Phys- Mechanics of Breathing

Question 1

Between breaths, ___ exactly opposes ___

Answer 1

Transmural pressure (-4) exactly opposes elastic recoil of the lung

Question 2

Inspiratory muscles

Answer 2

Diaphragm

Accessory = external intercostals, scalenes, SCM

Question 3

Expiratory muscles

Answer 3

Normally passive, but accessory = internal intercostals and abdominal muscles

Question 4

How do the external intercostals assist in inspiration?

Answer 4

Move ribs up and out

Question 5

How do the internal intercostals assist in inspiration?

Answer 5

Move ribs down and in

Question 6

What occurs before transpulmonary pressure changes during breathing?

Answer 6

Chest wall expands/recoils, which causes the change in pressure (remember inverse relationship between volume and pressure)

Question 7

What is the transpulmonary pressure mid-inhalation? Transrespiratory?

Answer 7

Both are negative, drawing air into lungs

more negative in case of Ptp

Question 8

When is intrapleural pressure at its max?

Answer 8

End of inspiration = max lung capacity

Question 9

What change occurs between mid-inhalation and mid-expiration?

Answer 9

Transpulmonary and transrespiratory pressures become less negative, drawing air out of the lungs

Question 10

Describe the mechanism of pneumothorax.

Answer 10

Chest wall/pleura pierced
Pip becomes 0/equalizes with Patm
Chest wall then can spring out and lung can collapse

Question 11

Slope of a pressure-volume curve

Answer 11

Compliance

Question 12

Compliance =

Answer 12

V/P

Question 13

Increased volume = ___ compliance

Answer 13

Increased

Question 14

Decreased compliance = decreased __

Answer 14

Volume

Question 15

Increased compliance = decreased ___

Answer 15

Pressure

Question 16

What is hysteresis?

Answer 16

Difference in expiratory and inspiratory curves on pressure volume graph

Question 17

What causes hysteresis?

Answer 17

Surfactant - When inspiration begins, alveoli must overcome surface tension to open (pressure builds but volume doesn’t increase); when expiration begins, there is no surface tension.

Question 18

FRC =

Answer 18

ERV + RV

1.2 + 1.2 ~ 2.5L

Question 19

The stiffer the lung, the (more/less) compliant

Answer 19

Less

Question 20

The more elasticity a lung has, the (more/less) compliant

Answer 20

Less
(elasticity and compliance are inversely related: a thick rubber band with more elastic tissue has low compliance; a thin rubber band with less elastic tissue has high compliance)

Question 21

A disease causing increased FEC1:FRC would cause (increased/decreased) compliance

Answer 21

Decreased
(Increased FEC1:FRC is a restrictive lung disease, meaning the lungs are stiffer = decreased compliance; fibrosis, pulm edema)

Question 22

Obstructive lung diseases have (increased/decreased) FEC1:FRC and (increased/decreased) compliance

Answer 22

Decreased FEC1:FRC
Increased compliance
(decreased elasticity = increased compliance)

Question 23

What is the consequence of increased elasticity in obstructive diseases?

Answer 23

Lungs are prone to collapse because pressure in the airways and alveoli is less so air can’t get out

Question 24

Why is the FEV1 decreased in obstructive diseases?

Answer 24

Takes longer to get air out

Question 25

Is lung compliance greater during inspiration or expiration?

Answer 25

Expiration | C=V/P, so when volume is greater at beginning of expiration, lungs are more compliant

Question 26

What is the obstructive ventilatory defect in emphysema?

Answer 26

Decreased pressure difference | (so decreased flow, F=P/R

Question 27

What is the obstructive ventilatory defect in asthma/bronchitis?

