Respiratory 3 Flashcards
(112 cards)
1
Q
lung blood flow when supine
A
uniform throughout the lung
2
Q
lung blood flow when standing
A
it is lowest at apex (zone 1) and highest at the base of the lung(zone 3)
3
Q
why is the distribution of blood flow in the lung uneven
A
it is uneven due to the effects of gravity
4
Q
West zone 1- what is blood flow
A
Blood flow is the lowest
5
Q
west zone 1 pressures
A
alveolar pressure>arterial pressure>venous pressure.
6
Q
west zone 1- should it exist, it exist when?
A
no, can occur if arterial blood pressure decreases as a result of hemorrhage or if alveolar pressure is increased because of positive pressure ventilation. (v/q=8)
7
Q
factors that expand zone 1
A
decrease pa pressure (shock) pul hypOtension
increase alveolar pressure (peep)
occlusion of blood vessel (pe)
8
Q
factors that reduce zone 1
A
increase pa pressure - pul htn
9
Q
what is blood flow like at west zone 2
A
blood flow is medium
10
Q
what is blood flow at west zone 3
A
blood flow is highest
11
Q
west zone 2 pressures
A
arterial pressure>alveolar pressure>venous pressure
12
Q
west zone 3 pressures
A
arterial pressure>venous pressure>alveolar pressure
13
Q
why in zone 2 is arterial pressure greater than alveolar pressure?
A
because blood flow is driven by the difference between arterial pressure and alveolar pressure (water fall zone)
14
Q
in zone 2 why does arterial pressure progressively increased
A
because of gravitation effects on hydrostatic pressure.
15
Q
in zone 3 how is blood flow driven?
A
by the difference between arterial and venous pressure as in most vascular beds.
16
Q
arterial pressure is highest at zone 3 why is that
A
due to gravitational effects and venous pressure is finally increased to the point where it exceeds alveolar pressure
17
Q
At the apex what is VQ?
A
( highest V/Q) , PO2 is highest and PCO2 is lowest because gas exchange is more efficient
18
Q
At the base what is vq
A
( lowest V/Q) ,PO2 is lowest and PCO2 is highest because gas exchange is less efficient
19
Q
In lung diseases what is vq
A
V/Q inequalities are more pronounced than in the normal lung; consequently , there can be severe hypoxia and modest hypercapnia
20
Q
V/Q ratio
what is it?
A
Is the ratio of alveolar ventilation (V) to pulmonary blood flow (Q) . Matching V and Q is important to achieve the ideal exchange of O2 and CO2
Ideally , ventilation is matched to perfusion (i.e. V/Q=1) for adequate oxygenation to occur efficiently
21
Q
what is normal vq?
A
0.8
22
Q
what is the normal ventilation
A
4l/m
23
Q
what is the normal perfusion
A
5l/m
24
Q
ventilation is lowest where?
A
is also lowest at the apex and highest at the base, but the regional differences for ventilation are not as great as for perfusion
25
Blood flow is lowest where?
at the apex and highest at the base because of gravitational effects.
26
vq at apex
~3
27
vq at base
~0.8
28
explain regional differences for p02 and pco2
As a result of the regional differences in V/Q ratio, there are corresponding differences in the efficiency of gas exchange and in pulmonary capillary PO2 and PCO2. Regional differences for PO2 are greater that those of PCO2
29
V/Q ratio in airways obstruction
If the airways are completely blocked (e.g. by a piece of steak caught in the trachea), than ventilation is zero. If blood flow is normal then V/Q is zero, which is called a shunt.
30
V/Q ratio in airways obstruction- tell me about the gas exchange?
