Measures of lung physiology Flashcards
Inspiratory reserve volume definition
amount of air in excess tidal inspiratory that can be inhaled wth maximum effort
what does IRV stand for
inspiratory reserve volume
what is the average value of IRV
3l
Expiratory reserve volume definition
amount of air in excess tidal expiration that can be exhaled with maximum effort
what does ERV stand for
expiratory reserve volume
what is the average value of ERV
1.2L
residual volume definition
amount of air remaining in lungs after maximum expiration
what does RV stand for
residual volume
what is the average value of RV
1.2L
what is the purpose of RV
keeps alveoli inflated between breaths and mixes with fresh air on next inspiration
vital capacity definition
amount of air that can exhaled with maximum effort after maximum inspiration
what does VC stand for
vital capacity
what is the average value of VC
4.7L
what is useful about VC
assess strength of thoracic muscles as well as pulmonary function
what is an equation for VC
ERV + TV + IRV
functional residual capacity definition
amount of air remaining in lungs after normal tidal expiration
what is FRC
functional residual capacity
what is the average value of FRC
2.4L
what is an equation for FRC
FRC = RV + ERV
inspiratory capacity definition
maximum amount of air that can be inhaled after a normal tidal expiration
what is IC
inspiratory capacity
what is an average value for IC
3.5L
what is an equation for IC
IC = TV + IRV
total lung capacity equation
maximum amount of air the lungs can contain
what does TLC stand for
total lung capacity
what is an average value for TLC
5.9L
what is an equation for TLC
TLC = RV + VC
tidal volume definition
amount of air inhaled or exhaled in 1 breath
what does TV stand for
tidal volume
what is an average TV
500ml
what is an equation for pressure
pressure = flow x resistance
what is Poiseuilles law
airways resistance is proportional to 4th power of radius
describe a flow volume curve
flow greatest at start of expiration and declines linearly with volume
what is carbon monoxide single breath transfer factor used for
good measure of gas exchange in alveolar capillary
why is CO used to estimate DLco
has high affinity for binding to Hb
what is the exhaled nitric oxide test
indirect measure of airway inflammation
what does total blody plethysmography measure
total lung capacity including air trapped in bullae
what does gas dilution measure
all air in lungs that communicates with airways - doesn’t measure air in non-communicating bullae
what gas is used in gas dilution
helium
what is compliance (in regard to lungs)
change in volume per unit change in pressure gradient between pleura and alveoli (transpulmonary pressure)
what does a larger lung compliance mean
lungs are more readily expanded
what determines lung compliance
Stretchability if lung tissue and surface tension of air-water interfaces in alveoli
what is FEV1
forced expiration volume in 1st second of expiration
OR
volume of air expelled after 1 second of forced expiration
what is a value of FEV1
80% of VC in health
what does FVC stand for
forced vital capacity
FVC definition
volume of air that can be forcefully exhaled with a maximal inspiration
what does FVC measure
lung size
what does a low value FVC show
restriction
what is peak expiratory flow
single measure of highest flow during expiration
what shows airway obstruction
FEV1/ FVC ratio < 0.70
what shows airway restriction
low value FVC (< 80%)
why does airway restriction have low value FVC
reduced compliance of lungs so FEV1 and FVC reduced, but ratio remains the same
describe the signs of asthma
obstruction
PEF variation
reduced mix-expiratory flow
good response to treatment
describe the signs of COPD
obstruction lack of significant PEF variation reduced mid-expiratory flow partial/ poor response to treatment low DLco because capillary interface destroyed so transfer problems
describe the signs of pulmonary fibrosis
restriction
lack of PEF variation
reduced mid-expiratory volume
