Pulmonary Function Testing

PULM

ONARY FU

NCTION

TESTI

NG

EDW

ARD OM

RON MD, M

PH, FCCP

PULMONARY S

ERVIC

ES

LEXICON OF PULMONARY FUNCTION TESTS (PFT’S)

Spirometry (measurement of flow) Bronchodilator response Bronchoprovocation (methacholine, histamine, exercise)

Measurement of lung volumes Plethysmography Gas dilution

Gas exchange DLCO Arterial blood gas analysis

LEXICON OF PULMONARY FUNCTION TESTS (PFT’S)

Respiratory muscle strength Pi-max; Pe-max; MVV; Others

Cardiopulmonary exercise testing (CPET) Determines area of performance limitation

Exhaled monoxides Nitrous oxide; Carbon monoxide

DyspneaPre-op evaluationGeneralPre-lung resection

Abnormal radiograph

Follow pulmonary disease & therapy

Fitness for employment, recreation

Work compensation & disability

Surveillance of occupational lung dx

Aid in dx of lung disease

Rotating through pulmonary

INDICATIONS FOR PFT’S

PHYSIOLOGY AND PATHOPHYSIOLOGY

Chest Skeleton, and Muscles of Inspiration and Expiration. Elastic Force of chest is to EXPAND OUTWARD

Chest Skeleton, and Muscles of Inspiration and Expiration. Elastic Force of chest is to EXPAND OUTWARD


Movement of chest in breathing. Mobility of thoracic cage is reduced with age, neuromuscular disease, arthritis, kyphoscoliosis, others.

Movement of chest in breathing. Mobility of thoracic cage is reduced with age, neuromuscular disease, arthritis, kyphoscoliosis, others.


Green bands represent ELASTIN

Tendency of normal lung is to CONTRACT INWARD (COLLAPSE)

DECREASED ELASTICITY – RELATIVE INCREASE IN VOLUME

INCREASED ELASTICITY – RELATIVE DECREASE IN VOLUME

Green bands represent ELASTIN

Tendency of normal lung is to CONTRACT INWARD (COLLAPSE)

DECREASED ELASTICITY – RELATIVE INCREASE IN VOLUME

INCREASED ELASTICITY – RELATIVE DECREASE IN VOLUME

PHYSIOLOGY AND PATHOPHYSIOLOGYDETERMINATION OF VOLUME

Balance between OUTWARD ELASTIC FORCE OF CHEST

and

INWARD ELASTIC FORCE OF LUNGS that

DETERMINES LUNG VOLUME

Held together by intact pleural space

Balance between OUTWARD ELASTIC FORCE OF CHEST

and

INWARD ELASTIC FORCE OF LUNGS that

DETERMINES LUNG VOLUME

Held together by intact pleural space

PHYSIOLOGY AND PATHOPHYSIOLOGYDETERMINATION OF VOLUME

ZEN POINT ZEN POINT

Balance of forces at various lung volumes. FUNCTIONAL RESIDUAL CAPACITY is point where no muscle force is added; resultant lung volume is balance of elastic forces of chest wall and lung

Balance of forces at various lung volumes. FUNCTIONAL RESIDUAL CAPACITY is point where no muscle force is added; resultant lung volume is balance of elastic forces of chest wall and lung

PHYSIOLOGY AND PATHOPHYSIOLOGYCAUSES OF RESTRICTION

Increased lung elasticity Interstitial fibrosis, pneumonitis,edema, pneumonia

Airspace filling processes Edema, pneumonia, blood, protein, tumor, BOOP

Pleural disease and pleural space filling Effusions, pleural fibrosis, tumors, inflammatory rinds

Decreased Chest wall elasticity/compliance Edema, burns, tumors, kyphoscoliosis, prolonged immobility, severe obesity,

arthritis.

PHYSIOLOGY AND PATHOPHYSIOLOGYCAUSES OF RESTRICTION – CONT.

Neuromuscular diseases Paralysis, ALS, Guillian Barre, MS, spinal disease, SLE shrinking lung

syndrome, polymyositis, etc. Posts general anesthesia, especially abdominal surgery

Airspace removing (lung resection).

Pulmonary vascular Chronic thromboembolic disease

PHYSIOLOGY AND PATHOPHYSIOLOGYREDUCED VOLUME = RESTRICTION

PHYSIOLOGY AND PATHOPHYSIOLOGYAIRWAY PHYSIOLOGY

Bronchi are tethered by elastin in interstium. Higher lung volumes and increased elastic recoil will increase diameter of airways. Decreased elastin will allow airways to flop closed.

