Transcript Pulmonary Function Testing The Basics of Interpretation

Mohammad Tohidi M.D.
Professor of Internal Medicine
Department of Pulmonary Medicine
Ghaem Hospital MUMS Mashhad IRAN
PFTs
Objectives
 Identify the components of PFTs
 Describe the indications
 Develop a stepwise approach to interpretation
 Recognize common patterns
 Apply this information to patient care
Pulmonary function tests (PFTs)
• Pulmonary function testing is a valuable
tool for evaluating the respiratory system
• comparing the measured values for
pulmonary function tests obtained on a
patient at any particular point with normal
values derived from population studies.
• The percentage of predicted normal is used
to grade the severity of the abnormality.
Pulmonary Function Tests
• Evaluates 1 or more major
aspects of the respiratory
system
PFTs
• Four lung components include :
The airways (large and small),
Lung parenchyma (alveoli, interstitium),
Pulmonary vasculature, and
The bellows-pump mechanism
PFTs
• PFTs can include: simple screening
spirometry, Flow Volume Loop
Formal lung volume measurement,
Bronchoprovocation testing
Diffusing capacity for carbon monoxide,
and Arterial blood gases.
Measurement of maximal respiratory
pressures
• These studies may collectively be referred
to as a complete pulmonary function
survey.
Spirometry
• Measurement of the pattern of air
movement into and out of the lungs during
controlled ventilatory maneuvers.
• Often done as a maximal expiratory
maneuver
Importance
• Patients and physicians have inaccurate
perceptions of severity of airflow
obstruction and/or severity of lung disease
by physical exam
• Provides objective evidence in identifying
patterns of disease
Spirometry
 Simple, office-based
 Measures flow, volumes
 Volume vs. Time
 Can determine:
- Forced expiratory volume in one second (FEV1)
- Forced vital capacity (FVC)
- FEV1/FVC
- Forced expiratory flow 25%-75% (FEF25-75)
Spirometry
the most readily available
most useful pulmonary function test
It takes ten to 15 minutes
carries no risk
Spirometry
• Spirometry is the most commonly used
lung function screening study.
• should be the clinician's first option
• other studies being reserved for specific
indications
• easily performed
• in the ambulatory setting, physician's
office, emergency department, or inpatient
setting.
Patient care/preparations
• Two choices are available with respect to
bronchodilator and medication use prior to
testing. Patients may withhold oral and
inhaled bronchodilators to establish
baseline lung function and evaluate
maximum bronchodilator response, or they
may continue taking medication as
prescribed. If medications are withheld, a
risk of exacerbation of bronchial spasm
exists.
Spirometry
• The slow vital capacity (SVC) can also be
measured with spirometers
collect data for at least 30 seconds
when airways obstruction is present, the
forced vital capacity (FVC) is reduced and
slow vital capacity (SVC) may be normal
Spirometry
• When the slow or forced vital capacity is
within the normal range:
No significant restrictive disorder .
No need to measure static lung volumes
(residual volume and total lung capacity).
Indications — Diagnosis
 Evaluation of signs and symptoms
- SOB, exertional dyspnea, chronic cough
 Screening at-risk populations
 Monitoring pulmonary drug toxicity
 Abnormal study
- CXR, EKG, ABG, hemoglobin
 Preoperative assessment
Indications — Diagnosis
 Evaluation of signs and symptoms
- SOB, exertional dyspnea, chronic cough
 Screening at-risk populations
Smokers > 45yo
 Monitoring pulmonary drug(former
toxicity & current)
 Abnormal study
- CXR, EKG, ABG, hemoglobin
 Preoperative assessment
Indications — Diagnosis
 Evaluation of signs and symptoms
- SOB, exertional dyspnea, chronic cough
 Screening at-risk populations
 Evaluation of occupational symptoms
 Monitoring pulmonary drug toxicity
 Abnormal study
- CXR, EKG, ABG, hemoglobin
 Preoperative assessment
Indications — Prognostic
■ Assess severity
■ Follow response to therapy
■ Determine further treatment goals
■ Referral for surgery
■ Disability
Contraindications for
spirometry
• Relative contraindications for spirometry
include hemoptysis of unknown origin,
pneumothorax, unstable angina pectoris,
recent myocardial infarction, thoracic
aneurysms, abdominal aneurysms, cerebral
aneurysms, recent eye surgery (increased
intraocular pressure during forced expiration),
recent abdominal or thoracic surgical
procedures, and patients with a history of
syncope associated with forced exhalation
Spirometry
• Spirometry requires a voluntary maneuver
in which a seated patient inhales
maximally from tidal respiration to total
lung capacity and then rapidly exhales to
the fullest extent until no further volume is
exhaled at residual volume
Spirometry
• The maneuver may be performed in a
forceful manner to generate a forced vital
capacity (FVC) or in a more relaxed
manner to generate a slow vital capacity
(SVC).
