Respiration 2 Flashcards
definition of lung compliance
change in lung volume for a given change in pressure
2 factors that contribute to compliance
- lung elasticity
2. surface tension
what is the equation for lung compliance
lung compliance= change in volume of the lung / transpulmonary pressure
where is the surface tension of alveoli detected
at the air water interface (lining of alveoli)
what force constantly acts on the surface of the alveoli
an inward force
tends to make alveoli collapse
how is tension reduced at the air water interface of alveoli
surfactant
what cells secrete surfactant
type II alveoli cells
how is surface tension created
intermolecular attractive forces
forces on the liquid side are stronger than the air side
- pulls surface molecules toward water phase reducing surface area
- remaining molecules at the surface exert opposing force called surface tension
what is the equation for surface tension in bubbles
pressure= 2x surface tension / radius
what happens to pressure when surface tension increases in alveoli
pressure increases
what happens to pressure when alveoli radius decreases
increases pressure
what would happen if bubbles of different radii were attached to each other
air will flow from high pressure to low pressure so bubble with smaller radii will collapse in absence of surfactant
what does surface tension do in alveoli during inspiration
resists expansion
how does surfactant reduce surface tension in alveoli
reduces intermolecular forces between water
what are 2 things surfactant does for alveoli in lung
- increasing ability to expand lung (alveoli)
- allow alveoli to be small and not collapse on itself
- helps for gas exchange
what is molecular make up of surfactant
amphipathic phospholipid and protein
has hydrophobic tails that play a huge role in function
what do the hydrophobic tails of surfactant do in terms of force
hydrophobic tails wants to move away from water
contributes an upward force at the air-water interface that minimizes the downward force that is constantly pulling the water molecules inward causing the surface tension
therefore the upward force by hydrophobic tails decreases the total surface tension
besides force contribution what other way does surfactant serve to decrease surface tension
decreases the density of water molecules at the air-water interface which will reduce surface tension
what cell regulates the production of surfactant and how is it regulated
type II cells in alveoli regulate surfactant
stretch receptors-
sense the need to inflate the lungs (when breathe deep) because the surface tension will increase; then the cells will produce more surfactant
what is primary factor in determining lung compliance
being able to overcome surface tension
requires muscle energy
what happens if surfactant deficient
harder to breathe
respiratory distress–cannot inflate lung well
what is ARDS
Acute Respiratory Distress Syndrome
2nd leading cause of death in premature infants
if child is born with ARDS, what will happen to the lungs
insufficient surfactant production so lungs will stick together and lungs resist expansion
what is 2 therapeutic measures that can be taken for child with ARDS
- deliver artificial surfactant
2. mechanical ventilation
what are two factors that determine air flow through the tubules
- change in pressure
2. resistance
what is the primary determinant for resistance
radius of the tubule
equation for resistance
equation for flow rate
R=1/r^4 R: resistance; r: radius
Flow=change in pressure / resistance
some other factors in determining resistance
- transpulmonary pressure
- elasticity of tissue
- neuronal and chemical control of smooth muscle
what happens when increase resistance but do not change lung compliance
breathe deeply-
exerts more muscle force to increase change in pressure
breathe slowly-
to conserve muscle energy
what happens when decrease lung compliance
breathe more rapidly-
there is not much change in pressure happening because the lungs don’t change in volume much so have to breathe air more rapidly to bring in enough oxygen
breathe shallow-
conserve muscle
asthma is caused by…
excessive contraction of smooth muscle in bronchioles (hypersensitivity)
what happens to resistance in asthma
increase resistance so decrease airflow
even during non-attack times, can have increased resistance due to inflamed airway
what can induce asthma
exercise
allergies
treatments for asthma
glucocorticoid therapy
-reduces inflammation
bronchodilators
- epinephrine agonists
- acetylcholine antagonists
what does COPD stand for
chronic obstructive pulmonary disease
what is main concern with COPD
increased airway resistance
not getting enough oxygen into blood
COPD is associated with…
smoking
two major components that make up disease of COPD
emphysema
chronic bronchitis
what is emphysema
destroyed alveolar tissues by overproduction of proteolytic enyzmes (destroy elastic tissue)
what complications present in emphysema
reduced elasticity so increased resistance
airway collapse
difficulty in expiration
what is chronic bronchitis
inflammation and production of mucous impairs airflow
what is a complication of chronic bronchitis
increased resistance
deeper breathing
what does heimlich maneuver do
increases pressure within alveolus to overcome resistance and expel trapped artifact
define tidal volume
(TV): the volume of air that enters the lungs per breath at normal (resting) breath rate
about 500 ml
define inspiratory reserve volume
