Respiratory System: Ventilation and Gas Exchange Flashcards
The volume of air in the lungs is determined by what two factors?
- the magnitude of the pressure change during inspiration or expiration
- the stretchability of the lung
What describes the stretchability of the lung? How is it defined?
Lung compliance describes the stretchability of the lung (specifically, their elastic connective tissues)
it is defined as the change in lung volume for a given change in pressure or
CL = ∆VL/(Palv-Pip) = ∆VL / Ptp
Compliance is the inverse of ___ and is indicative of the amount of muscle ___ needed to ___ the lung.
stiffness; force; ventilate
What two factors contribute to compliance?
- lung elasticity
2. surface tension
If the lung elasticity is high, V ___ rapidly per unit change in P. However, if the lung elasticity is low, V ___ slowly per unit change in P.
increases; increases
What happens to compliance if lung tissues thicken?
there would be a decrease in compliance
What is the measure of the intermolecular attractive forces that stabilize liquid?
Surface tension
T/F. Surface tension pulls molecules together at an air-liquid interface.
True.
For polar molecules like water, what creates the surface tension?
electrostatic force
Forces are strong on the ___ side, but weak on the ___ side.
liquid; air
T/F. A net force pulls the surface molecules toward the air phase which reduces the surface tension.
False, A net force pulls the surface molecules toward the WATER phase which reduces the surface tension.
The remaining surface molecules exert an opposing force called ___ ___.
surface tension
Because there is a ___ charge at the surface to repel molecules, water forms ___.
negative; droplets
Surface tension in a ___ cause the liquid lining to be pulled toward the ___. These forces generate an inner pressure that is ___ to surface tension and ___ proportional to the radius of the bubble.
bubble; center; proportional; inversely
P = 2x ___ ___ / ___
P = 2x surface tension / radius
increase in ST = increase in P
decrease R = increase P
T/F. If bubbles of different sizes are connected, the pressure difference will be different in each bubble.
False, If bubbles of different sizes are connected, the pressure difference will EQUILIBRATE as air flows from bubble 2 into bubble 1
T/F. Surface tension tends to pull the alveolar walls outward.
False, surface tension tends to pull the alveolar walls INWARD.
Like connected bubbles, alveoli are connected to each other so the smallest ones are at the ___ risk of collapsing.
greatest
Ventilation must produce enough force to counteract what? How is this force minimized?
tension
by using surfactant
What cells produce surfactant? What does surfactant do?
Type II cells
reduces the surface tension by reducing intermolecular forces between water molecules.
Why is surfactant important in small alveoli?
So that alveoli can be small and numerous (which increases surface area for gas exchange)
Surfactant is a ___ phospholipid + protein that forms a ___ between air and water. The ___ tails pulls the surfactant molecule upwards.
amphipathic; monolayer; hydrophobic
What concentrates surfactant at the surface? How does this reduce surface tension?
hydrophilic / hydrophobic interactions
by decreasing density of H2O molecules
T/F. Surfactant creates additional surface tension and will decrease compliance.
False, Surfactant does NOT create additional surface tension and will INCREASE compliance.
T/F. Surfactant has a greater effect in larger alveoli as compared to small.
False, Surfactant has a greater effect in SMALL alveoli
T/F. The reduction in surface tension helps to maintain a pressure in smaller alveoli equal to that in larger ones.
True.
How is the production of surfactant regulated?
- by stretch receptors in Type II cells
2. deep breathing increases surfactant production
Which is more important in determining lung compliance, surface tension or lung elasticity?
surface tension
Surfactant deficiency leads to ___ ___. Acute ___ ___ syndrome is the ___nd leading cause of death in premature infants. Why?
respiratory distress; respiratory distress; 2
- insufficient surfactant production
- lungs resists expansion so not enough O2 enters
What type of therapy is given to these premature infants?
artificial surfactant and mechanical ventilation (high O2 environment)
Airflow is ___ ___ to airway resistance (flow = ∆P/R) and the tube ___ is the primary determinant of resistnace with resistance being proportional to ___.
inversely proportional; radius; 1/r^4
What factors other than airflow affect R? How?
transpulmonary pressure - dilates bronchioles during inspiration
elasticity of tissues between outside of airways and alveolar walls also open airways during inspiration
neural and chemical control of smooth muscles
T/F. Epi dilates smooth muscles to increase flow and cytokines released during inflammation cause muscular constriction causing an increase in R and a decrease in F.
True.
