Lung Volumes Flashcards
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Lung volume
One of the the 4 primary non overlapping sub divisions of total lung capacity
IRV
Air you can breathe in on top of normal breathing
RV
Air in your lungs you can’t breathe out
Four lung volumes?
Tv, irv, Erv, rv
Lung capacity
Measurement comprised of more than one lung volume
Four lung capacitied
TLC, vc, ic, frc
Techniques for measuring residual volume?
Helium dilution method
Nitrogen washout method
Body box plethysmography (applies boyle’s law)
Tv estimation in children?
6 to 10 mls/kg
Erv reflects?
Thoracic and abdominal muscle strength
Vital capacity?
Max volume of gas that can be exhaled after maximum inspiration
Restrictive lung disease affects
Total lung capacity and vital capacity
Frc
Volume of air remaining in lungs at the end of normal tidal expiration
Frc =
Erv + rv
What happens if frc closed to certain volume
Small airways begin to close
Frc functions as a reservoir to supply oxygen during apnea
Tlc
Volime of air contained in the lungs at the end of maximum inspiration. Sum of all 4 lung volumes
Closing capacity?
Lung volume below which small airways begin to close
Fev1
Volume of air that can be expelled in the first second of maximum expiration after maximum inspiration
Fev1 is about 80% of FVC
Values lead than 70 indicate airway obstruction
Fvc
Volume of air that is expelled during forced max expiration after max inspiration
When Fvc is less than lower limit, there may be restrictive pulmonary disorder
Fef 25 to 75
Measures the air flow in the middle of a forced exhalation
Flow equals?
Volume per time
Obstructive lung disease and restrictive
Obstructive is problem with airways eg asthma
Restrictive is problem with lung itself
LOOK AT SLIDE 110
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PEF rate
Maximal rate that a person can exhale during a short maximal expiratory effort after a full inspiration
Use of spirometry in respiratory diagnostics
Obstructive disease(narrow airways eg copd or asthma) Fev1/Fvc ratio reduced
Restrictive(small lung volume). Restricted lung expandion. eg lung fibrosis, kyphoscoliosis, …
Fvc reduced. Fev1/fvc ratio normal
Mixed
Both features present
Note
Pulmonary obstruction brings about involving of second part of expiratory loop
PEF reduced
Restrictive lung disease
Forced vital capacity(segment between TLC and rv reduced)
Breath holding time greater than 25 seconds indicates which VC
Greater than 3.5L
For match blowing test of snider, able to blow match represents?
Fev1 > 1.6l
What is spirometry ideally used for
To diagnose obstructive pulmonary disorders
Flow volume curves may also diagnose intra or extra thoracic airway obstruction
