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What is the most common measurement of lung function?
- Pulmonary Function Test: measures vital capacity
- varies with height, age, and position
true or False: Abnormal PFTs diagnose a disease.
FALSE. They are not diagnostic!!
What are PFT's used for?
- a) follow progress of patients with lung disorders
- b) assess results of treatment
- c) identify patients with abnormal lung function
What is a pulmonary function test specifically measuring?
What is a normal value for vital capacity (even though it changes with age, position, etc.)?
A patient has an abnormal vital capacity if it is less than _____% of the predictive value.
A decreased vital capacity may result from:
- 1. lung pathology (ex. pnemonia, atelectasis, pulm fibrosis)
- 2. loss of lung tissue (ex following surgical incision)
- 3. causes other than lung disease (ex. muscle weakness, abdominal swelling, pain)
What is FEV?
Forced Expiratory Volume
-Typically measured over 1 second
What is FVC?
Forced vital capacity
Ration of FEV/FVC helps categorize a lung disease as ___________ or ___________.
Obstructive or Restrictive
A key thing to remember about obstructive lung disorders, is that their FEV/FVC ration will be ____________.
Characteristically, these patients have a % way less than normaL!
What is a normal FEV/FVC ratio?
What are some examples of obstructive lung disorders?
What are some examples of restrictive lung diseases?
Pulmonary fibrosis, pulmonary edema, pneumonia
What is another name for the Maximum Breathing Capacity test?
Maximum Ventilatory Volume
Describe how you would perform a Maximum Breathing Capacity test.
Have the patient breath as fast as they could for 60 seconds. Young man WNL is 150-175 L/min
What are some problems with the Maximum Breathing Capacity test?
- -it identifies an abnormality is present, but doesn't explain what/where
- -depends on the patients tolerance to stress, inspiratory efforts, and motivation
What measures are used to gauge the muscle strength of the ventilatory muscles?
Pimax and Pemax
What does Pimax measure? When is the measurement taken? What is a normal value?
Pimax measures the maximum inspiratory pressure. It is measuring the tension in the diaphragm.
Pimax is measured just before inspiration starts.
Pimax normal value is -100 (when performing a NIF looking for value of at least -25)
What does a Pemax measure? When is the measurement taken? What is a normal value?
Pemax measures maximum expiratory pressure.
Pemax measured just before exhalation starts.
Pemax normal value is +200.
A patient you are taking care of has a Pemax of +20. What does this indicate?
The patient has an impaired ability to cough post-operative, putting them at an increased risk for pneumonia.
Looking for a Pemax of at least +40
What 3 physiologic determinants are there for Maximum flow rates?
- 1. Degree of Effort (strength of muscle contraction)
- 2. Elastic recoil pressure of lungs
- 3. Airway resistance
True or False: A patient with restrictive lung disease breathes at HIGH lung volumes.
A patient with restrictive lung disease, breathes at low lung volumes with quick exhales
True or False: A patient with obstructive lung disease breathes at HIGH lung volumes.
A patient with obstructive lung disease breathes at high volumes related to gas trapping.
What is the difference between a capnogram and capnography?
Capnogram: just the numerical representation of exhaled CO2
Capnography: tracing/chart: must have LMA/ETT to get
True or False: In a normal capnograph the plateau should be wavy and irregular.
In a normal capnograph, the plateau should be flat (representing where the CO2 is leaving the alveoli)
If the capnography plateau is sloped, this indicates what type of disease?
In regards to capnography, describe phase 0-III.
- Phase 0: inspiring, nothing happening with CO2
- Phase I: 1-2 seconds into inhalation, no CO2 coming out because this gas is from dead space
- Phase II: rapidly rising level of CO2 indicating mix of gases
- Phase III: Alveolar plateau
What is the most commonly seen capnography abnormality?
Altered Time Constant
-Patient with obstructive disease, time to exhale isn't constant
-Bigger the upslope: worse the disease.
When a patient rebreathes CO2, what will the capnography look like?
The plateau will never completely drop off, because the patient is never really clearing the CO2
**check your anesthesia machine! this isnt normal!
Where does peripheral airway disease mainly occur?
Small airways... ie alveoli
What is an example of patient with peripheral airway disease?
Young smoker of 5 years
What tests can you use to detect peripheral airway disease (before a PFT would pick up on changes)?
- 1. Alveolar-arterial oxygen tension difference
- 2. frequency dependence of compliance
- 3. nitrogen washout
- 4. closing volume
- 5.V/Q inequality
Tell me about the alveolar-arterial oxygen tension difference test.
Theoretically, would be used to detect small airway disease; however, it's not generally used.
Determine alveolar 02 through PA02...since
In someone with small airway disease, the gradient would be higher than normal [WNL: young adult: 2-15, elderly: 37]
What does the frequency of dependence of compliance imply?
The frequency of dependence of compliance implies that asynchronous behavior of the lung (some parts of the lung are moving out of sync with other parts of the lung)
Proves point that when patients with small airway disease strain lungs and increase respiratory rate, they trap gas.
What is Nitrogen Washout?
A pulmonary function test to detect small airway disease.
Hyperoxygenate the patient and then measure N2 exhaled; patients with small airway disease will exhale N2 when healthy patients would have cleared N2 during hyperoxygenation (or denitrogenation)
How does closing volume indicate peripheral airway disease?
Peripheral airway disease patients have a lower closing volume
True or False: A V/Q Inequality is present in early lung diseases.
- Exhibited by:
- 1. A-a O2 gradient
- 2. Physiologic shunt of venous admixture
- 3. alveolar dead space