Pulmonary Function Testing Flashcards

Pulmonary Function Testing Day 1

• Wilkins Ch. 7, Egan’s Ch. 20, Ruppel’s 2,3,4
• Rowan University Salva School of Nursing Professionals Bachelor of Science in Respiratory
• James Fields, MS RRT, RRT-ACCS, CPFT, AE-C

Pulmonary Function Testing (PFT)

• Commonly include:
  • Spirometry
  • Static lung volume measurements (lung volumes)
  • Diffusing capacity studies (DLCO)
  • Mechanical properties of the lungs and thorax
    • Airway resistance and compliance
  • Assess airway hyperresponsiveness
    • Methacholine Bronchoprovocation Test

Purpose of PFT

• Determine causes of dyspnea
• Differentiate between obstructive and restrictive lung disease
• Assess severity of pulmonary disease
• Assess treatment response
• Follow course of a disease
• Preoperative assessment
• PFT’s do not provided specific diagnosis of pulmonary disease

PFT Equipment

• Two general types of measuring devices exist, those that:
  • Measure volume
  • Measure flow
• Volume-measuring devices—spirometers
• Flow-measuring devices—pneumotachometers
• Every measuring device has capacity, accuracy, error, resolution, precision, linearity, and output

Types of PFT Machines

• Vyntus BODY

Principles of Measurement and Significance

• For tests of pulmonary function, three general principles should be considered:
  • Test sensitivity and specificity
    • Address the test’s ability to detect disease, or absence of it
  • Validity (accuracy)
    • Relates to its meaningfulness, or the ability to measure what it is intended to measure
  • Reliability (reproducibility)
    • Consistency

Testing

• All tests must be acceptable and reproducible, and must meet standards to be valid results.
• Standard variations:
  • ATS - ERS
  • ACCP
• All reference information / comparative data is based upon:
  • Age
  • Gender
  • Height (or Arm span distance)
  • Race

Quality Control

• 3L super syringe: \pm 3% volume & flow
• Two-pt cals: For diffusion and lv
• All testing within 10% of previous effort
• Subjective testing minimized by reproducible data
• Acceptable data: Performed to standard

Equipment Calibration

• The American Thoracic Society (ATS) guidelines specify that:
  • Spirometers should be capable of measuring volumes of 8 L or more and capturing exhalation maneuvers for at least 15 s
  • Volume accuracy should be at least \pm 3.5% or \pm 0.065 L, with the measured flow range between 0 and 14 L/s (−14 to + 14 L/s for flow-volume loops)
  • Flow measurements should be accurate within \pm 5% of the true value over a range of −14 to +14 L/s with a sensitivity (minimal detectable flow) of 0.025 L/s

Equipment Calibration (Cont.)

• Spirometers should be able to produce printouts of both volume-time and flow-volume plots
• Biologic control: A healthy subject for whom quality control data are available

Patient Preparation

• Arrive on time. Being late by 30 minutes or more may require rescheduling.
• Avoid tight clothing.
• Do not eat a large meal within 2 hours of the test.
• Do not exercise heavily for at least 30 minutes before the test.
• Do not drink alcohol for at least 4 hours before the test.
• Do not smoke on the day of the test.
• If scheduled for spirometry pre or post bronchodilation, stop using bronchodilator according to the table.

Medications - Time to Stop Before Test

• Short-acting beta agonists (albuterol, salbutamol): 4-6 hours
• Short-acting anti-cholinergic Ipratropium (Atrovent): 12 hours
• Long-acting beta agonists (formoterol, salmeterol): 24 hours

Reference Range for PFTs

• FVC and FEV1: Data collected from 10,000 healthy individuals of various ages, sexes, and heights. The average values for FVC and FEV1 would be calculated, and the range that includes 95% of the population (2 standard deviations from the mean) would be established as the reference range. These values would then be adjusted based on height and sex.
• Global Lung Function Initiative (GLI): Provides global reference equations for spirometry, including FEV1, FVC, and other lung function tests.
• NHANES (National Health and Nutrition Examination Survey): Data from the NHANES survey has been used to develop reference ranges for PFTs in the U.S.
• European Respiratory Society (ERS): European datasets contribute to the reference ranges used in Europe.

