Respiratory Flashcards
1
Q
Where does gas exchange happen?
A
Occurs in the lungs
2
Q
Inspiration
A
O2 inhaled in lungs
3
Q
Expiration
A
CO2 exhaled from lungs
4
Q
How is O2 and CO2 transported?
A
By the blood
5
Q
Divisions of the trachea
A
divides into 2 main bronchi (lobar and segmental)
6
Q
Smallest airways without alveoli are
A
the terminal bronchioles
7
Q
Purpose of air inhaling air through the nose
A
cleans air of large dust particles
8
Q
Parts of the nose where air passes through
A
nasal septum and nasal turbinates
9
Q
Properties of right bronchi
A
3 lobar bronchi, 3 lobes
10
Q
Properties of left bronchi
A
2 bronchi, 2 lobes
11
Q
Pleura
A
Thin cellular sheet attached to thoracic cage interior and, the lung surface
12
Q
parietal pleura
A
thoracic cage interior
13
Q
visceral pleura
A
lung surface
14
Q
What do the visceral pleura and parietal pleura form?
A
two enclosed pleural sacs (one around each lung) in thoracic cage
15
Q
pneumothorax
A
collapsed lung
16
Q
Two zones of the airways
A
conducting and respiratory
17
Q
What does the conducting airways consist of?
A
mouth and nose opening down to the terminal bronchioles
18
Q
What do the respitory airways consist of?
A
begins where the terminal bronchioles divide into respitory bronchioles
19
Q
The smallest physiological unit of the lungs
A
the acinus
20
Q
Which zone makes up most of the lungs due to abundant branching of the airways
A
Respiratory Zone
21
Q
Does the conducting zone contribute to gas exchange? why?
A
Does not contribute to gas exchange
compose the anatomical dead space
22
Q
What is beyond the respitory bronchioles?
A
alveolar ducts lined with alveoli
23
Q
what region is the site of gas exchange
A
alveolar region
24
Q
4 main functions of the conducting airways
A
Defense against bacterial infection/foreign particles
Warm and moisten inhaled air.
Sound and speech are produced by the movement of air passing over the vocal cords.
Regulation of air flow: smooth muscle around the airways may contract or relax to alter
25
Functions of the Respiratory zone
Site of gas exchange between the air in alveoli and the blood in pulmonary capillaries
26
The approximate number of alveoli and capillaries in body
300 million each will 1000 capillaries
27
Two lung circulations
Pulmonary and Bronchial circulation
28
Pulmonary circulation
Brings mixed venous blood that comes from different body organs to the lungs
29
Bronchial circulation
Supplies oxygenated blood from the systematic circulation to the tracheobronchial tree
30
Supply blood to all capillaries
Pulmonary arteries
31
three alveolar cell types
Epithelial type i and ii cells
Endothelial cells
Alveolar macrophages
32
Epithelial type i and ii cell
Alveoli are lined by epithelial type I and II cells
| Form the epithelial layer sealed by tight junctions
33
Epithelial type ii cells
Produce pulmonary surfactant
34
pulmonary surfactant
Substance that decreases the surface tension of alveoli
35
Endothelial cells
Constitute the walls of the pulmonary capillaries (0.1 um thin)
36
Alveolar macrophages
Remove foreign particles that escaped the mucocilary defence system of the airways and found their way into the alveoli
37
How does the surface tension arise of the liquid film lining the lungs
Tension arises because the surface molecules tend to arrange themselves in the configuration wth lowest energy
38
Laplace‘s law
P=4T/R
| Shows that the pressure inside a small bubble is greater than that inside a large bubble.
39
Why is expiration passive during quiet breathing
recoil of lungs/chest wall
40
When does expiration become active
at high levels of ventilation (exercise), or in pathological states when expiratory resistance increases while movement of airflow out of the lungs is impeded
41
Muscles involved in active expiration
internal intercostal muscles and abdominal muscles
42
What does the contraction of the abdominal muscles do?
compress the abdominal content, depress the lower ribs, and pull down the anterior lower chest
They force the diaphragm upwards
43
Why is forcing the diaphragm upwards essential?
Essential for coughing, singing, talking, vomiting
44
The main inspiratory muscle
diaphragm
45
What is the diagphragm inervated by
phrenic nerves from cervical segments 3, 4, 5
46
Contraction of the diaphragm causes
its dome to descend and the chest to expand longitudinally
47
What happens to the chest when the ribs are elevated?
the anterior-posterior and transverse dimensions of the chest enlarge
48
What muscles can also assist in inspiration? What conditions?
the external intercostal muscles and the parasternal inter- cartilaginous muscles, the neck muscles (sternocleidomastoid and
scalenes muscles)
during high levels of ventilation as well as severe asthma and other disorders that obstruct the movement of air into the lungs
49
What do the neck muscles do in inspiration?
The neck muscles elevate and fix the uppermost part of the rib cage, elevate the sternum and slightly enlarge the posterior and longitudinal dimensions of the chest
50
Spirometry
Useful clinical tool in order to measure the volume of air inhaled under a different circumstances
51
Spirometer
Measures volumes of inhaled
52
What can the spirometer measure?
tidal volume, vital capacity, inspiratory capacity, expiratory reserve volume, and inspiratory reserve volume
53
What can't the spirometer measure?
functional residual capacity, total lung capacity or residual volume
54
Tidal Volume
amount of air inhalded or exhaled in one breath
55
Residual Volume
Air remaining in lungs after one expiration, keeps alveoli inflated between breaths and mixes with fresh air on next inspiration
56
Functional residual capacity
Air remaining in the lungs after a normal tidal expiration
57
Total lung capacity
maximum air of the lungs
58
How can the FRC (Functional Residual Capacity) be measured
helium dilution
59
helium dilution steps
C1 = helium concentration in a spirometer of volume V1 and let the subject breath out to FRC
Open the valve and ask the subject to breath in and out from the spirometer
After equilibrium with the subjects lungs, the concentration in the spirometer is C2
Equation: C1 x V1 = C2 x (V1 + FRC) so that: FRC = (C1 x V1 /C2) - V1
60
ventilation
The amount of air inspired into the lungs over some period of time
61
minute ventilation
The amount of air inspired into the lungs over a minute
62
The formula for minute ventilation
tidal volume * number of breaths per minutes
63
Normal Adult male minute ventilation
VT = 500 mL; f = 12 breaths / min; VE = 6000 ml/min
64
Does all of the air inhaled to reach the respiratory zone?