Bronchi are tethered by elastin in interstium. Higher lung volumes and increased elastic recoil will increase diameter of airways. Decreased elastin will allow airways to flop closed.


Airway resistance is inversely proportional to lung volume

Airway resistance is inversely proportional to lung volume

Flow rate higher at higher lung volumes and with increasing effort. At low lung volumes flow rate doesn’t change with increased effort

Flow rate higher at higher lung volumes and with increasing effort. At low lung volumes flow rate doesn’t change with increased effort


Curve A is maximal effort:

Curve B is initially slow than forced

Curve C is sub maximal effort throughout.

Note that towards Residual Volume, flow cannot be increased with increasing effort

Curve A is maximal effort:

Curve B is initially slow than forced

Curve C is sub maximal effort throughout.

Note that towards Residual Volume, flow cannot be increased with increasing effort


CONCEPT OF EQUAL PRESSURE POINT: Point of airway collapse by resulting pleural pressure. As lung volume is reduced on exhalation, EPP moves toward periphery, so lung cannot collapse with exhalation. Increasing pleural pressure (effort) does not change point for given volume. Cartilaginous rings in proximal airways prevent collapse at high lung volumes. Tracheomalacia results in early obstruction to flow.

CONCEPT OF EQUAL PRESSURE POINT: Point of airway collapse by resulting pleural pressure. As lung volume is reduced on exhalation, EPP moves toward periphery, so lung cannot collapse with exhalation. Increasing pleural pressure (effort) does not change point for given volume. Cartilaginous rings in proximal airways prevent collapse at high lung volumes. Tracheomalacia results in early obstruction to flow.


Equal Pressure Point maintains lung volume even at residual volume (RV) (CXR on right)

Equal Pressure Point maintains lung volume even at residual volume (RV) (CXR on right)

Pleural Pressure Gradient with gravity accounts for difference in ventilation and alveolar volume

Pleural Pressure Gradient with gravity accounts for difference in ventilation and alveolar volume

PHYSIOLOGY AND PATHOPHYSIOLOGYOBSTRUCTION AND HYPERINFLATION

In emphysema, loss of elastic recoil & loss of airway tethering

In emphysema, loss of elastic recoil & loss of airway tethering

Early distal airway closure at high lung volume. PEEP maneuver to increase airway pressure

Early distal airway closure at high lung volume. PEEP maneuver to increase airway pressure


REASONS FOR HYPERINFLATION: 1) Loss of lung elastic force inward shifts equalibrium to higher volume. 2) Early distal airway closure causes air trapping. 3) Patients attempt breathing at higher lung volume to maintain airway patency. Chest becomes fixed (barrel chest).

REASONS FOR HYPERINFLATION: 1) Loss of lung elastic force inward shifts equalibrium to higher volume. 2) Early distal airway closure causes air trapping. 3) Patients attempt breathing at higher lung volume to maintain airway patency. Chest becomes fixed (barrel chest).


Mechanisms of obstructionMechanisms of obstruction Obstruction and air trappingObstruction and air trapping

ASTHMAASTHMA

Emphysema and Bronchitis:Emphysema and Bronchitis:

DISEASES OF OBSTRUCTION

COPD Asthma, Emphysema, Chronic bronchitis, mixed

Acute bronchitis

Bronchiolitis obliterans

Bronchocentric granulomatosis

DISEASES TYPICALLY WITH MIXED OBSTRUCTION AND RESTRICTIONSarcoidosis

Lymphangiomyomatosis

Langerhans Cell Granulomatosis

CHF

Pneumonia

Lung removal with obstruction in remaining lung.

PULMONARY FUNCTION TESTINGVOLUMES AND CAPACITIES

Capacities are made up of two or more Volumes

Capacities are made up of two or more Volumes

Note that Residual Volume, and hence any Capacity including it, cannot be measured by spirometry alone.

Note that Residual Volume, and hence any Capacity including it, cannot be measured by spirometry alone.

PULMONARY FUNCTION TESTINGVOLUMES AND CAPACITIES

Total Lung Capacity (TLC),

Functional Residual Capacity (FRC), &

Residual Volume (RV)

For normal and disease states.

Total Lung Capacity (TLC),

Functional Residual Capacity (FRC), &

Residual Volume (RV)

For normal and disease states.

