Pulmonary Function Tests Flashcards
Assessing the functional status of the lungs as it relates to:
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- How much air volume can be moved in and out of the lungs
- How fast the air in the lungs can be moved in and out
- How stiff the lungs and chest wall are - a question about compliance
- The diffusion characteristics of the membrane through which the gas moves (determined by special tests)
- Measurement of how the lungs have responded to treatment
Indications for PFT?
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- Screening for lung disease in patients with symptoms
- Following the progression of pulmonary disease - restrictive or obstructive
- Evaluating the effectiveness of therapeutic intervention
- Evaluating the patient prior to certain types of surgery:
- Objective assessment of impairment or disability
Evaluating the patient prior to certain types of surgery is an indication for PFTs. What would this help us with? 4
What kind of patients would benefit from this evaluation?? 3
- risk for postoperative respiratory complications
Reflects the patient’s ability to - take a deep breath,
- to cough, and
- to clear the airways of excess secretions
COPD, CHF, Do they have enough pulomnary reserve to get them off the ventilator?
Types of Pulmonary Function Tests?
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Spirometry
Peak flow
Measurement of lung volumes
Quantification of diffusion capacity
Oxygen uptake (VO2)—exercise capacity
What does spirometry measure?
2
- Forced expiratory volume in one second (FEV1)
- Forced vital capacity—(FVC)
Most readily available and most useful PFT
$1,500 – $2,500
Definition of spirometry?
What does it assess?
Spirometry with flow volume loops assesses the mechanical properties of the respiratory system by measuring expiratory volumes and flow rates
(how much they can inhale and exhale and how fast they can do it)
Flow volume loops provide what?
How is the chart plotted?
a graphic illustration of a patient’s spirometric efforts
flow against volume
The normal volume time curve for spirometry is shaped how?
The maximum volume attained represents what?
while the volume attained after one second represents what?
has a rapid upslope and approaches a plateau soon after exhalation
the forced vital capacity (FVC),
the forced expiratory volume (FEV1)
Variables that might affect a spirometry test?
4
Age
Gender
Race
Body height and size
Why would age change the PFT?
2
Why would gender affact the PFT?
2
How does race affect PFTs?
- The natural elasticity of the lungs decreases
- This translates into smaller and smaller lung volumes and capacities as we age
- Usually the lung volumes and capacities of males are larger than the lung volumes and capacities of females.
- Even when males and females are matched for height and weight, males have larger lungs than females.
- Blacks, Hispanics and Native Americans have different PFT results compared to Caucasians
If person becomes too obese how will this affect the PFT?
the abdominal mass prevents the diaphragm from descending as far as it could and the PFT results will demonstrate a smaller measured PFT outcome
What are some examples of obstructive disorders?
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- Asthma
- Bronchitis
- Excessive mucus plugging
- foreign object inhalation
- invasive tumors
- COPD
- Emphysema
- “Restriction” in lung disorders always means a what?
- This term can be applied with confidence to patients whose total lung capacity has been what?
- What is total lung capacity?
- Why cant TLC be measured by spirometry?
- TLC is the summation of what?
- decrease in lung volumes
- measured and found to be significantly reduced
- Total lung capacity (TLC) is the volume of air in the lungs when the patient has taken a full inspiration.
- because air remains in the lungs at the end of a maximal exhalation - i.e. the residual volume or RV
- The TLC is therefore the summation of FVC + RV
What are the ways you can measure TLC?
4
- Helium dilution
- Nitrogen washout
- Body plethysmography (gold standard)
- Chest radiograph or HRCT measurements
Neuromuscular Restrictive lung Disorders
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- Generalized Weakness – malnutrition
- Paralysis of the diaphragm
- Myasthenia Gravis
- Muscular Dystrophy
- Poliomyelitis
- Amyotrophic Lateral Sclerosis
Intrinsic Restrictive Lung Disorders?
4
- Sarcoidosis
- Tuberculosis
- Pneumonectomy
- Pneumonia
Extrinsic Restrictive
Lung Disorders
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- Scoliosis, Kyphosis
- Ankylosing Spondylitis
- Pleural Effusion
- Pregnancy
- Gross Obesity
- Tumors
- Ascites
- Pain on inspiration
- -Pleurisy, rib fractures
What is FEV1?
forced expiratory volume in1sec:
the volume of air that is forcefully exhaled in one second
It is 75% of FVC
What is FVC?
forced vital capacity
the volume of air that can be maximally forcefully exhaled
NOT the TLC
What is the FEF 25-75%?