Not all air inhaled into the lungs reaches the gas exchanging area (the respitory zone)
65
Why does not all air reach the respiratory zone?
Some air remains in conducting airways (anatomical dead space)
66
the alveolar ventilation (VA)
The amount of air that reaches the respiratory zone per minute
67
Average VA
4200 ml/min
68
The volume of the anatomical dead space
150 mL
69
Physiological Dead Space
inspired air that reaches the respiratory zone and does not take part in the gas exchang
70
Why is there physiological Dead Space represented by alveolar dead space
Due to alveoli either receiving a decreased blood supply or no blood supply at all
71
Physiological dead space (VD) is the sum of
alveolar and anatomical dead space
72
The difference between minute and alveolar ventilation is
the dead space ventilation that is wasted from gas exchange point of view
73
What keeps at artierial PaCO2 at a constant level
alveolar ventilation
74
PO2 of Air
160 mmHg
75
PCO2 of Air
0.3 mmHg
76
PO2 of alveoli
105 mmHg
77
Pco2 of alveeoli
40 mmHg
78
PO2 in pulmonary veins
100
79
PO2 of systemic artieries
100
80
PCO2 in pulmonary veins
40
81
PCO2 of systemic artieries
40
82
PO2 in cells
<40 mmHg (mitochondrial Po2 <5 mmHg)
83
PCO2 in cells
>46 mmHg
84
PO2 in systemic veins
40
85
PCO2 in systemic veins
46
86
PO2 in pulmonary arteries
40
87
PCO2 in pulmonary arteries
46
88
Alveolar hyperventilation
When more O2 is supplied and more CO2 is removed than the metabolic rate requires (VE exceeds needs of body)
89
Is ventilation during excersise considered hyperventilation? why?
ventilation has to be considered with respect to metabolism so ventilation during exercise is not
90
How are the PACO2 and PAO2 affected during hyperventilation
Results in alveolar partial pressure of O2
| (PAO2) rises and CO2 (PACO2) decreases
91
Alveolar hypoventilation
Fall in overall level of ventilation —> reduce alveolar ventilation below that required by the metabolic activity of the body
92
How are the PACO2 and PAO2 affected during hypoventilation
PAO2 falls and PACO2 rises
93
Is the blood in the pulmonary capillary more or less oxygenated?
The blood in the pulmonary capillary is less oxygenated
94
Why can Alveolar hypoventilation occur?
May occur during severe disorders of the lungs (chronic obstructive lung disease) or when there is damage to the respitory muscles; also when the chest cage is injured and lungs collapse or when the CNS is depressed
95
Affect on Alveolar PO2 and PCO2 when breathing air with low PO2
PO2 decreases
| PCO2 no change
96
Affect on Alveolar PO2 and PCO2 when alveolar ventilation increases and unchanged metabolism
PO2 increases
| PCO2 decreases
97
Affect on Alveolar PO2 and PCO2 when alveolar ventilation decreases and unchanged metabolism
PO2 decreases
| PCO2 increases
98
Affect on Alveolar PO2 and PCO2 when metabolism increases and alveolar ventilation unchanged
PO2 decreases
| PCO2 increases
99
Affect on Alveolar PO2 and PCO2 when metabolism decreases and alveolar ventilation unchanged
PO2 increases
| PCO2 decreases
100
Affect on Alveolar PO2 and PCO2 when proportional increases in metabolism and alveolar ventilation
PO2 no change
| PCO2 no change
101
Oxygen from the alveolar gas must be transferred across the alveolar-capillary membrane for ventilation by
passive diffusion
102
What is passive diffusion governed by
Fick’s Law
103
Fick’s Law
Rate of diffusion of a gas through a tissue is
- Proportional to the tissue area and the difference in gas partial pressure between the 2 sides
- Inversely proportional to the tissue thickness
104
Diffusion rate is proportional to
surface area
partial pressure gradient
1/thickness
105
What direction is diffusion
Diffusion direction is from higher to lower pressure
106
How does O2 and CO2 diffuse in the alveolar and blood
O2 diffuses from the alveolar gas to the blood, and
| CO2 diffuses in the opposite direction
107
What must the gas be in order to diffuse through a liquid?
the gas must be soluble in the liquid
108
Solubility of CO2 vs O2
CO2 is more soluble than O2 (diffuses 20 times more rapidly than O2)
109
difference between PO2 on either side of the alveolar-capillary membrane
At the beginning of the pulmonary capillaries there is a large difference between PO2 on either side of the alveolar-capillary membrane.
110
the O2 gradient between the blood and the lungs
large
111
How does the O2 gradient change with time as blood flows through the lung capillaries?
smaller
112
By the end of the capillary, as more O2 has moved from the lungs to the blood, how does the O2 gradient and rate of diffusion change?
O2 gradient becomes less
| the rate of diffusion must decrease (due to a smaller pressure gradient)
113
At the beginning of the capillaries, what is the PCO2
46
114
what is the PCO2 in the alveolar gas
40
115
The difference in PCO2 and PO2 between the 2 sides of the alveolar-capillary membrane is
10 times smaller than that for PO2
116
The time required for equilibrium between alveolar air and capillary blood is
approximately the same for the two gases.
117
the transit time of blood through the pulmonary capillaries is
only 0.75 seconds at rest
118
Times of diffusion for both O2 and CO2 compared to the red blood cell transit time
1/3 time
119
condition of a resting person with an impaired rate of diffusion
a patient with pulmonary edema
120
PCO2 and PO2 of a resting person with an impaired rate of diffusion
in a resting person with an impaired rate of diffusion PO2 and PCO2 may be normal (because CO2 and O2 may still be able to diffuse during the transit time).
121
when blood flow increases in this person and the transit time consequently becomes shorter (during exercise). What is the affect on arterial PO2 and PCO2
arterial PO2 may decrease and arterial PCO2 may increase
122
Blood pressure in the pulmonary circulation vs systemic circulation
Blood pressure in the pulmonary circulation is lower than in the systemic circulation
123
The walls of the pulmonary capillaries are thicker/thinner than those of similar vessels in the systemic circulation
thinner
124
Why are the pulmonary capillaries thinner than the systemic circulation vessels?
