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pulmonology > PFTs > Flashcards

PFTs Flashcards

1
Q

What information is obtained from PFTs?

A

assesses functional status of the lung as it relates to:

  • 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 (compliance?)
  • diffusion characteristics of the membrane through which gas moves
  • measurement of how long the lungs have responded to tx
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2
Q

Indications for PFTs?

A
  • screening for lung disease in pts with sxs
  • following progression of pulmonary disease (restrictive or obstructive)
  • evaluating the effectiveness of therapeutic intervention
  • evaluating the pt prior to certain types of surgery (risk for post op respiratory complications, reflects the pts ability to take a deep breath, to cough, and to clear the airways of excess secretions (high risk pts: smokers, COPD)
  • objective assessment of impairment or disability
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3
Q

What are the differeent types of PFTs?

A
  • spirometry
  • peak flow
  • measurement of lung volumes
  • quantification of diffusion capacity
  • VO2 uptake: exercise capacity
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4
Q

What does spirometry measure?

A
  • FEV1
  • FVC
  • it is the most readily available and most useful PFT
  • $1500-2500
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5
Q

What is the definition of spirometry? What is the test dependent on?

A
  • spirometry with flow volume loop assesses the mechanical properties of the respiratory system by measuring expiratory volumes and flow rates
  • test is dependent on pt cooperation
  • flow volume loops provide illustration of pt’s spirometric efforts
  • flow is plotted against volume to display a continuous loop from inspiration to expiration
  • overall shape of the flow volume loop is impt in interpreting spirometric results
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6
Q

What does a normal volume-time curve look like?

A
  • rapid upslope and approaches a plateau soon after exhalation
  • max volume attained is FVC and the volume attained after 1 second is the FEV1
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7
Q

What do normal values of spirometry depend on?

A
  • age, gender, body, ht, wt, race
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8
Q

Why is age a variable?

A
  • natural elasticity of the lungs decreases with age

- smaller and smaller lung volumes and capacities as we age

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9
Q

Why is gender a variable?

A
  • usually lung volumes and capacities of males are larger than the lung volumes and capacities of females
  • even when males and females are matched for ht and wt, males have larger lungs than females
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10
Q

Why is race a variable?

A
  • Blacks, hispanics and Native Americans have diff PFT results compared to caucasians
  • so a race approp. table should be used to measure pulmonary function
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11
Q

Why is body height and size a variable?

A
  • body size has huge effect on PFT values
  • small man will have smaller PFT result than a man the same age who is much larger
  • if person becomes too obese, the abdominal mass prevents the diaphragm from descending as far as it could and PFT results will demonstrate a smaller measured PFT outcome
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12
Q

What are the examples of obstructive disease?

A
  • asthma
  • bronchitis
  • excessive mucus plugging
  • foreign body inhalation
  • invasive tumors
  • COPD
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13
Q

What does restricted airflow mean?

A
  • restriction in lung disorders always means a decrease in lung volumes
  • TLC is significantly reduced
  • TLC is the volume of air in the lungs when the pt has taken a full inspiration
  • TLC can’t be measured by spirometry because air remains in the lungs at the end of max exhalation - RV
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14
Q

What is TLC?

A
  • FVC+ RV
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15
Q

What ways can we measure TLC?

A
  • helium dilution
  • nitrogen washout
  • body plethysmography (gold std)
  • chest radiograph or HRCT
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16
Q

What is FEV1?

A
  • forced expiratory volume in 1 sec

- it is 75% of FVC

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17
Q

What is FVC?

A
  • volume of air that can be max forcefully exhaled
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18
Q

What is the FEF 25-75% measuring? Why do we measure this? What is it a sensitive test for?

A
  • avg FEF during the middle portion of FVC
  • value of this: first quarter of FVC is effected by pt’s effort in overcoming the inertial forces which resist thoracic wall expansion
    the last quarter is polluted by the pts diminishing effort in instigation of bronchospasm during forced expiration and the breathlessness associated with terminal completion of a FVC test (middle portion is less pt dependent)
    sensitive test for early obstructive airway disease
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19
Q

What is the PEFR?