Measures of Lung Function

• Lung Volumes include
  • Inspiratory Reserve Volume (IRV)
  • Tidal Volume (Vt)
  • Expiratory Reserve Volume (ERV)
  • Residual Volume (RV)
• Capacities
  • Total Lung Capacity (IRV+Vt+ERV+RV)
  • Functional Residual Capacity (ERV+RV)
  • Inspiratory Capacity (IRV+Vt)
  • Vital Capacity (IRV+Vt+ERV)

Lung Volumes and Capacities

• Tidal Volume (VT): Volume of air inhaled or exhaled during each normal breath
• Inspiratory Reserve Volume (IRV): Maximal volume of air that can be inhaled over and above the inspired tidal volume
• Expiratory Reserve Volume (ERV): Maximal volume of air that can be exhaled after exhaling a normal tidal breath
• Residual Volume (RV): Volume of air remaining in the lungs after a maximal exhalation
• Total Lung Capacity (TLC): Maximal volume of air in the lungs at the end of a maximal inhalation (sum of RV + VT + ERV + RV)
• Functional Residual Capacity (FRC): Volume of air present in the lung at end-expiration during tidal breathing (sum of RV + ERV)
• Inspiratory Capacity (IC): Maximal volume of air that can be inhaled from the resting end-expiratory level (sum of IRV + VT)
• Vital Capacity (VC): Maximal volume of air that can be exhaled after a maximal inhalation (sum of IC + VT + ERV)

Measures of Lung Function

• Tidal volume
  • Volume during quiet breathing
  • Adults: 350 to 600 mL
  • Stiff lungs: small volumes at higher rate
  • Obstruction: normal volume at slower rate
• Minute volume
  • Rate × volume
  • Normal range from 5 to 10 L/min
  • Can rise to 60 L/min during strenuous exercise

Measures of Lung Function (Cont.)

• Vital capacity: maximal volume exhaled, measured after deepest breath possible
• Slow vital capacity (SVC): Patient gently but fully exhales from a maximal inspiration
• Forced vital capacity (FVC): Patient forcefully empties the lungs from a maximal inspiration
• Proper coaching is essential !!!
• SVC <20 mL/kg: an increased risk for postoperative respiratory complications

Spirometry

• Dr. Roger Goldstein talks about spirometry

Instructions - FVC

• Have patient sit upright in chair (good posture)
• Explain procedure to patient
• Place nose clips on patient
• Mouth on mouthpiece
• Breath normal for few breaths
• ”Big deep breath all the way in”
• “Blast out hard and fast, keep going, keep blasting….)
• Quick deep breath back in

Spirometry

• Tests of pulmonary mechanics
  • Forced vital capacity (FVC)
  • Forced expiratory volume in 1 second (FEV1)
  • Other forced expiratory flow measurements
  • Maximum voluntary ventilation (MVV)
• These measurements assess ability of lungs to move large volumes of air quickly through airways

Forced Vital Capacity

• Most common test of pulmonary mechanics
• Many measurements are made while patient is performing FVC maneuver
• FVC is an effort-dependent maneuver requiring careful patient instruction and cooperation
• To ensure validity, each patient must perform at least three acceptable FVC maneuvers

Technique Validation

• FVC maneuvers are highly technique dependent
• Goal is to obtain at least three acceptable and error-free maneuvers that are repeatable
• To assure repeatability (or reproducibility):
  • Therapist must confirm that the key volume measures (FVC and FEV1) are free of significant variability
  • The two largest values of FVC must be within 0.150 L of each other, and
  • The two largest values of FEV1 must be within 0.150 L of each other

Technique Validation (Cont.)