Less smooth muscle
125
The mean pulmonary arterial pressure
15 mmHg
126
Left atrial pressure
5 mmHg
127
Right Ventricle pressure
25
128
Left Ventricle pressure
120
129
The mean systemic arterial pressure
100
130
Blood flow depends on
vascular pressure and resistance
131
flow equation
pressure/resistance
132
pressure change from pulmonary artery to left atrium
from pulmonary artery to left atrium of about 10 mm Hg,
133
pressure change from systemic artery to right atrium
~100mmHg for the systemic artery to right atrium
134
Pulmonary vs systemic resistance
the pulmonary resistance is only 1/10 that of the systemic circulation
135
The low vascular resistance in the pulmonary circulation relies
the thin walls of the vascular system
136
The low vascular resistance/high compliance of the pulmonary circulation allows
the lung to accept the whole cardiac output at all times.
137
with little change in pulmonary arterial pressure the pulmonary circulation has the capacity to
accommodate two- to three-fold increases in cardiac output
138
The increase in blood flow with little changes in driving pressure indicates
that as pulmonary blood flow increases, pulmonary resistance falls
139
Blood vessels may do two things?
already perfused increase their caliber (distension), and previously closed vessels may open as the cardiac output rises (recruitment)
140
How does Drugs (serotonin, histamine, norepinephrine) affect smooth muscle and pulmonary vascular resistance?
cause the contraction of smooth muscle increase pulmonary vascular resistance in the larger pulmonary arteries.
141
How does Drugs (acetylcholine, isoproteranol) affect smooth muscle and pulmonary vascular resistance?
can relax smooth muscle may decrease pulmonary vascular resistance.
142
What is the reflex in regions of the lungs that are poorly oxygenated
a reflex vasoconstriction
143
Nitric oxide is produced by what cells
endothelial cells
144
What does nitric acid do to smooth muscle?
Nitric oxide produced by endothelial cells relaxes vascular smooth muscle leading to vasodilation
145
How is pulmonary blood flow affected by gravity?
it differs with body posture
| In the upright position, blood flow increases almost linearly from top to bottom of the lungs
146
Why does blood flow increase from top to bottom of the lungs
The vessels are more distended toward the bottom of the lungs because gravity increases vascular pressure
147
How is distribution of blood flow in the upright human lung measured? what element?
using radioactive xenon. The dissolved xenon is evolved into alveolar gas from the pulmonary capillaries.
148
Why is there lower blood flow observed at the very very bottom of the lung?
due to some vessels being less expanded at low lung 47 volumes
149
What may happen at the top of the lungs, if alveolar pressure is greater than blood pressure in the capillaries?
Near the top of the lungs, the pulmonary capillaries may be completely compressed if alveolar pressure is greater than blood pressure in the capillaries
150
The hydrostatic pressure of the blood
the pressure due to the weight of the blood
151
The hydrostatic pressure of the blood affect on blood flow
The hydrostatic pressure of the blood (the pressure due to the weight of the blood) causes an uneven distribution of blood flow from the top to bottom of the lung
152
the lungs can be looked at as consisting of 3 zones
top, middle, bottom
153
Top zone pressures
pulmonary arterial pressure< alveolar pressure
154
Top zone capillaries
capillaries are compressed
155
When does top zone only occur?
Occurs only in cases of low arterial pressure or positive ventilation
156
Middle zone pressures
pulmonary arterial pressure> alveolar pressure > venous pressure
157
Bottom
pulmonary arterial pressure> venous pressure> alveolar pressure
158
Flow in bottom zone depends on
So the flow depends on the arterio-venous pressure difference
159
Flow in middle zone depends on
So the flow depends only on the difference between arterial and alveolar pressures
160
Does gravity affect the distribution of ventilation
yes
161
In an upright lung at rest, in normal gravity, the alveoli at the top vs bottom
In an upright lung at rest, in normal gravity, the alveoli at the top of the lungs are more opened than the bottom ones
162
preferential ventilation occurs at what parts of the lungs
the bottom of the lungs, the alveoli from the bottom of the lungs are opened wider than those at the top
163
How can the distribution of ventilation be measured?
a similar way as that of perfusion but with inhaled radioactive Xenon instead of infused in the blood
When the gas is inhaled, its radiation can be detected by counters outside the chest
164
Ventilation vs blood flow in the lung top to bottom?
Ventilation increases slowly from top to bottom of the
| lung but blood flow increases more rapidly.
165
ventilation- perfusion ratio at the top of the lung vs the bottom
the ventilation- perfusion ratio is abnormally high at the top and much lower at the bottom.
166
VO2
O2 consumption per minute
167
CvO2
The [O2] in the blood entering the lungs
168
CaO2
The [O2] in the blood exiting the lungs
169
Where is CaO2 measured
measured from an artery
170
Where is CvO2 measured
measured via a catheter from the pulmonary artery
171
Does O2 dissolve in the plasma?
O2 dissolves in plasma
172
Why is O2 proportional to PO2
Because O2 is relatively insoluble in H2O, the amount of O2
| dissolved in blood is very small
173
Henry’s Law
The amount of dissolved gas carried by the blood is directly proportional to the partial pressure of the gas
174
In 100 ml of plasma, ho2 much O2 is there? (ml)
0.3 ml when equilibrated with PO2 of 100 mmHg
175
What can we infer from henrys law about the # of gas molecules and the partial pressure of the gas
that the number of gas molecules dissolved in a liquid is proportional to the partial pressure of the gas above the liquid
176
O2 consumption (VO2) by the body cells vs what can be supplied from the amount dissolved in blood
O2 consumption (VO2) by the body cells, even at rest, is much greater than what can be supplied from the amount dissolved in blood
177
At rest, O2 is
300 ml O2/min
178
What would happen if O2 were only found in plasma
the tissue demand for O2 would never be met
179
What is O2 bound to?