There is no gas exchange in a lung that is perfused but not ventilated
31
V/Q ratio in airways obstruction-
The PO2 and PCO2 of pulmonary capillary blood (and therefore, of systemic arterial blood) will approach their values in mixed venous blood
32
V/Q ratio in airways obstruction- what happens to the aa gradient
There is an increased A-a gradient (calculated by using alveolar gas equation)
33
V/Q ratio in pulmonary embolism
If the blood flow to a lung is completely blocked (PA embolism), then the blood flow to lung is zero. If ventilation is normal , then V/Q is infinite (), which is called dead space
34
V/Q ratio in pulmonary embolism
There is no gas exchange in a lung that is ventilated but not perfused. The PO2 and PCO2 of alveolar gas will approach their values in inspired air
35
At V/Q zero or infinity what happens to gas exchange
NO gas exchange occurs resulting hypoxemia
36
slide 18
slide 18
37
V/Q = infinite =?
=blood flow obstruction. Assuming <100% dead space, 100% O2 improves PO2
38
V/Q of 0 =
V/Q of 0 = airway obstruction (shunt), In shunt, 100% oxygen does not improve PO2
39
PULMONARY EDEMA and causes
```
Fluid in alveoli and interstitial space
Causes
Left-sided heart failure
Infections
Noxious gases like Cl2 , SO2
```
40
Pleural Effusion
Pleural Effusion: flooding of large amount of fluid in the pleural space
41
```
OUTWARD Forces (mmHg)
Capillary pressure
```
7mmhg
42
```
OUTWARD Forces (mmHg)
interstitial osmotic pressure
```
14mmhg
43
OUTWARD Forces (mmHg)negative interstitial fluid pressure
8mmhg
44
OUTWARD Forces (mmHg)total
29
45
```
INWARD Forces (mmHg)
Plasma protein osmotic pressure
```
28mmhg
46
Mean Filtration Pressure
29-28= +1 mmHg
47
Partial Pressure ‘P’ of gases
It is the pressure exerted by any one gas in a mixture of gases and equal to the total pressure times the fraction of the total amount of gas.
48
PO2 (Partial Pressure of Oxygen)
what is it ensuring the lungs are able to do?
is oxygen gas dissolved in the blood. It primarily measures the effectiveness of the lungs in pulling oxygen into the blood stream from the atmosphere
49
Elevated PO2 levels are associated with
Increased oxygen levels in the inhaled air
| Polycythemia
50
Decreased PO2 levels are associated with
```
Decreased oxygen levels in the inhaled air
Anemia
Heart decompensation
Chronic obstructive pulmonary disease
Restrictive pulmonary disease
Hypoventilation
```
51
PO2=
PO2=160 mmHg (760x0.21=160)
52
PN2=
PN2=600 mmHg (760x0.79=600)
53
Dalton’s law of partial pressure
Partial pressure = Total pressure fractional gas pressure
54
In humidified air at 37C, consider the PH2O which is 47 mmHg
PO2 = (760-47) x 0.21= 150 mmHg
55
O2 Bound to Hemoglobin
how much 02 is carried on each gram of Hb
in 100ml what is the normal hemoglobin concentration amount
1.34 x 15 = 20.1 ml O2/100 ml of blood
The amount of O2 carried by each gram of fully saturated (100%) Hb = 1.34 ml O2 per gram of Hb
Normal Hb = 15 g/100ml
56
henrys law
The amount of gas dissolve in a solution (e.g. in blood) is proportional to its partial pressure (Henry Law)
57
Dissolve [ O2 ] =
100 mmHg x 0.03 mL O2/L / mmHg
= 0.3 mL O2/100 mL blood
PO2 x solubility of O2 in blood
58
DIFFUSION rate of 02 and co2
what pressure does the diffusion rate depend on?
what in the lungs does it depend on?
Diffusion rate of O2 and CO2 depend on the partial pressure difference across the respiratory membrane and the area (total number of intact alveoli) available for diffusion.
59
PO2(alveoli) >
PO2(blood)
60
PCO2(blood) >
PCO2(alveoli)
61
tell me ficks law
slide 33
62
Ideally PAO2-PaO2 gradient should be
zero. However normal lungs shows some V/Q mismatch.
