Breathing Mechanics

Question 1

What establishes the pressure gradient in eupnea?

Answer 1

The alveolar pressure is less than atmospheric pressure

Question 2

How is the pressure gradient established in forced ventilation?

Answer 2

The mouth pressure is higher than alveolar pressure

Question 3

What is the typical value assigned to atmospheric pressure in the context of pulmonary physiology?

Answer 3

0

Question 4

What are the two types of work used in breathing?

Answer 4

Elastic work and resistance work

Question 5

What is the general term for diseases that affect the resistance work done in breathing? For elastic work?

Answer 5

Obstructive diseases; Restrictive diseases

Question 6

What happens to total cross sectional area moving down the respiratory tree?

Answer 6

Cross sectional area increases geometrically

Question 7

What are the parts of the chest wall?

Answer 7

Diaphragm and rib cage

Question 8

At the point between breaths following expiration, what is alveolar pressure?

Answer 8

0

Question 9

What is the name of the pressure of the pleural cavity?

Answer 9

Intrapleural pressure

Question 10

What kind of recoil does the lung have? The chest wall?

Answer 10

Inward; Outward

Question 11

What is the functional residual capacity?

Answer 11

The balance point between lung inward recoil and chest wall’s outward recoil

Question 12

What is transmural pressure?

Answer 12

The pressure difference across the wall of alveoli

Question 13

How can alveolar pressure be calculated?

Answer 13

Intrapleural pressure and aleolar elastic recoil pressure

Question 14

What physical changes in the chest wall occur during inspiration?

Answer 14

Diaphragm moves down and the ribcage moves up and out

Question 15

How does chest wall expansion facilitate inspiration?

Answer 15

As the chest expands it yanks alveoli open since the lung is effectively stuck to the chest wall, and the increase in volume decreases pressure

Question 16

What is the alveolar pressure relative to atmospheric pressure during inspiration?

Answer 16

Alveolar pressure is less that atmospheric for the extent of inspiration

Question 17

How is air exhaled in eupnea?

Answer 17

BY relaxing the inspiratory muscles

Question 18

What muscles are used for normal inspiration? What are the accessory muscles?

Answer 18

External intercostals, parasternals, and diaphragm; sternocleidomastoid and scalenes

Question 19

Approximately what fraction of tidal volume is due to the diaphragm’s movement in a supine position? In an upright position?

Answer 19

2/3; 1/2

Question 20

What muscles are involved in forced expiration?

Answer 20

Internal intercostals, abdominal muscles

Question 21

What muscle(s) is/are necessary for effective respiration?

Answer 21

Diaphragm and external intercostals

Question 22

What happens to intrapleural pressure during inspiration? To alveolar transmural pressure gradient?

Answer 22

It becomes more negative; Transmural pressure increases

Question 23

What is the effect of an increased transmural pressure gradient on elastic recoil?

Answer 23

Increases

Question 24

At functional residual capacity, what is the inward elastic recoil of the alveoli relative to the intrapleural pressure?

Answer 24

Equal and opposite

Question 25

What is the direction of airlow at function residual capacity?

Answer 25

No airflow

Question 26

True or false: The time spent during inspiration is equal to the time spent in expiration?

Answer 26

False

Question 27

What is the difference between the pressure volume curves generated during inspiration and during expiration? What is the name of this difference?

Answer 27

Surfactant; Hysteresis

Question 28

What is the formula for compliance?

Answer 28

Change in volume/ change in pressure

Question 29

How does alveolar compliance change going from low lung volumes to high lung volumes?

Answer 29

More compliance at low volumes and less compliance with higher lung volumes

Question 30

True or False: All alveoli are equally compliant.

Answer 30

False

Question 31

How does compliance add in seried? In parallel?

Answer 31

Compliance in series adds reciprocally in series and directly in parallel

Question 32

What sort of pulmonary conditions decrease lung compliance?

Answer 32

Fibrosis, pulmonary vasculature congestion, pneuothorax, obesity, kyphoscoliosis

Question 33

What sort of pulmonary conditions increase lung compliance?

Answer 33

Emphysemia

Question 34

How can tension be estimated using LaPlace's Law?

Answer 34

Tension is proportional to pressure * radius

Question 35

What reduces the alveolar surface tension below that of water?

Answer 35

Pulmonary surfactant

Question 36

What is the name of alveolar collapse?

Answer 36

Atelectasis

Question 37

What is the result of disturbing the mechaical interdependence of the lungs and the chest wall?

Answer 37

The lung will collapse

Question 38

Pressure measured at the mouth is the sum of what pressures?

Answer 38

Inward recoil pressure and outward chest wall pressure

Question 39

How does standing up facilitate inspiration?

Answer 39

When standing up, gravity is pulling abdominal contents and the diaphragm down

Question 40

How does laying down affect the FRC

Answer 40

Decreases it by 1/3

Question 41

In a healthy person what accounts for most resistance to airflow?

Answer 41

Airway resistance

Question 42

What airways have more resistance?

Answer 42

Upper airways

Question 43

Which method of inhalation has more resistance in adults?

Answer 43

Through the nose

Question 44

What is the formula for resistance?

Answer 44

R= (8*viscosity*length)/(pi*r^4)

Question 45

Flow through the majority of airway is what kind of flow?

Answer 45

Turbulent

Question 46

In what airways does laminar flow occur?

Answer 46

Very small airways

Question 47

What is the formula for Reynold's number?

Answer 47

Re=(density*velocity*diameter)/(viscosity)

Question 48

What is the effect of increased blood flow on pulmonary vascular resistace?

