L18 - Mechanics of Breathing

Question 1

what is respiration

Answer 1

exchange of gases between atmosphere blood and cells

contributes to homeostasis
regulates pH of internal environemtn

Question 2

what is pulmonary ventilation

Answer 2

breathing

Question 3

diff between external and internal respiration

Answer 3

external = pulmonary, between pulmonary caps and alveoli

internal = tissue, between systemic caps and tissue cells

Question 4

what law is pulmonary ventialtion dependent on

Answer 4

Boyles law

states that at constant temp, pressure of gas inverse to volume

and also
that air flows from high to low pressure

Question 5

what is atm pressure at sea level (normal)

Answer 5

760mm Hg

Question 6

what happens when lung vol increases

Answer 6

intrapulmonary pressure drops
air moves in

and vice versa

Question 7

what are the 4 diff pressures to know about

Answer 7

intrapleural
intrapulmonary
transpulmonary
atmospheric

see onenote for more info on each

Question 8

what is lung compliance and what 3 things is it affected by

Answer 8

the ease with which the lungs can expand

depedns on
- elasticity of lung tissue
- mobility of chest wall
- surface tension

Question 9

what does elastic recoil oppose and aid

Answer 9

opposes inspiration
aids expiration

Question 10

why is the intrapleural pressure not linear during inspiration and expiration

Answer 10

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

Question 11

formula for compliance (litres/cmH2O)

Answer 11

change in volume/change in pressure

measures the elastic recoil

Question 12

what equation tells us the pressure in each alveolus bubble

Answer 12

P = 2T/r
where T is surface tension
and r is radius

at equilibrium the pressures are balanced so it doesnt collapse

Question 13

what does surfactant to in relation to surface tension

Answer 13

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

Question 14

what is neonatal respiratory distress sydrome

Answer 14

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

Question 15

whats the 2nd biggest ersistance to gas flow

Answer 15

airway resistance

Question 16

what is resistance mainly determined by

Answer 16

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

Question 17

what 2 factors affect airway resistance

Answer 17

lung volume - bronchi dilate as the lung expands

bronchial smooth muscle - bronchoconstriction or bronchodilation (allows more or less O2 to be absorbed)

Question 18

what is FVC

Answer 18

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)

Question 19

how can breath sounds be sed to assess lung fucntion

Answer 19

can check for presence of mucous or fluid

or
absence of breath sounds (couold be a collapsed lung)

Question 20

what does a peak flow meter do

Answer 20

measures speed at which u can breath out
(the thing you used to check if u had asthma)

Question 21

what device used to measure lung volumes and capacities>

Answer 21

spirometer

(see onenote for spirometry graphs)

Question 22

which volume cant be measured by spirometry

Answer 22

functional residual capacity

Question 23

respiratory volumes : avg tidal volume

Answer 23

m= 0.5L
f=0.5L

Question 24

respiratory volumes : avg expiratory reserve volume

Answer 24

m=1L
f=0.7L

Question 25

respiratory volumes : avg inspiratory reserve volume

Answer 25

m= 3.3L
f = 1.9L

Question 26

respiratory volumes : residual volume

Answer 26

m= 1.2L
f 1.1L

Question 27

respiratory capacities: avg vital capacity

Answer 27

m= 4.8L
f= 4.2L

Question 28

respiratory capacities: avg total lung capacity

Answer 28

m=6L
f=4.2L

Question 29

equation for respiratory minute volume (ie amount of air moved per minute)

Answer 29

tidal volume x breathing frq

(cuz tidal vol is just how much air moved per breath)

Question 30

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)

Answer 30

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)

Question 31

equation to calculate alveolar ventilation?

Answer 31

respiratory rate x (tidal volume - anatomical dead space)