Lecture 25 - Dynamic Mechanisms Of Breathing

Question 1

What does Poiseuilles law suggest

Answer 1

That the smallest tubes should have the greatest airway resistance, but since there is lots of them the cumulative resistance is lower

Question 2

In resp physiology what is airway resistance

Answer 2

The resistance of the respiratory tract to airflow during inspiration and expiration

Question 3

How is airway resistance measured

Answer 3

By body plethysmography

Question 4

What happens during a traditional body plethysmograph

Answer 4

The test subject is in a sealed chamber with a single mouth piece. At the end of normal expiration the mouth piece is sealed off and the subject is asked to try to inhale

Question 5

What occurs within the lungs during a body plethysmograph

Answer 5

When the subject tries to inhale, the lungs expand decreasing the pressure within the lungs and increasing the lung volume

Question 6

What factors determine resistant in the lung

Answer 6

Lung volume and branching, bronchiolar smooth muscle tone, density and the viscosity of gas

Question 7

What is laminar flow a function of

Answer 7

Gas viscosity

Question 8

What does turbulent flow depend on

Answer 8

Gas density

Question 9

Where does the bronchiolar smooth muscle line

Answer 9

The upper airway

Question 10

What does bronchiolar smooth muscle allow for

Answer 10

Alterations in tone which alter the radius of the bronchiole

Question 11

How is the tube radius decreased

Answer 11

By contraction

Question 12

What factors causes the contraction of the tube

Answer 12

Parasympathetic activity, ACh, irritants and decreased alveolar Pco2

Question 13

How is the tone radius increased

Answer 13

By muscular relaxation

Question 14

What factors cause an increased tube radius

Answer 14

Sympathetic activity, pulmonary stretch, noradrenaline, adrenaline and salbutamol

Question 15

What does bronchiolar smooth muscle have a major role in

Answer 15

Ventilation-perfusion matching and is also linked to lung diseases that are linked to increased resistance

Question 16

In pressure-volume curve what direction is the inspiration and expiration curve

Answer 16

The inspiration curve is upwards and the expiration curve is downwards

Question 17

What can pressure-volume curves be used is assess

Answer 17

Lung overdistension, airway obstruction, bronchiolar response and respiratory mechanics

Question 18

What does the top part of the pressure-volume curve represent

Answer 18

Dynamic compliance

Question 19

What occurs to the pressure-volume curve as airway resistance increases

Answer 19

The curve becomes wider

Question 20

During inhalation what occurs to airway resistance, gas flow and lung volume

Answer 20

The airway resistance decreases as gas flow and lung volume increase

Question 21

What is known as dynamic lowering of resistance during lung expansion

Answer 21

The airways being physically widened

Question 22

During expiration what does the resistance of the upper airway help

Answer 22

To keep airway pressure high to maximise gas movement out of the alveoli

Question 23

What does exhalation work against

Answer 23

Smooth muscle contraction and upper airway resistance

Question 24

What does smooth muscle contraction cause

Answer 24

Dynamic compression

Question 25

What is asthma caused by

Answer 25

An allergic inflammation which can be caused by dust mite fecal allergen or cat saliva allergen

Question 26

What does asthma cause

Answer 26

Hyper-reactivity of the airway smooth muscle contraction which in turn causes bronchial smooth muscle thickening

Question 27

What effect does asthma have on the convective gas flow of the lungs

Answer 27

For it to be much less efficient

Question 28

When gas flow slows to the molecular diffusion rate in the upper airway what are the consequences

Answer 28

There is poor gas exchange in the respiratory acinus

Question 29

When gas fails to reach the distal regions of the respiratory zone what happens

Answer 29

Alveolar Pco2 increases

Question 30

What is the work of breathing used to overcome

Answer 30

The elastic and non-elastic resistances

Question 31

What is work equal to

Answer 31

The force times the distance, which is equal to the pressure times the volume

Question 32

In the quiet breathing cycle, during inspiration the energy input is required to overcome

Answer 32

The elastic component and the surface tension

Question 33

During expiration the energy input is required to overcome

Answer 33

The airway and tissue resistance

Question 34

During inspiration and expiration in panting what is the energy input required for

Answer 34

Inspiration - surface tension

Expiration - dynamic compression and upper airway resistance

Question 35

In deep breathing during inhalation what is the energy input required for

Answer 35

Inhalation - elastic component