63
Alveolar-arterial (PAO2-PaO2) gradient normal value??
Normal value is 5 to 15 mmHg.
64
Alveolar-arterial PCO2 difference is
2-10 mmHg
65
why do we calculate the alveolar-arterial po2 difference?
Alveolar-arterial PO2 difference calculation is used to differentiate between causes of hypoxemia. (extrapulmonary vs. intrapulmonary).
66
A-a gradient =
PAO2 – PaO2
67
PAO2 =
alveolar PO2 (calculated by multiplying O2 percentage in inspired gas mixture by 6)
68
PaO2 =
arterial PO2(calculated by multiplying O2 percentage in inspired gas mixture by 5)
69
normal aa gradient why are they approximately equal
Since O2 normally equilibrates between alveolar gas and arterial blood, PAO2 is approximately equal to PaO2
70
when is A-a gradient increased?
if O2 does not equilibrate between alveolar gas and arterial blood (e.g. diffusion defect, V/Q defect, right-to-left shunt)
71
In hypoxemia (PaO2 < 60 mmHg normal gradient means?
if either PAO2-PaO2 or PACO2-PaCO2 gradient is normal then hypoxemia is due to hypoventilation.
72
In hypoxemia (PaO2 < 60 mmHg) higher gradient means?
if either PAO2-PaO2 or PACO2-PaCO2 gradient is higher then hypoxemia is due to V/Q mismatch.
73
In airways obstruction what happens to vq mismatch
In airways obstruction, no air is getting in and blood is shunting; creating a V/Q mismatch that will increase the A-a gradient (calculated by using alveolar gas equation)
74
In hypoventilation what happens to vq mismatch
So hypoventilation differs from airway obstruction (no ventilation). In hypoventilation some air is getting in and equilibrates with the blood at a low level, therefore A-a gradient will stay normal
75
hypoventilation and equilibration of 02
Hypoventilation causes hypoxemia by decreasing alveolar PO2 (less fresh air is brought into alveoli). Equilibration of O2 is normal, and systemic arterial blood achieves the same (lower) PO2 as alveolar air. PAO2 and PaO2 are nearly equal (although low) and the A-a gradient is normal. In hypoventilation ,breathing supplemental oxygen raises arterial PO2 by raising the alveolar PO2
76
Normal A-a gradient
suggests that the lungs are quite normal and the problem is somewhere else, e.g. hypoventilation or breathing in thin air at high altitude
77
High (e.g. 30 mmHg) A-a gradient always associated with problems with lung or heart. In lung, there may be problems with:
Ventilation:
```
No ventilation (e.g. in airways obstruction)
Perfusion OK, but produces an intrapulmonary shunt: aspiration pneumonia, atelectasis ,ARDS
```
78
High (e.g. 30 mmHg) A-a gradient always associated with problems with lung or heart. In lung, there may be problems with:
PERFUSION:
Ventilation OK, but no perfusion produces an increase in dead space as in pulmonary embolism
79
High (e.g. 30 mmHg) A-a gradient always associated with problems with lung or heart. In lung, there may be problems with:
DIFFUSION:
```
Interstitial fibrosis (diffusion block)
Sarcoidosis
Scleroderma
```
80
High (e.g. 30 mmHg) A-a gradient always associated with problems with lung or heart. In lung, there may be problems with:
SHUNTING
Right-to-left shunt
| Intrapulmonary or cardiac
81
O2 binding capacity of blood
| what does it depend on?
HB concentration in blood
82
O2 binding capacity of blood
| how many mls?