A
  • the peak expiratory flow rate during expiration
  • measure of highest expiratory flow rate during PFT test
  • becomes sensitive test for presence of obstructive disease
  • pts with low PEFR would have to be further evaluated
    • useful measure to see if tx is improving obstructive disease (asthma - bronchoconstriction)
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20
Q

What is the VC?

A
  • vital capacity: max vol expired after max inspiration
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21
Q

What is the TV?

A
  • volume inspired and expired during normal breathing
22
Q

What is the only way that you can measure lung volumes?

A
  • can only be measured with body box (body plethysmography)
23
Q

What is considered the normal range of FVC and FEV1?

A
  • over 80% of predicted are defined as normal
  • normal flow volume loop has rapid peak expiratory flow rate with gradual decline in flow back to 0
  • the inspiratory portion of the loop is a deep curve plotted on teh negative portion of flow axis
24
Q

What are the criteria for acceptability of a properly done PFT?

A
  • lack of artifact induced by coughing, glottic closure, or equipment problems (leak)
  • satisfactory start to test without hesitation
  • satisfactory exhalation with 6 seconds of smooth continuous exhalation and or plateau in the volume time curve of at least one second,
25
Q

What is the primary abnormalitiy that is detected by spirometry? What is reduced?

A
  • airway obstruction

- The FEV1 is reduced disproportionately more than the FVC this results in an FEV1/FVC ratio less than 70%

26
Q

How does obstructive disease change the appearance of the flow volume curve?

A
  • there is a rapid peak expiratory flow
  • the curve descends more quickly than normal
  • it takes on a concave shape (decrease in FEF 25-75)
27
Q

When is the bronchoprovocation challenge used?

A
  • used in pt who as sxs of asthma, normal PFTs and no response to bronchodilator therapy
  • pt who experiences sxs not usually assoc with asthma
  • individuals who require screening tests for asthma such as scuba divers, military personnel or others where bronchospasm would pose a risk
28
Q

What patients cannot be challenged?

A
  • those who have unstable cardiac disease
  • heart attach in last 3 months
  • stroke in last 3 months
  • uncontrolled HTN
  • those with significant bronchospasm already present
  • pregnancy or nursing mother
29
Q

What steps are done in bronchoprovocation challenge?

A
  1. adequate spirometry (baseline)
  2. administer the agent - methacholine via nebulizer (at decreasing dilutions of the agent)
  3. repeat spirometry - 30-90 seconds after
    - positive test is a decrease of 20% in FEV1
30
Q

How do you determiine if there is reversible airway obstruction?

A
  • pre and post bronchodilator spirometry
  • used to determine if there is a reversible airway obstruction
  • used to determine if an intervention is helpful in tx
31
Q

What are the measurements that have to be improved to establish that pt has reversible airway obstruction that is responsive to medication?

A
  • 2 out of the 3 measurements (FVC, FEV1, and FEF25-75) improve
  • the amt of improvement is variable b/t clinics so std are that if FEV1 or FVC increase more than 12% and more than 200 mL (in adults) or just 12% in ages 5-18 than they have responsive reversible obstructive disease
32
Q

What is reduced in restrictive lung disease?

A
  • FEV1 and FVC are reduced proportionately

- by affecting both the FEV1 and FVC, restrictive lung disease presents with normal or increased FEV1/FVC ratio

33
Q

What decreases in obstructive disease?

A
  • FEV1, FVC (or could be normal), so ratio would decrease, disporportionate reduction in FEV1 to FVC
34
Q

What changes in restrictive disease?

A
  • FEV1 and FVC both decrease
  • ratio is either normal or increases
  • there is a proportionate reduction in FEV1 to FVC
35
Q

What is the criteria for obstructive disease?

A
  • 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 disease: the lungs air volume will be more slowly expelled
  • it will be a smaller volume over the time course of the FVC test
36
Q

What is the criteria for restrictive disease?

