Respiratory Physiology Lecture 2 Flashcards
(83 cards)
1
Q
What does Boyle’s Law state?
A
The pressure and volume of a gas are inversely related
P1*V1 = P2*V2
2
Q
A decrease in PIP causes the lungs to ______
A
expand
3
Q
What does Henry’s Law state?
A
The amount of gas that dissolves into a fluid is related to:
- solubility of the gas into that fluid
- Temperature of the fluid
- Partial pressure of the gas
4
Q
What does Dalton’s Law state?
A
The total pressure of a gas mixture is equal to the sum of the pressures that each gas exerts independently
Ex: PB = PO2 + PN2……
5
Q
What are normal atmospheric pressure (PB) as well as partial pressures of N2 (PN2) and O2 (PO2)?
A
PB: 760 mm Hg
PN2: 600 mm Hg (~79%)
PO2: 160 mm Hg (~21%)
6
Q
PO2 = ?
A
PO2 = PB * FO2
(FO2 = fraction of O2)
7
Q
What happens to PB, PO2, and FO2 when elevation increases? Why?
A
PB: decreases
PO2: decreases
FO2: no change
Gravity is decreased at higher elevations, which causes pressures to decrease.
8
Q
What is the purpose of your lungs diluting gas with water vapor during inspiration?
A
Keeps alveoli moist; Decrease PO2 without changing the percentage of O2
9
Q
VE = ?
A
VE = VT * f
VE = total ventilation (mL/min)
VT = tidal volume (mL/breath)
f = respiratory rate or frequency (breaths/min)
10
Q
What is a normal total ventilation at rest?
A
~6000 mL/min
500 mL/breath * 12 breaths/min
11
Q
What are the two types of dead space? How are they different?
A
Anatomical dead space: in conducting airways (~150 mL) prior to alveoli
Alveolar dead space: alveoli with poor circulation (varies); lethal in diseased lungs
12
Q
VA = ?
A
VA = (VT - VD) * f
VA = alveolar ventilation (more important than VE)
VT = tidal volume
VD = anatomic dead space
f = respiratory rate
13
Q
What is a normal alveolar ventilation?
A
~4200 mL/min
(500 mL/breath - 150 mL) * 12 breaths/min
14
Q
What happens to alveolar ventilation during shallow, rapid breathing?
A
Decreases drastically (“wasted ventilation”)
15
Q
What is the best way to increase alveolar ventilation?
A
By increasing tidal volume
16
Q
What is PaCO2?
A
Partial pressure of CO2 in arterial blood
17
Q
What happens to PaCO2 during hyperventilation (increase VA)?
A
Decreases
18
Q
What happens to PaCO2 during hypoventilation (VA decreases)?
A
Increases
19
Q
Changing VA is the mechanism for regulating _____? (2)
A
PaCO2
pH
20
Q
What are some reasons as to why VA would not be adequate to overcome high PaCO2? (2)
A
Not enough ventilation (CNS depression or respiratory muscle weakness)
Too much ventilation ending up as dead space ventilation (COPD or rapid, shallow breathing)
21
Q
If PaCO2 is > 45 mmHg, what happens to the blood and alveolar ventilation?
A
Blood: Hypercapnia
VA: Hypoventilation
22
Q
If PaCO2 is 35-45 mmHg, what happens to the blood and alveolar ventilation?
A
Blood: eucapnia
VA: normal
23
Q
If PaCO2 is < 35 mmHg, what happens to the blood and alveolar ventilation?
A
Blood: hypocapnia
Alveolar ventilation: hyperventilation
24
Q
What is the alveolar gas equation?
A
Measures partial pressure of a gas in an alveolus
Ex: PAO2 = PIO2 - PACO2 / R
PIO2 = PO2 in
PACO2 = PO2 leaving alveoli
R = ratio of CO2 to O2 exchanged in alveoli (assume 0.8)
25
What is PO2 under the following conditions?
