Spirometry: Objective Testing for Assessing Impairment

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SpirometryObjective Testing forAssessing
Impairment

• Mary Bouthiette RN, AE-C
• Dartmouth Hitchcock Manchester
• January 2009

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What is Spirometry?

• Spirometry is a pulmonary function test that
  measures the volume of air an individual inhales
  or exhales as a function of time.
• Flow, or the rate at which volume is changing
  as a function of time, can also be measured with
  spirometry.

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Spirometry

• A crucial tool for the assessment of the
  impairment domain of asthma control
• Reported patient symptoms alone may not
  necessarily reflect objective pulmonary function
• Although a normal reading does not exclude
  asthma, spirometry provides an objective measure
  of airflow obstruction

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Spirometry Suitable for Primary Care

• Inexpensive and user-friendly spirometers are now
  readily available for office use
• Modern office spirometers are portable, process
  numeric results automatically and print out a
  report
• Spirometry ideally should take place before the
  clinician examines the patient so that results
  are available at the point of diagnosis

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Indications for Spirometry

• Diagnostic
• Evaluation of symptoms, signs, or abnormal lab
  tests
• Measure the effect of disease on pulmonary
  function
• Screen at risk individuals
• Assess preoperative risk
• Assess prognosis
• Assess health status prior to initiation of
  activity

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Indications for Spirometry (cont.)

• Monitoring
• Assess therapeutic interventions
• Describe the course of diseases affecting the
  lungs
• Monitor for effects of occupational exposure
• Monitor for adverse reactions to drugs with known
  pulmonary toxicity

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Indications for Spirometry (cont.)

• Disability/Impairment evaluations
• Assess patients as part of a rehabilitation
  program
• Assess risks as a part of insurance evaluation
• Assess for legal reasons

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Indications for Spirometry (cont.)

• Public health
• Epidemiologic surveys such as validation of
  subjective complaints in occupational/environmenta
  l settings

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• Objective Measures
• Objective assessments of pulmonary function are
  necessary for the diagnosis of asthma because
• Medical history and physical examination alone
  are not reliable means of excluding other
  diagnoses or of characterizing the status of lung
  impairment in the clinicians office.

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Importance of Spirometry

• Provides objective measure of lung function
• Establishes airflow obstruction and reversibility
• Assists in asthma diagnosis and treatment
• Assists in asthma severity

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SpirometryWhen?

• Initial assessment and diagnosis
• Improvement in symptoms and peak flows following
  asthma treatment
• At least once per year

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Spirometry Components

• Forced Vital Capacity (FVC) - the maximal volume
  of air forcibly exhaled from the point of maximal
  inhalation
• Forced Expiratory volume in 1 second (FEV 1) -
  the volume of air exhaled during the first second
  of the FVC
• FEV1/FVC - ratio of FEV1 to FVC, expressed as a
  percentage
• Peak Expiratory Flow Rate (PEFR) is the maximum
  air flow (rate) during forced exhalation

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Spirometry Results

• Airflow obstruction is indicated by reduced FEV1
  and FEV1 /FVC values relative to reference or
  predicted values
• The predicted values for FVC and FEV1 for a
  patient depend on the individuals age, gender,
  height, and race
• The numbers are presented as percentages of the
  average expected in someone of the same age,
  height, sex, and race. This is called percent
  predicted.

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Objective Measures Spirometry

• Is airflow obstruction present and is it at least
  partially reversible?
• Use spirometry to establish airflow obstruction
• FEV1 lt 80 predicted
• FEV1/FVC below the lower limit of normal, as
  compared to the individuals own predicted value
• Use spirometry to establish reversibility
• FEV1 increases gt12 and at least 200 ml. after
  using a short-acting inhaled beta2-agonist
• A 2- to 3-week trial of oral corticosteroid
  therapy may be required to demonstrate
  reversibility

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Flow Volume Loop

• A normal flow volume loop has a rapid peak
  expiratory flow rate with a gradual decline in
  flow back to zero.

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• Obstructive lung disease changes the appearance
  of the flow volume curve
• As with a normal curve, there is a rapid peak
  expiratory flow, but the curve descends more
  quickly than normal and takes on a concave shape

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Example of Spirometry results demonstrating
obstruction
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(No Transcript)
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Flow volume loop
Volume (L)
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Reliability of Spirometry

• Spirometry is an effort-dependent maneuver that
  requires understanding, coordination, and
  cooperation by the patient-subject, who must be
  carefully instructed
• Technicians must be trained and must maintain a
  high level of proficiency to assure optimal
  results
• Spirometry should be performed using equipment
  and techniques that meet standards developed by
  the American Thoracic Society

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Reliability of Spirometry

• Criteria for acceptability include
• lack of artifact induced by coughing, glottic
  closure, or equipment problems (primarily leak).
• satisfactory start to the test without
  hesitation.
• satisfactory exhalation with six seconds of
  smooth continuous exhalation, or a reasonable
  duration of exhalation with a plateau.

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Unacceptable Efforts
Cough
Variable Effort
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Reliability of Spirometry

• Correct technique, calibration methods, and
  maintenance of equipment are necessary to achieve
  consistently accurate test results
• Maximal patient effort in performing the test is
  required to avoid important errors in diagnosis
  and management
• Spirometry is generally valuable in children over
  age 4 however, some children cannot conduct the
  maneuver adequately until after age 7

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The Expert Panel recommends that spirometry tests
be done

• at the time of the initial assessment
• after treatment is initiated and symptoms and
  peak flow have stabilized to document attainment
  of (near) normal airway function
• at least every 1 to 2 years to assess the
  maintenance of airway function
• Ref Expert Panel NAEPP Guidelines

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Spirometry May be Done More Frequently

• Depending on clinical severity, Spirometry is
  also useful
• As a periodic check on the accuracy of the peak
  flow meter
• When more precision is desired
• Evaluating response to therapy
• When Peak Flow results are unreliable

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References

• Clinical Guidelines for the Diagnosis, Evaluation
  and Management of Adults and Children with
  Asthma-2007
• NAEPP Expert Panel Report-Update on Selected
  Topics 2007
• National Heart Lung and Blood Institute
• United States Environmental Protection Agency
• Asthma and Allergy Foundation of America
• Acknowledgements
• Mary Bouthiette, RN, AE-C
• Asthma Educator and Consultant
• Lynn Feenan, RN, MSN, AE-C