O2 Bound to Hemoglobin
180
Where is Hemoglobin found
Hemoglobin, Hb, is found in red blood cells
181
total weight of red blood cells from hemoglobin
1/3
182
Hb in each liter of blood
147g
183
How much more O2 can be taken up by hemoglobin compared to plasma
65 times as much O2 as plasma
184
Hb structure
Each molecule consists of 4 subunits bound together
185
Hemoglobin subunit structure
Each subunit is made up of a heme joined to a globin
contains an Fe++ ion that can bind 1 molecule of O2
186
an Fe++ ion can bind how many molecules of O2
1
187
How many oxygens does hemoglobin bind to?
4
188
Why is hemoglobin essential
for the transport of O2 by blood because it combines rapidly and reversibly with O2
189
the total amount of O2 physically dissolved in the blood is?
0.3 vol.%,
190
total amount of O2 bound to Hb is?
19.5 vol. %
191
the total amount of O2 in arterial blood is about
20 vol. %
192
Do the O2 that is bound to Hb contribute to the PO2 of the blood?
No,
| the O2 that is bound to Hb does not contribute to the PO2 of the blood
193
What molecules are responsible for PO2?
Only molecules
| physically dissolved in the blood plasma are responsible for PO2
194
How does the PO2 of the plasma affect Hb?
the PO2 of the plasma does determine the amount of O2 that combines with Hb`
195
The HbO2 dissociation curve determines
determines the amount of O2 carried by Hb for a given partial pressure of O2
196
The HbO2 dissociation curve key results
The curve is flat at high values of PO2 (at alveolar levels of PO2) and steep at low values of PO2 (at peripheral tissue levels of PO2)
197
At low values of PO2, how does a small drop in PO2 affect O2?
a small drop in PO2 unloads the O2 from Hb to the tissue
198
HbO2 dissociates into Hb and O2 more readily at what PO2 levels?
lower
199
at the tissue level, PO2 may get as low as
1-3 mmHg
200
As blood enters the tissue capillaries, how does plasma PO2 compare to interstitial fluid PO2?
As blood enters the tissue capillaries, plasma PO2 is greater than interstitial fluid PO2
201
Does O2 readily diffuses across the capillary membrane into the interstitial fluid?
Yes
202
What does the diffuse of O2 across the capillary membrane do to the PO? how does this affect Hb dissociation?
This lowers plasma PO2, and O2 diffuses out of the erythrocytes into the plasma
The lowering of erythrocyte PO2 causes the dissociation of HbO2 into Hb and O2
203
What percentage of Hb is saturated under resting conditions?
Under resting conditions, Hb is still 75% saturated at the end of the tissue capillaries
204
myoglobin
function is to act as an intracellular carrier which facilitates the diffusion of oxygen throughout the muscle cell
205
What determines Hbs affinity for O2
The quaternary structure of Hb determines its affinity for O2
206
cooperative binding in Hb and O2
The combination of the first heme in Hb with O2 increases the affinity of the second heme for O2
207
Is myoglobin similar to hemoglobin? differences?
yes, Myoglobin, resembles Hb but binds only one O2 molecule.
208
Shape of O2- myoglobin curve
hyperbolic in shape. myoglobin will release its O2 only at very low PO2
209
The total amount of O2 in the blood depends mostly on
Hb concentration
210
anaemia
conditions of decreased Hb concentration
211
The Bohr Effect
The Bohr Effect is the shift of the HbO2 dissociation curve to the right when blood CO2 or temperature increases or blood pH decreases
212
What happens to CO2, acid production and heat, as we exercise?
when we exercise, we increase our CO2 and acid production and generate heat
213
How is the amount of O2 released affected by the curve shifting to the right means that for a given drop in PO2?
an additional amount of O2 is released from Hb to the working tissues
214
when 2,3- diphosphoglycerate (2,3-DPG), increases how does this affect the amount of O2 released?
an additional amount of O2 is released from Hb to the working tissues
215
2,3- diphosphoglycerate
an end product of red blood cell metabolism,
216
2,3-DPG levels may increase during what disease? conditions?
chronic hypoxia
| high altitude or lung disease
217
How do a decrease in temperature, an increase in pH, and a decrease in CO2 affect the dissociation curve?
opposite effect on the dissociation curve, shifting it to the left
218
Do these factors, such as temperature and PH have a large affect on the total amount of O2 combines with Hb over 80 mmHg?
all of these factors, have little effect on the total amount of O2 combined with Hb above 80 mm Hg
219
Affinity of CO on hemoglobin
CO has an extremely high affinity for the O2 binding sites in hemoglobin (210-fold)
220
Carbon monoxide poisoning affect on bound O2
it reduces the amount of O2 bound to hemoglobin
221
Carbon monoxide poisoning shift on O2-hemoglobin curve
left decreasing the unloading of O2 to the tissue
222
How is the stimulation to increase ventilation affected in CO poisoning?
In CO poisoning, there is little stimulation to increase ventilation because PaO2 remains normal
223
the primary product of the oxidative processes taking place in the body cells
CO2
224
How is CO2 removed from the tissues
blood
225
How much O2 does a person use at rest?
300 ml/min
226
How much CO2 does a person produce at rest?
250 ml/min
227
How does O2 use and CO2 production change during heavy exercise?
can go up twenty time during heavy exercise
228
Forms that CO2 can be carried in
Physically dissolved in blood
Combined with Hb to form HbCO2
As bicarbonate
229
% of CO2 Physically dissolved in blood
10
230
% of CO2 Combined with Hb to form HbCO2
11
231
% of CO2 As bicarbonate
79
232
CO2 physically dissolves in the blood by which law
According to Henry’s Law, CO2 from the tissues diffuses into the plasma where it is physically dissolved.
233
Which portion of the hemoglobin does CO2 combine with
Contrary to O2 that combines with the heme portion of Hb, CO2 combines with the globin portion
234
Is there compition for binding on Hb from O2 and CO2
there is no competition for binding on Hb.
| Contrary to O2 that combines with the heme portion of Hb, CO2 combines with the globin portion
235
How is CO2 produced in bicarbonate form?
CO2 combines with H2O to produce carbonic acid (H2CO3)
236
Bicarbonate reaction in plasma speed
This reaction is very slow in plasma
237
How is the Bicarbonate reaction sped up
the reaction is aided by the enzyme carbonic anhydrase (CA)
238
Are the bicarbonate reactions reversible?