Ambient air (dry)
Moist tracheal air
**Alveolar gas (R = 0.8)**
**Systemic arterial blood**
Mixed venous blood
Ambient air (dry): 159 mmHg
Moist tracheal air: 150 mmHg
**Alveolar gas (R = 0.8): 102 mmHg**
**Systemic arterial blood: 90 mmHg**
Mixed venous blood: 40 mmHg
26
What is PCO2 for the following conditions:
Ambient air (dry)
Moist tracheal air
**Alveolar gas (R = 0.8)**
**Systemic arterial blood**
Mixed venous blood
Ambient air (dry): 0 mmHg
Moist tracheal air: 0 mmHg
**Alveolar gas (R = 0.8): 40 mmHg**
**Systemic arterial blood: 40 mmHg**
Mixed venous blood: 46 mmHg
27
Why does PACO2 = PaCO2?
CO2 has a high diffusibility
28
What are the two circulations that the lungs receive? What do they do?
Pulmonary circulation: perfuse alveoli for gas exchange; arises from RV; receives 100% of RV output
Bronchial circulation: meet the needs of the lung (similar to coronaries for the heart); arises from aorta; 2% of LV output
29
Pulmonary blood flow has _____ flow and _____ pressure.
High flow (5 L/min)
Low pressure (25/8 mmHg)
30
What factors contribute to a very compliant, low resistance pulmonary circulation which relies on a weak pump (RV)? (4)
Pulmonary arteries are shorter and more dilated
Pulmonary arterioles are thin-walled (less smooth muscle & tone)
More distensible (7x more compliant)
Enormous number of capillaries, in unique arrangement to create sheets of blood flow past alveoli (resistors in parallel)
31
What three factors alter pulmonary vascular resistance?
Changes in blood flow (perfusion)
Changes in lung volume
Changes in local O2 concentrations
32
What happens to pulmonary blood flow and resistance during times of increased cardiac output (exercise)?
Increased pulmonary blood flow
Decreased resistance
33
What happens to pulmonary blood flow and resistance during times of low cardiac output (heart failure)?
Decreased pulmonary blood flow
Increased resistance
34
How is resistance decreased at high lung volumes?
PIP becomes more negative
Transmural pressure increases
**Distended extra-alveolar vessels**
Resistance decreases
35
How is resistance increased at high lung volumes?
Alveolar diameter increases, crushing alveolar vessels
36
How is resistance increased at low lung volumes?
PIP becomes more positive
**compresses extra-alveolar vessels**
increases resistance
37
How is resistance decreased at low lung volumes?
Alveolar diameter decreases
38
What is the difference between hypoxia and hypoxemia? What do they trigger?
Hypoxia: low O2 in alveoli
Hypoxemia: low O2 in blood
Both trigger vasoconstriction of the pulmonary circulation and vasodilation systemically
39
What are the differences between regional and generalized hypoxia?
Regional: vasoconstriction localized to specific regions of the lungs; often caused by bronchial obstruction
Generalized: vasoconstriction throughout both lungs; caused by high altitudes and chronic hypoxia (asthma, emphysema, etc)
40
Which factor has the greatest effect on regional distribution of blood flow in the lungs?
Pulmonary circulation
Gravity
Gravity
41
In an upright person, blood flow in the lungs is highest near _____ and lowest near \_\_\_\_\_
Highest: near base
Lowest: near apex
42
Every 1 cm above the heart, hydrostatic pressure decreases \_\_\_\_\_?
0.74 mmHg
43
What three pressure affect pulmonary blood flow and help differentiate lung zones (1, 2, and 3)?
Alveolar (PA)
Venous (PV)
Arterial (Pa)
44
Describe zone 1 of the lungs. How is it created?
Apex
Occurs when PA \> Pa (positive pressure ventilation or hemorrhage)
Usually small/nonexistent in healthy people
45
Describe zone 2 of the lungs. What are the differences in pressure for Pa, PA, and PV?
Middle 1/3 of the lung
Pa \> PA \> PV
46
Which zone of the lungs is the primary area of distension and recruitment of vessels during exercise?
Zone 2
47
What are the pressure differences between PV, PA, and Pa in zone 3 of the lungs?