What does it measure?
the average forced expiratory flow during the mid (25 - 75%) portion of the FVC
measures of the flow rate in liters per second of the middle half of a FVC test
Why do we want to look at the middle half of the forced expiratory flow?
2
The first quarter is effected by the patients effort in overcoming the inertial forces which resist thoracic wall expansion
The last quarter is polluted by the pts dimishing physical effort in instigation of bronchospasm during forced expiration and the breathlessness associated with the terminal completion of a FVC test.
What is FEF 25%-75% a senstive test for?
obstructive airway disease
What is PEFR?
What does it measure?
The peak expiratory flow rate (PEFR) during expiration
Peak Expiratory Flow Rate (PEFR) is a measure of the highest expiratory flow rate during the PFT test
What is PEFR best used for?
Patients with a low PEFR would have to be further evaluated for obstructive pathologies
A useful measure to see if treatment is improving obstructive disease (like bronchoconstriction in asthma)
What is TLC?
Total lung capacity (TLC): The volume in lungs at maximum inspiration
What is VC?
Vital capacity (VC): The maximum volume expired after a maximum inspiration
What is TV?
Tidal volume (TV): The volume inspired and expired during normal breathing
What is RV?
Residual volume (RV): The volume left in the lungs after maximal expiration
What can lung volumes only be measured with?
body plethysmography (body box)
Values for FVC and FEV1 that are over ____ of predicted are defined as within the normal range?
80%
A normal flow volume loop has a ____ peak expiratory flow rate with a _____ decline in flow back to zero?
rapid
gradual
How does the inspiratory portion of the loop look like of the flow axis?
The inspiratory portion of the loop is a deep curve plotted on the negative portion of the flow axis
Criteria for acceptability of a properly done PFT include?
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- 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 and/or
- a plateau in the volume time curve of at least one second, or a reasonable duration
What is the primary abnormality detected by spirometry?
airway obstruction
Name three obstructive lung diseases?
How is the FEV1 affected?
How does this affect the FEV1/FVC?
- COPD,
- asthma, or
- chronic bronchitis:
the FEV1 is reduced disproportionately more than the FVC
resulting in an FEV1/FVC ratio less than 70%.
How does obstructive disease change the appearance of the flow volume curve?
3
- There is a rapid peak expiratory flow
- The curve descends more quickly than normal
- It takes on a concave shape (reflected by the marked decrease in the FEF25-75)
What is a Bronchoprovocation challenge used in?
3
- Patient who has symptoms of asthma, normal PFTs and no response to bronchodilator therapy
- Patient who experiences symptoms not usually associated with asthma
- Individuals who require screening tests for asthma such as scuba divers, military personnel or others where bronchospasm would pose a risk
Patients who CANNOT be Bronchoprovocation challenged?
6
- Those who have unstable cardiac disease
- Heart attack in the last 3 months
- Stroke in the last three months
- Uncontrolled hypertension
- Those with significant bronchospasm already present
- Pregnancy or nursing mother
Describe the Methodology behind a Bronchoprovocation challenge?
4
- Adequate spirometry—baseline
- Administer the agent—methacholine via nebulizer: at decreasing dilutions of the agent
- Repeat spirometry—30 and 90 seconds after
- Positive test is a decrease of 20% in FEV1
HOw would we determine the reversibility of an airway obstruction?
3
- Pre- and post- bronchodilator spirometry (example of a bronchodilator?)
- Used to determine if there is reversible airway obstruction
- Used to determine if an intervention is helpful in treatment
With the bronchodilator test, when is it said that the pt has reversible airway obstruction?
If two out of three measurements (FVC, FEV1 and FEF25% - 75%) improve, then it can be said that the patient has a reversible airway obstruction that is responsive to medication
What values are reduced in restrictive lung disease? 2
HOw does this affect the FEV1/FVC ratio?
both the FEV1 and FVC are reduced proportionately
by affecting both the FEV1 and the FVC, restrictive lung disease presents with a normal or increased FEV1/FVC ratio
Obstructive: FEV1? FVC? Ratio? What kind of reduction?
Restrictive: FEV1? FVC? Ratio? What kind of reduction?