PULMONARY FUNCTION TESTING SPIROMETRY

Forced Vital Capacity Maneuver: Seated patient. Blows out forcefully from TLC and carries out for > 6 seconds. Spirometer measures FLOW VOLUME and FLOW RATE

Forced Vital Capacity Maneuver: Seated patient. Blows out forcefully from TLC and carries out for > 6 seconds. Spirometer measures FLOW VOLUME and FLOW RATE


Normal Volume-Time curve above; note leveling. ATS requirement is to carry out for minimum six seconds.

Normal Flow-Volume to right; note rapid rise, convex curve down, round inspiratory limb.

Normal Volume-Time curve above; note leveling. ATS requirement is to carry out for minimum six seconds.

Normal Flow-Volume to right; note rapid rise, convex curve down, round inspiratory limb.


Fev1; litres & % predicted.

FVC; litres & % predicted.

Fev1/FVC >> ABSOLUTE RATIO OF VOLUMES (not % predicted)

Fev1/FVC nl ~.80 (.70-.90)

Reduced Fev1/FVC is sine qua non of obstruction

Fev1; litres & % predicted.

FVC; litres & % predicted.

Fev1/FVC >> ABSOLUTE RATIO OF VOLUMES (not % predicted)

Fev1/FVC nl ~.80 (.70-.90)

Reduced Fev1/FVC is sine qua non of obstruction

PULMONARY FUNCTION TESTSPREDICTED VALUES

Studies of large number of normals in a population – Caucasian, African, Asian

Bell shaped curve

Variables taken into account Race, height, age, gender --Not weight

“Normal” generally considered (80-120%)

Applies to Spirometry, Volumes, DLCO

PULMONARY FUNCTION TESTSPREDICTED VALUES CONT.Problems: Not all populations represented precisely – eg, Filipinos are classified

as “Asian” Some normals can fit out of bell curve

FORCED VITAL CAPACITY MANEUVER

Artificial maneuver

Standard means of measuring function

Very reproducible with coaching and observation

Learning phenomenon occurs

Poor cooperation or malingering can be detected by comparison of flow volume loops

FEV1 AND FEV1/FVC

Fev1 single most important value in following and prognosticating COPD and preoperative evaluation for lung resection

Fev1/FVC Down in obstruction May be supranormal, normal, or down in restriction, depending on pathology.

Pure interstitial fibrosis- up Mixed restriction / obstruction – normal Lung removal with existing lung obstructed – down

SPIROMETRYPATTERNS IN FLOW & FLOW VOLUME

Mild obstructionMild obstruction Mod obstructionMod obstruction Severe obstructionSevere obstruction


ObstructionObstruction


FVC vs. Slow VC In severe obstruction FVC can be reduced despite hyperinflation because of early airway closure

Comparison with Slow VC (unforced, un-timed maneuver) can show large difference

ObstructionObstruction


Fixed ObstructionFixed Obstruction Variable Extrathoracic Obstruction:

Variable Extrathoracic Obstruction:

Variable Intrathoracic Obstruction

Variable Intrathoracic Obstruction


Typical Spirometry:

FVC = 65% predicted

Fev1 = 65% predicted

Fev1/FVC = .90

Typical Spirometry:

FVC = 65% predicted

Fev1 = 65% predicted

Fev1/FVC = .90Mild to Moderate Restriction

Mild to Moderate Restriction

Severe Restriction

Severe Restriction


Fev1 90%

FVC 110%

Fev1/FVC .65

Fev1 90%

FVC 110%

Fev1/FVC .65

OBSTRUCTIONOBSTRUCTION

Fev1 65%

FVC 82%

Fev1/FVC .52

Fev1 65%

FVC 82%

Fev1/FVC .52

Fev1 30%

FVC 66%

Fev1/FVC .45

Fev1 30%

FVC 66%

Fev1/FVC .45

SPIROMETRYBRONCHODILATOR RESPONSE

Albuterol by MDI/spacer given after baseline spirometry reveals obstruction.

ATS criteria; Increase in Fev1 or FVC by 12% AND 200cc.