Pa \> PV \> PA
48
What is the optimal ventilation/perfusion (V/Q) ratio for gas exchange?
0.8 - 1.0
49
What are the two types of gas movement in the lungs? How are they different from each other?
**Bulk flow**: how gas moves in airways from trachea to alveoli; mass movement like water out of a faucet; occurs when there are differences in total pressure
**Diffusion**: how gas moves in us from air --\> liquid; liquid --\> air; gases move due to their individual pressure gradients
50
Gas diffusion is determined by what two factors?
Diffusion properties of a membrane (Fick's Law)
Pulmonary capillary blood flow
51
What does Fick's Law state? Which variable is the biggest determinant of rate of diffusion?
Vgas α **(A \* D \* (P1-P2)/T)**
A = surface area
D = diffusion constant of a specific gas
P1-P2 (biggest determinant) = partial pressure difference of the gas on each side of the tissue
T = tissue thickness
**Vgas is directly related to numerator; inversely related to T**
52
How many Hb molecules are there in one red blood cell?
280 million
53
The amount of HbO2 is a function of _____ in blood.
PO2
54
When blood PO2 is high in the pulmonary capillaries, \_\_\_\_\_.
forms HbO2 (increased % saturation)
55
When blood PO2 is low in systemic capillaries, \_\_\_\_\_.
O2 is released from Hb (decreased % saturation)
56
SO2 = ?
**SO2 = (HbO2 content/HbO2 capacity) \* 100**
SO2: % saturation of Hb with O2
HbO2: oxyhemoglobin
57
Does binding of O2 to each heme group increase or decrease the affinity of Hb for O2?
Increase
58
What does it mean when the oxyhemoglobin dissociation curve "shifts right"? What factors can cause this? (Hint: CADET face right)
Decrease in Hb's affinity for O2; aids in release/unloading of O2
CO2
Acidity
2,3 diphosphoglycerate (end product in RBC metabolism)
Temperature
59
What does it mean when the oxyhemoglobin dissociation curve "shifts left"?
Increase in Hb's affinity for O2; aids in uptake/binding of O2
60
Carbon monoxide (CO) shifts the oxyhemoglobin curve \_\_\_\_\_\_. Why?
Left
CO and O2 compete for the same Hb binding site, but CO has a 240x greater affinity than O2
61
How is CO2 transported in the blood? (3)
As bicarbonate ions (60%)
Physically dissolved (10%)
Chemically bound to Hb (30%)
62
Total CO2 content in arterial blood is \_\_\_\_\_\_.
59 mL CO2/100 mL blood
63
Total O2 content in arterial blood is \_\_\_\_\_\_.
19.7 mL O2/100 mL blood
64
What does CaO2 represent? How is it calculated?
The total number of O2 molecules in arterial blood, both bound and unbound to Hb
**CaO2 = (Hb (g/dL) \* 1.34 mL O2/g Hb \*SaO2) + (PaO2 \* (0.003 mL O2/mmHg/dL))**
1. 34 mL/g Hb: fully saturated Hb
0. 003 mL O2/mmHg/dL: how much O2 can be dissolved for each mmHg of pressure at body temperature
65
On one visit, a patient has a PaO2 of 85 mmHg, an SaO2 of 98%, and a Hb of 14 g/dL. One year later her hemoglobin is 7 g/dL. Assuming no lung disease, what will be her new PaO2, SaO2, and CaO2?
PaO2 unchanged
SaO2 unchanged
CaO2 reduced
66
Which patient is more hypoxemic (total O2)?
A: PaO2 85 mmHg, SaO2 95%, Hb 7 g/dL
B: PaO2 55mmHg, SaO2 85%, Hb 15 g/dL
Patient A
67
How do the effects of gravity on the upright lung affect the following at the apex:
Blood flow
Ventilation
V/Q ratio
PaO2
PaCO2
Drastically decreases blood flow
Decreases ventilation (overventilated)
Increased V/Q ratio
Increased PaO2
Decreased PaCO2
68
How do the effects of gravity on the upright lung affect the following at the base:
Blood flow
Ventilation
V/Q ratio
PaO2
PaCO2
Drastically increases blood flow (overperfused)
Increases ventilation
Decreases V/Q ratio
Drastically decreased PaO2 (blood not fully oxygenated)
Increased PaO2
69
What is the Alveolar-arterial O2 difference (A-a gradient) and what is it used for? What is the equation for it? What is a normal value for it?
