Pulmonary function test

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Pulmonary Function Test

Transcript of Pulmonary function test

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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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