Work of ventilation 2

Question 1

non elastic work in breathing

Answer 1

frictional/resistive work

force to overcome air-flow resistance - force to move air through airways

Question 2

airway resistance definition

Answer 2

the impedance of air flow through the tracheobronchial tree as a result of friction of gas molecules
Very important contribution to the work of breathing

Question 3

when is airway resistance present

Answer 3

during both inspiration and expiration

Question 4

what does increased airway resistance require

Answer 4

greater pressure gradient to drive airflow and result in the same tidal volume of approximately 500 ml

Question 5

2 main components to determine the airway resistance

Answer 5

Diameter of the airway (cross sectional area) and distance air has to travel
Lung volume
Bronchial smooth muscle tone
Thickness of mucous lining and submucosa
Mucus layer
flow type/pattern - laminar or turbulent

Question 6

driving pressure

Answer 6

pressure difference between mouth and alveoli

Question 7

hagen-poiseuille law relates to

Answer 7

Relates flow rate (volume transported per time unit) to airway radius and to distance the air is transported

Question 8

flow rate

Answer 8

(V/t) = ΔP π r4/ 8 η l
ΔP = Driving Pressure; r = Radius; η = viscosity; l = Length

Question 9

what law is used to express airway resistance

Answer 9

hagen-poiseuille law

Question 10

resistance definition

Answer 10

the ratio between the driving pressure and the associated flow rate.

Question 11

resistance formula

Answer 11

Resistance (R) = ΔP/V/t = 8ηl /πr4

Question 12

if airway radius is reduced to 50% by how much is the resistance increased

Answer 12

increased 16 fold

1/(0.5)4*

Question 13

is the resistance in trachea or bronchioles higher and why

Answer 13

bronchioles have smaller radius than trachea but a more of them than trachea - overall the airway widens
resistance in trachea is higher than bronchioles

Question 14

as the airway resistance decreases ..

Answer 14

lung volume increases

increases airway diameter

Question 15

what contributes to the diameter airways of trachea and bronchi

Answer 15

cartilage prevent collapse

Question 16

what contributes to the airway diameter in the small bronchi and bronchioles

Answer 16

no supporting cartilages 
pull of surrounding tissue
innervated smooth muscle
small diameter easily obstructed
offer little resistance

Question 17

what features of the lungs in the walls of the airways contribute to the airway diameter

Answer 17

Smooth muscle tone

Thickness of mucosa/submucosa

Question 18

what features in the lumen of the airway contribute to the airway diameter

Answer 18

mucus

Question 19

what intrinsically controls the smooth muscle tone

Answer 19

chemical mediators - mast cell degranulation (via release of histamine) and inflammatory mediators lead to bronchoconstriction

Question 20

when CO2 is raised it leads to

Answer 20

bronchodilation

Question 21

when CO2 is lowered it leads to

Answer 21

bronchoconstriction

Question 22

factors influencing secretions

Answer 22

Secretions of seromucous glands and goblet cells that line respiratory system

Question 23

where are the seromucous glands and goblets cells

Answer 23

5-10 μm thick, inner layer more watery to allow ciliary action and upper layer more viscid to trap particles

Question 24

seromucous glands and goblet cells are controlled by what category of the CNS

Answer 24

by parasympathetic nervous system reflexes and local chemical stimulation

Question 25

activities of seromucous glands and goblet are increased in

Answer 25

bronchitis

Question 26

activities of seromucous glands and goblet are decreased in

Answer 26

atropine

Question 27

how does turbulence affect air flow resistance

Answer 27

increase airflow resistance

Question 28

how is reynolds number expressed in straight tubes

Answer 28

``` R = 2rvd/η r = Radius; v = velocity; d = Fluid density; η = Fluid viscosity ```

Question 29

what promotes turbulences

Answer 29

high velocities and large diameters

Question 30

turbulence in airway can lead to

Answer 30

Empty Nose Syndrome/paradoxical obstruction

Question 31

why don't turbulences occur in bronchioles

Answer 31

velocities are low and diameters are small

Question 32

sites of airway resistance

Answer 32

greatest resistance in large airways | 1/2 in nose, pharynx and larynx

Question 33

where does 80% of airway resistance occur

Answer 33

Below larynx –in trachea and main bronchi

Question 34

where does less than 20% of airway resistance occur

Answer 34

in bronchioles

Question 35

how is asthma caused

Answer 35

lung inflammation

Question 36

how is asthma treated and explain the treatments mechanism

Answer 36

Treat with bronchodilators and corticosteroids Bronchodilators relax bronchial smooth muscle and widen airways Corticosteroids reduce inflammation and reduce secretions

Question 37

chronic obstructive pulmonary disease examples

Answer 37

chronic bronchitis | emphysema

Question 38

how is chronic bronchitis affect work of ventilation

Answer 38

excess production of mucus increased flow work leads to cough, production of sputum

Question 39

how is chronic bronchitis treated

Answer 39

cessation of smoking, antibiotics (if bacterial), bronchodilators

Question 40

how does emphysema impact work of ventilation

Answer 40

Loss of elastic tissue due to uncontrolled action of proteolytic enzymes loss of elastic work

Question 41

how is emphysema treated

Answer 41

Treat by cessation of smoking, avoiding irritants, lung transplant

Question 42

pulmonary fibrosis

Answer 42

Formation of excess fibrous connective tissue in the lung. | Restrictive lung disease, reduces compliance

Question 43

causes of pulmonary fibrosis

Answer 43

Idiopathic Inhalation of pollutants (coal dust, asbestos) Certain medications (bleomycin) Disease (Sarcoidosis)

Question 44

treatment of pulmonary fibrosis

Answer 44

Immune supressive agents (corticosteroids) Oxygen supplementation (improves QOL) Lung transplantation

Question 45

what is the difference between obstructive and restrictive respiratory disease

Answer 45

Obstructive - interfere with MOVEMENT of air, increase FLOW- RESISTIVE work, no effect on ELASTIC work, decrease FEV1, NOT FVC Restrictive - Interfere w/ ABILITY to EXPAND LUNGS, increases ELASTIC work, NO EFFECT on FLOW- RESISTIVE work, decrease FEV1 AND FVC

Question 46

determinants of airway diameters

Answer 46

lung volume bronchial smooth muscle tone thickness of mucous lining and submucosa mucus layer

Question 47

what features outside the airway contribute to the airway diameter

Answer 47

radial traction of elastic tissue | pressure from lymph nodes

Question 48

smoking can cause goblet cell hyperplasia which subsequently causes increased mucus production. What effect would this have on the work of breathing.

Answer 48

increases flow resistive work

Question 49

how do we know if turbulence occurs in reynolds number

Answer 49

if reynolds number is greater than approx. 2000

Question 50

how does the hagen poiseuille equation relate to another law

Answer 50

resistance = driving pressure/ flow rate | ohm's law resistance = voltage / current