢ Doesnāt exclude asthma if spirometry is normal but may diagnose it ā¢ Normal Spirometry doesnāt mean there is no problem Pulmonary vascular disease: Normal spirometry but reduced TLCO
- 20. Technical feedback notes should be included by operators on all spirometry reports and these comments should be considered when interpreting spirometry results
- 21. Types of ventilatory defects Obstruction: ā¢ Airflow limitation ā unable to blow out quickly: āreduced FEV1/FVC e.g. asthma and/or COPD āReversibility: assesses improvement with therapy āReactive airways: abnormal airway hyper-responsiveness (feature of asthma) Restriction: ā¢ Limitation to inspiration ā small lungs āLow FVC (and TLC) e.g. fibrosis, pleural/chest wall disease, weak inspiratory muscles, obesity Mixed defect: ā¢ Small lungs and unable to blow out quickly āLow FEV1 and FEV1/FVC plus low FVC (and TLC)
- 22. The VC, FEV1, FEV1/VC ratio and TLC are the basic parameters used to properly interpret lung function. FVC is often used in place of VC. The FVC is usually reduced more than SVC in airflow Obstruction.
- 23. FVC ā¢ Interpretation of % predicted: ā80-120% Normal ā70-79% Mild reduction ā50%-69% Moderate reduction ā<50% Severe reduction FVC
- 24. FEV1 ā¢ Interpretation of % predicted: ā >80 Mild obstruction ā 60-79 Moderate obstruction ā 50-59 Moderately severe obstruction ā 35-49 Severe obstruction ā <35 Very severe obstruction FEV1 FVC
- 25. FEF25-75 ā¢ Interpretation of % predicted: ā>65% Normal ā45-65% Mild obstruction ā35-44% Moderate obstruction ā<35% Severe obstruction
- 26. Interpretation ā¢ Use the FEV1/FVC ratio to detect obstruction ā¢ Use FEV1 as % predicted to grade severity of obstruction ā¢ Use FVC (or VC) to assess restriction o Low FVC (VC) in presence of significant obstruction does not necessarily indicate restriction o Need to confirm and quantify restriction with measurement of TLC ā¢ A low FEF25ā75% in the presence of normal FEV1 can be used to detect āearlyā airflow obstruction but only if FVC is within normal limits. ā¢ Lower limit of normal FEF25ā75% is about 65% predicted
- 28. Obstruction
- 29. Assessment of bronchodilator reversibility Spirometry should be performed before and after bronchodilator (whenever possible) ļ¶4 puffs (400ug) of salbutamol from MDI + spacer ļ¶wait 10 - 15 minutes for short acting Ī²2-agonist (salbutamol) ļ An increase in FEV1 of ā„ 12% and ā„ 200ml after administration of a bronchodilator indicates reversible airflow limitation consistent with asthma.
- 30. Age: 47, Male, Height 163 cm; Weight 84 kg Caucasian CLINICAL COMMENTS: ā¢ Painter with recent SOBOE ā¢ Night cough; symptomatically better on weekends and holidays ā¢ History of childhood rhinitis and asthma ā¢ Nonsmoker
- 33. Restrictive Ventilatory Defects (volume limiting) In restrictive disorders there is a reduction in the overall lung volume.Low FVC (and TLC) This can be either intrapulmonary or extrapulmonary ā¢ Intrapulmonary (increase in elastic recoil): e.g. pulmonary fibrosis, alveolitis, edema, pneumoconioses (e.g asbestosis) effects of drugs (amiodarone, methotrexate), rheumatoid arthritis ā¢ Intrapulmonary (reduction in volume): e.g. tumours, lobectomy/pneumonectomy, pneumonia ā¢ Extrapulmonary: e.g. pleural effusion, thoracic cage deformity (scoliosis),neuromuscular disorders obesity and pregnancy
- 35. Pulmonary Factors Can Reduce Vital Capacity ā¢ Loss of Distensible Tissue ā e.g. pneumonectomy, atelectasis. ā¢ Decreased Compliance. ā e.g. respiratory distress syndrome, alveolar edema, or infiltrative interstitial lung diseases. ā¢ Increased Residual Volume. ā e.g. emphysema, asthma, or lung cysts.