A
  • pts with restrictive 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 so the FEV1/FCV may well be calculated to be b/t 85% and 100% normal
  • if FEV1/FVC is 85% or greater suspect the pt has restrictive disease
37
Q

What are the criteria for a mixed disorder?

A
  • if the pt demonstrates a reduced FVC, the pt may repeat the test after inhaling a bronchodilator
  • the post bronchodilator test often shows an improved FVC
  • the test suggests that the FVC was low due to obstructive phenomenon
  • if the FVC didn’t change, it suggests the FVC was possible due to restrictive pathologies
38
Q

How is the severity of the disease graded?

A 
- FEV1% of predicted:
Mild greater than 70
moderate: 60-69
moderately severe: 50-59
severe: 35-49
very severe: less than 35
39
Q

How do you interpret if pt has disease?

A
  • step 1: determine FEV1/FVC ratio (if less than 70% its abnormal)
  • step 2: dermine if FVC (if less than 80% than abnormal)
  • step 3: if both FVC and FEV1 are normal then pt has normal PFT test. If either are abnormal then do bronchodilator challenge, if any change at 12% or 200 mL in FEV1 or FVC?
  • step 4: if FVC and or FEV1 are low than the presence of disease is highly likely
  • step 5: if step 4 indicates that there is disease, then you need to go with % predicted for FEV1/FVC - if % predicted for Fev1/FVC is normal or increased then the pt has a restrictive lung disease ( next step order a DLCO)
  • if % predicted for FEV1/FVC is 69% or lower than the pt has obstructive lung disease
40
Q

When is the DLCO test useful?

A
  • for 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
41
Q

What is the methodology of DLCO?

A
  • pt quickly inhales a mix of 0.3% CO and 10% helium
  • hold their breath for 10 sec
  • exhales quickly and measurement is obtained
  • range of “normal” wide
  • more helpful to get baseline and compare with subsequent measurements
  • smoking substantially lowers DLCO
42
Q

What are some neuromuscular restrictive lung disorders?

A
  • generalized weakness (malnutrition)
  • paralysis of the diaphragm
  • myasthenia gravis
  • muscular dystrophy
  • poliomyelitis
  • amyotrophic lateral sclerosis
43
Q

What are intrinsic restrictive lung disorders?

A
  • sarcoidosis
  • TB
  • pneumonectomy
  • pneumonia
44
Q

What are extrinsic restrictive lung disorders?

A
  • scoliosis, kyphosis
  • ankylosing spondylitis
  • pleural effusion
  • pregnancy
  • gross obesity
  • tumors
  • ascites
  • pain on inspiration (pleurisy, rib fractures)
45
Q

Why is measurement of CO preferred in DLCO?

A
  • 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
46
Q

What does a low DLCO with obstruction usually mean?

A
  • emphysema

- in children: cystic fibrosis

47
Q

What does a low DLCO with restriction mean?

A
  • pulmonary fibrosis

- hypersensitivity pneumonitis

48
Q

What does a low DLCO witb normal spirometry mean?

A
  • chronic PE
  • anemia
  • early interstitial lung disease
  • increased carboxyheme level
  • CHF
49
Q

What does a high DLCO mean?

A
  • asthma
  • left to right intracardiac shunt
  • polycythemia
50
Q

When is VO2 testing used?

A
  • used to determine a pts functional exercise capacity
  • measuring oxygen uptake
  • VO2 reflects the max ability of a person to take in, transport, and use oxygen - defines that person’s functional aerobic exercise capacity
51
Q

What are the clinical applications for exercise testing?

A
  • work up for heart transplant
  • aid in determining the etiology of cardiac vs pulmonary limitations in exercise
  • eval of pt who is going to undergo lung resection
  • eval of exercise capacity when indicated for medical reasons in pts in whom the estimates of exercise capacity from exercise test time or work rate is unreliable
  • objective grading system for pts with CHF
  • CIs: pts that can’t increase thoracic pressure (post op), or recent eye surgery (increases intracranial pressure) and non-compliant pts

pulmonology (20 decks)

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