PFTs Flashcards
what kind of information can you obtain from PFTs?
- 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 the chest are
- the diffusion characteristics of the membrane through which the gas moves
- measurement of how the lungs have responded to tx
Indications for PFTs
- screening for lung disease
- following progression of disease
- evaluating effectiveness of therapy
- evaluating before surgery
- assessment of impairment or disability.
What are they types of PFTs?
- spirometry
- peak flow
- measurement of lung volumes (body box)
- quantification of diffusion capacity
- oxygen uptake –exercise capacity
Spirometry
- measures what?
- what graphic illustration does this provide?
- Forced expiratory volume in 1 second (FEV1)
- Forced Vital Capacity (FVC)
- Flow Volume Loop
list some examples of obstructive disease?
- asthma
- bronchitis
- excessive mucus plugging
- foreign object inhalation
- invasive tumors
- COPD
Can TLC be measured by spirometry?
-no, because air remains in the lungs at the end of maximal exhalation.
A decrease in lung volumes means what kind of lung disease?
restrictive
How do you measure Total Lung Capacity?
- Helium dilution
- Nitrogen Washout
- Body plethysmography (gold standard)
- Chest radiograph or HRCT
What are some examples of restricitve disorders?
Neuromuscular:
- malnutrition
- paralysis of diaphragm
- Myasthenia Gravis
- Muscular dystrophy
- Poliomyelitis
- ALS
Intrinsic Disorders:
- Sarcoidosis
- TB
- Pneuomonectomy
- Pneumonia
What is:
- FEV1
- FVC
- FEF
FEV1: forced expiratory volume in 1 sec
FVC: forced vital capacity (volume of air that can be maximally forcefully exhaled)
FEF 25-75%: average forced expiratory flow during the mid portion of the FVC.
what test is sensitive for early obstructive airway disease?
FEF 25-75%
what is PEFR?
-the peak expiratory flow rate during expiration, it is the measure of the highest expiratory flow rate during PFT test.
Define:
- TLC
- VC
- TV
- RV
TLC: volume in lungs at maximal inspiration
VC: maximum volume expired after a maximum inspiration
TV: the volume inspired and expired during normal breathing
RV: volume left in the lungs after maximal expiration
What is the normal and abnormal range of values for FVC and FEV1
FVC and FEV1 are over 80% of predicted values.
Abnormal if they are below 70%
what would you expect the FEV1/FVC ratio to be with obstructive & restrictive disease?
WHat would you expect to flow volume curve to look like?
FEV1/FVC for obstructive disease is less than 70%
FEV1/FVC for restrictive disease is greater than 70%
CURVE:
obstructive- concave, descends more quickly than normal, sharp point
restrictive- smaller version of normal flow.
Bronchoprovocation Challenge:
- when do you perform this test?
- how does this work?
- what is a positive test value?
When do you perform this:
- pt who has sx of asthma, but has normal PFTs and no response to bronchodilator therapy
- patient who experiences sx not usually associated with asthma
- those who require screening tests for asthma such as scuba divers, military ppl.
How does it work:
- pre test spirometry for baseline reading
- give pt an irritant(methacholine) to try to induce bronchoconstriction, repeat spirometry 30 and 90 seconds afterwards
Positive Test value:
-decrease of 20% in FEV1
Who cannot have a bronchoprovocation challenge??
- unstable cardiac dz
- MI in last three mo
- Stroke in last 3 mo
- uncontrolled HTN
- significant bronchospasm already present
- prenancy/nursing
Bronchodilators
- what can this test determine?
- if the patient improves 2 of their FVC, FEV1, and FEF 25-75% tests what does this mean?
- What are the improvement standards? (indicating the dz is reversible)
- determines reversibility of airway obstruction
- if two of three measurements improve then the pt has a reversible airway obstruction that is responsive to medication.
- require FEV1 or FVC to increase more than 12% AND more than 200mL in adults or just 12% increase in ages 5-18.
WIth restrictive lung disease both FEV1 and FVC present with normal or increased FEV1/FVC ratio, true or false?
True!!!
Explain the expected FEV1, FEV, FEV1/FVC for someone with restrictive and obstructive disease.
Obstructive: FEV1: decreased FVC: decreased FEV1/FVC: decreased. *ratio less than 70%
Restrictive: FEV1: decreased FVC: decreased FEV1/FVC: increased or normal *Ratio greater than 70%
Diffusion Capacity (DLCO) -useful test for?
Useful:
- determining the degree of emphysema in smokers
- differentiating chronic bronchitis from emphysema in smokers
- restrictive disease differentiating interstitial lung disease from restrictive etiologies of disease
- recurrent PE
- Pulmonary HTN
- Disability measurement.
How does DLCO work?
- inhale CO and helium
- hold breath for 10 seconds and then exhale quickly
- obtain measurement.
- smoking lowers DLCO
- CO preferred in this test because its not normally present in alveoli/blood and avidly binds to Hgb
What do the results of DLCO mean? Which disease is associated?
Low DLCO with obstruction: emphysema or CF in kids
Low DLCO with restriction: pulmonary fibrosis or hypersensitivity pneumonitis
High DLCO: Asthma, polycythemia
VO2 Testing
-what does this determine?
- determines how efficient the cardio-resp system is together. (according to jeN)
- determines patients functional exercise capacity
- the ability of a person to take in, transport, and use oxygen.