Answer 48

Increased blood flow decreases pulmonary vascular resistance

Question 49

What is the effect of parasympathetic stimulation on airways?

Answer 49

Constriction

Question 50

What chemical species induce airway constriction?

Answer 50

ACh, Histamine, Leukotrienes, Thromboxane A2, Seotonin, and alpha-adrenergic agonists

Question 51

How does PCO2 affect airway diameter?

Answer 51

Decreased PCO2 mediates constriction in the small airways; increased PCO2 mediates dilation in small airways

Question 52

What ANS system induces bronchodilation? Through what main receptor?

Answer 52

Sympathetic; Beta 2

Question 53

What chemical species induce bronchodilation?

Answer 53

Circulating beta 2 agonists, NO, increased PCO2

Question 54

At what point in the tracheobronchiole tree is there no more cartilage surrounding the airways?

Answer 54

Terminal bronchioles

Question 55

What is the relationship between lung volume and airway resistance?

Answer 55

Airway resistance decreases with increasing lung volume

Question 56

What are the two reasons that airway resistance decreases with more lung volume?

Answer 56

1) Small airways are compressible/distensible- therefore greater transmural pressures will open the airways more 2) Traction pulls the airway open

Question 57

During forced expiration what happens to intrapleural pressure?

Answer 57

Intrapleural pressure gets more and more positive

Question 58

What is the relationship of lung volume and alveolar elastic recoil?

Answer 58

The alveolar elastic recoil pressure decreases at lower lung volumes bc the alveolus is not as distended

Question 59

What is the main reason that airway resistance appears to be approaching infinity at low lung volumes?

Answer 59

Small airway collapse

Question 60

What is dynamic compression of airways?

Answer 60

Increased airway resistance during a forced expiration

Question 61

When dynamic compression occurs what serves as the effective pressure gradient?

Answer 61

Alveolar pressure minus intrapleural pressure

Question 62

What is the effective driving pressure for airflow from the lung during dynamic compression?

Answer 62

Alveolar elastic recoil pressure

Question 63

What is forced vital capacity?

Answer 63

The volume of air a subject is able to expire through a maximal expiratory effort following a maximal inspiration to the total lung capacity

Question 64

Following expiration of the FVC, what volume remains in the lungs?

Answer 64

Residual volume

Question 65

What is FEV1?

Answer 65

Forced expiratory volume in 1 second

Question 66

What ratio is a good index of expiratory airways resistance?

Answer 66

FEV1/FVC

Question 67

What is the typical value of the FEV1/FVCin young healthy persons?

Answer 67

~0.8

Question 68

What is the forced expiratory flow rate?

Answer 68

The slope of a line drawn between the points on the expiratory curve at 25% and 75% of the FVC

Question 69

What is the main concept underlying the FVC pulmonary function test?

Answer 69

Elevated airways resistance takes time to overcome

Question 70

At what lung volumes is airflow entirely effort dependent? How?

Answer 70

High lung volumes; Alveolar elastic recoil pressure is high (increasing traction and airflow pressure gradient) and because highly positive intrapleural pressures cannot be attained

Question 71

What is the equal pressure point hypothesis?

Answer 71

An explanation for flow limitation during forced expiration that says that at any instant during a forced expiration, there is a point along the airways where the pressure inside the airway isjust equal to the pressure outside the airway-- the point at which the transmural pressure gradient is 0

Question 72

As forced expiratory effort continues, what happends to the equal pressure point?

Answer 72

Moves down the airway from larger to smaller airways towards the alveoli

Question 73

What causes effort independence in forced expiration?

Answer 73

Airways resistance is increasing with more effort due to greater dynamic compression. The equal pressure point moves down to small compressible airways and is fixed there. Increasing the intrapleural pressure increases the alveolar pressure by the same amount

Question 74

True or false: No effort independence is seen with forceful inspiration through the mouth

Answer 74

True

Question 75

Patients with what sort of conditions would demonstrate inspiratory effort independence?

Answer 75

Upper airway problems (obstructive sleep apnea or vocal cord paralysis)

Question 76

What are obstructive pulmonary diseases? Restrictive?

Answer 76

Diseases that interfere with airflow; diseases that restrict expansion of the lung

Question 77

Why is the maximal airflow rate lower in patients with restictive disease?

Answer 77

The total lung capacity is decreased

Question 78

What is the effect of a fixed obstruction on the flow-volume loop?

Answer 78

Truncated inspiratory and expiratory curves

Question 79

What is the effect of an variable intrathoracic obstruction on the flow-volume loop? Variable extrathoracic?

Answer 79

Intra- truncated expiratory loop; extra- truncated inspiratory loop

Question 80

What is dynamic compliance of the lungs?

Answer 80

The change in the volume of the lungs divided by the change in the alveolar-distending pressure durin the course of a breath

Question 81

What is the relationship between obstructive pulmonary disease and dynamic compliance? Why?

Answer 81

Obstructive disease decreases dynamic compliance; There is more resistance in small airways and so alveoli take longer to fill and empty and so with faster breathing they don't contribute to changing the total lung volume and so it, and therefore dynamic compliance decrease

Question 82

What is the name of the condition which can occur when putting patients with obstructive pulmonary disease on positive pressure-ventilation where more air is coming in the lungs than can leave?

Answer 82

Auto- PEEP or stacked breath

Question 83

When does alveolar elastic recoil become negative?

Answer 83

Alveolar elastic recoil pressure is NEVER negative