pulmonary function test
TRANSCRIPT
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Pulmonary Function Test
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DR S RAGHU M.D.,ASST PROF DEPT. T B & CDGUNTUR MEDICAL COLLEGEGUNTUR
Dr s. raghu m.d.,Associate professor Department of TB & CD R I M S medical collegeONGOLE
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•11,000 Lts air every day
• Patency of airways
VENTILATION
PERFUSION
• 11,000 Lts blood every day
• Lung Volume available
• Diffusibility across membrane
550 L of O2 consumes every day
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THE STETHOSCOPE
• Presence or absence of air entry
• Presence of airway narrowing
•Cavities in the Lung
BUT NO REAL OBJECTVE MEASURE OF LUNG FUNCTION
Laennec’s Stethoscope
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EARLY MEASURES OF LUNG FUNCTION
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How strong are your lungs?
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Volume of displaced water = Volume of air in balloon
(Stephen Hales, UK, 1727)
MEASURING LUNG VOLUMES WITH A BALLOON AND THE ARCHIMEDES
PRINCIPLE
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MEASURING LUNG VOLUMES WITH A BALLOON AND THE ARCHIMEDES PRINCIPLE
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DISCOVERY OF THE SPIROMETER
Sir John Hutchinson, 1846
Hutchinson J, The Lancet 1846; 1: 630-632
Vital capacity
- More sensitive to detect Tuberculosis than auscultation
- Can predict life expectancy. Suggested this test for routine life insurance cover.
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spirometry • John Hutchinson (1811-1861)—
inventor of the spirometer and originator of the term vital capacity (VC).
• “Spirometry is a physiological test that measures the volume of air an individual inhales or exhales as a function of time. (ATS / ERS 2005 ) .
• Simple, office-based
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• Volume Displacement-based
• Flow sensor-based
TYPES OF SPIROMETERS
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VOLUME DISPLACEMENT SPIROMETER
Water seal, Rolling Piston, Bellows
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Pneumotachograph(Changes in Pressure)
Anemometer(Changes in temperature)
Turbine(Changes in number of revolutions)
Ultrasonic(Ultrasound transit time analysis)
FLOW-SENSOR BASED SPIROMETER
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Introduction• The term encompasses a wide variety of
objective methods to assess lung function. They Provide quantifiable, reproducible measurement of lung function .
• They do not act alone.• They act only to support or exclude a
diagnosis.• A combination of a thorough history and
physical exam, as well as supporting laboratory data and imaging will help establish a diagnosis.
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The various components of pulmonary function tests
• Tests for ventilation : spirometry with helium dilution technique & body plethysmography.
• Tests for diffusion : diffusion capacity for CO (DLCO) .
• Tests for ventilation / perfusion : V/Q scan , nitrogen wash out test.
• Exercise testing :
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5. Arterial blood gas analysis
6. Bedside tests : Peak expiratory flow (PEF), trans-cutaneous O2
(SpO2) and CO2 (tCO2) monitoring
7. Tests for respiratory muscle function: PI max and PE max
8. Tests for respiratory center function: CO2 stimulation test
9. Tests for sleep related respiratory disorders: poly-
somnography (PSG)
However spirometry is the most basic and widely used method
of evaluating pulmonary functions
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Peak expiratory flow
(PEF) is measured by a maximal forced expiration through Peak flow meter
Correlates well with the FEV1 and is used as an estimate of airway caliber.
PEFR should be measured regularly in asthmatics to monitor response to therapy and disease control.
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Indications of spirometry
• Diagnostic• Monitoring• Disability/impairment evaluations
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Indications of spirometry
• Diagnostic• To evaluate symptoms, signs or abnormal
laboratory tests• To measure the effect of disease on
pulmonary function• To screen individuals at risk of having
pulmonary disease• To assess pre-operative risk• To assess prognosis• To assess health status before beginning
strenuous physical activity programmes.
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• Monitoring• To assess therapeutic intervention• To describe the course of diseases
that affect lung function• To monitor people exposed to
injurious agents• To monitor for adverse reactions to
drugs with known pulmonary toxicity.
