19 Flashcards
What instruments do we use to assess lung function?
- Stethoscopes
- Spirometer
- Peak flow meter
What are we listening for when using a stethoscope?
to listen for
-breath sounds
presence of mucus/fluid
-absence of breath sounds: collapsing lung?
What is a peak flow meter used to measure? And in who?
- measure the speed at which you can exhale
- used by chronic asthmatics on a regular basis, keep diaries of results
- need to have a certain amount of skill to use this
- very specific tool
How does a Spirometer work?
- nose clip worn
- breathe in and out of the mouth piece
- water in a container with a floating drum which moves up and down and feeds info into the computer
tidal volume
normal amount of air moved in or out in one quiet breath
vital capacity
amount of air that can be expelled from the lungs after forceful inhalation
inspiratory reserve volume
amount of air that can be inhaled after tidal inhalation
total lung capacity
the amount of air that can be held in the lungs after mac
residual volume
the amount of air that remains in the lungs during deep exhalation
total lung capacity women
4.2L
total lung capacity men
6L
residual volume men
1.2L
residual volume women
1.1L
expiratory reserve volume men
1.0L
expiratory reserve volume women
0.7L
inspiratory reserve volume men
3.3l
inspiratory reserve volume women
1.9L
Tidal volume for men
500ml
Tidal volume for women
500ml
what will happen if you breathe out all the air in your lungs
they will collapse
expiratory reserve volume
the amount of air that can be forcibly exhaled after normal tidal exhalation
total capacity=
IRV + tidal volume + ERV + residual volume
Functional residual capacity
-volume of air left in the lungs after normal exhalation
ERV+RV
-cannot be measured by spirometer (because RV can’t)
-helps to stabilise the composition of alveolar air
inspiratory reserve volume
the amount of air that can be forcibly inhaled after normal tidal inhaliation
Vital capacity
amount of air that can be expired after maximum inspiratory effort
VC=IRV+TV+ERV
Vital capacity men
4.8L
Functional residual capacity
volume of air remaining in the lungs after tidal expiration
FRV= ERV+RV
vital capacity women
3.4L
Inspiratory capacity
amount of air that can be inspired after TIAL exhalation
IC = IRV +TV
Bigger volumes for males because
higher muscle mass and bigger thoracic cavity due to general size
respiratory system adapts to changing oxygen demands by changing the
number of breaths per minute (resp rate)
volume of air moved per breath (tidal volume)
resp volume x tidal volume =
pulmonary ventilation rate/respiratory minute volume
average resp rate =
12
pulmonary ventilation rate at rest is
6L per min
how much air never reaches alveoli per breath
150ml
name the parts of the respiratory system where air is present but no gas exchange takes place
anatomical dead space
alveolar ventilation
amount of air reaching alveoli per minute
resp rate x (TV - air in anatomical dead space) 12 x (500-150) =4.2L per minute
Smaller lung volumes in:
females shorter people non athletes people at low altitude smokers
higher lung volumes in:
males tall people athletes non smokers people at high altitude (coz there is less oxygen)
forces to overcome while breathing
Pulmonary compliance - ease with which lungs can be expanded. effected by:
- elasticity of lung issue
- surfactant
- mobility of chest wall
-Airway resistance
elastic recoil
inhibits inhalation
aids exhalation (passive process)
we need to overcome elastic recoil on inhaling
forces to overcome while inhaling
- elastic recoil
- surface tension of alveoli
- airway resistance
the intra pleural pressure is a smooth straight line in healthy lung. true or false?
false. its a bit wibbly coz we have to overcome certain things when inhaling
measuring elasticity of the lung tissue
- a measure of elastic recoil
- done by measuring the compliance of the lung - volume change of the lung resulting from a given change in pressure
compliance
volume change of the lung resulting from a given change in pressure c=change in
cV/c P L/cmH2O
How does mobility of the cage effect breathing?
problems with mobility of the cage will increase resistance in breathing
What is surface tension?
Forces between molecules in a liquid causing them to stick together
every time you breathe in your alveoli
stretch
-the air fluid interface surface of the fluid is under tension like a thin membrane being stretched
Laplaces law
P = 2T/r pressure surface tension radius of an alveolus at equilibrium, the tendency of increased pressure to expand the alveolus balances the tendency of the surface tension to collapse it.
pulmonary surfactant
increases compliance
reduces surface tension
-equalizes the pressure differences between different sized alveoli
so
why do we want equal pressure across all aveoli
because otherwise air will flow from the high pressure to the low pressure ones and thats just inefficient
how do we change the pressure in an alveoli
change the amount of surfactant. more surfactant = less tension = less pressure
why is there more surfactant in small alveoli
to make them easier to inflate coz they are harder
to equalize the pressure across all sizes of alveoli
when is surfactant produced
28-32 weeks of gestation
what is dangerous for babies born at 28-32 weeks
their lack of surfactant =
- reduced compliance
- alveolar collapse on exhalation
- difficult to inflate lungs
- 50% die without rapid treatment
- treatment is steroids to mature lungs as quickly as possible
Air resistance is the
and is mainly determined by
main ‘non-elastic’ resistance to airflow
radius
where is the highest level of air resistance in the lungs?
bronchi.
although they are wider than the bronchioles etc there are more of the smaller passages
airway resistance reduces as
lung volume increases and the bronchi dilate
when do the bronchi dilate
- as the lung expands reducing resistance
- in response to the sympathetic nerves and adrenaline
when do the bronchi constrict
- parasympathetic causes smooth muscle to contract and bronchoconstriction
- in response to stimuli causing reflex bronchoconstriction
- smoke
- dust
- irritants
- allergens (histamine)
another way of measuring respiration (expiration)
get someone to breathe out as fast and hard as you can
FVC (forced vital capacity) and FEV1 Forced expiratory volume in 1st second.
majority of air should be breathed out in first second
Find the FEV1 as a percentage of the FVC - should be around 80%
used to assess changes in resistance to airflow for e.g. asthma patients
how do you measure changes in resistance to airflow
with FVC and FEV1