- 36. Extrapulmonary Factors Can Reduce Vital Capacity ā¢ Limited Thoracic Expansion. ā e.g. thoracic deformities (Kyphoscoliosis) and pleural fibrosis. ā¢ Limited Diaphragmatic Descent. ā e.g. ascites and pregnancy. ā¢ Nerve or Muscle Dysfunction. ā Pain (surgery, rib fracture) ā Primary neuromuscular disease (e.g. Guillain- BarrĆ© Syndrome).
- 37. FEF 25-75% ā¢ What is it? ā Mean expiratory flow during middle half of FVC maneuver ā¢ What does it measure? ā Flow from airways that empty in the middle half of FVC maneuver ā¢ Is it a measure of small airways? ā Maybe in normals ā In asthma, or obstructive disease, it measures flow from more obstructed airways which could be small or larger with more obstruction
- 38. A problem with FEF: Variability
- 40. Static Lung Volumes ļ 4 Volumes ļ 4 Capacities ļ¬ Sum of 2 or more lung volumes IRV TV ERV RV IC FRC VC TLC RV
- 41. Indication for lung volume test : ļ Low FVC : -? Restrictive -? Obstructive with hyperinflation and air trapping -? Mixed pattern
- 42. Changes in Lung Volumes in Various Disease States
- 43. ļ The static lung volumes can be measured by a simple spirometer. ļ The inspiratory reserve volume (IRV) and expiratory reserve volume (ERV) can be calculated from such a tracing.
- 44. The functional residual capacity (FRC), the volume of gas remaining in the lung at the end of a quiet expiration, and the residual volume (RV), the volume of gas remaining in the lung after a maximal expiration, can be determined by one of two methods: 1. Nitrogen Washout Method 2. Gas dilution tests. Dilutional: helium, 100% oxygen 3. Body plethysmography (Body Box).
- 46. ļ With the helium (He) dilution method [the subject is connected, at the end of a quiet expiration, to a closed spirometer containing a known concentration and volume of He, a gas that is almost insoluble in blood. ļ After a period of equilibration, the concentration of He in the lungs and the spirometer stabilizes at a new level and the FRC can be calculated
- 47. ļ§ The most accurate way ļ§ The patient sits inside a fully enclosed rigid box and breath through mouthpiece connected through a shutter to the internal volume of the box
- 48. ļ Preventing Patient entering the box ļ¬ Mental confusion ļ¬ Poor muscular co-ordination ļ¬ Body cast ļ¬ Wheelchair ļ¬ Claustrophobia ļ¬ Extreme Obesity ļ¬ Presence of devices - continuous I.V. infusion
- 49. ļ Conditions that interfere with pressure changes ļ¬ Chest tube ļ¬ Trans-tracheal O2 catheter ļ¬ Ruptured ear drum. ļ¬ Continuous O2 therapy that cannot be removed
- 50. ļ During inspiratory efforts against the occlusion
- 52. Obstructive Lung Disease ļ§ Narrowing and closure of airways during expiration tends to lead to gas trapping within the lungs and hyperinflation of the chest. ļ§ Air trapping ā increase in RV ļ§ Hyperinflation ā increases TLC ļ§ RV tends to have a greater percentage increase than TLC ļ§ RV/TLC ratio is therefore increased (nl 20-35%) ļ§ Gas trapping may occur without hyperinflation (increase in RV & normal TLC)
- 53. Obstructive Lung Disease cont. RV increased TLC Nl/increased RV/TLC increases FRC increased VC decreased *Air trapping :Normal TLC with increase RV/TLC *Hyperinflation: Increase in both TLC and RV/TLCl/
- 55. Reduction in TLC is a cardinal feature 1. In Intrinsic RLD (Interstitial Lung Disease) ļ§ TLC will decrease ļ§ RV will decrease because of increased stiffness of the lung and loss of the alveoli. ļ§ Breathing take place at low FRC because of the increased effort needed to expand the lung . ļ§ RV/TLC normal
- 56. 2. In extrinsic RLD (chest wall disease :kyphoscoliosis or neuromuscular disease) ļ§ TLC is reduced either because of mechanical limitation to chest wall expansion or because of respiratory muscle weakness ļ§ RV is Normal because Lung tissue and elastic recoil is normal So RV/TLC ratio will be high ļ§ Breathing take place at low FRC because of the increased effort needed to expand the lung .
