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Physiology 214 > Section 6: Respiratory Physiology > Flashcards

Section 6: Respiratory Physiology Flashcards

1
Q

What is PaO2 ?

A

arterial (partial) pressure of oxygen

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2
Q

What is PAO2 ?

A

alveolar partial pressure of oxygen

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3
Q

What is PVCO2

A

mixed venous (pulmonary arterial) (partial) pressure of carbon dioxide

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4
Q

What is VD

A

anatomical dead space

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5
Q

What is VO2

A

flow (flux, consumption) of oxygen in L min-1

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6
Q

What is PB?

A

barometric pressure (~760mmHG, 0 atm)

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7
Q

What isFIO2?

A

fractional concentration of oxygen in inspired gas (~0.21)

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8
Q

What is CaCO2

A

concentration of carbon dioxide in areterial blood (~480 mL L-1 blood)

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9
Q

What is the flow equation ?

A

flow = pressure / resistance

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10
Q

oxygen and carbon dioxide pressure in lungs

A 
P<sub>O2</sub> = 100 mmHg
P<sub>CO2</sub> = 40 mmHg

same in lung and pulmonary vein

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11
Q

oxygen and carbond dioxide content in dry air

A

PO2 = 160 mmHg
PCO2 - 0.23 mmHg

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12
Q

oxygen and carbon dioxide content in venous blood

A 
P<sub>O2</sub> = 40 mmHg
P<sub>CO2</sub> = 46 mmHg
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13
Q

action of internal and external intercostal muscles

A

Internal: expiratory
External: inspiratory

Think of orientation similar to coat:
internal (chest) pocket, fingers (muscle fibres) medio-lateral orientation
external pockets, fingers (muscle fibres) superio-inferior orientation

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14
Q

inspiration or expiration passive ?

A

Expiration is typically passive in humans

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15
Q

active and passive components of the respiratory system

(2 each)

A

Active:
Respiratory muscles
Airway smooth muscle

Passive:
Airways
Gas exchange surfaces (alveoli)

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16
Q

Why does diffusion, not bulk flow, move gas in the alveoli?

a) the small dimensions of the alveoli increased
b) need for energy
c) the increased surface area available for diffusion
d) the greatly increased cross-sectional area of the airways
e) the need to ensure complete mixing of O2 , CO2, N2 and H2O

A

d) the greatly increased cross-sectional area of the airways

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17
Q

Flow is equal to:

  1. pressure times resistance
  2. pressure plus resistance
  3. pressure divided by conductance
  4. pressure plus conductance
  5. pressure times conductance
A

​5. pressure times conductance

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18
Q

Poiseuille’s Law

A

R = 8ηl/ πr4

Where:
R = resistance
η = the density of the fluid
l = the length of the tube
r = the radius of the tube

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19
Q

If the radius of a tube doubles (e.g., from 0.5 to 1.0), its resistance:

  1. doubles
  2. increases four fold
  3. is halved
  4. is decreased to an eighth (1/8) of the original value
  5. is decreased to a sixteenth (1/16) of the original value
A
  1. is decreased to a sixteenth (1/16) of the original value

Remember, resistance is proportonal to radius-4

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20
Q

List the ways airway resistance is controlled:

Actively (2)
Passively (2)

A

Passive:

  • Lung volume
  • Strength of airway wall (structures with cartilage have fairly consistant radius)

Active:

  • tone of airway smooth muscle
  • regulated tonicity of autonomic system
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21
Q

Pleural linings of the chest (2)

A

Visceral pleura (covers lung)

Pareital pleura (lines inside of chest)

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22
Q

Compare compliance in saline vs air-filled lung

A

Saline filled lungs have a higher compliance because surface tension is not a factor

23
Q

LaPlace’s law

(pressure)

A

P=2T/r

where
P = internal pressure
T = tension in the wall of the structure ( i.e. surface tension)
r = radius of the structure

24
Q

Explain the flow of air in the diagram below:

(remember that the surface tension in both alveoli are the same

Assume no surfactant

A

The smaller alveoli has a smaller radius and therefore exerts higher pressure (P=2T/r)

Without surfactant, the smaller alveolus would collapse and push all its air into the larger alveolus

25
Q

What cells make surfactant ?

A

Type II cells

26
Q

What does surfactant do ?

A

When the surface area of an alveolus is decreased (alveolus is stretched) the surfactant decreases the surface tension, ensuring smaller alveoli do not empty into larger ones.

27
Q

Treatment for surfactant defficency ?

A

Common in premature births, pts who do not produce surfactant are treated with artificial surfactant.

They used to be treated with high O2, but that can cause problems in neonates and infants.

28
Q

What is FRC ?

A

Functional residual capacity

Volume of respiratory at normal end-expiration

29
Q

Why is FRC important (2 reasons)

A

1) lung remains ~1/2 full, which allows gas exchange to continue during expiration
2) keeps lung at a volume where compliance is maximal

30
Q

Alveolar pressure as a function of transpulmonary pressure and pleural pressure

A

PA = PTP + PPL (= PL + PPL)

Thus, alveolar pressure (PA) is the sum of the transpulmonary pressure (or elastic recoil pressure, PL) and pleural pressure (PPL).