20.1ml02/100ml
83
is 02 binding capacity of blood limited?
its limited by the amount of 02 that can be carried in blood. the maximum amount of 02 that can be bound to Hb in blood at 100% saturation
84
02 content of blood
Is the total amount of O2 in blood, including bound and dissolved O2
Depends on the Hb concentration, PO2 and P50 of Hb
O2 content = (O2 binding capacity x%Sat.) + Dissolved O2
85
Methemoglobinemia
In hemoglobin iron is in ferrous from (Fe++) while in methemoglobin; iron in ferric form (Fe+++)
Methemoglobin does not bind to O2 as readily, but has affinity for CN-
86
In methemoglobinemia what happens to 02 transport
causes defective 02 transport resulting in low saturation
87
what can cause methemoglobinemia
nitrites, benzocaine, metabolites of prilocaine
88
treatment for methemoglobinemia
IV methylene blue converse ferric Fe+++ to ferrous form ++
89
Cyanide poisoning causes
```
Causes
Nitroprusside (releases CN ions)
Bitter almond oil
KCN
Wild cherry syrup
```
90
cyanide poisoning s/s
Tachycardia, hypotension, coma , acidosis, increase venous O2, rapid death
91
cyanide poisoning treatment
To treat cyanide poisoning, give sodium nitrite and amyl nitrites to oxidize Hb to metHb (inducing methemoglobinemia) which binds cyanide, allowing cytochrome oxidase enzyme to go free and function.
Use thiosulfate to bind this cyanide, forming thiocynate, which is excreted by kidneys.
92
what is can sodium NitroPrusside cause? two things?
Sodium NP can cause methemoglobinemia as well as cyanide poisoning. Watch the S/S and give treatment accordingly.
93
O2 is carried in blood in two forms
| what two forms and what percent do they carry oxygen?
Bound to Hb ( 97%) in RBCs – chemical form
Dissolve form ( 3%) in plasma – physical form
Only form of O2 that produces its partial pressure in blood (PO2)
Not enough to meet the demand
94
Hb binds with 02 to form oxyhemoglobin how does it do that?
rapidly and reversibly!
95
what is 02 tension considered
O2 tension is the driving force for the chemical reaction—Hb + O2 --HbO2 ( increase PO2 increase Affinity♥of Hb for O2)
96
how does binding of the first 02 molecule affect the binding of the second 02 molecule.?
Binding of the first O2 molecule increases the affinity for the second O2 molecule and so forth. This change in affinity facilitates the loading of O2 in the lungs (flat portion of curve) and the unloading of O2 at the tissue (steep portion of curve)
97
In the Lungs (Loading Zone) “flat portion”
Alveoli have high PO2 –100 mmHg (Affinity♥)
The very high affinity of Hb for O2 at PO2 of 100mmHg facilitates the diffusion process
O2 is loaded from alveoli to Hb
The curve is almost flat (shoulder) when the PO2 is between 60-100mmHg. Thus, human can tolerate changes in PO2 without compromise of the O2-carrying capacity of Hb.( Below PO2 of 60 mmHg there will be free fall of Sat.)
98
In the peripheral tissues (Unloading Zone) “steep portion”
Tissues have low PO2 – 40 mmHg (decreased Affinity♥)
| O2 is unloaded (released) from Hb to tissue
99
shift to the right
```
more 02 delivered
acidosis
increase c02
increase temp
increase 2,3 dpg
increased exercise
```
100
shift to the left
```
love 02
alkalosis
decrease c02
decrease temp
decrease 2,3 dog
decrease exercise
```
101
Bohr effect
The shift of oxyHb curve in response to increase or decrease PCO2 is
Shift the curve to right, decreases the affinity of Hb for O2 and facilitating the unloading/delivery/release of O2 in the tissues
102
Utility of Bohr Effect
At tissue level CO2 diffuses into the blood that shifts the curve to right more release of O2
At lungs CO2 diffuse from blood into alveoli that shifts the curve to left more loading of O2
103
blood flow -apex
lowest
104
blood flow base
highest
105
ventilation apex
lower
106
ventilation base
higher
107
vq apex
highest
108
vq base
lower
109
apex 02
highest
110
base 02
lowest
111
pco2 base
higher
112
pco2 apex
lower
