Respiratory Physiology

Question 1

Rate of gas exchange at rest

Answer 1

250ml/min O2 and CO2

Question 2

How much air in dead space at rest

Answer 2

150ml

Question 3

Effect of sympathetic on airways

Answer 3

Airway dilation

Question 4

Effect of parasympathetic on airways

Answer 4

Airway constriction

Question 5

What is lung compliance

Answer 5

Measure of lungs ability to change volume in relation to changes in pressure

(How easy it is to inflate lungs)

Question 6

What is the compliance in emphysema

Answer 6

High compliance (but low elasticity- easy to inflate lungs, hard to get back out)

Question 7

Surface area of alveoli

Answer 7

80m^2

Question 8

Total lung capacity

Answer 8

6L

Question 9

How much air in lung in normal inspiration? Normal tidal volume?

Answer 9

2.8L

Tidal volume = 500mL

Question 10

What is role of residual volume

Answer 10

Prevent alveolar collapse (reduce breathing work)

Question 11

What is boyles law

Answer 11

Pressure exerted by gas is inversely proportional to its volume (bigger volume = less pressure)

Question 12

Which muscles used in inspiration at rest and at increased respiratory effort

Answer 12

Rest: External intercostals and diaphragm (70%)

Increased respiratory effort: scalenes and sternocleidomastoid

Question 13

Muscles used in expiration

Answer 13

Passive at rest

Increased respiratory effort = internal intercostals and abdominal

Question 14

What is role of surfactant

Answer 14

Increase compliance and reduce tendency to recoil (law of laplace describes pressure required to keep alveoli open)

Question 15

What is the main breathing force in normal circumstances

Answer 15

CO2

Question 16

What is the pulmonary circulation pressure

Answer 16

Low pressure high flow

25/10

Question 17

Why does CO2 diffuse into alveoli so rapidly?

Answer 17

Very soluble in water (compared to O2)

Question 18

Where is ventilation and perfusion matched

Answer 18

Rib 3

Question 19

What causes decreased affinity/rightward curve shift

Answer 19

Acidosis, increased temperature, increased PCO2, increased DPG (diastolic pulmonary gradient)

Aids oxygen unloading in periphery (Bohr effect)

Question 20

What causes leftward shift

Answer 20

(Opposite to right shift)
+
Foetal haemoglobin

Leads to increased affinity

Question 21

Signs of carbon monoxide poisoning

Answer 21

Cherry red skin and mucous membrane

Brain damage

Question 22

What does dorsal respiratory group stimulate?

Answer 22

Inspiratory muscles

Question 23

What does ventral respiratory group stimulate

Answer 23

Tongue, pharynx and expiratory muscles

Question 24

What do central chemoreceptors respond to (where are they located)

Answer 24

Located in medulla

Respond to H+ concentration (CO2

Question 25

What do peripheral chemoreceptors respond to (where are they located)

Answer 25

Carotid and aortic bodies | Respond to H+ concentration and O2 (secondary Ventilatory drive)

Question 26

What is the effect of barbiturates and opioids on respiratory centres

Answer 26

Depress respiratory centres —> overdose can lead to respiratory failure

Question 27

Is nitrous oxide a safe sedative to use? When might it not be?

Answer 27

Safe in most individuals as only blunts peripheral chemoreceptor activity Not suitable for chronic lung disease patients relying on secondary Ventilatory drive

Question 28

What is a shunt

Answer 28

Blood shunted from one side of heart to other without participating in gas exchange

Question 29

Is respiratory acidosis or alkalosis associated with severe lung pathology?

Answer 29

Acidosis