Lecture 30 - Pulmonary Function Test Flashcards
What is flow rate?
Volume of air moved over time
What is a forced exhalation test?
Measure of flow rate during a maximal expiration
What is the forced expiratory volume? Notation? What kind of measure is this?
Volume of air exhaled in the first second of maximal expiration maneuver = FEV1
Measure of flow
What is the forced vital capacity? Notation?
Total volume of air exhaled during a forced expiration = FVC
What % of the FVC does the FEV1 comprise in a normal healthy individual? What will affect this normal number?
FEV1/FVC = 75-80% (or within 10% of the normal expected number)
Factors affecting this number: age, height, race, and gender
What does it mean if the FEV1/FVC ratio is lower than within 10% of the standard value for a particular patient?
Airway obstruction, like with asthma and COPD
FEV1/FVC ratio in restrictive respiratory diseases?
May reach 100% because they have a smaller volume to exhale due to bad compliance
Is the FEV1/FVC ratio used to gage obstructive or restrictive lung diseases?
Obstructive ones
Once obstruction is diagnosed through a forced exhalation test, how is severity determined?
Based on absolute FEV1 ONLY and its % of predicted normal:
Physiological variant > mild > moderate > moderate severe > severe > very severe
What is going on if the FEV1/FVC ratio is less than 10% of predicted normal, but the FEV1 alone is normal?
Physiologic variant: the FVC is much larger than normal (usually in great athletes)
What is representative of a restrictive lung disease?
TLC < 80% of predicted normal through a full pulmonary test
Once an obstructive lung disease has been diagnosed with a forced exhalation test, how can asthma and COPD be distinguished? What to note?
If issue with diffusion: emphysema (COPD)
If not issue then it’s either asthma or chronic bronchitis:
Asthma will show reversibility with an improvement of the FEV1 OR FVC by 12% (at least 200 cc*) with the use of bronchodilators
*this stipulation is necessary because in patients with emphysema have very very low FVCs so could have a 12% improvement that accounts for less than 200 cc
What does a full pulmonary test involve?
- Spirometry + tests for RV
- Forced exhalation test
- DLCO (diffusion capacity of the lungs for CO)
What can be said about the DLCO?
Sensitive test, but not specific
If there is decreased diffusion measured through the DLCO, what are potential causes?
- Decrease in surface area:
- Emphysema
- Pulmonary embolism
- Lung resection - Increased thickness of alveolar membrane:
- Interstitial lung disease (group of diseases that includes sarcoidosis)
- Pulmonary fibrosis
- Pulmonary hypertension
- Pneumonia - Anemia
What is the lung parenchyma?
Respiratory zone
Can you get patients with both COPD (emphysema + chronic bronchitis) AND asthma?
YUP
Since asthma is not a chronic disease, it may be missed on a forced exhalation test on a good day. What can be done to fix this? What patients is this done on?
Done on patients in which asthma is suspected but with normal pulmonary function tests
Bronchoprovocation: induced bronchoconstriction using methacholine inhalation, cold air, or exercise => start with a tiny bit until the FEV1 starts declining or until top dose
If the FEV1 declines by 20% => positive test for asthma, if not 95% sure they do not have asthma
What is the PC20? What does it mean?
Provocative challenge 20 = dose of methacholine causing a decline in FEV1 by 20% in asthma patients during a bronchoprovocation
- High: controlled mild asthma
- Low: severe asthma
What does a normal PFT look like?
- Top: age, race, height, gender to compare all normals on the sheet
- Forced expiratory test with FEV1 + FVC + FEV1/FVC ratio + peak expiratory flow
- Spirometry with 4 capacities + 4 volumes
- Diffusion measures: DLCO
- Back-page: flow-volume loop
What is a peak flow meter? Normal peak flow measured?
Plastic flow meter that patients can take home that records peak flow
Normal: 300-500 mL/min
Unit of peak flow on PFT?
mL/s
On a PFT, what is indicated next to the FRC measure?
PL, N2, or He for the test used to determine RV
On which patients should nitrogen washout and helium dilution should NOT be used to measure RV?
Obstructive lung disease patients because reading will not be accurate
What are pack years of smoking?
Packs of cigarettes they smoke a day x years they have been doing it
Measure on PFT that gives you an idea of how much air is being trapped inside the lungs in an obstructive lung disease?
RV/TLC
If an obstructive lung disease is diagnosed but diffusion is normal, what is going on?
Chronic bronchitis OR asthma
Other symptoms of sarcoidosis other than inflammation of interstitium?
- Hyperpigmented raised rash plaques
2. Dyspnea upon exertion
Classic PFT signs of sarcoidosis?
- TLC < 80% of normal predicted
2. DLCO below normal predicted
Do race, age, gender, and height affect all PFT expected normal values or only FEV1?
ALL PFT expected normal values
