Airflow & Gas Exchange

Normal breathing =
Increased RR =
Increased respiratory depth =
Increased respiratory effort =
Absence of breathing =

eupnoea
tachypnoea
hyperpnoea
dyspnoea
apnoea

How does inspiration work?

Ribcage moves up and out
Diaphragm contracts (flattens)
External intercostal muscles contract
Volume of thorax increases
Pressure decreases
Air moves into thorax down pressure gradient

Compliance of the lungs depends on:

elasticity of lungs and surface tension

___ surface tension = ___ lung compliance

Higher
Lower

What does lung surfactant do?

Reduces alveolar surface tension

O2 and CO2 dissolve in...

water
(not lung surfactant)

What factors affect airway resistance?

radius
length
viscosity

Is lower airway resistance greater during inspiration or expiration?

expiration

Lower airways are distended in inspiration

Is upper airway resistance greater during inspiration or expiration?

inspiration

How can the radius of airways be altered?

sympathetic β2 adrenoreceptors
Cause dilation of airways

Is there more turbulence in the trachea or bronchioles?

trachea
turbulence increases with increasing flow speed

Minute ventilation =

tidal volume x respiratory rate

What is the partial pressure of O2 in normal air?

0.21 x 760 (atmospheric pressure) = 160mmHg

How does a gas exert pressure

collisions with other particles and surfaces

Which is more soluble CO2 or O2?

CO2

(more dissolves when partial pressure increases)

Partial pressure of water at alveoli

50mmHg

PO2 = (760-50) x 0.21 = 149mmHg

This removes the water component

Alveolar pressure of O2 will always be ___ than pressure of O2 in airways

Lower

Alveolar pressure of CO2 will always be ___ than pressure of CO2 in airways

Higher

Va:Q ratio

alveolar ventilation and perfusion need to be in equilibrium (both pressures need to be at their normal amounts) for gas exchange to occur
Va = ventilation
Q = perfusion

Low Va:Q ratio =

High Va:Q ratio =

Overperfused and underventilated

Underperfused and overventilated

Hypocapnia and hypercapnia

Drop in PaCO2
Increased PaCO2

Dead space (and examples)

Ventilated areas that don't participate in gas exchange
- circuits
- ET tubes