If there is an increase in resistance due to mucus or an inflammatory response, one will breath more ___ to increase ∆P and breath more ___ because airflow during expiration is limited.
deeply; slowly
If there is a decrease in compliance due to the lungs not stretching as much, one will breath more ___ to compensate for reduced ∆V and ∆P and they will breath more ___ to minimize muscle effort (use less muscle energy).
rapidly; shallowly
Why does asthma cause increase airway resistance?
because of inappropriate contraction of smooth muscle
In asthma, an increase in R causes a ___ in airflow. This can be treated with ___ therapy and/or ___.
decrease; glucocorticoid (inhibit inflammation); bronchodilators (epi will stimulate relaxation of smooth muscle to dilate airways)
___ and ___ are examples of chronic obstructive pulmonary diseases that increase airway ___ and are often associated with ___.
Emphysema; chronic bronchitis; smoking
What causes emphysema?
alveolar tissues damaged or destroyed, perhaps due to overproduction of proteolytic enzymes
T/F. In emphysema, enzymes degrade elastic fibers in the lungs creating many large alveoli with low compliance that don’t expand easily.
True.
What does emphysema result in?
airway collapse
lack of recoil
difficulty in expiring
In chronic bronchitis there is ___ or ___ that impair airflow thereby ___ resistance and ___ breathing
mucus; inflammation; increased; deeper
The Heimlich maneuver dislodges particulate matter from the ___ respiratory tract by ___ the pressure in the thorax.
upper; increasing
Match the following:
- tidal volume
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- vital capacity
- total lung capacity
A. V exhaled beyond TV B. vital capacity + residual volume C. max V inspired D. V entering lungs per breath E. IRV + ERV + TV F. V in lungs after maximum exhalation
1 - D 2 - C 3 - A 4 - F 5 - E 6 - B
Match the following:
- tidal volume
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- vital capacity
- total lung capacity
A. 500ml B. 1000ml C. 1500ml D. 3000ml E. 5000ml F. 6000ml
1 - A 2 - D 3 - C 4 - B 5 - E 6 - F
What are the two clinically relevant measures?
- vital capacity - how well lungs expand relative to max pressure change
- forced expiratory volume in 1 second (FEV1) - indicates resistnance and how much VC can be exhaled in 1 sec
What are the FEV1 and VC in obstructive and restrictive lung disease?
Obstructive (take more muscle energy): ↓FEV1 and normal VC
Restrictive (nothing blocking air leaving lung): ↓VC and normal FEV1
What is the minute ventilation (ml.min) at rest?
Minute ventilation = tidal V x respiratory rate
= 500ml x 10 breaths/min
=5000ml/min
T/F. All air enters the alveoli.
False, all air does NOT reach the alveoli so must consider dead space
The ___ dead space (~___ml) reduces the amount of fresh air reaching the alveoli. It is the volume in the ___ airways left over from preceding breath.
anatomical; 150; conducting
T/F. The anatomical dead space increases the alveolar ventilation (AV) which is a more accurate measure of air reaching the alveoli.
False, The anatomical dead space DECREASES the alveolar ventilation (AV) which is a more accurate measure of air reaching the alveoli.
AV = (___V - ___ space) x ___ rate
AV = (tidal V - dead space) x respiratory rate
What does it mean if the AV is equal to zero?
that the patient is not breathing deeply enough to overcome the dead space
Alveolar ventilation differs dramatically and one sees a bigger change when taking a ___ breath (↑TV) than increasing the ___ rate.
deeper; respiratory
What happens during exercise to the ventilation?
↑ rate + breathing deeply to ↑ TV + frequency therefore don’t double ventilation by only ↑ rate
When does an alveolar dead space exist?
when there is a mismatch between ventilation and bloodflow
T/F. The alveolar dead space is always zero, even in normal lungs, due to the effects of gravity on bloodflow.
True.
The perfusion at the apex of the lung is not a good as at the base
___ dead space is the sum of anatomical dead space + alveolar dead space.
Physiologic
Define external and internal respiration.
External: gas exchange between air and blood in lung
Internal: gas exchange between blood and cells (interstitial fluid)
What are the steps of respiration?
- Ventilation (bulk flow) - moving gas from exchange of air
- external respiration (diffusion) - O2 diffuses into blood + CO2 diffuses into air
- gas transport in blood (bulk flow) - O2 in blood to tissues of body via blood flow
- internal respiration (diffusion) - O2 diffuses into ISF from blood at target cells
- cellular respiration (consume O2 and produce CO2) - get into mitochondria for oxidative phosphorylation → ATP
What does Dalton’s law for gases in a mixture of gases state?
that the total pressure is the sum of the individual pressures
Individual pressures are called ___ pressures.
partial
T/F. The pressure exerted by gas is independent of pressure exerted by other gases and is proportional to temperature and concentration.