• Back-extrapolated volume
  • Spirometry software programs typically identify a slow start to forced exhalation by detecting a delay in time to peak flow (>120 ms) or by calculating a back-extrapolated volume
  • If the back-extrapolated volume is more than 5% of FVC or more than 150 mL, the FVC is unacceptable

ATS-ERS Grading Scheme for Spirometry

• Grade A:
  • '>' 3 acceptable tests with repeatability within 0.150 L; ages 2-6, 0.100 L, or 10% of highest value, whichever is greater.
• Grade B:
  • '>' 2 acceptable tests with repeatability within 0.150 L; ages 2-6, 0.100 L, or 10% of highest value, whichever is greater
• Grade C:
  • '>' 2 acceptable tests with repeatability within 0.200 L; ages 2-6, 0.150 L, or 10% of highest value, whichever is greater
• Grade D:
  • '>' 2 acceptable tests with repeatability within 0.250 L; ages 2-6, 0.200 L, or 10% of highest value, whichever is greater
• Grade E:
  • One acceptable test
• Grade F:
  • No acceptable tests

Acceptability and Repeatability Criteria for Forced Vital Capacity Maneuvers

• The spirogram is acceptable if it meets the following criteria:
  • Free from artifacts
    • Coughing/breathing during the maneuver
    • Early termination or cutoff
  • Submaximal effort
  • Exhibits a rapid, forceful start
  • Time to peak flow <120 ms
  • Back-extrapolated volume <5% of FVC or 150 mL, whichever is greater
  • Achieves complete exhalation
    • Duration of at least 6 s (COPD patients may need >10 s), or
    • Attainment of a plateau (<25 mL change in volume for \ge 1 s)
• Results are repeatable if, after three acceptable spirograms have been obtained, the following criteria are met:
  • The two largest values of FVC must be within 0.150 L of each other, and
  • The two largest values of FEV₁ must be within 0.150 L of each other

Flow-Volume Loops

• Volume plotted on horizontal axis and flow on vertical axis
• Fixed or variable upper airway obstruction
• COPD/asthma
• Restrictive lung disease
• Prebronchodilator and postbronchodilator curves

Indices of Flows

• Forced expiratory volume at 1 s (FEV1)
• Forced expiratory volume at 3 s (FEV3)
• Forced expiratory flow, mid-expiratory (FEF25% to 75%)
• Peak expiratory flow (PEF)
• FVC
• FEV1/FVC ratio (FEV1%)
• And many more

Comparison of Spirometry Efforts

• Lists different test values Trial 1, Trial 2, Trial 3, and the Best Test Reported.

Forced Vital Capacity (FVC) Percentage of Predicted 80%-120%

• Forced vital capacity (FVC)
  • Patient forcefully empties the lungs from a maximal inspiration
  • Proper coaching is essential (#1 cause of erroneous results)
• Normal individual exhale > 75% in 1 second and >90% in 3 seconds (patients without obstruction)
• Minimal time is 6 second exhalation
• Some patient may take >10 seconds to empty (obstruction)

FEV1 The Percentage Predicted: 80% To 120%

• Maximal volume exhaled during 1st second of expiration
• It is a forced maneuver
• Varies with age, gender, race, and height
• The percentage predicted: 80% to 120%
• Reduced in obstructive

Interpretation of FEV1 Percent Predicted

• The FEV1 percent predicted is used to categorize the severity of airway obstruction, especially in diseases like COPD or asthma:
  • Normal or Mild Obstruction:
    • FEV1 \ge 80% predicted
    • No significant airflow obstruction. The patient may still experience minimal symptoms.
  • Moderate Obstruction:
    • FEV1 50-79% predicted
    • This indicates moderate airflow limitation, with symptoms becoming more noticeable, especially on exertion.
  • Severe Obstruction:
    • FEV1 30-49% predicted
    • Significant limitation in airflow, with patients often experiencing severe symptoms, including shortness of breath and difficulty with physical activity.
  • Very Severe Obstruction:
    • FEV1 < 30% predicted or FEV1 < 50% with respiratory failure
    • This is a critical stage of disease, often associated with frequent exacerbations, and may require interventions like oxygen therapy.

FEV3

• FEV3 refers to the volume of air exhaled during the first 3 seconds of a forced exhalation after a deep inhalation
• 3-s point of the expiratory curve
• Not as reproducible as FEV1
• Reported as percentage of the FVC (normal \sim 95%)

(FEV1/FVC) Ratio 70% Gold Standard Global Initiative for Chronic Obstructive Lung Disease

• The FEV1/FVC ratio compares the amount of air exhaled in 1 second with the total amount exhaled during an FVC maneuver
• Expressed as a percentage (FEV1%)
• FEV1% and the FEV1/FVC ratio progressively decrease with age