All these reactions are reversible, so they can proceed in either direction, depending upon the prevailing conditions
239
If CO2 production increases, the production of HbCO2, HCO3-, and H+
increases
240
Lowering of blood PCO2 affect on HCO3- and HbCO2
HCO3- getting transformed into H2CO3 and further into CO2 and H2O, and HbCO2 generating Hb and CO2.
241
In what vessels does HCO3- getting transformed into H2CO3 and further into CO2 and H2O, and HbCO2 generating Hb and CO2.
This situation occurs when venous blood flows through the lung capillaries
242
The Haldane Effect
that mixed venous blood can carry more CO2 than can arterial blood.
243
The presence of reduced Hb in the tissue capillaries helps with what?
with the blood loading of CO2
244
The O2 saturation of blood influences the CO2 dissociation curve by shifting it to the
right
245
as Hb unloads O2 into the tissues, it is able to take up CO2 in what amounts?
take up increased amounts of CO2 from the tissues
246
for a given PCO2, how does CO carried in deoxygenated blood compare with in oxygenated blood
for a given PCO2, more CO2 is carried in deoxygenated blood than in oxygenated blood
247
In the tissue capillaries, Hb free of O2, can combine with what? reaction
may combine with H+, in the reaction:
| H+ + HbO2 -> HHb +O2
248
Why does H+ combine with Hb that isn't with O2?
occurs because reduced Hb
is less acidic than HbO2
Hb acts as a buffer
249
How does a sudden lowering of blood PCO2, affect the HCO3- and HbCO2 levels? where does venus blood flow
esults in HCO3- going to H2CO3 and further into CO2 and H2O, and HbCO2 generating Hb and CO2
venous blood flows through the lung capillaries
250
Unlike the HbO2 curve, the CO2 dissociation curve
has no steep or flat portions
251
the relationship between CO2 content and PCO2
the relationship between CO2 content and PCO2 is almost linear.
252
if we hypoventilate and alveolar PCO2 rises, how is the arterial, capillary, tissue, and venous CO2 affected?
then arterial, capillary, tissue and venous CO2 also rise
253
Doubling alveolar ventilation affect on alveolar PCO2? what does this conclude?
halves alveolar PCO2
follows that an increase in alveolar ventilation proportionally increases CO2 removal
254
Respiratory Failure
occurs when the respiratory system is unable to do its job properly
255
3 reasons respiratory failure can occur
the gas exchanging capabilities of the lungs
the neural control of ventilation (i.e. the drive to breathe)
the neuromuscular breathing apparatus (i.e. the respiratory muscles and their innervation
256
Blood hypoxia
deficient blood oxygenation
| i.e. low PaO2 and low % Hb saturation
257
In hypoxic conditions, if PaO2 decreases below 60 mm Hg, O2 content in arterial and venous blood is affected how?
becomes lower than the normal values at sea level
258
5 general causes of hypoxia:
1. Inhahlation of low PO2 (e.g. at high altitude).
2. Hypoventilation
3. Ventilation/perfusion imbalance in the lungs
4. Shunts of blood across the lungs
5. O2 diffusion impairment
259
Hypoventilation occurs due to:
diseases affecting the CNS, neuromuscular diseases, barbiturates, other drugs
260
Ventilation/perfusion imbalance in the lungs occurs when
the amount of fresh gas reaching an alveolar region per breath is too little for the blood flow through the capillaries of that region
261
Shunts of blood across the lung occurs when? example
venous blood bypasses the gas exchanging region of the lungs and returns to systemic circulation, deoxygenated. Example: foramen ovale.
262
O2 diffusion impairment example
thickening of the alveolar-capillary membrane, or pulmonary edema
263
automatic breathing
involuntary activity that brings enough air into the pulmonary alveoli to maintain the O2 and CO2 tensions of alveolar gas or arterial blood at optimal levels in different conditions
264
When does automatic breathing occur
During sleep, rest, or exercise
265
Is breathing under voluntary or involuntary control?
Under both voluntary and involuntary control
266
What neurological structure controls voluntary breathing?
The cerebral hemisphere
267
What neurological structure controls involuntary breathing?
Brainstem
268
Are the involuntary and voluntary control two separate neurological structures?
Anatomically, there are separate neurological structures for automatic and voluntary control, although the two systems interact
269
How does the CNS affect breathing?
The CNS controls gas exchange by integrating all the information coming from the periphery: gives an adequate depth and frequency of breathing (minute ventilation)
270
If automatic control no longer functions, what will happen to voluntary breathing?
Can be effective even when automatic control no longer functions
271
Breaking Point (PCO2, PO2)
point voluntary control is over-ridden
occurs because the arterial PCO2 has reached about 50 mm Hg and arterial PO2 has reached about 70 mm Hg
272
The over-riding of the voluntary control by the automatic control depends upon
the information from the receptors sensitive to CO2 and O2 levels (in arterial blood and/or cerebro-spinal fluid)
273
What parts of the brainstem are involved in the involuntary control of breathing
pons and medulla
274
3 elements in respiratory control system
Sensors, controllers, effectors
275
Sensors
these gather information about lung volume (pulmonary receptors) and O2 and CO2 content (chemoreceptors)
276
Controllers
information from the sensors is sent to the controller, in the pons and medulla, via afferent neural fibers. Once it has reached the
pons and medulla, the peripheral information and inputs from the higher structures of the central nervous system are integrated
277
Effectors
neuronal impulses are generated and sent via spinal motoneurons to the effectors, i.e. the respiratory muscles.
