BSCI450: Pulmonary Forces

Boyles Law

P = 1/V

does Boyles law apply to the lungs

not completely - open system

air leaves when pressure rises

how much does the diaphragm move during normal breathing

1 cm

how much does the diaphragm move during exercise

10 cm

what happens to pressure and volume during…

inspiration

exhalation

V increases, P decreases
V decreases, P increases

flow formula

F = deltaP/R

what regulates resistance in the respiratory system

bronchiole diameter

muscles of inspiration

diaphragm

external intercostals

muscles of expiration

abdominal

internal intercostals

atmospheric pressure

760 mm Hg

lung layers

lung, pleural sac, chest wall

function of pleural sac

reduce friction between lungs and chest wall

relative to the atmosphere, what is intrapleural pressure (at rest)

-4 mm Hg

relative to the atmosphere, what is intra-alveolar pressure

0 mm Hg

transpulmonary pressure

Palv - Pip = 4 mm Hg

what is the chest wall made of

ribcage + tissue

what is the pleural sac made of

fluid-filled doubled membrane around each lung

why is intrapleural pressure negative

significance

lungs recoil inward and chest wall recoils outward (elasticity)

negative pressure keeps lungs inflated and prevents collapse

example of noncompressible substance

water

what happens when pleural sac is ruptured

lung collapse

spirometer

measures air flow volumes, rates, pressures

when can air flow in

Palv < 0

when is alveolar pressure 0

switch between inspiration and expiration

when is there no net air flow

Palv = 0

tidal volume

normal breathing

expiratory reserve volume

amount you can still exhale after normal breath

inspiratory reserve volume

amount you can still inhale after normal breath

residual volume

air that you can never breathe out

total lung capacity

all air that can fit in lungs, including residual volume

vital capacity

total amount of air you can move (everything but residual volume)

inspiratory capacity

tidal volume + inspiratory reserve

functional residual capacity

expiratory reserve + residual

which part of lung volume includes dead space

residual volume

at FRC (lung volume after a normal, passive exhale)

no net movement of air since outward force of chest wall = inward force of lungs

dead space volume

volume of upper airways that doesn’t do gas exchange

two types of airways

conducting - move air + warm, purify, humidify

respiratory - gas exchange

total pulmonary ventilation

ventilation rate x tidal volume

alveolar ventilation rate formula

ventilation rate(tidal volume - dead space volume)

asthma

obstructive disease

airways narrow -> increase resistance

why do obstructive diseases make breathing hard

narrow airways -> can’t fully exhale -> air trapped in alveoli -> increases residual volume -> overinflate lungs -> inhalation and exhalation require more effort

is inhalation active or passive

active

is exhalation active or passive

depends

what happens do exhalation in obstructive airway disease

active

how to beta 2 agonists help asthma

mechanism

bronchodilation decreases resistance

agonist binds B2 receptor -> Gs activated -> activates AC -> activates cAMP -> activates PKA -> PKA phosphorylates MLCK -> MLCK less active -> less myosin light chain phosphorylated -> less cross bridge