PFTs Flashcards
There will be a question on the graph of FEV1% as a function of age - comparing normal decline in FEV1 to the accelerated decline in COPD
just know it
know your lung volumes, capacities, and how to calculate
will be on test (TV, IRV, ERV, RV, VC, FRC, TLC)
in the ICU, we can use PEEP to oxygenate patients. what lung volume or capacity does PEEP affect in order to be effective?
PEEP increases FRC
when you evaluate a spirometry, you compare to predicted normal. what are the factors (3) that go in to predicting normal, and how do they correlate
1) sex (male larger lungs)
2) age (negative correlation)
3) Height (positive correlation)
what one key factor is NOT a predictor of normal for lung function measured by spirometry?
weight
what is the definition of a positive bronchodilator response seen on PFT
an increase in FEV1 of 200 mL AND 12%
or
15% from basal FEV1
does obstructive lung disease reduce FVC?
yes
does restrictive lung disease reduce FVC?
yes
how does obstructive lung disease affect FEV1/FVC ratio?
obstructive lung disease dec FEV1/FVC
how does restrictive lung disease affect FEV1/FVC ratio?
restrictive lung dz inc FEV1/FVC
what volume can you not measure with spirometry? what capacity can you not measure with spirometry?
cannot measure RV
so cannot measure FRC or TLC
how do you measure RV and FRC?
body box (plethysmograph)
what 4 factors will reduce TLC?
1) dz of thorax
2) inspiratory muscles
3) pleural dz
4) loss of functioning alveoli
what 3 factors will reduce VC?
1) chest pain
2) fatigue
3) poor effort
what is the mechanism of dyspnea in COPD, especially upon exercise?
dynamic hyperinflation - at baseline, a COPD pt has an inc FRC, which means their inspiratory capacity is already less. Once start exercising, they inc breathing rate, so they start trapping more air, stacking more air into their lungs on each breath, until their FRC is essentially at TLC, i.e. there is no more inspiratory capacity left and they can no longer breathe
define compliance
the change in volume a lung has for a given change in pressure
does asthma dec or inc compliance?
there is no change in compliance, if there are no complications
emphysema compliance?
compliance is inc
fibrosis compliance
compliance is dec
a normal VC excludes what kind of disorder?
a normal VC excludes a significant restrictive disorder - i.e. in restriction, volumes must be dec
restrictive lung diseases have hyperflows - define this and what does this mean about the elasticity of the lung
flow velocities are higher for each given instantaneous volume - thus there is greater elastic recoil
what is the characteristic shape of expiratory arm of flow volume loop for COPD? what does this indicate?
scooping - indicates slower flow rates for the effort independent portion of the curve
if you see a hamburger shape of the flow volume loop (both the inhalation and exhalation arms are dec) what does this indicate
fixed obstruction of upper airways
what is the diffusion capacity of CO compared to O2?
Diffusion capacity of CO 210x the diff cap of O2
what is a functioning capillary bed? how do we measure?
a capillary bed that is perfused that is in contact with ventilated alveoli
the DLCO measures this components - of diffusion
what does the DLCO “single breath” technique require
an inhaled VC of more than 1L and 10 sec of breath holding
Muthiah - how do we determine a spirometry was of good quality
exhalation time greater than 6 seconds
Muthiah - what are 3 conditions that will dec FRC
1) obesity
2) ascites
3) pregnancy
Muthiah - which part of flow volume loop is effort dependent
the first part of the exhalation arm, the peak flow, is effort dependent
Muthiah - on the flow volume loop what indicates obstruction
scooping
Muthiah - what cannot you not measure by spirometry
RV
Muthiah - define RV
the air that is left after complete exhalation
Muthiah - what is the mechanism of dyspnea in pts w/ obstructive lung dz
dynamic hyperinflation
Muthiah - what indicates dynamic hyperinflation on spiromtery/ in life
a reduction in the inspiratory capacity
Muthiah - what composes the inspiratory capacity
TV + IRV
Muthiah - what happens to TLC in restrictive lung dz
TLC decreases
Muthiah - what appearance do you see in flow volume loop when there is a fixed upper airway obstruction
hamburger
Muthiah - what does an isolated decrease in DLCO indicate
pulmonary vascular disease