- 57. Restrictive Lung Disease: Extrinsic RLD TLC decreased RV normal RV/TLC High VC decreased FRC decreased RLD Intrinsic TLC decreased RV decreased RV/TLC normal FRC decreased VC decreased
- 61. Diffusion
- 62. The process of carbon monoxide transfer from the environment to the pulmonary capillary blood includes five steps, as follows: 1. Flow of carbon monoxide to the airways and alveolar spaces; 2. Mixing and diffusion of carbon monoxide in the alveolar ducts, air sacs and alveoli; 3. Transfer of carbon monoxide across the gaseous to liquid interface of the alveolar membrane; 4. Mixing and diffusion of carbon monoxide in the lung parenchyma and alveolar capillary plasma; 5. Diffusion across the red-cell membrane and within the interior of the red blood cell;
- 63. The process of carbon monoxide uptake can be simplified into two transfer or conductance properties: 1. Membrane conductivity (DM), which reflects the diffusion properties of the alveolar capillary membrane; 2. Binding of carbon monoxide and Hb.
- 64. Diffusion limitations ā¢ Distribution Transport to the alveoli ā¢ Diffusion Transport through membrane ā¢ Perfusion Transport through the the blood plasma to the hemoglobin
- 65. Diff-Measurements Diffusion can be determined by DLCOSB: Single Breath DLCORB: Rebreathing DLCOSS: Steady State
- 67. Single-breath testing technique The single-breath determination of DLCO involves measuring the uptake of carbon monoxide from the lung over a breath-holding period. To minimise variability as much as possible, the following specifications for the standardisation of testing techniques are provided.
- 68. Patient condition Factors that affect VC: ļµ Exercise , ļµ Body position, ļµ Hb affinity for carbon monoxide, ļµ Alveolar oxygen tension (PAO2), ļµ Level of carboxyhaemoglobin (COHb)) must be standardized.
- 69. If clinically acceptable, ļµ The subject should not breathe supplemental oxygen for ā©¾10 min prior to a DLCO manoeuvre. ļµ In addition, when using exercise or the supine position to assess the ability of the lung to increase gas transfer, the level of exercise and/or the duration of the supine position must be noted.
- 70. ļµ Subject must be seated comfortably ļµ COHb produces an acute, reversible decrease in DLCO, āanaemia effectā from decreased Hb binding sites for test gas carbon monoxide. As cigarette smoking is the most common source of COHb, subjects must be asked to stop smoking or other sources of carbon monoxide exposure on the day of the test.
- 71. Inspired gas composition ļµ The test gas should contain very close to 0.3% carbon monoxide, 21% oxygen, a tracer gas and a balance of nitrogen. ļµ The tracer gas must be relatively insoluble and relatively chemically and biologically inert.
- 72. ļµ Its gaseous diffusivity should be similar to carbon monoxide and it should not interfere with the measurement of carbon monoxide concentration. ļµ The tracer gas should also not ordinarily be present in alveolar gas or else be present at a known, fixed concentration (e.g. argon).
- 73. ļµ Commonly used tracer gases include helium and methane. ļµ Helium meets most of the previous criteria; however, its gaseous diffusivity is considerably higher than that of carbon monoxide. ļµ Methane gaseous diffusivity is closer to carbon monoxide but it has a slightly higher liquid solubility than helium. ļµ No clinical difference in DLCO using either helium or methane .
- 75. Inspiratory maneuvers ļµ Once the mouthpiece and nose clip are in place, tidal breathing must be carried out for a sufficient time to assure that the subject is comfortable with the mouthpiece with no leaks. ļµ The DLCO maneuver begins with unforced exhalation to residual volume (RV).
- 76. ļµ In obstructive lung disease, a reasonable recommendation is that this portion of the manoeuvre must be limited to <12 s. ļµ Submaximal inhalation occurs most frequently in patients with airflow obstruction who are not given adequate time to exhale prior to the inhalation of test gas.
- 77. ļµAt RV, the subjectās mouthpiece is connected to a source of test gas, and the subject inhales rapidly to TLC. ļµA submaximal inspired volume of test gas (i.e. less than the known VC) can affect carbon monoxide uptake depending upon whether it is a result of an initial suboptimal exhalation to RV (maneuver performed at TLC) or whether it is due to a suboptimal inhalation from RV (maneuver performed below TLC).