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• Disability/impairment evaluations• To assess patients as part of a rehabilitation
programme• To assess risks as part of an insurance
evaluation• To assess individuals for legal reasons• Public health• Epidemiological surveys• Derivation of reference equations• Clinical research
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Acceptable & reproducible criteria
(ATS / ERS 2005 guidelines)• Acceptable criteria :
a.Free from artefacts ( cough , glottis closure )
b.Free from leaksc.Good starts ( extrapolation back from the
peak flow – “new time zero” should occur with in 5% / with in 150 ml.)
d.Acceptable exhalation : (adults – 6 secs & a plateau& in children < 10yrs – 3 secs )
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• Repeatability criteria :a. Three acceptable manoeuvers
( meeting above criteria ) b. The two largest FVC measurements
with in 150 ml of each otherc. The two largest FEV 1
measurements with in 150 ml of each other
Upto 8 manoeuvers should be performed until criteria met
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Performance of FVC maneuver
• Check spirometer calibration.• Explain test.• Prepare patient.
– Ask about smoking, recent illness, medication use, etc.
(adapted from ATS/ ERS 2005 ) .
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Performance of FVC maneuver (continued)
• Give instructions and demonstrate:– Show nose clip and mouthpiece.– Demonstrate position of head with
chin slightly elevated and neck somewhat extended.
– Inhale as much as possible, put mouthpiece in mouth (open circuit), exhale as hard and fast as possible.
– Give simple instructions.
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spirometry
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Information we get from a spirometer
• A spirometer can be used to measure the following:– FVC and its derivatives (such as FEV1, FEF
25-75%)– Forced inspiratory vital capacity (FIVC)– Peak expiratory flow rate– Maximum voluntary ventilation (MVV)– Slow VC– IC, IRV, and ERV– Pre and post bronchodilator studies
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The spirometric recording is represented in 2 forms:absolute values and graphic forms
– Flow-volume curve---flow meter measures flow rate in L/s upon exhalation; flow plotted as function of volume
– Classic spirogram---volume as a function of time
Vo
lum
e
FVC
FEV1
1 second
FET
Tim e
volume
flow
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Acceptable and Unacceptable Spirograms (from ATS, 1994)
cough
0 1
poor start
0
actual FVC
not at TLC priorto blow
0
Vol
ume
Time
good effort
0
Submaximal effort
0
actual FVC
premature term inationor glottic closure
0
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Spirometry Interpretation: So what
constitutes normal• Normal values vary and depend
on:–Height –Age –Gender EthnicitySpirometry can demonstrate two basic patterns of disorders
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1) obstructive pattern2) Restrictive pattern
Sometimes both patterns can be seen - mixed pattern
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Obstructive Lung Disease — Differential Diagnosis
Asthma
COPD - chronic bronchitis
- emphysema
Bronchiectasis
Bronchiolitis ( small airway diseases)
Upper airway obstruction
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Obstructive Pattern
• Decreased FEV1
• Decreased FVC • Decrease in FEV1>
decrease in FVC
• Decreased FEV1/FVC
- <80% predicted
• FEV1 used to follow severity in COPD
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• FEV1/FVC• Interpretation of absolute value:
>80 : Normal<79 : Abnormal
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Spirogram in obs.. Airway disea…
FEV1 / FVC < 80%
NormalObs.. Lung D isease
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Flow -volume loop in obs.. Airway diseases
Mild OLD
Moderate - Severe OLD
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Obstructive Pattern — Evaluation
Spirometry FEV1, FVC: decreased
FEV1/FVC: decreased (<80% predicted)
FV Loop “scooped”
Lung Volumes TLC, RV: increased
Bronchodilator responsiveness
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is the airway obstruction reversible?
Bronchodilator response
Asthma versus COPD
• Degree to which FEV1 improves with inhaled bronchodilators.
