Dynamic Mechanics of Breathing

Question 1

What are dynamic mechanics of breathing?

Answer 1

mechanical properties affecting flow of air into and out of lung as volume changes with time

Question 2

What are the forces of the dynamic mechanics?

Answer 2

resistance
flow
turbulence

Question 3

What is the equation for flow?

Answer 3

Flow = deltaP/R

Question 4

What is the equation for resistance?

Answer 4

R=8nl/pi r4

Question 5

Why is the resistance of small tubes actually lower?

Answer 5

the cumulative resistance is actually lower despite the smallest tubes having greater resistance

Question 6

What is the airflow resistance factor in the trachea?

Answer 6

100%

Question 7

What is the airflow resistance factor in the 17th branch?

Answer 7

0.9%

Question 8

What are the factors determining resistance in the airway?

Answer 8

lung volume and branching
bronchiolar smooth muscle tone
density and viscosity of gases

Question 9

What is the density and viscosity of gases affected by?

Answer 9

altitude

Question 10

What decreases the radius of bronchiolar smooth muscle?

Answer 10

parasympathetic activity
ACh
Irritants
Decreased alveolar PCO2

Question 11

What increases the radius of the bronchiolar smooth muscle?

Answer 11

sympathetic activity
pulmonary stretch
NAdr
Adr B2-adrenoceptors

Question 12

What is the issue with asthma and resistance?

Answer 12

contraction of parabronchial smooth muscle raises upper airway resistance

Question 13

What happens to the molecular diffuse rate and what does this cause in asthamatics?

Answer 13

molecular diffusion rate in upper airway slows and results in poor gas exchange in the respiratory acinus

Question 14

What causes the alveolar pCO2 to rise in asthmatics?

Answer 14

gas fails to penetrate the distal regions of the respiratory zone

Question 15

What causes the asthmatic wheeze?

Answer 15

increased turbulence in the airway

Question 16

What is the asthmatic wheeze complicated by?

Answer 16

dichotomous branching causing turbulence

Question 17

What is used to measure airway resistance?

Answer 17

whole body plethysmography

Question 18

How is the plethysmography system calibrated?

Answer 18

have the subject breathing against a closed shutter

Question 19

How is airway resistance calculated from the plethysmography?

Answer 19

R = deltaPa/V

Question 20

What values are V and Pa during expiration?

Answer 20

both are positive

Question 21

What is used to calculate the negative deltaPa during inhalation?

Answer 21

the positive deltaPbox

Question 22

What is used to measure V?

Answer 22

pneuomotachometer

Question 23

What value is V when inhaling?

Answer 23

negative

Question 24

WHat happens to resistance during inhalation?

Answer 24

resistance falls as gas flow and lung volume increase

Question 25

What does the increased resistance do during exhalation?

Answer 25

helps to keep airway pressure high to maximise gas movement out of alveoli

Question 26

What does smooth muscle contraction cause?

Answer 26

dynamic compression leading to upper airway resistance

Question 27

What can dynamic compression be compared to?

Answer 27

squeezing a toothpaste tube with the lid still on and then releasing the lid

Question 28

What does upper aireway resistance do?

Answer 28

helps gas clearance from the alveoli

Question 29

What do you see in moderate COPD?

Answer 29

inhalation and exhalation are both a bit fuzzy larger resistance change between inhalation and exhalation -15 to 15cmH2O

Question 30

What is normally seen in an inhalation exhalation cycle?

Answer 30

pressure change from -5 to 5cmH2O

Question 31

What is seen in severe COPD?

Answer 31

normalish inhalation phase to +5cmH2O | exhalation phase is fuzzy and tends to fail due to increased resistance

Question 32

What can be seen over time with moderate COPD?

Answer 32

high resistive pressure during inhalation and exhalation

Question 33

What can be seen over time with severe COPD?

Answer 33

nearly normal resistive pressure during inhalation and very deep resistive pressure during exhalation

Question 34

What happens in COPD?

Answer 34

alveoli destruction reduced surface area reduced elasticity

Question 35

What work is involved in breathing?

Answer 35

the energy required to overcome the elastic and non-elastic resistances

Question 36

What are the equations involved in work?

Answer 36

``` Work = force * distance Work = pressure * volume ```

Question 37

What work is required during inspiration?

Answer 37

energy input required to overcome elastic component | energy input required to overcome surface tension

Question 38

What work is involved in exhalation?

Answer 38

energy input to overcome airway and tissue resistance

Question 39

What work can be expected from normal breathing?

Answer 39

540ish

Question 40

What work can be expected from panting?

Answer 40

672 - surface tension and airway resistance, dynamic compression

Question 41

What work can be expected from deep breathing?

Answer 41

660 - overcoming the elastic component