True.
How do gases diffuse?
from high to low partial pressures
In the atmosphere, what does Patm equal?
sum of all the partial pressures
T/F. Partial pressures will not vary with altitude, but the composition does.
False, Partial pressures WILL vary with altitude, but the composition does NOT.
What is the PO2 at sea level? In Denver?
sea level: 760mmHg = total pressure (21% O2 but diff PO2 = 160mmHg
in Denver: 640mmHg = total pressure (21% O2 but diff PO2 = 130mmHg
___ law states that the amount of gas dissolved in a liquid is proportional to the partial pressure of that gas in equilibrium with the liquid.
Henry’s
T/F. At equilibrium, Pgas in gas phase equals the Pgas in the liquid phase. At a gas mixture/liquid interface, gas will diffuse along a partial pressure gradient.
True.
What two things does the parital pressure vs concentration of a gas in liquid depend on?
- which gas it is and partial pressure of the gas
2. temperature (↑temp = ↓ solubility of a gas)
Match the different tissues with the partial pressures.
- alveolar air
- alveolar venous capillaries
- systemic arteries
- tissue capillaries
- systemic veins
- arterial alveolar capillaries
- air
A. PO2 = 105mmHg, PCO2 = 40mmHg
B. PO2 = 40mmHg, PCO2 = 46mmHg
C. PO2 = 100mmHg, PCO2 = 40mmHg
D. PO2 = 160mmHg, PCO2 = 0.3mmHg
1 - A 2 - C 3 - C 4 - B 5 - B 6 - B 7 - D
Why is the PO2 less than 5mmHg in the mitochondria?
O2 is being consumed quickly to maintain gradient for more O2 to diffuse in
Alveolar PO2 (how much O2 is available to the blood) is determined by what three factors?
- atmospheric PO2
- rate of alveolar ventilation
- rate of cellular O2 consumption
Match the following conditions with the change in alveolar PO2 and alveolar PCO2.
- breathing air with low PO2
- ↑ alveolar ventilation and unchanged metabolism (not consuming or producing more O2)
- ↓alveolar ventilation and unchanged metabolism
- ↑ metabolism and unchanged alveolar ventilation
- ↓ metabolism and unchanged alveolar ventilation
- proportional increases in metabolism and alveolar ventilation (balanced; majority of homeostatic mechanism)
A. Increase; Decrease
B. Decrease; Increase
C. Decrease; No Change
D. No Change; No Change
1 - C 2 - A 3 - B 4 - B 5 - A 6 - D
In ___ the ventilation is decreased relative to the metabolism so a patient breathes more slowly. The alveolar PO2 is ___ and alveolar PCO2 is ___.
Hypoventilation; decreased; increased
In ___ the ventilation is decreased relative to the metabolism so a patient breathes more frequently. The alveolar PO2 is ___ and alveolar PCO2 is ___.
Hyperventilation; increased; decreased
Why does hyperventilation not occur during exercise?
the metabolic rate also increases during exercise to counteract the ↑PO2 and ↓PCO2
What happens the to PO2 at high altitudes?
there is lower PO2 in the air so lower alveolar PO2 therefore the rate at which O2 diffuses into blood is severely reduced
T/F. O2 uptake continues along the length of the alveolar capillaries.
True
T/F. The alveolar has a small safety factor.
False, it is not used in the normal lung and large for diseased lungs to allow for diffusion of sufficient O2
Pulmonary edema fills some alveoli with ___. Diffuse ___ ___ thickens the alveolar walls.
fluid; interstitial fibrosis
Why are gas exchange problems greater for O2 than CO2?
O2 is not a soluble in H20 as CO2 so CO2 is able to move faster from one fluid to another than O2
Ventilation-perfusion inequalities will ___ blood PO2. List two conditions.
lower
- vascularized space with no ventilation
- ventilated space with no blood supply
How do local responses in smooth muscle minimize ventilation, such as perfusion mismatches due to bronchoconstriction and vasoconstriction?
bronchoconstriction: ↓air flow → ↓alveolar PO2 → ↓blood PO2 → vasoconstriction → ↓blood flow
vasoconstriction: ↓blood flow → ↓alveolar PCO2 → bronchoconstriction → decreased air flow