• Documents reversible airflow obstruction
• Significant response if:- FEV1 increases by 12% and >200ml
• Request if obstructive pattern on spirometry
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• FEV1 improvement by
• 12% and 200mL
with
• 200-400mcg Salbutamol by
inhaler
• or
• 40-80mcg Ipratropium
Bromide by inhalerReversible airway disease
diagnostic of asthmaSome COPD patients show
airway reversibility
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Staging Severity of Asthma
• Rule “60-80”• FEV1/FVC%<80%
Severity FEV1
Intermittent Normal
Mild persistent 80%
Moderate persistent 60-80%
Severe persistent 60%
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Bronchial provocation test
Useful for diagnosis of asthma in the setting of normal pulmonary function tests
Common agents:- Methacholine, Histamine, others
Diagnostic if: ≥20% decrease in FEV1
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Indications
• History suggestive of bronchospasm induced by environmental or occupational agent in the setting of normal PFT
• Cough Variant Asthma
Contraindications and Precautions• Baseline FEV1/FVC% <70• Recent upper respiratory tract
infection• Recent influenza vaccination• Recent administration of
bronchodilator• Ingestion of caffeine within 6 h
before testing• Cold-air breathing,
hyperventilation, exercise within 6 h before testing
• Recent acute myocardial infarction or cerebrovascular accident, uncontrolled hypertension, or known aortic aneurysm
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Restrictive Lung Disease —Differential Diagnosis
Pleural
Parenchymal
Chest wall
Neuromuscular
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Restrictive Pattern
Decreased FEV1
Decreased FVC
FEV1/FVC normal or increased
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Flow – volume loop & spirogram
Reduced flowMiniature curve/Witches hat
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Restrictive Pattern – Evaluation
Spirometry FVC, FEV1: decreased
FEV1/FVC: normal or increased
FV Loop “witch’s hat”/ miniature of curve
DLCO decreased
Lung Volumes TLC, RV: decreased
Muscle pressures may be important
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Grading of severity
(Restriction)Severity FVC %
predictedMild 60-70%
Moderate 50-60%
Severe 35-49%
Very Severe <35%
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Mixed type
• Low FEV1/ FVC – obstr• Reduced VC & TLC – restr• D/D
– Sarcoidosis– Interstitial fibrosis– Lobar pneumonia or large pl effusion in
COPD
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Contraindications• Hemoptysis of unknown origin, • Pneumothorax, • Unstable angina pectoris, • Recent myocardial infarction• Thoracic aneurysms, • Abdominal aneurysms, • Cerebral aneurysmsRecent abdominal or thoracic
surgical procedures• History of syncope associated with forced exhalation.• Recent eye surgery (increased intraocular pressure
during forced expiration)
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Activities that should preferably be avoided prior to lung function testing
• Smoking within at least 6 h of testing• Consuming alcohol within 24 h of testing• Performing vigorous exercise within 30 min of
testing• Wearing clothing that substantially restricts
full chest and abdominal expansion• Eating a large meal within 2 h of testing• Short acting B2 agonists & anticholinergics -4
hours• Long acting B2 agonists – 12 hr• Oral methylxanthine -12 hours
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Upper airway obstruction
• Upper airway is the segment of conducting airways that extends between the nose ( during nasopharyngeal breathing) or mouth during oropharyngeal breathing) and the carina.
• Fixed obstruction .• Variable intra-thoracic .• Variable extra-thoracic.
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Fixed upper airway obstruction
• Post-intubation stenosis• Large Goiters compressing the trachea• Endotracheal neoplasms• Stenosis of both main bronchi• Obstruction of the internal airway
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Variable extrathoracic upper airway obstruction
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Variable extrathoracic upper airway obstruction
• Bilateral vocal cord palsy• Unilateral vocal cord palsy• Adhesions of vocal cord• Vocal cord constriction• Obstructive sleep apnea• Burns of nasopharynx
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Variable intrathoracic upper airway obstruction
• Obstruction of lower trachea • Obstruction of a main bronchus
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Indices that show UAO in spirometry
• Fixed obstruction: FEF50%/FIF50%=1
FEV1/FIV1=1
• Variable extra thoracic:FEF50%/FIF50%>2
FEV1/FIV1>1
• Variable intra thoracic:FEF50%/FIF50%<1 ( even 0.3)
FEV1/FIV1<1
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F-V loop in Upper Airway Obstruction
normal
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EMPEY index
• It is the ratio of FEV1 to PEF• The best indicator in large airways
obstruction• Significant value is greater than 8 • The higher the index the more severe the
obstruction
• As a clinical screen in the absence of a flow-volume loop it is a reasonable guide to
the presence of UAO
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Lung volumes• Measurement:
- helium dilution method- nitrogen washout- body plethysmography
• Indications: - Diagnose restrictive component
- Differentiate chronic bronchitis from emphysema
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• 4 volumes: inspiratory reserve volume, tidal volume, expiratory reserve volume, and residual volume
• 2 or more volumes comprise a capacity.
