4. Respiratory Physiology II Flashcards
To understand gas exchange We need to know a few basic laws • how gas behaves alone(\_\_\_\_) • in a mixture(\_\_\_\_) • in a fluid(\_\_\_\_)
diffusion
dalton’s law
henry’s law
Diffusion of gases
• Diffusion of gasses moves along concentra3on gradient, from areas
of ____ to areas of ____
• Movement of gases between cells and the blood in the capillaries and across the respiratory membrane of the alveoli is via ____
• ____ mo%on of molecules provides energy for movement
high partial pressure
low partial pressure
diffusion
kinetic
Partial pressure of gas: Dalton’s Law
Pressure is an effect which occurs when a ____ is applied on a surface. P=F/A
The partial pressure of an ideal gas in a mixture is equal to the pressure it would exert if it occupied the same volume ____ at the same temperature.
Dalton’s Law of Partial Pressures: The total pressure of a mixture of ideal gases is equal to the sum of the partial pressures of the ____ in the mixture.
Ptotal = Pgas1 + Pgas2 +…. + PgasN
• The partial pressure of various gases is additive
force
alone
partial pressures
Consequences of Dalton’s Law
Each gas in a mixture (air) tends to diffuse ____ of all other gases
Diffusion of oxygen does not interfere with diffusion of ____ or vice versa
Each gas diffuses at a rate proportional to its ____ until it reaches ____
This allows for ____ traffic of gases in the lungs and in the
body tissues
• Forces on O2 and CO2 are independent ○ Movement of O2 in one direction doesn't interfere with CO2 going in the other direction • Dalton's law lets us understand that gases in a mixture behave independently ○ How we have O2 going out, and CO2 going in
independently carbon dioxide partial pressure gradient equilibrium two-way
What about gas in fluid?
- Important because O2 and CO2 are exchanged between air and blood, which is mostly ____
- Even when dissolved in water, gases exert a partial pressure and diffuse from regions of ____ toward regions of ____
water
higher partial pressure
lower partial pressure
Henry’s Law: solubility of gases in a liquid
- Concentration of gas in fluid proportional to amount of gas in air above ____
- If more ____, get higher ____ of gas before building pressure
- So, partial pressure of gas in liquid determined by ____
• Henry’s Law:
partial pressure = concentration divided by solubility coefficient
• CO2 is more soluble in \_\_\_\_ than O2 • The more soluble, the more that gas can \_\_\_\_ before exerting a given partial pressure • (Partial pressure of a gas in fluid) • Solubility coefficient ○ Constant for a given gas ○ Affected by what it's dissolved \_\_\_\_ and the \_\_\_\_
fluid
soluble
concentration
concentration divided by solubility coefficient
H2O
dissolve
in
temp
Solubility coefficients of gasses in water
Oxygen: ____
Carbon dioxide: ____
Nitrogen: ____
CO2 stable in H20, ____x more soluble than ____
Thus, the same concentration of CO2 will exert proportionally less ____ than O2 as the solubility coefficient is much greater
• The solubility of CO2 is 20x more soluble than O2 ○ Can have same cxn of CO2, and the partial pressure will be 1/20th that of oxygen • Based on the: ○ Binding of atoms in \_\_\_\_ ○ How well they fit before exerting a pressure
0.024
0.57
0.012
20
O2
partial pressure
lattice
How rapidly do gasses move in fluid? Diffusion Rate
Although DP for CO2 low in gas exchange, moves quickly because of increased ____
* Diffusion is going to be approx equal to the difference in partial pressure, times the SA and solubility coefficient * Length of diffusion distance > the further apart your capillaries are in the tissue, the \_\_\_\_ it will take * Want to make sure you optimize the \_\_\_\_ for gas exchange in the lung
solubility
longer
area
Diffusion through tissues
Key gasses of respiratory importance are very ____
Thus diffusion through tissue basically ____ through water
If tissues ____ and length ____, takes longer
• In alveoli most of the gas exchange occurs ○ Type I cells ○ Covered in surfactant • The O2 and CO2 have to go from liquid compounds in blood through the cells ○ Both are very lipophilic, \_\_\_\_, small ○ Want to make this distance as short as possible § \_\_\_\_ situations arise when length increases ◦ When the length increases diffusion goes down, which may make it \_\_\_\_ for getting enough oxygen across the membrane
lipophilic
diffusion
thicken
increases
uncharged
pathological
rate-limiting
• The partial pressure of oxygen and carbon dioxide in each breath is dependent on
whether you are taking a ____ breath.
deep or shallow
Partial pressures of respiratory gasses
How does pO2 of expired air vary with shallow vs. deep breaths?