• In normal persons, the inspiratory vital
capacity, the expiratory SVC, and
expiratory FVC are essentially equal.
However, in patients with obstructive
airways disease, the expiratory SVC is
generally higher than the FVC.
Interpretation of spirometry
results(1)
• should begin with an
assessment of test quality.
to inspect the graphic data
(the volume-time curve and the
flow-volume loop)
Interpretation of spirometry
results(2)
• to ascertain whether the study
meets certain well-defined
acceptability and
reproducibility standards
acceptable spirometry
(ATS)
• 1) minimal hesitation at the start of the
forced expiration (extrapolated volume
(EV) <5% of the FVC or 0.15 L, whichever
is larger
• Time to PEF is <120 ms (optional until
further information is available)
(2) no cough in the first second of forced
exhalation,
• 3) meets 1 of 3 criteria that define a valid
end-of-test
Valid end-of-test
• (a) smooth curvilinear rise of the volumetime tracing to a plateau of at least 1second duration;
(b) if a test fails to exhibit an expiratory
plateau, a forced expiratory time (FET) of
15 seconds; or
(c) when the patient cannot or should not
continue forced exhalation for valid
medical reasons.
• If both of these criteria are not met,
continue testing until: Both of the criteria
are met with analysis of additional
acceptable spirograms or
• A total of eight tests have been
performed or
• Save a minimum of three best maneuvers
Acceptability Criteria
•
•
•
•
•
Good start of test
No coughing
No variable flow
No early termination
Reproducibility
The volume-time tracing
• The volume-time tracing is most useful in
assessing whether the end-of-test criteria
have been met
Spirometry
Flow-volume loop
• the flow-volume loop is most
valuable in evaluating the
start-of-test criteria.
Flow-Volume Loop
Ruppel GL. Manual of Pulmonary Function Testing, 8th ed.,
Mosby 2003
Repeatability Criteria
• After three acceptable spirograms have
been obtained, apply the following tests.
Are the two largest FVCs within 0.2 L of
each other?
• Are the two largest FEV1s within 0.2 L of
each other?
• If both of these criteria are met, the test
session may be concluded
• Well trained technician
Lung Volumes
Lung Volumes
• 4 Volumes
• 4 Capacities
IRV
IC
VC
TV
TLC
ERV
FRC
RV
RV
– Sum of 2 or
more lung
volumes
Spirometry
Lung Factors Affecting
Spirometry
• Mechanical properties
• Resistive elements
Mechanical Properties
• Compliance
– Describes the stiffness of the lungs
– Change in volume over the change in
pressure
• Elastic recoil
– The tendency of the lung to return to it’s
resting state
– A lung that is fully stretched has more elastic
recoil and thus larger maximal flows
Resistive Properties
• Determined by airway caliber
• Affected by
– Lung volume
– Bronchial smooth muscles
– Airway collapsibility
Factors That Affect Lung Volumes
•
•
•
•
•
•
Age
Sex
Height
Weight
Race
Disease
Technique
• Have patient seated comfortably
• Closed-circuit technique
– Place nose clip on
– Have patient breathe on mouthpiece
– Have patient take a deep breath as fast as
possible
– Blow out as hard as they can until you tell
them to stop
Terminology
• Forced vital capacity
(FVC):
– Total volume of air that can
be exhaled forcefully from
TLC
– The majority of FVC can be
exhaled in <3 seconds in
normal people, but often is
much more prolonged in
obstructive diseases
– Measured in liters (L)
FVC
• Interpretation of % predicted:
–
–
–
–
80-120%
70-79%
50%-69%
<50%
Normal
Mild reduction
Moderate reduction
Severe reduction
FV
Terminology
• Forced expiratory volume
in 1 second: (FEV1)
– Volume of air forcefully
expired from full inflation
(TLC) in the first second
– Measured in liters (L)
– Normal people can exhale
more than 75-80% of their
FVC in the first second;
thus the FEV1/FVC can
be utilized to characterize
lung disease
FEV1
• Interpretation of % predicted:
–
–
–
–
>75%
60%-75%
50-59%
<49%
Normal
Mild obstruction
Moderate obstruction
Severe obstruction
FE
F
Terminology
• Forced expiratory flow 2575% (FEF25-75)
– Mean forced expiratory flow
during middle half of FVC
– Measured in L/sec
– May reflect effort
independent expiration and
the status of the small
airways
– Highly variable
– Depends heavily on FVC
FEF25-75
• Interpretation of % predicted:
– >60%
– 40-60%
– 20-40%
– <10%
Normal
Mild obstruction
Moderate obstruction
Severe obstruction
Flow-Volume Loop
• Illustrates maximum
expiratory and
inspiratory flowvolume curves
• Useful to help
characterize disease
states (e.g.