278
Has pacemaker cells
Medulla
279
Pacemaker cells are located in how many groups? names?
mainly located in two groups of cells
| ventral respiratory group and dorsal respiratory group
280
Dorsal respiratory group
Receives several sensory inputs
281
ventral respiratory group
generate the basic rhythm
282
Respiratory neurons in the medulla generate
the basic respiratory rhythmicity
283
Where are the upper pons located?
cells located in the rostral (upper) pons
284
rostral (upper) pons is known as
called the pneumotaxic center
285
What do the pons do?
modify the inspiratory activity of the centers in the medulla
286
Which cells "turn off" inspiration leading to smaller tidal volume?
pons
287
what does "turn off" inspiration lead to ?
smaller tidal volume which leads to an increase in breathing frequency to maintain adequate alveolar ventilation
288
What does cutting the pneumotaxic centers cause?
breathing to become deep and slow
289
Where are the lower pons cells located?
lower pons
290
What are the the lower pons called?
the apneustic center
291
What do the lower pons do?
send exicitatory impulses to the respiratory groups of the medulla
292
What does excitatory impulses to the respiratory groups of the medulla promote?
inspiration
293
```
Match the following:
upper pons, lower pons, medulla
- promote inspiration
- rhythm
- turn-off inspiration
```
upper pons- turn-off inspiration
lower pons- promote inspiration
medulla - rhythm
294
Removing the influence of both the upper pons and the vagus nerves causes
apneuses
295
apneuses
tonic inspiratory activity interrupted by short expirations
296
What does chemoreceptors detect in the blood?
Detect PO2, PCO2, and pH in arterial blood
297
If the PO2, PCO2, and pH in arterial blood change, what will occur?
ventilation will change to return the gas pressures to their normal values
298
The information from chemorecptors is carried to?
respiratory neurons
299
At what levels of PaO2 and PaCO2 do the activity of respiratory neurons increase
PaO2 is to low <60
| PaCO2 is to high >40
300
At what levels of PaO2 and PaCO2 do the activity of respiratory neurons decrease
PaO2 is to high >100
| PaCO2 is to low <40
301
Two types of chemoreceptors
central and peripheral
302
Where are central chemoreceptors located?
the ventral surface of the medulla
303
Where do central chemoreceptors detect?
the pH of the cerebrospinal fluid that is around them
304
PCO2 and pH of the CSF are influenced by
Those of arterial blood
305
What gives rise to the main drive to breathe under normal conditions?
central chemoreceptors
306
The sensitivity of these central chemoreceptors may be easily assessed by
a CO2 rebreathing test
307
What occurs in the a CO2 rebreathing test
subject breathe different CO2 mixtures, or rebreathe expired air from a bag filled with O2 so that with each expiration, the inspired PCO2 gradually increases
308
How does hyperventilation affect PCO2 in the blood and CSF
hyperventilation reduces PCO2 in the blood, and therefore in the CSF.
309
Stimulation of the chemoreceptors increases
minute ventilation
310
What are central chemoreceptors bathed in? why?
They are bathed in brain extracellular fluid (ECF)
through which CO2
easily diffuses from the blood vessels to cerebrospinal fluid (CSF).
311
What reduced the CSF pH? what does this stimulate?
The CO2 reduces the CSF, thus stimulating the chemoreceptor.
312
Can H+ and HCO3- easily cross the blood-brain barrier?
no
313
How do small increases in PCO2 affect minute ventilation, respiratory rate, and tidal volume?
Small increases in PCO2, increase minute ventilation (left) due to an increase in respiratory rate (center) and tidal volume (right).
314
hypercapnia
elevated CO2 in blood
315
What are Peripheral Chemoreceptors sensitive/ stimulated by?
are mainly sensitive to changes in PO2, but are also stimulated by
increased PCO2 and decreased pH
316
Where are Peripheral Chemoreceptors located in?
located in the carotid bodies (i.e. the bifurcation of the common carotid arteries) and in the aortic bodies (next to the ascending aorta)
317
Where do the afferent fibers of the peripheral chemoreceptors project?
the afferent fibers of these receptors project to the dorsal group of respiratory neurons in the medulla
318
What are the carotid and aortic bodies made up of?
blood vessels, structural supporting tissue, and numerous nerve endings of sensory neurons of the glossopharyngeal (in carotid bodies, IX nerve) and vagus nerves (in aortic bodies, X nerve)
319
The effects of hypoxia on ventilation can be studied by
having a subject breathe gas mixtures with decreased concentrations of O2
320
When do changes in minute ventilations occur? PO2 levels?
During normocapnia (normal levels of CO2 in blood), the alveolar PO2 can be reduced to about 60 mm Hg before appreciable changes in minute ventilation occur
321
at increased PCO2, a decrease of PO2 below 100 mmHg results in
can already cause an increase in minute ventilation
322
Pulmonary Vagal Receptors
Afferent fibres from all of these receptors travel in the vagus nerves. If the vagus nerve is sectioned, the result is slow, deep breathing
323
Three types of receptors in the lungs that respond to mechanical stimuli
Pulmonary Stretch Receptors, Irritant Receptors, Juxta-capillary or J receptors (C-fibres)
324
Where are Pulmonary Stretch Receptors located?
located in smooth muscles of the trachea down to the terminal bronchioles
325
What are pulmonary stretch receptors innervated by? what do they discharge in response to?
innervated by large, myelinated fibres, and they discharge in response to distension of the lung
326
How is the Pulmonary Stretch Receptors activity sustained?
as long as the lung is distended
327
How does the activity of these Pulmonary Stretch receptors change during each inspiration?
Activity of these receptors phasically increases as lung volume increases during each inspiration
328
the Hering-Breuer Inflation Reflex
is a decrease in respiratory frequency due to a prolongation of expiratory time
329
What is the main reflex effect of stimulating pulmonary Stretch receptors?
The main reflex effect of stimulating these receptors
330
Where are Irritant Receptors located?
are located between airway epithelial cells in the trachea down to the respiratory bronchioles
331
How are Irritant Receptors stimulated?
They are stimulated by noxious gases, cigarette smoke, histamine, cold air, and dust
332
What are Irritant receptors innervated by? what does it result in?
innervated by myelinated fibers, and their stimulation leads to bronchoconstriction and hyperpnea (increased depth of breathing)
333
What reflex are Irritant receptors important in? triggered by?
irritant receptors may be important in the reflex bronchoconstriction triggered by histamine release during an allergic asthmatic attack
334
Where do the J receptors originate from?
these fibres originates from their location in the alveolar walls close to the capillarie
335
What are J receptors innervated by?
innervated by non-myelinated fibres and have short lasting bursts of activity
336
What are J receptors stimimulated by?
stimulated by an increase in pulmonary interstitial fluid, like what may occur in pulmonary congestion and edema
337
What conditions might J receptors be stimulated by?
pulmonary congestion and edema
338
The reflex effects caused by these receptors
include rapid and shallow respiration, although intense stimulation causes apnea
339
What receptors may play a role in dyspnea?