• 4 capacites: vital capacity, inspiratory capacity, functional residual capacity, and total lung capacity
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• Functional Residual Capacity (FRC): – Sum of RV and ERV or
the volume of air in the lungs at end-expiratory tidal position
– Measured with multiple-breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography (not by spirometry)
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Lung volume patterns
• Obstructive - TLC > 120% predicted
- RV > 120% predicted
• Restrictive- TLC < 80% predicted- RV < 80% predicted
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Diffusion capacity
• Diffusing capacity of lungs for CO
• Measures ability of lungs to transport inhaled gas from alveoli to pulmonary capillaries
• Depends on:- alveolar—capillary membrane- hemoglobin concentration- cardiac output
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Alveolo – capillary membrane
• Gas diffuses across this alveolar-capillary barrier.
• This barrier is as thin as 0.3 μm in some places and has a surface area of 50-100 square meters!
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Normal lung parenchyma
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Decreased DLCO (<80% predicted)
• Obstructive lung disease
• Parenchymal disease
• Pulmonary vascular disease
• Anemia• Lung resection
Increased DLCO (>120-140% predicted)
• Asthma (or normal)
• Pulmonary hemorrhage
• Polycythemia
• Left to right intra cardiac shunts
• Obesity, exercise , supine po
Isolated DLCO decrease : primary PAH ,recurrent pulmonary emboli , obliterative -vasculopathy
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Emphysematous lung parenchyma
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Thickned interstitium in IPF
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DLCO - indications Differentiate asthma from emphysema
Evaluation and severity of restrictive lung disease
Early stages of pulmonary hypertension
• Expensive!
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70%
80%
MIXED OBSTRUCTIVE & RESTRICTIVE LUNG
DISEASE
RESTRICTIVE
LUNG DISEASE
OBSTRUCTIVE
LUNG DISEASESE
FEV1 / FVC %age
FVC(%age
predicted)
100%
100%
NORMAL
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Approach to interpreting commonly
performed PFT
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Pre-operative Evaluation For Surgery Other Than Pulmonary Resection
High Risk
Moderate Risk
75%
FEV1
FVC
50%
25%
75%
Low Risk
“Normal risk”
25% 50%
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Pre-operative Risk Assessment For Pulmonary Resection Surgery
• Calculate predicted post operative (ppo) FEV1
• For pneumonectomy,
predicted P.O FEV1 = preoperative FEV1 X % perfusion to remaining lung
(regional quantitative perfusion scans may be used)
• For lobectomy,
Predicted P.O. FEV1 =
preoperative FEV1 X no of lung segments remaing after resection /total no segments in both lungs
• Using “Rule of Five”• FEV1 > 1L makes patient suitable for any lung resection surgery
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Spirometry interpretation
?
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Case 1: Spirometry interpretation
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Diagnosis?
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Spirometry Report
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Severe obstruction with bronchodilator test positive
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1. Acceptable exhalation in children <10 years in spirometry
a. 3 Secs b. 6 Secs c. 9 Secs d. None
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2. Flow volume curve shows a. Poor effort b. bronchial
asthma c. Emphysema d. ILD
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3.Conditions that cause isolated decrease in DLCO
a. Pulmonary thromboembolism
b. Pulmonary hypertension c. Vasculitis d. Scleroderma e. Early ILD f. all
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Case 2
49 y/o Female Shortness of breath and nonproductive cough
FEV1/FVC: 85% FVC: 1.17 L (34%) FEV1: 1.00 L (37%) VC: 1.17 L (34%)a.Pulmonary fibrosis b. Br.asthmac.COPD C. None
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