FEV1 - down FVC - nl or down Ratio – down Disproportionate reduction in FEV1 to FVC
FEV1 - down FVC - down Ratio - nl or up Proportionate reduction in FEV1 To FVC
Criteria for Obstructive Disease ?
4
- Air in the lungs will not be readily exhaled because of physical obstruction
- There will be airway collapse during exhalation (loss of elastic recoil of the lungs)
- In obstructive diseases, the lung’s air volume will be more slowly expelled
- It will be a smaller volume over the time course of the FVC test
Criteria for Restrictive Disease?
3
- Patients with restrictive lung disease, the FEV1 will be lower than predicted normal values and so will the FVC
- Both of these values may equally be effected in restrictive disease, the FEV1/FEV may well be calculated to be between 85% - 100% of normal
- In restrictive disease look closely at FEV1/FVC when FEV1 and FVC are low and if the FEV1/FVC is 85% or greater, then you should suspect the patient has a restrictive pathology.
Criteria for a Mixed Disorder?
4
- If the patient demonstrates a reduced FVC, the patient may repeat the test after inhaling a bronchodilator
- The post-bronchodilator test often shows an improved FVC
- This simple clinical test strongly suggests that the FVC was low due to obstructive phenomenon
- If the FVC did not change, it suggests the FVC was possibly low due to restrictive pathologies
Grading the severity of disease
American Thoracic Society Criteria for FEV1 % of predicted:
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- Mild: > 70
- Moderate: 60-69
- Moderately Severe: 50-59
- Severe: 35-49
- Very Severe: less than 35
A Systematic Way To Interpretation of PFTs
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Step 1 - Determine the FEV1/FVC ratio (if (if less than 70% then abnormal)
Step 2 – Determine if the FVC (if less than 80% of predicted then abnormal)
Step 3 -
a) If both FVC and FEV1 are normal, then the patient has a normal PFT test (do they need a challenge test?)
b) if either are abnormal then do a bronchodilator challenge. Is there are change of at least 12% or 200mL in the FEV1 or FVC?
Step 4 - If FVC and/or FEV1 are low, then the presence of disease is highly likely
Step 5 - If Step 4 indicates that there is disease, then you need to go to the % predicted for FEV1/FVC
If the % predicted for FEV1/FVC is normal or increased then the patient has what?
If the % predicted for FEV1/FVC is 69% or lower, then the patient has what?
restrictive lung disease (next step is to order DLCO)
an obstructive lung disease
Diffusion Capacity (DLCO)
It is a useful test for:
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- Determining the degree of emphysema in smokers
- Differentiating chronic bronchitis from emphysema in smokers
- In restrictive disease differentiating interstitial lung disease from external restrictive etiologies of disease
- Recurrent PEs
- Pulmonary HTN
- Disability measurement
Methodlology for DLCO?
3
Patient quickly inhales a mixture of 0.3% CO and 10% helium
Holds their breath for 10 seconds
Exhales quickly and measurement obtained
Why is CO preferred?
(in DLCO)
4
- not normally present in alveoli/blood
- transfer is diffusion limited rather than perfusion limited
- Avidly binds to Hb
- CO diffusion is less affected by other factors
Results of DLCO
Low DLCO with obstruction:
2
Low DLCO with restriction:
2
Low DLCO with normal spirometry: 5
High DLCO:
3
- emphysema
- In children: cystic fibrosis
- Pulmonary fibrosis
- Hypersensitivity pneumonitis
- Chronic pulmonary emboli
- Anemia
- Early interstitial lung disease
- Increased carboxyhemoglobin level (?)
- CHF
- Asthma
- Left to right intracardiac shunt
- Polycythemia
What test is Used by exercise physiologists, pulmonologists and cardiologists to determine a patient’s functional exercise capacity?
What is it based on?
VO2 Testing
Based on the Fick equation:
VO2 = (SV x HR) x CaO2 – CvO2)
VO2 = oxygen uptake
The VO2 reflects what?
3
the maximal ability of a person to take in, transport, and use oxygen—it defines that person’s functional aerobic exercise capacity
Clinical Applications for Exercise Testing?
5
- Work up for heart transplant
- Aid in determining the etiology of cardiac vs. pulmonary limitations of exercise
- Evaluation of a patient who is going to undergo lung resection
- Evaluation of exercise capacity when indicated for medical reasons in patients in whom the estimates of exercise capacity from exercise test time or work rate is unreliable
- Objective grading system for patient’s with CHF