Pts come to test BD free

No response does not predict lack of benefit

Can have partial responses, even in asthma

SPIROMETRYBRONCHOPROVOCATION

Used to prove or disprove bronchial hyper responsiveness (BH) – asthma or bronchial dysfunction

Nonselective Direct StimulantsHistamine – systemic side effects undesirableMethacholine – most commonly usedNonselective Indirect StimulantsAMP - may be more specific for airway inflammation than methacholine – causes release of histamine from mast cells

Cold air, exercise, hyperventilation, nonisotonic solutions

Selective StimulantsNSAIDS, allergens, foods and food additives


Methacholine most standardized and common Logarithmically increasing doses inhaled per strict protocol. Drop in Fev1 by

20% considered positive Grades of certainty based on how much required to effect drop

False negative response Bronchodilators, anticholinergics, anti-leukotrienes, theophylline or caffeine,

steroids, can blunt response


Should not be a screening tool

“Asthma” diagnosis is clinical; demonstration of BH is one piece of puzzle - Other entities cause BH

Absolute contraindications include Severe airflow limitation, recent MI, severe hypertension, aortic aneurysm

Relative Moderate airflow limitation, pregnancy, lactation use of cholinesterase inhibitors

of Myasthenia Gravis

SPIROMETRY QUESTIONS

81 y/o caucasian male

Fev1 2.04 litres 68%

FVC 2.56 litres 65%

Fev1/FVC .8

81 y/o caucasian male

Fev1 2.04 litres 68%

FVC 2.56 litres 65%

Fev1/FVC .8

29 y/o Caucasian male

Fev1 1.91 44%

FVC 3.04 56%

Fev1/FVC .63

29 y/o Caucasian male

Fev1 1.91 44%

FVC 3.04 56%

Fev1/FVC .63

MEASUREMENT OF LUNG VOLUMES

Recall that spirometry can only measure volume from RV to TLC. Volume below RV is not “seen” by spirometry.

Recall that spirometry can only measure volume from RV to TLC. Volume below RV is not “seen” by spirometry.


Two Common Methods of Measuring FRC

Two Common Methods of Measuring FRC

Helium DilutionHelium Dilution PlethysmographyPlethysmography


HELIUM DILUTION

Pt breathes at tidal volume for several minutes. Known initial volume and concentration of Helium before and after equilibration.

Lastly,

Pt inspires from FRC to TLC which is added to FRC measurement

HELIUM DILUTION

Pt breathes at tidal volume for several minutes. Known initial volume and concentration of Helium before and after equilibration.

Lastly,

Pt inspires from FRC to TLC which is added to FRC measurement

Will seriously underestimate volume in obstruction, especially bullous lung disease.

Will seriously underestimate volume in obstruction, especially bullous lung disease.


BODY PLETHYSMOGRAPHY

BOYLE’S LAW

P1V1 = P2V2

At FRC, shutter closes at mouth and measures pressure at mouth and at box during slow panting against shutter

BODY PLETHYSMOGRAPHY

BOYLE’S LAW

P1V1 = P2V2

At FRC, shutter closes at mouth and measures pressure at mouth and at box during slow panting against shutter

Makes assumption that pressure at mouth equals pressure in alveoli, which may not be true in obstructed patients

Makes assumption that pressure at mouth equals pressure in alveoli, which may not be true in obstructed patients


A large difference between plethysmography and helium dilution would suggest “non-communicating airspace”

Valuable to measure FRC when spirometry yields a question regarding volumes

Often difficult for elderly, severely obstructed, dyspneic

Nomogram algorithm for separating obstructive from restrictive defects

Nomogram algorithm for separating obstructive from restrictive defects

CARBON MONOXIDE DIFFUSING CAPACITY (DLCO)

Known concentration of CO is inhaled in single breath and held. CO binds avidly to hemoglobin and uptake is measured. Not truly diffusion-limited and not true “capacity”

Known concentration of CO is inhaled in single breath and held. CO binds avidly to hemoglobin and uptake is measured. Not truly diffusion-limited and not true “capacity”

Better term is “Transfer Factor”

Better term is “Transfer Factor”

DECREASED DLCOLoss of pulmonary vasculature PE, acute and chronic Emphysema Interstitial lung disease Lung resection

SmokingCarbon Monoxide poisoning

Acute lung diseaseAnemia*

INCREASED DLCOPolycythemia*Alveolar hemorrhage, acute and chronic

Mild bronchitis, mild asthma

CARBON MONOXIDE DIFFUSING CAPACITY (DLCO)

* DLCO can be “corrected” for hemoglobin if value is known

* DLCO can be “corrected” for hemoglobin if value is known

CARDIOPULMONARY EXERCISE TESTING

Used for evaluation of exercise limitation

Cardiac PulmonaryPoor conditioningHyperventilation syndromes

Vocal cord dysfunction

Pulmonary Function Testing

Health & Medicine

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