Answer 27

``` Increased resistance (so decreased flow, (F=P/R) ```

Question 28

Describe the flow volume loop for an obstructive disease.

Answer 28

Inspiratory phase is normal, but expiratory flow rate is reduced while expiratory volume is normal

Question 29

Describe the flow volume loop for a restrictive disease.

Answer 29

Volume of expiration and inhalation are reduced; inspiratory flow rate is reduced greatly; expiratory flow rate is also reduced

Question 30

Describe the volume flow loop in a healthy person.

Answer 30

Volume of inspiration and expiration are equal. Inspiratory flow rate makes a bell curve; expiratory flow rate peaks toward the end of expiration

Question 31

What two factors determine lung compliance?

Answer 31

Elastic forces of lung tissue | Surface forces

Question 32

Describe the support of alveoli structure

Answer 32

Interdependence - wall of one alveolus forms part of the wall of another; if one has tendency to collapse, it's overcome by the expanding forces of surrounding alveoli

Question 33

What creates surface tension?

Answer 33

Nothing to counterbalance force on liquid molecules on top of solution so creates air-liquid interface

Question 34

Surfactant (increases/decreases) compliance

Answer 34

Increases

Question 35

What is the main component of surfactant?

Answer 35

PL (specifically DPPC)

Question 36

LaPlace's Law

Answer 36

P=2T/r

Question 37

Small alveoli without surfactant have (increased/decreased) compliance. Why?

Answer 37

Decreased; C=V/P and P=2T/r; since r is decreased, P is increased and C is decreased; in other words, the strong intermolecular forces between water are strong in a small alveolus because they're in closer contact.

Question 38

Where is surfactant made? Stored?

Answer 38

Type II pneumocytes; Lamellar bodies in those cells

Question 39

Why do we take a deep breath every few minutes?

Answer 39

Stretches type II pneumocytes, releasing surfactant

Question 40

What is respiratory distress syndrome of the newborn/hyaline membrane disease?

Answer 40

Preemies born before 24 weeks gestation can't produce surfactant; this decreases compliance and prevents lungs from expanding so it's a restrictive disease; small alveoli are unstable and pop upon expiration, releasing hyaline into the aveoli.

Question 41

Name for a collapsed airway

Answer 41

Atelectasis

Question 42

Why not have larger alveoli rather than surfactant?

Answer 42

Need small alveoli to increase surface area for gas exchange

Question 43

How does surfactant decrease surface tension?

Answer 43

Disrupts intermolecular forces between water lining alveoli via its amphipathic nature

Question 44

Flow =

Answer 44

P/R

Question 45

Resistance =

Answer 45

8nl/pi(r^4)

Question 46

If radius is halved, resistance (increases/decreases) by ___

Answer 46

Increased, 16

Question 47

4 factors determining airway resistance

Answer 47

1. Anatomic factors 2. Lung volume 3. Bronchial smooth muscle contraction 4. Density and viscosity of inhaled gas

Question 48

Which has more resistance: trachea or respiratory bronchiole?

Answer 48

Trachea | respiratory bronchioles have greater TOTAL surface area, so trachea has smaller radius = greater resistance

Question 49

What role do elastic fibers play in airway resistance?

Answer 49

They tend to attach to exterior of airway and pull out, thus opening the airway and increasing radius = decreasing resistance

Question 50

How does lung volume contribute to airway resistance?

Answer 50

Greater the volume, the more airway diameter increases; increased radius = decreased resistance

Question 51

How do asthmatic overcome increased resistance due to strong airway contraction?

Answer 51

They breathe at higher volumes = increased diameter = reduced resistance = increased flow (Increased V also decreases P; R=FP, so R also decreases)

Question 52

3 diseases for which constriction of bronchial smooth muscle plays important role

Answer 52

Asthma, bronchitis, emphysema

Question 53

Neurotransmitter which causes dilation of BSM

Answer 53

Epi (via B2R)

Question 54

Mediators which cause constriction of BSM

Answer 54

ACh and leukotrienes

Question 55

How does asthma cause airway obstruction?

Answer 55

BSM contraction = decreased radius = increased resistance = decreased flow