Topic 3 - Ventilation and The Breathing Cycle

Question 1

Important pressures?

Answer 1

Atmospheric pressure (Patm): at nose/mouth; 760mmHg - at sea level
Alveolar pressure (Palv): within alveoli, changes thru breathing cycle to be more, less or equal to Patm (similar to Patm)
Intrapleural pressure (Pip): within pleural cavity, lower than Patm during normal breathing, this space has - pressure, functions like a vacuum to “pull” lungs open

Question 2

Why pressure difference?

Answer 2

creates gradient for air to flow thru airways (pressure difference between 2 ends of the airway - high to low pressure)

Question 3

Ventilation is

Answer 3

exchange of air between atm & alv by bulk flow (flows high to low pressure area)

Question 4

In lung capillaries, what assists exchange of O2 & CO2 between alv air and blood

Answer 4

diffusion

Question 5

what are the 2 circulations in lungs? what drives circulation?

Answer 5

pulmonary (blood flow between heart & lungs)
&
systemic (blood flow between heart & rest of body)
driven by diffusion

Question 6

where does oxygenated blood flow

Answer 6

to left heart (left side of heart), then cells in body

Question 7

where does deoxygenated blood flow

Answer 7

from cells (that used the O2) to right heart, then breathed out to atmosphere

Question 8

what is tidal volume

Answer 8

volume of air that enters the lungs during a single breath

Question 9

compare the pressures when air is entering lungs

Answer 9

Palv is less than Patm, air will enter the lungs (air flows high pressure to low)

Question 10

Flow is proportional to what

Answer 10

Flow is proportional to the pressure difference
and inversely proportional to airway resistance

Question 11

pressures at inspiration vs expiration

Answer 11

inspiration = Palv less than Patm (lungs expand)
expiration = Palv more than Patm (passive, relaxes, air is squeezed/forced out)

Question 12

what is the equation for air flow

Answer 12

F = (Palv - Patm)/R
air flow is equal to Palv - Patm, divided by resistance

Question 13

What happens due to Boyle’s Law

Answer 13

Changes in lung dimensions (volume) cause changes in alveolar pressure
Ex: breathing in, compression, ↓V & P ↑
Ex: breathing out, decompression, ↑V & ↓P

Question 14

Boyle’s Law is (equation)?

Answer 14

P1V1=P2V2

Question 15

What determines direction of air flow

Answer 15

Palv- Patm is the driving pressure
gradient

Question 16

what is Ptp

Answer 16

Transpulmonary pressure (major determinant for lung size)
Ptp = Palv - Pip