obstructive vs.
restrictive)
Ruppel GL. Manual of Pulmonary Function Testing, 8th ed.,
Mosby 2003
Categories of Disease
• Obstructive
• Restrictive
• Mixed
Obstructive Disorders
• Characterized by a
limitation of expiratory
airflow
– Examples: asthma,
COPD
• Decreased: FEV1,
FEF25-75, FEV1/FVC
ratio (<0.8)
• Increased or Normal:
TLC
Spirometry in Obstructive
Disease
• Slow rise in upstroke
• May not reach
plateau
Restrictive Lung Disease
• Characterized by diminished lung
volume due to:
– change in alteration in lung
parenchyma (interstitial lung
disease)
– disease of pleura, chest wall
(e.g. scoliosis), or
neuromuscular apparatus (e.g.
muscular dystrophy)
• Decreased TLC, FVC
• Normal or increased: FEV1/FVC
ratio
Restrictive Disease
• Rapid upstroke as
in normal
spirometry
• Plateau volume is
low
Large Airway Obstruction
• Characterized by a
truncated
inspiratory or
expiratory loop
Normal Spirometry
Obstructive Pattern
■ Decreased FEV1
■ Decreased FVC
■ Decreased FEV1/FVC
- <70% predicted
■ FEV1 used to follow severity in COPD
Obstructive Lung Disease —
Differential Diagnosis
 Asthma
 COPD
- chronic bronchitis
- emphysema
 Bronchiectasis
 Bronchiolitis
 Upper airway obstruction
Restrictive Pattern
 Decreased FEV1
 Decreased FVC
 FEV1/FVC normal or increased
Restrictive Lung Disease —
Differential Diagnosis
 Pleural
 Parenchymal
 Chest wall
 Neuromuscular
Spirometry Patterns
Bronchodilator Response
 Degree to which FEV1 improves with inhaled
bronchodilator
 Documents reversible airflow obstruction
 Significant response if:
- FEV1 increases by 12% and >200ml
 Request if obstructive pattern on spirometry
Flow Volume Loop
 “Spirogram”
 Measures forced inspiratory and expiratory
flow rate
 Augments spirometry results
 Indications: evaluation of upper airway
obstruction (stridor, unexplained dyspnea)
Flow Volume Loop
Upper Airway Obstruction
 Variable intrathoracic obstruction
 Variable extrathoracic obstruction
 Fixed obstruction
Upper Airway Obstruction
Lung Volumes
 Measurement:
- helium
- nitrogen washout
- body plethsmography
 Indications:
- Diagnose restrictive component
- Differentiate chronic bronchitis from
emphysema
Pulmonary Function Testing
The Basics of Interpretation
Jennifer Hale, M.D.
Valley Baptist Family Practice Residency
Lung Volumes – Patterns
 Obstructive
- TLC > 120% predicted
- RV > 120% predicted
 Restrictive
- TLC < 80% predicted
- RV < 80% predicted
Diffusing 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
Diffusing Capacity
 Decreased DLCO
(<80% predicted)
 Increased DLCO
(>120-140% predicted)
 Obstructive lung disease
 Asthma (or normal)
 Parenchymal disease
 Pulmonary hemorrhage
 Pulmonary vascular
disease
 Polycythemia
 Anemia
 Left to right shunt
DLCO — Indications
 Differentiate asthma from emphysema
 Evaluation and severity of restrictive lung
disease
 Early stages of pulmonary hypertension
 Expensive!
Case 1
CC/HPI: A 36yo WM, nonsmoker, presents to your
clinic with c/o episodic cough for 6mo. Also
reports occasional wheezing and dyspnea with
exertion during softball practice.
Exam: Heart RRR, no murmurs; Lungs CTAB, no
labored breathing
Based on your exam and a thorough review of
systems, you suspect asthma and decide to
order spirometry for further evaluation.
