L18 - Mechanics of Breathing Flashcards
what is respiration
exchange of gases between atmosphere blood and cells
contributes to homeostasis
regulates pH of internal environemtn
what is pulmonary ventilation
breathing
diff between external and internal respiration
external = pulmonary, between pulmonary caps and alveoli
internal = tissue, between systemic caps and tissue cells
what law is pulmonary ventialtion dependent on
Boyles law
states that at constant temp, pressure of gas inverse to volume
and also
that air flows from high to low pressure
what is atm pressure at sea level (normal)
760mm Hg
what happens when lung vol increases
intrapulmonary pressure drops
air moves in
and vice versa
what are the 4 diff pressures to know about
intrapleural
intrapulmonary
transpulmonary
atmospheric
see onenote for more info on each
what is lung compliance and what 3 things is it affected by
the ease with which the lungs can expand
depedns on
- elasticity of lung tissue
- mobility of chest wall
- surface tension
what does elastic recoil oppose and aid
opposes inspiration
aids expiration
why is the intrapleural pressure not linear during inspiration and expiration
graph curves cuz of airway resistance
see powerpoint for the graph
starts at -5cm H2O
kinda curves cuz faster at the beginning
and cuz of air resistance, the pressure increases not linear during expiration
formula for compliance (litres/cmH2O)
change in volume/change in pressure
measures the elastic recoil
what equation tells us the pressure in each alveolus bubble
P = 2T/r
where T is surface tension
and r is radius
at equilibrium the pressures are balanced so it doesnt collapse
what does surfactant to in relation to surface tension
decreases surface tension
this increases compliance
allows the pressure differences between alveoli to equalise, so they inflate and deflate equally (more surfacted concentrated in smaller alveoli)
see slides for the diagram
what is neonatal respiratory distress sydrome
surfactant made at 28-32 weeks
so in preemie babies theres a lack of surfactant
so reduced compliance
and on initial exhalation when baby comes out
the alveoli collaps
and its hard to inflate the lungs
so 50% die w/o rapid treatment
whats the 2nd biggest ersistance to gas flow
airway resistance
what is resistance mainly determined by
radius of airways
(similar to blood vessels)
but it acc decreases as airways get smaller just cuz theres so many more so increased surface area
what 2 factors affect airway resistance
lung volume - bronchi dilate as the lung expands
bronchial smooth muscle - bronchoconstriction or bronchodilation (allows more or less O2 to be absorbed)
what is FVC
forced vital capactiy
amount of air u can forcibly breathe out
Describde as %
FEV1 (volume of air expired in 1 second)/FVC x100
acts as a comparison, and can check for abnormalities if someones having trouble breathing out (asthma)
how can breath sounds be sed to assess lung fucntion
can check for presence of mucous or fluid
or
absence of breath sounds (couold be a collapsed lung)
what does a peak flow meter do
measures speed at which u can breath out
(the thing you used to check if u had asthma)
what device used to measure lung volumes and capacities>
spirometer
(see onenote for spirometry graphs)
which volume cant be measured by spirometry
functional residual capacity
respiratory volumes : avg tidal volume
m= 0.5L
f=0.5L
respiratory volumes : avg expiratory reserve volume
m=1L
f=0.7L
respiratory volumes : avg inspiratory reserve volume
m= 3.3L
f = 1.9L
respiratory volumes : residual volume
m= 1.2L
f 1.1L
respiratory capacities: avg vital capacity
m= 4.8L
f= 4.2L
respiratory capacities: avg total lung capacity
m=6L
f=4.2L
equation for respiratory minute volume (ie amount of air moved per minute)
tidal volume x breathing frq
(cuz tidal vol is just how much air moved per breath)
why’s there a diff between the amount of air u take in (pulmonary ventilation) and the amount of air acc used in respiration (alveolar ventilaion)
for every 0.5L, 0.15L doesnt reach alveolar surfaces
it just stays in conducting passages that dont participate in gas exchange (anatomical dead space)
equation to calculate alveolar ventilation?
respiratory rate x (tidal volume - anatomical dead space)