• Humidified air is normal air, but inside the body it's not as dry > concentrations \_\_\_\_ with a little bit of \_\_\_\_ • Humidified air ○ 150mmHg of O2 ○ Close to 0 of CO2 ○ Dead space air > air in mouth that gets as far as conducting passageways § No exchange of gases • Alveolar air ○ O2 > 100mHg ○ CO2 > 40mmHg • Expired air ○ Will vary ○ Shallow > a lot of \_\_\_\_ and alveolar air > closer to humidified ○ Deep breath > as you force air out from bottom > partial pressure of closer to \_\_\_\_ in alveoli
change
humidity
dead space air
O2/CO2
Replacement of alveolar air
Functional residual capacity (FRC) = ____ L, 0.35 L new air into alveoli per ____ breath, Takes ____ effort to fully dilute out old air with new, normally >____ min
Slow change useful, stops sudden change in blood gas concentration
Buffers ____, O2, ____ in blood
• Consequence of normal breathing > takes \_\_\_\_ breaths to turnover the air in your alveoli • FRC - when you breathe out the whole way • A lot of breath goes to the \_\_\_\_ (0.35 of 2.3L goes to alveoli) • Normally, exponential decay > after a minute you have some air left ○ You want to \_\_\_\_ concentrations; our bodies do not response well to sudden changes in concentration of oxygen in the alveoli
2.3
normal
exponential
1
pH
CO2
16
deadspace
buffer
Respiratory unit
Or, where the real business takes place
____ million alveoli in both lungs
____ mm diameter hole surrounded by epithelial cells that are in turn surrounded by blood
Exchange takes place in ____, alveolar ducts, ____ (necks), alveoli
* Epithelial cells are surrounded by capillaries * The lungs are designed to optimize interaction between air and blood * Gas exchange in bronchioles, but most occurs in the alveoli
300
0.2
respiratory bronchioles
atria
Exchange of gas
across respiratory membrane – designed to increase ____
Maximize exchange, blood always close to ____
Surrounded on all sides “Sheet of flowing blood”
70 m2 SA, perfused by 100 ml blood – very ____
Imagine spilling 100 ml of water over 25 x30 foot room
- very thin coating if spread across whole surface
* Interstitial space in between the capillaries * Lymphatic vessel - drainage, that stops the buildup of fluid in the lungs; \_\_\_\_ * There to optimize the exchange of gases from blood in your alveoli - depends on \_\_\_\_
contact alveolar membrane thin negative pressure diffusion
Exchange of gas
across respiratory membrane
Layers for gas to cross for exchange
Mean thickness ____ μm (Typical cell 10 μm)
- ____ (+ surfactant)
- ____ epithelium
- ____membrane
- ____
- ____
- ____
Pulmonary capillary 5 μm diameter so red blood cell must squeeze, touch wall, less ____ through plasma
• Fluid and surfactant covers edges of alveolar epithelial cells • Then it goes through epitheilail cells, basement membrane, interstitial space, capillary BM, and the tissue > and then in the portio • This distance is typically 0.6um ○ Each cell is 10 um ○ 1/20th the diameter • RBC have to line up \_\_\_\_ in this orientation, so they optimize the \_\_\_\_ for exchange, and squeezed in capillaries > \_\_\_\_ releases compounds that facilitates gas exchange • Getting oxygen into your tissues becomes a key aspect for life on earth
0.6 fluid alveolar epithelial basement interstitial space + matrix capillary basement membrane capillary endothelial membrane
diffusion
single-file
area
squeezing
Diffusion of gas across respiratory membrane
- Diffusion equation applies
- l - diffusion distance – increased by ____ in interstitial fluid, ____
- A = surface area - ____, walls collapse, less area,
- DP - # ____ of a given gas striking alveolar or capillary membrane• If you have an edema, and you swell the space; you have fibrosis and the interstitial distance is ____, you will take longer to get oxygen into the capillary and to get CO2 out
• The system has evolved with the capacity for ____
• Area decreases in emphysema > walls collapse and you have less area
○ Hundreds of little alveoli > decreased the area for gas exchange across that surface
○ As this decreases, the diffusion rate goes down
• Difference in partial pressure is the number of molecules striking the surface to go ____ (inside or outside)
ede,a
fibrosis
molecules
increased
adaptation
this way or that way
Ventilation-perfusion: matching blood flow and air flow
. V-____
. Q-____
Even if total blood flow and total air flow are ok, they must meet
The ventilation:perfusion (V:Q) ratio summarizes how the amount of ____ coming into the lungs matches with the amount of ____ that comes into the lungs
◦This matching is essential for efficient transfer of gases from alveoli to the blood and vice