FEF25% To 75%

• Used to evaluate the status of medium-to-small airways in obstructive lung disorders
• Average flow rate during middle half of expiratory curve
• Normal 65% to 100%
• More sensitive to airway obstruction than FEV1

FVC, FEV1, and FEV1%

• Clinically, the FVC, FEV1, and FEV1% are commonly used to:
  • Assess the severity of a patient’s pulmonary disorder
  • Determine whether the patient has an obstructive or a restrictive disease

Pathophysiologic Patterns

• Two major categories of pulmonary disease exist:
  • Obstructive
  • Restrictive
• Some pulmonary disease cause both!
• Primary abnormality in obstructive disease is increased airways resistance (causing a change in exhaled flow)
• Primary problem in restrictive disease is decrease in either lung compliance or lung volumes or both (causing an overall change in inhaled volume)

FVC, FEV1, and FEV1%

• In an obstructive disorder:
  • FEV1 and FEV1% are decreased
  • The FVC is often normal
• In a restrictive disorder:
  • FVC and FEV1 are decreased
  • FEV1% is normal or increased

Disease Types

• Obstructive
  • Cystic Fibrosis
  • Bronchitis (Chronic)
  • Asthma
  • Bronchiectasis
  • Emphysema
• Restrictive
  • Intrinsic: Sarcoidosis, pulmonary fibrosis
  • Extrinsic: Neuromuscular (Myasthenia Gravis, Guillain Barré), Chest wall (kyphoscoliosis, obesity)

Peak Expiratory Flow (PEF)

• Maximum flow rate achieved during FVC maneuver
• Effort dependent
• Peak flowmeters are inexpensive
• Asthma action plans:
  • Green zone: 80% to 100% of personal best
  • Yellow zone: 50% to 80%
  • Red zone: <50% = urgent physician intervention

Bronchodilator Responsiveness Testing

• Spirometry can be performed before and after bronchodilator administration to determine the reversibility of airway obstruction
• An FEV1% of less than predicted is a good indication for bronchodilator studies.
• Inhaled bronchodilators can be administered by a metered-dose inhaler (MDI) or a small-volume nebulizer.
• An interval of 10 to 15 minutes between administration and repeat testing is recommended for short-acting β2 agonists

Bronchodilator Responsiveness Testing

• Bronchodilator Positive response:
  • \uparrow FEV1 or FCV by \ge 12% and \ge 200ml
• Lack of bronchodilator response does not preclude bronchodilator therapy

Maximal Voluntary Ventilation

• Patient breathes as rapidly and deeply as possible for 12 to 15 s
• Extrapolated to obtain MMV in 1 min
• MMV reflects:
  • Status of respiratory muscles
  • Compliance of thorax-lung complex
  • Airway resistance
  • Patient motivation and ability to move air
• Important in the preoperative patient (abdominal or thoracic)

Maximal Voluntary Ventilation (MVV)

• Effort-dependent test; patient asked to breathe deep and fast for 12 seconds
• Results reflect:
  • Patient effort
  • Function of respiratory muscles
  • Ability of chest wall to expand
  • Patency of airways

Upper Airway Obstruction

• The utility of flow-volume loops for detection of obstructing lesions of the upper airway (defined as that portion of the airway extending from the mouth to the lower trachea) was first reported by Miller and Hyatt, who described three distinct patterns:
  • variable extrathoracic obstruction;
  • variable intrathoracic obstruction; and
  • fixed obstruction
• The upper airway is divided into intra- and extrathoracic components by the thoracic inlet, which projects one to three cm above the suprasternal notch on the anterior chest at the level of the first thoracic vertebra.

Summary of Spirometry

• FVC (forced vital capacity) - maximum amount of air that can be expired forcefully.
• FEV1 (forced expiratory volume/time) - volume of gas exhaled in first 1-second of FVC maneuver
• FEV1/FVC - ratio of FEV1 over FVC expressed as %. (75%-85% in normal young adults)
• FEF25-75 (forced expiratory flow/time) - measure of flow during middle 50% of FVC
• PEFR (peak expiratory flow) - max exp. flow rate during FVC maneuver. Highest point on flow-volume graph
• MVV (maximal voluntary ventilation) – volume of air a person can generate over 12 sec. – related to VE.