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Pulmonary Function TestsPulmonary Function Tests

J.B. Handler, M.D.J.B. Handler, M.D.

Physician Assistant ProgramPhysician Assistant Program

University of New EnglandUniversity of New England

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AbbreviationsAbbreviations

ARDS- adult respiratory ARDS- adult respiratory distress syndromedistress syndrome

DLDLCOCO- diffusion capacity for - diffusion capacity for

carbon monoxidecarbon monoxide Ht- heightHt- height Wt- weightWt- weight SOB- short of breathSOB- short of breath Pred- predictedPred- predicted Meas- measuredMeas- measured PFT- pulmonary function testPFT- pulmonary function test ABG- arterial blood gasABG- arterial blood gas

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PFT’s: IndicationsPFT’s: Indications

Detect abnormalities and severity of lung function Detect abnormalities and severity of lung function in presence of disease.in presence of disease.– Monitor course of disease.Monitor course of disease.

Baseline pulmonary function prior to surgical, Baseline pulmonary function prior to surgical, medical or radiation therapy.medical or radiation therapy.

Differentiation of obstructive vs restrictive Differentiation of obstructive vs restrictive disease.disease.

Evaluate response to therapy, reversibility.Evaluate response to therapy, reversibility. Determine the preoperative risk of thoracic Determine the preoperative risk of thoracic

surgery.surgery.

Lung VolumesLung Volumes

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Lung VolumesLung Volumes

Tidal VolumeTidal Volume (TV): (TV): amount of air inhaled amount of air inhaled and exhaled at rest; and exhaled at rest; normal= 500-750 ml.normal= 500-750 ml.

Inspiratory Capacity Inspiratory Capacity (IC): beginning of (IC): beginning of normal inhalation to normal inhalation to maximum inspirationmaximum inspiration..

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IC

Lung VolumesLung Volumes

Inpiratory Reserve Inpiratory Reserve Volume (IRV): Volume Volume (IRV): Volume measured from “top” of measured from “top” of the TV (point of normal the TV (point of normal exhalation) to maximum exhalation) to maximum inspiration.inspiration.

Expiratory Reserve Expiratory Reserve Volume (ERV): Volume Volume (ERV): Volume measured from the measured from the “bottom” of the TV (point “bottom” of the TV (point of normal inhalation) to of normal inhalation) to maximum expiration.maximum expiration.

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Lung VolumesLung Volumes

Residual VolumeResidual Volume (RV): (RV): The amount of air left in The amount of air left in the lungs following full the lungs following full exhalation to the ERV..exhalation to the ERV..

Functional Residual Functional Residual Capacity (FRC) = ERV + Capacity (FRC) = ERV + RV: amount of gas RV: amount of gas remaining in the lungs at remaining in the lungs at the end of the tidal the end of the tidal volume.volume.

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Lung VolumesLung Volumes

Vital CapacityVital Capacity (VC): (VC): volume of air volume of air measured from full measured from full inhalation to inhalation to maximum exhalation maximum exhalation

Total Lung Capacity Total Lung Capacity (TLC): summation of (TLC): summation of the RV + vital the RV + vital capacitycapacity..

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SpirometerSpirometer

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SpirometrySpirometry

Forced Vital CapacityForced Vital Capacity (FVC)- Following full (FVC)- Following full inspiration, patient exhales as rapidly as possible, inspiration, patient exhales as rapidly as possible, forcibly and completely- volume of air exhaled is forcibly and completely- volume of air exhaled is measured; takes 5-6 seconds with measured; takes 5-6 seconds with majority in 1 majority in 1 second. second. Wide range of normal (see below).Wide range of normal (see below).

Volume obtained is expressed as a % of predicted Volume obtained is expressed as a % of predicted normal. Normals are based on volumes obtained normal. Normals are based on volumes obtained from thousands of healthy individuals of similar from thousands of healthy individuals of similar age, sex, ht and wt and race.age, sex, ht and wt and race. Normal Normal 80% of 80% of predicted.predicted.

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SpirometrySpirometry

FEVFEV11 :Amount of air forcibly exhaled in the 1st :Amount of air forcibly exhaled in the 1st

second of the FVC maneuver (second of the FVC maneuver (80% of FVC 80% of FVC volume). Normal volume). Normal 80% predicted; wide range of 80% predicted; wide range of normal (see below).normal (see below).

Volume obtained is expressed as a % of predicted Volume obtained is expressed as a % of predicted normal. Normals are based on volumes obtained normal. Normals are based on volumes obtained from thousands of healthy individuals of similar from thousands of healthy individuals of similar age, sex, ht and wt and race.age, sex, ht and wt and race. Normal Normal 80% of 80% of predicted.predicted.

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SpirometrySpirometry

FEVFEV11/FVC/FVC: Very important ratio; when reduced, : Very important ratio; when reduced,

helps identify presence of helps identify presence of obstructive diseaseobstructive disease. . Percentage reduction correlates with severity of Percentage reduction correlates with severity of obstruction; normal is 75-80obstruction; normal is 75-80++%. %. Normal (or Normal (or ) in ) in patients with restrictive disease.patients with restrictive disease.

Obstructive airway disease:Obstructive airway disease: Asthma, COPD Asthma, COPD.. Restrictive disease: Restrictive disease: Interstitial lung diseaseInterstitial lung disease, ,

kyphoscoliosis, pleural disease & others).kyphoscoliosis, pleural disease & others).

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Peak Expiratory Flow RatePeak Expiratory Flow Rate

Measured using simple hand held device.Measured using simple hand held device. Occurs within the first milliseconds of forced Occurs within the first milliseconds of forced

expiration and is a measure of maximum airflow expiration and is a measure of maximum airflow rate.rate.