J receptors associated with left heart failure and lung edema or congestion
340
dyspnea
sensation of difficulty in breathing
341
Pleural Space
The ventilatory apparatus consists of the lungs and the surrounding chest wall
342
Importance of the lungs filling for visceral and partiental pleura
The lungs fill the chest so that the visceral pleura are in contact with the parietal pleura of the chest wall
343
What does the chest wall include?
The chest wall includes not only the rib cage, but also the diaphragm and the abdominal wall
344
Mechanically, how do the lung and chest wall act together
Operate in series with one another, but they are not directly attached together
345
How are the viseral and pariental pleura coupled together?
The viseral and pariental pleura are coupled together by a thin layer of liquid that fills the intrapleural space
346
What does the thin layer of liquid that fills the intrapleural space do?
Allows the lungs to slide against the internal wall of the chest during breathing and to follow the change in thoracic configuration
347
Ppl
Pleural pressure
348
Pleural pressure
pressure that can be measured in the liquid-filled space between lung and chest
349
Pressure in the pleural space is positive/negative? why?
negative
| due to the opposing forces acting on the lung and chest wall
350
pneumothorax
if a hole is punctured through the chest wall, the lungs collapse and the chest springs outwards
351
pneumothorax pressure
0, same as outside
352
To evaluate the elastic properties of the respiratory system
we measure changes in the recoil pressure of each separate structure for a given change in lung volume by a spirometry
353
Pressures are measured using
manometers or pressure transducer as reference to atmospheric pressure
354
negative pressure
below atmospheric pressure
355
positive pressure
above atmospheric pressure
356
trans chest wall pressure
difference between Ppl and the pressure at the body surface
357
recoil pressure of a structure
the pressure difference between the inside and outside of the structure (transmural pressure)
358
How can Ppl be measured
a flexible balloon introduced into the esophagus, between the two pleural spaces
359
What gives a close approximation of pleural pressure?
esophageal pressure
360
The recoil pressure of the lungs
transpulmonary pressure (Pl)
361
transpulmonary pressure (Pl) measured by? what requiredments?
the difference between Palv and Ppl
| no air flow (closed nose and mouth)
362
The recoil pressure of the total respiratory system
the trans-respiratory system pressure (Prs)
363
the trans-respiratory system pressure (Prs) measured by
measured as the difference between Palv and Pbs:
also,
the sum of the pressures generated by its two components, lung and chest
Prs = Pl + Pw
364
Compliance of the lungs
is a parameter that refers to the ease with which each of these structures can be distended`
365
Compliance of the lungs is expressed as
expressed as the volume change in the lungs for a unitary change in pressure
- the slope of the pressure-volume curve
366
Compliance of the lungs formula
C = dV/dP
367
The standard procedure for measuring the respiratory system compliance in humans
to determine the static pressure-volume relationship while lung volume is decreased step by step from TLC
368
The pressure difference between the alveoli (Palv) and the pleural space (Ppl) equals the
pressure drop across the lung tissues also known as the pressure required to maintain the lungs at a given inflation volume against their tendency to recoil elastically
369
Compliance of the lungs with certain diseases
Compliance of the lungs is also altered in diseases such emphysema and fibrosis
Emphysema: TLC and compliance increases
Fibrosis: TLC and compliance decreases
370
a large part of the recoil forces arises from the? why?
properties of the liquid film lining the inside of the lungs
The surface tension in this film generates substantial force because the surface area of the film is very large
371
Compliance of the chest wall
defined in terms of a change in thoracic volume dV (the change in volume of the thorax is the same as the change in volume of the lungs) and a change in pressure across the chest wall (w), dPpl
372
What do the elastic properties of the tissues of the thorax (i.e. the chest wall) cause?
it to recoil either inward or outward, depending on its volume
373
Compliance of the lungs is positive or negative
the pressure reported when measuring the compliance of the lungs were always positive because the lungs always tended to collapse
374
Compliance of the chest wall is positive or negative
Pressure reported is sometimes positive sometimes negative
- the chest wall tends to collapse only after reaching a volume after 60% vital capacity whereas it wants to spring out below that value
375
Compliance of respiratory system
the compliance of the respiratory system, Crs, is related to the compliances of the lung and chest wall by
Crs = dV/dPrs
376
The pressure drop across the respiratory system
Prs, is the sum of the pressure drop across the lung and that across the chest wall
377
Prs at Functional Residual Capacity (FRC)
Prs is zero because the system is at rest
378
stable condition is caused by the
inward recoil of the lungs (Pl is about +5 cmH2O) which is balanced by the outward recoil of the chest wall (Pcw is about -5 cmH2O)
379
at FRC, what is the resting volume of the lungs and chest?
at FRC, the lungs are above their resting volume and the chest is below its resting volume
380
The lungs collapse to its
resting position below RV,
381
the chest wall expands towards its
resting position
382
Air enters the pleural space because
Ppl is less than atmospheric pressure
383
At rest, the lungs are at
FRC
384
At rest, the Ppl of the lungs? why?
is negative due to the opposite forces acting on the lungs and chest wall
385
During inspiration what does the diaphragm and chest wall do? what does this do to Ppl
During inspiration, the diaphragm contracts and the chest wall is pulled open
creates a more negative Ppl that causes expansion of the lungs
386
Flow equation
Flow = F = ( Palv - Patm ) / R
387
As the lungs are pulled further away from their resting position (which is below RV), Ppl becomes
even more subatmospheric
388
As the volume of the lungs is increased, gas in the lungs is
decompressed
389
The pressure in the alveoli (Palv) drops below
atmospheric pressure
390
What generates air flow to the lungs?
The negative pressure gradient created between the alveoli and atmosphere
391
As inspiration proceeds, the lungs are filling up with air, how is the pressure gradient and air flow change?
the pressure gradient and the air flow gradually decreases
392
At the end of inspiration, why does air flow stop?