- 78. ļµ Due to these effects, it is important that the inspired volume of test gas, VI, be as close to the known VC as possible. ļµ The inspiration must be rapid, since the DLCO calculations assume instantaneous lung filling . ļµ Slower lung filling decreases the amount of time the lung is at full inspiration with a consequent reduction in carbon monoxide uptake.
- 79. ļµ Inspiration of test gas should be sufficiently rapid such that 85% of VI must be inspired in <4.0 s. If longer inspiratory times are needed to inspire 85% of VI, this must be noted on the test report.
- 80. Breath-hold and expiratory maneuvers ļµ During the breath-hold, both the Valsalva and MĆ¼ller manoeuvres (expiratory or inspiratory efforts against a closed glottis, respectively) can affect DLCO calculation by decreasing or increasing thoracic blood volume, respectively, resulting in a corresponding decrease or increase in DLCO, respectively, for each maneuver.
- 81. ļµ The intrapulmonary pressure during the breath-hold should thus be near atmospheric and this is best accomplished by having the subject voluntarily maintain full inspiration using only the minimal necessary effort. ļµ The breath-hold time must be 10Ā±2 s, a target easily achieved in the vast majority of subjects.
- 82. ļµ The expiratory maneuver must be smooth, unforced and without hesitation or interruption. ļµ The exhalation time for washout and discrete sample collection should not exceed 4 s. ļµ In subjects who require a longer expiratory time to provide an appropriate alveolar gas sample, the expiratory time must be noted in the test report.
- 83. Washout and sample collection maneuvers ļµ DLCO calculations are performed by analysis of discrete alveolar gas samples containing carbon monoxide and tracer gas. ļµ During expiration, a volume of gas must be expired to clear the total anatomical and equipment dead- space volume (VD) and then discarded before the alveolar sample is collected.
- 84. Collecting an alveolar gas sample before the point of dead-space washout will underestimate DLCO, while delaying sample collection beyond the point of dead-space washout will overestimate DLCO .
- 85. Maneuver intervals ļµ The 2005 ERS/ATS recommendations state that at least 4 min must be allowed between maneuvers to allow for adequate elimination of test gas from the lungs. ļµ The subject should remain seated during this interval.
- 86. ļµ In patients with airflow obstruction, a longer period (e.g. 10 min) should be considered. Several deep inspirations during this period may help to clear test gases more effectively.
- 87. Parameters SB Important parameters: ā¢ DLCOSB transfer factor for CO ā¢ VASB alveolar volume ā¢ KCOSB Krogh factor ( = DLCOSB / VASB ) ā¢ RVSB-He residual volume ā¢ TLCSB-He total lung capacity
- 88. Parameters SB Important parameters: HB hemoglobin DLCOSB,c transfer factor for CO, HB-corrected KCOSB,c Krogh factor, HB-corrected VIN inspired volume VDan anatomic dead space
- 89. Criteria for repeatability At least two acceptable DLCO measurements within 2 mL/minĀ·mmHg (0.67 mmol/minĀ·kPa) of each other
- 90. DL VA (He) # VA* VA (He) = VA* Ventilatory disturbance 1 2 3 4 5 6 Normal distrib. of ventilation Loss of lung units Loss of functioning lung units Inhomo- geneity of ventilation: additional reduction Anaemia Nonperfusion of ventilated alveoli Alveolar capillary membrane thickening VA: Alveolar enlargemet with loss of gas exchange surface, e.g. Emphysema VA DLCO / VA normal DLCO / VA Maldistribution of ventilation 1 Abnormal N2 washout 2 VA less than 80% of measured TLC 1 Fewer binding sites for CO in plasma 2 More plasma between alveolar air and binding sites VA* = VA (ITGV) or VA (RB) according to He-washin (FRC-rebreathing) No ventilatory disturbance Interpretation
- 91. DLCO Interpretation ļµ Low DLCO with normal spirometry ā Pulmonary Vascular Disease ā Anaemia - correct for Hb ā Early ILDs or early emphysema ā Chronic pulmonary embolism ā Primary pulmonary hypertension ļµ Low DLCO with restriction ā Interstitial Lung Disease ļµ Low DLCO with obstruction ā Emphysema ā COPD DO NOT USE DLCO/VA or KCO Often Normal in Interstitial Lung Disease
- 92. Possible Causes of High DLCo ļµ Intrapulmonary Haemorrhage ļµ Asthma ļµ Obesity ??? *DLCO is not always high in these patients