Measure of gas exchange efficiency across alveolar-capillary membrane; used to determine cause of hypoxemia
**P(A-a)O2 = [(PB-H2O) \* (FIO2) - PaCO2/R] - PO2**
\*FIO2 = fraction of O2 in
≤ 20mmHg
70
What are the five causes of hypoxemia? What must PaO2 be in order to be considered hypoxemic?
1. Hypoventilation
2. Low inspired O2
3. Right-to-left shunt (deoxy blood bypasses lungs)
4. V/Q mismatch (emphysema)
5. Diffusion impairment
**PaO2 \< 80 mmHg**
71
In hypoxemia, how is A-aO2 difference affected under each of the five causes?
Hypoventilation
Low inspired O2
R-L shunt
V/Q mismatch
Diffusion impairment
Hypoventilation: no change
Low inspired O2: no change
R-L shunt: increase
V/Q mismatch: increase
Diffusion impairment: increase
72
In hypoxemia, how is FIO2 affected under each of the five causes?
Hypoventilation
Low inspired O2
R-L shunt
V/Q mismatch
Diffusion impairment
Hypoventilation: increases
Low inspired O2: increases
R-L shunt: no change
V/Q mismatch: increases
Diffusion impairment: increases
73
What are the three components of the ventilatory system? What are they each responsible for?
Sensors (chemoreceptors & mechanoreceptors) = feedback
Central controller (respiratory control center) = the driver
Effectors (respiratory muscles) = carry out the orders
74
What are the components of the respiratory control center (2)?
Medullary Centers
Pontine centers
75
What are the two components of the medullary center? What are their functions?
**Dorsal respiratory group (DRG):** comprised mainly of inspiratory neurons
**Ventral respiratory group (VRG):** responsible for inspiration and expiration, but inactive during quiet breathing
**\*major rhythm generator\***
76
What is the pre-botzinger complex?
Anatomical location of the respiratory pattern generator; display pacemaker activity; located superior to the ventral respiratory group
77
What are the two components of the pontine center? What are their functions? Which component dominates over the other?
Modulate rhythms generated in the medulla
**Pneumotaxic center**: terminates inspiration (increases rate of breathing because limiting inspiration shortens expiration)
**Apneustic center:** prevents inspiratory neurons from being shut off; prolongs inspiration
**Apneustic center dominates**
78
Describe central chemoreceptors. Where are they located? What is their function?
Located on the surface of the medulla; separate from respiratory center; responsible for 80% of the total ventilatory response
Sensitive to pH (PaCO2); most important mechanism controlling ventilation at rest (CO2-induced H+ in CSF)
The reason why we can't hold our breath beyond ~1 minute
79
Describe peripheral chemoreceptors. Where are they located? What conditions do they respond to?
Glomus cells in the carotid and aortic bodies
Responds to hypoxia (PaO2) by inhibition of K+ channels
Responds to hypercapnia when CO2 diffuses into glomus as bicarbonate, H+ inhibits K+ channels
Responds to acidosis when H+ inhibits K+ channels
**responds to all by signaling to medulla to increase ventilation**
80
What are pulmonary stretch receptors? What do they respond to?
Mechanoreceptors in smooth muscle of conducting airways
Respond to lung distension (excites inspiratory off switch; shortens inspiration when VT is large)
81
What are joint and muscle receptors? Function?
Mechanoreceptors in joints and muscle that signal DRG to increase breathing frequency
Activated during movement, when O2 demand is or will be high (feed-forward mechanism with exercise)
82
What are irritant receptors? Location? Function?
Mechanoreceptors in airway epithelium of larger conducting airways
Respond to irritation of the airways by touch, dust, smoke, etc
Protects by inducing a cough and hyperpnea
83