Palv is equal to atmospheric pressure (no pressure gradient)
393
At the onset of expiration, what happens to the diaphragm, and Palv?
he diaphragm relaxes, elastic recoil of the respiratory system compresses the gas in the lungs, and Palv increases
394
As lung volume decreases, Ppl
slowly returns to its resting level
395
At the end of expiration, air flow, Palv, Ppl, equals.
At the end of expiration, i.e. at FRC, air flow=0 ml/s and Palv=0 cmH2O, and Ppl is about -5 cmH20
396
Values of intrapleural pressure range between
-5 to -8
397
alveolar pressure ranges between
1 to -1
398
The time course of changes in pleural pressure during inspiration and expiration depends on
contraction of the diaphragm and airway resistance
399
What is Airway Resistance important for?
related to airway caliber and is an important determinant of lung function
400
In certain diseases (such as asthma) airway resistance can become
very high making breathing difficult
401
The resistance of the airways to gas flow (Raw)
is the ration of the pressure difference and the flow
402
In order to have gas flow through the airways, the pressure at the airway opening compared to the pressure at the alveoli
(Pao) must be different from that in the alveoli (Palv)
403
Flow and resistance of a large diameter airway
A large diameter airway can carry a large flow for a given pressure difference and so has a smaller resistance than a small diameter airway
404
When a subject inspires to TLC and exhales to RV, during expiration, what happens to flow
flow rises very rapidly to a high value and then declines over the rest of expiration.
405
Why is the the descending portion of the flow-volume curve is independent of effort
because of the compression of the airways by intrathoracic pressure
406
Before inspiration (A), what is the airway and intrapleural pressure?
airway pressure is zero and intrapleural pressure is -5cm H2O.
407
```
During inspiration (B), what
happens to the airway and intrapleural pressure?
```
During inspiration (B), pleural and airway pressures fall.
408
End of inspiration (C), what is the airway and transmural pressure pressure?
airway pressure=zero and airway transmural pressure=8 cm H2O.
409
During forced expiration (D), what
| happens to the alveolar and intrapleural pressure?
During forced expiration (D), intra-pleural and alveolar pressures increase.
410
restrictive diseases
pulmonary fibrosis
411
obstructive diseases
emphysema
412
the maximum flow rate and maximum volume exhaled in restrictive diseases
In restrictive diseases (e.g. pulmonary fibrosis), the maximum flow rate and maximum volume exhaled are reduced (lungs are stiff).
413
the flow rate and appearance in obstructive diseases
In obstructive diseases(e.g. emphysema), the flow rate is very low and a scooped out appearance is often seen (lungs are floppy)
414
Inspiration process
```
Diaphragm and intercostal muscles contract
↓
Thoracic cage expands
↓
Intrapleural pressure becomes more negative (subatmospheric)
↓
Transpulmonary pressure increases
↓
Lungs expands
↓
Alveolar pressure becomes subatmospheric
↓
Air flows into alveoli
```
415
Expiration process
Diaphragm and external intercostal muscles stop contracting
↓
Chest wall moves inwards
↓
Intrapleural pressure goes back towards preinspiratory value
↓
Transpulmonary pressure goes back towards preinspiratory value
↓
Lung recoils towards preinspiratory volume
↓
Air in lungs is compressed
↓
Alveolar pressure becomes greater than atmospheric pressure
↓
Air flows out of the lungs
416
Asthma
Chronic inflammatory disease of the airways
clinically characterized by airway obstruction, and enhanced airway responsiveness to contractile agonists and/or allergens
417
Emphysema
Enlargement of air spaces due to destruction of the alveoli walls The airways tend to collapse because of the loss of radial traction.
The lungs actually self-destruct, attacked by proteolytic enzymes secreted by leukocytes in response to a variety of factors
418
Fibrosis
Progressive distortion of the alveolar architecture with inflammation and accumulation of fibrotic tissue
419
When exercise starts, How do tidal volume (VT) and breathing frequency (f) change?
increase proportionally
420
peak expiratory flow rate vs peak inspiratory flow rate
peak expiratory flow rate increases more than peak inspiratory flow rate
421
During exercise, what happens to do tidal volume (VT) and breathing frequency (f)?
VT plateaus; therefore, high ventilatory rates during hard exercise are due to incremental increases in f
422
In both untrained and trained subjects, how does minute ventilation (VE) and metabolic rate (VO2) change?
In both untrained and trained subjects, minute ventilation (VE) increases linearly with metabolic rate (VO2) up to about 50% to 65% of VO2 max
423
How does VE change compared to VO2?
VE increases at a rate disproportionately greater than the change in VO2
424
effect of endurance training
to delay the ventilatory inflection point (Tvent)
425
Affect of Resting values of VE with exercise
Resting values of VE can increase 35 folds during exercise (from 5L/min to 190 L/min, in a fit individual)
426
Affect of Resting values of cardiac output (CO) with exercise
can increase 5-6 folds during exercise (from 5L/min to 25-30 L/min, in a fit individual)
427
How does VE/Q change with excersise?
Because VE can increase more than Q
-The VE/Q
during exercise, there is an increase in VE/Q
428
The alveolar surface area
50m2 (1/2 of a single tennis court
429
What % of blood is in the pulmonary system at any one time during maximal exercise
4%
430
Does ventilation limit aerobic performance? why?
Reason why ventilation is not believed to limit aerobic performance
there is a large capacity for gas exchange
431
During excersise , what is the reponse in the medullary ECF?
alkalotic (increase pH)
432
During exercise, there is an alkalotic ( pH), how is the ventilatory response?
decreased
433
During excerise, what are peripheral chemorecpetors sensitive to?
Peripheral chemoreceptors are mainly sensitive to changes in PO2, but are also stimulated by increased PCO2 and decreased pH
434
PaO2 change during exercise? why?
PaO2 remains rather constant during exercise
| the increase in ventilation cannot come from the stimulation of the peripheral chemoreceptors by changes in O2
435
PaCO2 change during exercise? why?
PaCO2 is often seen to decrease during exercise
the increase in ventilation cannot come from the stimulation of the peripheral chemoreceptors by CO2
436
How does arterial pH change with exercise?
during exercise, arterial pH does decrease and PaO2 fluctuates subtly with arterial pulse waves
437
The control for minute ventilation before excercise?
neural`
