Objective Measures of Pulmonary Function Flashcards
What is a PFT
Pulmonary Function Test
RR nl for adult and neonate
Adult- 10-20
Neonate 30-40
Pulse oximeter optimal level
> 95
Pulse ox, when should you change your intervention
<90
remember the steep drop off bc of the dissociation curve
Pulse ox, when should you stop activity
<85
Can you do chest percussion to someone with a pneumothorax
NO, it is a contraindication - it might make the pneumothorax bigger
Two ways to treat a pneumothorax
Chest tube if it is big
or
DBE
When might you see a pneumothorax and who is at high risk
- May be seen post surgically
- May result from a stab wound or MVA
- Can occur spontaneously
At high risk:
Very tall, thin people
People with connective tissue disease like Marfan’s
People with dz that leads to blebs and bullae like CF
What are V-Q scans
It is how we decide if we have equal ventilation and perfusion in equal measure
Tests reveal how alveolar ventilation and pulmonary perfusion are matched
How are V-Q scans done
The subject inhales xenon gas and then holds his/her breath while photoscintigrams – ventilation scans – are taken
To measure perfusion in lungs, the subject receives an IV injection of radioactive iodine and photoscintigrams – perfusion scans – are taken
Then you put the two test together
What is the symbol for perfusion
Q
What are V-Q scans diagnostic for
Can be diagnostic for Blood Clots or SHUNTING
What other test might be done if you have a V-Q mismatching
D-Dimer
How is D-dimer produced
D-Dimer is produced when fibrin degrades
How is a D-Dimer test scored
A negative score virtually rules out thromboembolism
A positive score indicates the possibility of DVT or PE
A PFT provides information on, and can help determine (4 points)
- Provide information regarding the integrity of the airways
- Help to determine if a patient has obstructive or restrictive lung disease
- Used by insurance companies to determine whether someone qualifies for pulmonary rehab
- Provide an objective measure for improvement or decline
How is a PFT done and what is used to do a PFT
A simple spirometer is used to obtain lung capacities
A graphic tracing called a spirogram is used to interpret test results
For testing, the patient sits upright with a clip
over the nose
The patient breathes in the spirometer through a tight-fitting mouthpiece
What is a tracing
A graphic tracing called a spirogram is used to interpret test results of the PFT
What are the 8 things that a spirogram measures
TLC - Total lung capacity
VC - Vital capacity
RV - Residual volume
IC - Inspiratory Capacity
FRC - Functional reserve capacity
IRV - Inspiratory reserve volume
TV - Tidal volume
ERV - Expiratory reserve volume
What is TLC
total lung capacity - everything together
What is VC
Vital capacity is the IRV + TV + ERV
What is RV
Residual volume - amount of air that doesn’t leave lungs
you do not want lungs to be empty
What is IC
Inspiratory Capacity is your TV plus your IRV
What is FRC
It is the RV+the ERV
What is TV
Tidal Volume - breathing in and out
What is ERV
Expiratory reserve volume - it is how much you can exhale past the tidal volume
What happens to the RV of someone who has an air trapping disease
Their RV gets very big
How are the results of spirogram measures reported
in percentages - this helps take into account age and size
How does the performance that someone gives on a PFT tell you if the person has normal function
Performance is compared to a huge data base of
age and size matched controls
If accurate it will reveal what % of normal function a person has
Can someone have a VC above 100%
Yes, it just means the person went above the norm.
ex: olympic swimmer is likely to be above 100%
A PFT tracing gives you a …
visual picture of airflow and volume
What would a PFT look like for person with an obstruction
If a person has and obstructive disease it is going to take them longer to breath out so you will get a concavity
What would a PFT look like for person with a restrictive disease
Looks like a normal shape but everything is smaller
What is normal IC between
3000 and 4000ml
What does FVC stand for and what is it
Forced vital capacity (FVC) is the amount of air that can be forcefully exhaled as quickly as possible
What would cause the FVC to change
Obstructive disease
FEV1, what is it and what are the normal and abnormal values
Volume of air that can be forcefully expired in the first second of a FVC
An FEV1 > 2.0 liters is normal
An FEV1 < 1.0 liter is considered indicative of
severe obstruction
Can you measure RV using a spirometer
NO
How do you measure RV
Either the subject is measured using an air-tight booth and pressure changes are recorded as the subject breathes
or
The subject inhales a small amount of an inert gas like helium and residual volume is calculated based on how much is expired
Would someone with COPD have a RV greater than 100% or less than 100%
Greater bc air is trapped
FEV1/FVC, how is it different than other readings, what is it measuring and what is the nl
FEV1/FVC is different than the other readings
Most values are converted to percentages,
after comparison to matched norms
FEV1/FVC is already reported as a percentage
so we look at the raw number (80% is ≈ nl)
How much you can get out in one second verses how much you can get out completely
FEV1/FVC, how is it different than other readings, what is it measuring and what is the nl
FEV1/FVC is different than the other readings
Most values are converted to percentages,
after comparison to matched norms
FEV1/FVC is already reported as a percentage
so we look at the raw number (80% is ≈ nl)
How much you can get out in one second verses how much you can get out completely
Is FEV1/FEC more useful with restrictive or obstructive disease and why
Obstructive Disease!
obstructive disease everything is smaller so you might get the same ratio out but everything is reduced
What FEV1/FVC percentage is our value to justify services
60% or less is the value often used as criteria to justify services