31
Q

For flow between the mouth and the alveoli to be 0 (zero) L/min

  1. the transmural pressure across the alveolar wall (PL or PTP) = 0 cmH2O
  2. alveolar pressure (PA) = ambient barometric pressure (PB)
  3. PA < PB
  4. PA > PB
  5. pleural pressure (PPL) > PB
A
  1. alveolar pressure (PA) = ambient barometric pressure (PB)
32
Q

PA, PTP, PPL at rest

A

Before inspiration starts, the typical values are :

PA = 0 cmH2O (or atmospheric, because there is no flow)
PTP (= Pl) = +5 cmH2O (because the lung wants to collapse),
PPL = -5 cmH2O (because the chest wall wants to
expand)

33
Q

Types of pneumothorax (2)

A 
Traumatic pneumothorax (hole in chest wall)
Spontaneous pneumothorax (hole in lung)
34
Q

What is the EPP ?

A

EPP is equal pressure point

It is the point where the pleural pressure is equal to the pressure in the alveolus / airway

35
Q

What happens to the EPP (equal pressure point) during forced exhalation ?

A

Due to elevated pressure in the pleural space, the EPP is found inside the intrathoracic airway, causing the airway to constrict

36
Q

What is VT

A

Tidal volume (volume taken during normal breath)

37
Q

Why does the airway cross section decrease during a cough ?

And how does this clear the airway ?

A

The EPP moves into the thoracic airways, causing constriction.
It helps remove obstruction because if cross section decreases at same flowrate, linear velocity must increase, hopefully dislodging the obstruction

38
Q

Which of the following lists volumes correctly in order of small to large?

  1. dead space, tidal volume, total lung capacity
  2. vital capacity, functional residual capacity, dead space
  3. total lung capacity, functional residual capacity, residual volume
  4. vital capacity, total lung capacity, inspiratory reserve volume
  5. expiratory reserve volume, vital capacity, tidal volume
A
  1. dead space, tidal volume, total lung capacity
39
Q

obstructive vs restrictive breathing disorders

A

obstructive:
Trouble breathing out; will have higher resting volume

restrictive:
Trouble inspiring; will have lower resting volume than normal

40
Q

PAO2 (normal value)

A

Alveolar pressure of oxygen = ~100mmHg

41
Q

At a barometric pressure (PB) of 747 mmHg, the partial pressure of inspired (tracheal) O2 (PIO2) of a subject breathing 100% O2 is:

  1. 747 mmHg
  2. 700 mmHg
  3. 280 mmHg
  4. 102 mmHg
  5. cannot be determined
A
  1. 700 mmHg

It is reduced because of the addition of water upon inspiration

42
Q

To diffuse X volume/unit time of CO2 requires a small gradient (6 mmHg) vs a large (60 mmHg) for the same volume, X, of O2.
Why?

  1. CO2 is a smaller molecule
  2. CO2 is much more soluble than O2
  3. The alveolar – capillary membrane is more permeable to CO2
  4. CO2 diffuses a shorter distance than O2
  5. The area available for diffusion of CO2 is greater than that available for O2.
A
  1. CO2 is much more soluble than O2
43
Q

How does blood flow respond to decreased regional ventilation ?

A

Regional bronchoconstriction (or obstruction) is matched by hypoxic vasoconstriction to ensure the blood distribution matches available oxygen

44
Q

How does the lung respond to pulmonary vasoconstriction ?

A

Pulmonary vasoconstriction is met by hypercapnic broncodilation

45
Q

In the normal lung at sea level,
the diffusion of O2 into the blood through the alveolar-capillary membrane is complete within:

  1. 1 ms
  2. 10 ms
  3. 100 ms
  4. 300 ms
  5. never complet
A
  1. 300 ms
46
Q

PO2 of blood is determined by:

A

Dissolved O2 only.

Hb(O2)4 does not contribute to PO2

47
Q

Why does anaemia cause hypoxia ?

A

There are fewer haemoglobin molecules in the blood, and therefore less opportunity for transport.

The hemoglobin-oxygen affinity is NOT affected. There’s just less Hb

48
Q

Most O2 is transported in air and blood, respectively, as:

  1. chemically combined and chemically combined
  2. dissolved and dissolved
  3. dissolved and chemically combined
  4. chemically combined and dissolved
  5. none of the above
A
  1. chemically combined and dissolved
49
Q

An increase in [H+] will shift the O2 dissociation curve to:

  1. the left
  2. up
  3. right
  4. down
  5. no effect
A

3 right

(O2 will dissociate at a higher pressure)

50
Q

Full name for HbCO2

A

carbaminohaemoglobin

51
Q

What compensates for the charge change when HCO3- is taken into a RBC

A

HCO3- is exchanged for Cl- (chloride shift)

52
Q

What occurs (re respiration rate) during / shortly after excercise ?

A

Hyperpnea

(NOT hyperventilation.
Hyperventilation is when respiration > metabolism.
It is hyperpnea because the breathing increases to match metabolism )

53
Q

It is important to prevent large changes in arterial pH (regardless of direction) in order to:

A) optimize the activities of enzymes
B) prevent damage to cell membranes
C) prevent excessive changes in membrane potential
D) facilitate the metabolism of glucose
E) give your instructor something dumb to ask.

A

A) optimize the activities of enzymes

54
Q

Hypoxia increases ventilation most by directly stimulating:

  1. respiratory neurons of the cerebral cortex
  2. respiratory neurons of the brainstem
  3. pulmonary chemoreceptors
  4. carotid body chemoreceptors
  5. central (brainstem) chemoreceptors
A
  1. carotid body chemoreceptors

Physiology 214 (8 decks)

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