Continued…
PFTs: FEV1
FEV1/FVC
86% predicted
82% predicted
Flow Volume Loop: normal inspiratory and
expiratory pattern
You still suspect asthma. What is your next
step in the workup of this patient?
Bronchoprovocation
 Useful for diagnosis of asthma in the
setting of normal pulmonary function tests
 Common agents:
- Methacholine, Histamine, others
 Diagnostic if: ≥20% decrease in FEV1
Continued…
SYMPTOMS
↓
PFTs
↓
OBSTRUCTION?
↓
↓
NO
YES
↓
↓
BRONCHOPROVOCATION
TREAT
↓
↓
Obstruction?
No Obstruction?
TREAT
Other Diagnosis
PFT Interpretation Strategy
 What is the clinical question?
 What is “normal”?
 Did the test meet American Thoracic Society
(ATS) criteria?
 Don’t forget (or ignore) the flow volume loop!
Obstructive Pattern — Evaluation
 Spirometry
 FEV1, FVC:
decreased
 FEV1/FVC:
decreased
 FV Loop
“scooped”
 Lung Volumes
 TLC, RV:
increased
 Bronchodilator responsiveness
(<70% predicted)
Restrictive Pattern – Evaluation
 Spirometry
 FVC, FEV1:
 FEV1/FVC:
decreased
normal or increased
 FV Loop
“witch’s hat”
 DLCO
decreased
 Lung Volumes
 TLC, RV:
decreased
 Muscle pressures may be important
PFT Patterns
 Emphysema
 Chronic Bronchitis
 FEV1/FVC <70%
 FEV1/FVC <70%
 “Scooped” FV curve
 “Scooped” FV curve
 TLC increased
 TLC normal
 Increased compliance
 Normal compliance
 DLCO decreased
 DLCO usually normal
PFT Patterns
 Asthma
 FEV1/FVC
normal or decreased
 DLCO
normal or increased
But PFTs may be normal  bronchoprovocation
Pulmonary Function Testing
Jennifer Hale, M.D.
Which of the following is used to follow disease severity in
COPD patients?
a.
b.
c.
d.
e.
Total lung capacity (TLC)
Degree of responsiveness to bronchodilators
Forced vital capacity (FVC)
Forced expiratory volume in 1 second
Diffusing capacity (DLCO)
Pulmonary Function Testing
Jennifer Hale, M.D.
Which of the following is used to follow disease severity in
COPD patients?
a.
b.
c.
d.
e.
Total lung capacity (TLC)
Degree of responsiveness to bronchodilators
Forced vital capacity (FVC)
Forced expiratory volume in 1 second
Diffusing capacity (DLCO)
Pulmonary Function Testing
Jennifer Hale, M.D.
A 36yo WF, non-smoker, presents to your office for follow-up
of ‘recurrent bronchitis.’ You suspect asthma and decide
to order spirometry. Which of the following would you
include in your prescription for testing?
a.
b.
c.
d.
e.
Diffusing Capacity (DLCO)
If no obstruction present, add trial of bronchodilator
If no obstruction present, perform methacholine challenge
Flow volume loop
b and c
Pulmonary Function Testing
Jennifer Hale, M.D.
A 36yo WF, non-smoker, presents to your office for follow-up
of ‘recurrent bronchitis.’ You suspect asthma and decide
to order spirometry. Which of the following would you
include in your prescription for testing?
a.
b.
c.
d.
e.
Diffusing Capacity (DLCO)
If no obstruction present, add trial of bronchodilator
If no obstruction present, perform methacholine challenge
Flow volume loop
b and c
Pulmonary Function Testing
Jennifer Hale, M.D.
A 68yo HM is admitted to the ICU with acute respiratory
distress. A CXR obtained in the ED demonstrates
bilateral pulmonary infiltrates, and his DLCO is
elevated. What is the most likely diagnosis?
a.
b.
c.
d.
e.
Pulmonary edema
Aspiration pneumonitis
Pulmonary emboli
Alveolar hemorrhage
Interstitial lung disease
Pulmonary Function Testing
Jennifer Hale, M.D.
A 68yo HM is admitted to the ICU with acute respiratory
distress. A CXR obtained in the ED demonstrates
bilateral pulmonary infiltrates, and his DLCO is
elevated. What is the most likely diagnosis?
a.
b.
c.
d.
e.
Pulmonary edema
Aspiration pneumonitis
Pulmonary emboli
Alveolar hemorrhage
Interstitial lung disease
Questions?
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