Wide variation in normal ranges (age, ht and sex) Wide variation in normal ranges (age, ht and sex) adult males: 400-700L/minute.adult males: 400-700L/minute.adult females: 300-600L/minute.adult females: 300-600L/minute.

Effort dependent.Effort dependent. When abnormal- indicator of large airways When abnormal- indicator of large airways

obstruction.obstruction.

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Peak Expiratory Flow RatePeak Expiratory Flow Rate

Clinical use: Assessment of patients with Clinical use: Assessment of patients with asthma.asthma.

Patient determines “personal best” PEFR Patient determines “personal best” PEFR when most healthy, between asthma attacks.when most healthy, between asthma attacks.

PEFR often precedes symptoms.PEFR often precedes symptoms. Guide for responsiveness to meds, Guide for responsiveness to meds,

worsening of episodes, when to get help, worsening of episodes, when to get help, etc.etc.

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Diffusion CapacityDiffusion Capacity

Tests gas exchange across the alveolar-capillary Tests gas exchange across the alveolar-capillary membrane.membrane.

Per minute transfer of gas- Carbon Monoxide Per minute transfer of gas- Carbon Monoxide measured from alveoli to blood; measured from alveoli to blood; DLDLCO.CO.

Decreased if thickened alveolar capillary Decreased if thickened alveolar capillary membrane (pulmonary fibrosis, ARDS), or membrane (pulmonary fibrosis, ARDS), or following loss of surface area of the alveoli.following loss of surface area of the alveoli.

Most useful and decreased in interstitial lung Most useful and decreased in interstitial lung disease (lecture to follow).disease (lecture to follow).

Normal mean is 25-30 mL/min/mmHg.Normal mean is 25-30 mL/min/mmHg.

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Application of PFT’sApplication of PFT’s

Obstructive diseaseObstructive disease: asthma, COPD, : asthma, COPD, bronchiectasis.bronchiectasis.

Pattern: FVC normal or decreased mildly.Pattern: FVC normal or decreased mildly.FEVFEV11 decreased decreased; reduction reflects ; reduction reflects

severity.severity. FEVFEV11/FVC decreased- /FVC decreased- reflects severity.reflects severity.

Response to bronchodilator indicates Response to bronchodilator indicates reversible component.reversible component.

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Application of PFT’sApplication of PFT’s

Restrictive diseaseRestrictive disease: pulmonary fibrosis, : pulmonary fibrosis, sarcoidosis, kyphoscoliosis, neuromuscular sarcoidosis, kyphoscoliosis, neuromuscular disease, others.disease, others.

Pattern: Pattern: FVC decreasedFVC decreased, often markedly., often markedly.FEVFEV11 decreased decreased, often markedly., often markedly.

FEVFEV11/FVC normal /FVC normal or increased.or increased.

No response to bronchodilator.No response to bronchodilator.

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Problem SolvingProblem Solving

22 y.o male with cough, SOB, and wheezing.22 y.o male with cough, SOB, and wheezing. FVC – 3.63L (pred), 3.23L (meas), 89% predFVC – 3.63L (pred), 3.23L (meas), 89% pred FEVFEV11- 3.24L (pred), 2.24L (meas), 69% pred- 3.24L (pred), 2.24L (meas), 69% pred FEVFEV11/FVC 69% (meas)/FVC 69% (meas)

Post bronchodilator: Post bronchodilator: FVC- 3.23LFVC- 3.23L FEVFEV11- 2.70L (meas) 83% pred- 2.70L (meas) 83% pred FEVFEV11/FVC 84% (meas)/FVC 84% (meas) Interpretation: mild obstructive airways disease with post Interpretation: mild obstructive airways disease with post

bronchodilator reversibility.bronchodilator reversibility. Diagnosis: AsthmaDiagnosis: Asthma

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Problem SolvingProblem Solving

45 y.o black man with progressive shortness of 45 y.o black man with progressive shortness of breath.breath.

FVC- 3.05L (pred), 0.81L (meas), 22% predictedFVC- 3.05L (pred), 0.81L (meas), 22% predicted FEVFEV11- 2.9L (pred) 0.69L (meas), 24% predicted- 2.9L (pred) 0.69L (meas), 24% predicted

FEVFEV11/FVC 97% (meas)/FVC 97% (meas)

No change post bronchodilator No change post bronchodilator Interpretation: Severe restrictive disease; no Interpretation: Severe restrictive disease; no

evidence of airway obstruction.evidence of airway obstruction. Diagnosis: SarcoidosisDiagnosis: Sarcoidosis

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Pulse OximetryPulse Oximetry

Measures per cent oxygenation of Measures per cent oxygenation of hemoglobin (oxyhemoglobin).hemoglobin (oxyhemoglobin).

Non-invasive; measures absorption of light Non-invasive; measures absorption of light passing through tissue, then calculates Opassing through tissue, then calculates O22

saturation of arterial blood.saturation of arterial blood. Measured via electrodes placed on skin- Measured via electrodes placed on skin-

fingertips, ear lobes.fingertips, ear lobes. Normal = 97%Normal = 97%

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Arterial Blood Gas MeasurementArterial Blood Gas Measurement

Requires arterial punctureRequires arterial puncture pH of arterial bloodpH of arterial blood POPO22: partial pressure of oxygen (mmHg): partial pressure of oxygen (mmHg)

PCOPCO22: partial pressure of carbon dioxide (mmHg): partial pressure of carbon dioxide (mmHg)

HCOHCO33: calculated- bicarbonate; proportional to : calculated- bicarbonate; proportional to

dissolved COdissolved CO22 in blood. in blood.

OO22-Hemoglobin Dissociation-Hemoglobin Dissociation

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