Lecture 13 - Overview of respiratory pathology and lung pressures

Question 1

What is respiration?

Answer 1

The exchange of O2 and CO2 between the tissues and the environment

Question 2

What are the steps of respiration?

Answer 2

1) Ventilation: Process of moving air into and out of the lungs
-supply O2 to and remove CO2 from the alveoli BULK FLOW
2) Gas Exchange: Exchange of O2 and CO2 across alveolar membrane
(air to blood i.e. into body). DIFFUSION
3) Gas transport: Deliver O2 from lungs to tissues and and transport CO2
produced by metabolism to lungs. (Cardiorespiratory) BULK FLOW
4) Gas Exchange: Exchange of O2 and CO2 between the capillaries and
the cells DIFFUSION
5) Cellular respiration: Cells use O2 and produce CO2
METABOLISM

Question 3

What are the functions of the respiratory system? (8)

Answer 3

Provide oxygen
Eliminate carbon dioxide
Filters, warms and humidifies the air we breathe
Communication
Sense of smell
Regulate the pH of the blood, in association with the
kidneys
Defend against microbes
Temperature regulation

Question 4

What occurs during restful inspiration?

Answer 4

Diaphragm contraction

Question 5

What occurs during restful expiration?

Answer 5

lung elastic recoil which pulls thorax and relaxed diaphragm inwards.
No muscle contraction, therefore “passive”

Question 6

What occurs during deep inspiration?

Answer 6

diaphragm and external intercostal
muscle contraction

Question 7

What occurs during deep expiration?

Answer 7

lung elastic recoil and internal
intercostal muscle contraction

Question 8

What occurs during forceful inspiration?

Answer 8

diaphragm and external intercostal
muscle contraction plus contraction of
sternocleidomastoid and pectoralis minor
muscles

Question 9

What occurs during forceful expiration?

Answer 9

lung elastic recoil and internal intercostal muscle contraction plus abdominal muscle contraction

Question 10

What does the pleurae do?

Answer 10

The Pleurae form an envelope between the lungs & chest wall - Double membrane area
Attaches lung to chest wall - allow lung to move with chest

Question 11

From deep to superficial, what are the lung pleura?

Answer 11

Visceral Pleura
Parietal Pleura

Question 12

What does the parietal pleura do?

Answer 12

lines inside of chest wall &
diaphragm

Question 13

What does the visceral pleura do?

Answer 13

lines outside of lungs

Question 14

What is the pleural cavity?

Answer 14

slit-like potential space filled with pleural fluid

Question 15

What is ventilation?

Answer 15

Ventilation is the exchange of air between the atmosphere and alveoli

Question 16

What is bulk flow (F) proportional to?

Answer 16

Bulk flow (F) is proportional to pressure difference (DP)
between two points and inversely proportional to the
resistance (R).

Question 17

What are the P when F=0

Answer 17

Palv = Patm

Question 18

What is needed to generate flow in ventilation?

Answer 18

a PRESSURE gradient - Create a pressure difference (gradient)
between lung (Palv) and atmosphere (Patm)

Question 19

How can we create a lung pressure gradient?

Answer 19

changing lung volumes

Question 20

What is Boyle’s law?

Answer 20

At constant temperature, the volume of a
gas varies inversely with absolute pressure.

Question 21

What happens to pressure during inspiration?

Answer 21

During inspiration –
volume of lung (container)
is increased – decreased
pressure

Question 22

What happens to pressure during expiration?

Answer 22

During expiration – volume
of lung (container) is
decreased – increased
pressure

Question 23

What are the determinants for the changes in lung dimension?

Answer 23

• Difference in the pressure between the inside and outside of the lung - transpulmonary pressure (Ptp or PL )
• Stretchability of the lungs (compliance) – how much the lungs expand for a given change in Ptp

Question 24

What governs the static property of the lung?

Answer 24

Transmural pressure

Question 25

What does transmural pressure resist?

Answer 25

Transmural pressure resists the elastic
recoiling of the lung

Question 26

What is transpulmonary/transmural pressure defined by?

Answer 26

Ptp = Palv-Pip

Question 27

What is the relation between Ptp and lung size?

Answer 27

Lung requires positive Ptp to increase its volume
Lung assumes smallest size when Ptp is zero

Question 28

What is required to achieve stable balance between breathes and why?

Answer 28

Positive Ptp
Lung has the tendency to recoil
inwards and chest wall tends toexpand outwards
To keep the lungs open Ptp should be positive – which opposes elastic
recoil

Question 29

How can we have postive Ptp?

Answer 29

For Ptp to be positive Pip should be negative

Question 30

How can we have a negative Pip?

Answer 30

When the lung collapses and chest wall expands, there is a very minimal expansion in the fluid-filled intrapleural space.
As the fluid cannot expand like air, even this small increase in the pressure creates subatmospheric (negative) intrapleural pressure (Pip).