Dynamic Properties

Question 1

what are respiratory dynamics?

Answer 1

the properties of the respiratory system that depend on motion
- not statics but the movements of air

Question 2

what are the different types of air flow?

Answer 2

• laminar = orderly, smooth flow
• turbulent = bounces around
• tracheo-bronchial = mixture of both due to the branching and/or blockage (turbulent at branching, laminar in tubes)

Question 3

what is the relationship between the driving pressure and flow of:
laminar flow and turbulent flow?

Answer 3

• in laminar flow, the flow rate is directly (linear) related to the driving pressure so if you increase driving pressure, you increase flow rate (because there is minimal resistance)
• in turbulent flow, they are directly related (not linear) so you still increase flow rate as you increase driving pressure, but not as significantly because when you increase turbulent flow you increase resistance

Question 4

what is the most influential factor influencing resistance?

Answer 4

radius

Question 5

what is turbulent flow? what direction does it move? pressure required?

Answer 5

Question 6

when does turbulence occur?

Answer 6

when Reynold’s number exceeds 2000 which occurs when:
- density of liquid is higher
- diameter of tube is higher
- velocity is higher
- viscosity is lower

Question 7

what is Reynold’s number and what does it represent?

Answer 7

• basically = turbulence
• incorporates the factors of density of fluid or gas, diameter of tube, velocity of fluid or gas movement, and viscosity into how turbulent the flow is

Question 8

what happens when you increase density of a fluid or gas? how does this correlate to a real life scenario?

Answer 8

• you increase reynold’s number and increase the chance for turbulent flow
• the air we breath is 80% nitrogen 20% oxygen, so for patients in respiratory distress, we give the patient 80/20 helium and oxygen instead because the He is less dense than nitrogen and decreases the turbulence for better movement of air

Question 9

what happens when we increase the diameter of the tube? in this case, the trachea/airways

Answer 9

• the trachea itself has a large diameter and always has turbulent flow
• increase diameter, then you increase the turbulence
• this is why as you go down the airway, you reach the smaller branches and decrease turbulence and have more laminar flow

Question 10

what happens when you increase the velocity?

Answer 10

• so technically when you increase velocity, you increase the flow rate because they are directly proportional
• but in terms of the respiratory system, the flow rate stays the same
• when you branch into bronchi and bronchioles, etc the velocity decreases
• this is because the more branching that you have, increases the TOTAL cross sectional area, thus decreasing velocity
• has to add up to the whole flow
• increase the turbulence

Question 11

how does the total cross sectional area change as you go down the airways?

Answer 11

• increase total CSA
• this is why the velocity in the branches decrease but the flow is the same
• decrease in velocity = decrease in turbulence

Question 12

what is the airflow like in the respiratory tract?
- larger vs smaller airways

Answer 12

• larger airways = always turbulent
• smaller airways = never turbulent

Question 13

what factors affect airway radius?

Answer 13

1. bronchiolar smooth muscle
2. radial traction
3. dynamic airway compression
4. obstructions

Question 14

how does autonomic control affect the radius?
sympathetic

Answer 14

• release of noradrenaline
• causes smooth muscle dilation (bronchodilation) = relaxation of bronchioles
• inhibits mast cells and reduces mucous secretion bc mucous causes radius reduction (so we stop that)
• increases beating of cilia
• result: increased air flow via increase of radius

Question 15

how does autonomic control affect the radius?
parasympathetic

Answer 15

• release ACh
• smooth muscle contraction (bronchoconstriction)
• mucous secretion is increased (caused radius reduction)

Question 16

what is radial traction? how does it change when we breathe? how does it work?

Answer 16

• when you inhale = you increase lung volume = you decrease resistance
• this occurs because the increasing tension in the alveolar walls pulls the conducting airways open – essentially increasing radius which decreases resistance and increases flow
• when the lungs recoil, the alveoli are compressed and the traction to the airway pulls the airway open upon exhalation

Question 17

what happens when you compress the airways?

Answer 17

= forceful expiration
- pressure is applied to the alveoli so the chest is compressed and air is forced out of the lungs
- during this time, some pressure can squeeze the bronchioles because the pressure is so high – this limits how much air flow can be pushed out – also why the system has cartilage to help prevent breaking/resistance against pressure
- like a balloon – can get air out of the system with some effort, but extra effort is needed to increase how much air is let out
- although with extra effort, there is no increase in the maximal air FLOW

Question 18

how does the forced expired volume change over time?

Answer 18

• if you forcefully exhale, 80% of air leaves in the first second
• remember - you can’t expire 100% of the air volume in your lungs
• maximal expiration for 6 seconds – 3-6+ seconds there is no real change in volume expired and almost nothing is coming out
  FVC = forced vital capacity
  FEV = forced expiring volume

Question 19

where is airway resistance the highest?

Answer 19

upper airways
- about 40% of total resistance is here

Question 20

what happens when you have asthma?

Answer 20

• it’s an immune reaction
• obstructive
• causes constriction of smooth muscle because of fluid release and a thickened wall
• overall decrease in diameter

Question 21

what happens when you have emphysema?

Answer 21

• there is weakened and collapsed air sacs with excess mucus
• due to break down of elastic tissue

Question 22

what is emphysema? what does it cause?

Answer 22

• a lung disease that destroys alveolar walls
• lung recoil is decreased, radial traction is lost causing the airway to be more collapsible
• tendency for the airway to close and trap gas, increasing the residual volume
• obstructed airflow and increased resistance
• usually due to smoking because it alters elastin production

Question 23

what are the 2 types of disorders of pulmonary mechanics? what are examples? how do you test for them?

Answer 23

1. obstructive defects (decreased expiratory flow) like asthma, chronic bronchitis, emphysema
2. restrictive defects (reduced lung volumes) like fibrosis, pleural effusion, kyphoscoliosis, paralysis of diaphragm, polio
   - tested for by spirometry

Question 24

what happens to spirometry measurements with obstructive defects?

Answer 24

normal:
- TV = 2L
- FEV1 = 4L
- FVC = 5L
- FEV1/FVC = 0.8 = GOOD
obstructive:
- TV = 2L
- FEV1 = 2L
- FVC = 4L
- FEV1/FVC = 0.5 = BAD – indicative of obstructive pattern

Question 25

what happens to spirometry measurements with restrictive defects?

Answer 25

normal: - TV = 2L - FEV1 = 4L - FVC = 5L - FEV1/FVC = 0.8 = GOOD restrictive: - TV = 1L - FEV1 = 3L - FVC = 3.5L - FEV1/FVC = 0.88 = BAD -- indicative of restrictive defects