Versa
• In normal situations V is usually = to ____ (V:Q is about 1)
◦Right amount of air to blood
• If you have a shunt — blocks air into alveolus
◦Blood is still going there but the air has slowed down
◦Shunt is perfusion without ____
• Dead space
◦Plenty of air but the ____ is not getting there
• You can measure the amount of air going into lung and the total perfusion
◦You can have a mismatch even if the total levels are good
◦They need to go to the same part of the ____ — if its unbalance you wont get normal function
• Used to describe pathology by clinicians
ventilation perfusion air blood Q
ventilation
blood
lung
Partial pressure of alveolar air; healthy case
Healthy case
VA / Q = ____v
Alveolar air:
PO2= 104 mmHg, PCO2 = 40 mm Hg
• In healthy perfusion cases the ratio is about \_\_\_\_. There is the right amount of air and blood coming into the alveoli • In alveolar air there is a partial pressure of oxygen of about 104 mm Hg and 40 mm Hg of carbon dioxide. • ( She doesn’t make sense here, but this is what she says) We get those partial pressures because there is a compromised between air diffusing through the conducting pathways and then you have gas exchange from the blue arterial air coming into the lungs exchanging before it goes out. • And so this 104 vs 40 reflects the diffusion of Co2 and oxygen back and forth when it meets up with the \_\_\_\_
1
1
humidified air
Partial pressure of alveolar air in physiologic SHUNT; like venous levels
• Physiological SHUNT - When ventilation blocked Va/ Q => \_\_\_\_ Alveolar air Þ venous gas levels PO2=\_\_\_\_ mmHg, PCO2 = \_\_\_\_ mm Hg \_\_\_\_ has less O2
• Low ventilation, and very high normal perfusion • Exchange of arterial blood going through, and no opportunity for \_\_\_\_ to come in ○ The partial pressures of CO2 and O2 are very low • If you can ventilate adjacent alveoli, you will have a \_\_\_\_ in amount of oxygen in the blood
0 40 45 blood fresh air reduction
Partial pressure of alveolar air in DEAD SPACE; like humidified air
• Physiologic DEAD SPACE - When blood supply blocked VA /Q => \_\_\_\_ Alveolar air Þ Humidified air PO2=\_\_\_\_ mmHg, PCO2 \_\_\_\_ mm Hg Work of ventilation \_\_\_\_
• Don't have any extra CO2, or low O2 blood coming around ○ Good ventilation, and no perfusion > infinity ○ Alveolar air approaches \_\_\_\_ ○ The work of ventilation is wasted § Cannot deliver any gases inhaled to the \_\_\_\_
infinity 149 0 wasted infinity blood
Alveolar gas levels with V/Q variation
• Ventilation-perfusion relationship ○ Within the alveolar space (within the alveoli) • In a shunt - cannot get fresh air ○ O2 levels in alveoli become much \_\_\_\_ (40mmHg), and the CO2 levels \_\_\_\_ because you cannot dilute out the CO2 with \_\_\_\_ ○ More sensitive for \_\_\_\_ • In a dead space - blood is an issue ○ \_\_\_\_ levels of oxygen (150 mmHg) and no \_\_\_\_ because there's no ability for diffusion of blood from the alveoli ○ More sensitive for \_\_\_\_
lower
increase
fresh air
PO2
high
CO2
PCO2
Abnormal VA/Q in normal lung
At apex (under pathological condi8ons), ____ < ____
Physiologic ____
At Base, ____ > ____
Physiologic shunt
Blood to bronchial vessels also shunted normally - ____% does not get O2
____ increases blood flow to ____ of lungs, less dead space, more efficient
• Because of vertical posture, we have mild degrees of dead space in the apex of the lung ○ No zone 1 under normal conditions ○ Under pathological conditions > blood flow substantially less than \_\_\_\_, and dead space in apex ○ In the base > \_\_\_\_ > blood flow greater than air flow • Shunted blood from lungs normally (2% is used to supply tissue) - this is not used for gas exchange > leads to drop in levels of \_\_\_\_ leaving the lungs
blood flow
air flow
blood flow
air flow
2
exercise
top
air flow
shunt
oxygen
Abnormal V/Q in
Chronic Obstructive Lung Disease
• After smoking
– small bronchioles
obstructed – ____
– Alveolar walls destroyed but ventilation – ____ because no ____
Most common pulmonary disabilities due to V/Q mismatch
• Mismatch between ventilation and perfusion ○ All the diseases we look at will satisfy this
shunt
dead space
capillaries
Summary: Gas Exchange – Lung
- Dalton’s Law – partial pressures ____
- Henry’s Law – solubility of gas in fluid ____ partial pressure
- Diffusion rate ____ Dpressure, area, solubility
- Alveolar air replaced ____, ____ blood gasses
- Respiratory exchange across ____ distance, many layers
- V/Q matches ____
- V/Q >1 – ____
- V/Q <1 – ____
additive lowers proportional slowly buffers small
air to blood
physiologic dead space
physiologic shunt