(IRS): the amount of air you can continue to breath in passed the TV by breathing in deeply (forced inspiration)
MAX volume inspired
about 3000 ml
define expiratory reserve volume
(ERV): the amount of air you can force out of the lung after each breath
volume exhaled beyond TV
about 1500 ml
define residual volume
volume that remains in the lung after forced expiration
volume after MAX exhalation
about 1000 ml
define vital capacity
total amount of air that can be breathed into the lung after forced expiration (a lung that is as empty as possible)
IRV+ERV+TV=vital capacity
approx 5000 ml
define total lung capcity
total amount of air that can be held in the lung
vital capacity (vc)+residual volume=total lung capacity
approx 6000 ml
what is FEV1
the amount someone can expire from the vital capacity in 1 second
normal FEV1
approx 80% of vc should be exhaled in 1 second
obstructive lung disease
explain what happens to vc and FEV1
airway is obstructed
vc is normal but FEV1 decreases
vc is normal because can use more muscle force to breath in same amount of air
restrictive lung disease
explain what happens to vc and FEV1
lungs do not fully recoil
FEV1 is normal but vc is decreased
can be due to neuromuscular deficits
what is minute ventilation
TV X respiratory rate (breaths/min)
This gives the amount of ml that is breathed in per min
what is alveolar ventilation
measure of how much volume of air actually reaches the alveoli after being breathed in
why doesn’t all air that is breathed in reach the alveoli
because of the dead space (anatomic)
lose about 150 ml of air in a normal person before reaching alveoli
what is the equation for alveolar ventilation (AV)
AV= (TV-dead space)X respiratory rate
what are two ways to increase alveolar ventilation
- increase respiratory rate (but not the best way because have to consider dead space)
- increase tidal volume
breathe deeper and less frequent (best way to increase AV)
what happens during exercise to have optimal AV
increase respiratory rate but also increase tidal volume (breath deep) to counteract increased rate
what is alveolar dead space
mismatch between ventilation and blood flow
what are two possible scenarios of alveolar dead space
- no blood flow to the alveolus
2. reduced blood flow to the alveolus
why is the alveolar dead space always greater than zero in even normal lungs
because the effects of gravity on blood flow
what do the effects of gravity cause for the blood flow to the lung and in terms of gas exchange
blood flow is better at the bottom of the lung than at the top
the top of the lung does not have the same opportunity for gas exchange as the bottom of the lung and therefore is less oxygen rich at the top of the lung
what is the physiological dead space
it is the total sum of the air for ventilation that is not used for gas exchange
anatomical dead space + alveolar dead space
what is external respiration
gas exchange between the air in the lung and the blood
what is internal respiration
gas exchange between the blood and the cells in the interstitial fluid
what are the 5 steps of respiration
- ventillation
- external respiration
- gas transport in blood
- internal respiration
- cellular respiration
steps of respiration
1. ventilation
breathe in air into the alveoli
steps of respiration
2. external respiration
exchange O2 from air in lung to the blood in lung and CO2 from the blood in lung to the air in lung
steps of respiration
3. gas transport in blood
O2 goes to the left side of the heart and is pumped out to the rest of the body so gas exchange can happen with the cells
steps of respiration
4. internal respiration
gas exchange between the blood and the cells in the interstitial fluid
O2 goes to the cells and the cells give off CO2 to go back into the blood
steps of respiration
5. cellular respiration
the cells that got the O2 from the blood can now send it to the mitochondria of the cell for cellular respiration
dalton’s law
for a mixture of gases the total pressure is the sume of all the individual pressures (partial pressure)
when gases diffuse which direction do they flow
from high to low partial pressure
pressure exerted by gas is affected by…
temperature and concentration
when altitude changes what happens to the pressure of gas
the partial pressures will change but the percent composition will not
what is the partial pressure of oxygen in an atmospheric pressure at sea level of 760 mmHg?
oxygen makes up 21% of the atmospheric pressure and since composition does not change..
multiply 21% by 760 mmHg which equals 160 mmHg
what is percentage of oxygen that makes up the composition of the atmosphere
21%
henry’s law
amount of gas dissolved in a liquid is proportional to teh partial pressure of that gas in equilibrium with the liquid
what happens to the partial pressure of gases in body fluids as it flows through the blood
what is the partial pressure range
as the gas flows through the bodily fluids from the alveolar air through the body systemically back to the arterial alveolar capillaries the partial pressure of oxygen becomes more depleted as it move through the blood
starts at 105 mmHg and goes down to as low as 40 mmHg
what are three things that determine alveolar O2
- atmospheric PO2
- rate of alveolar ventilation
- rate of cellular O2 consumption
alveolar gas pressures are altered by two things
ratio of ventilation and metabolism
what happens to alveolar O2 and CO2 when breathing in air with low PO2
O2 decreases and CO2 has no change
what happens if increase alveolar ventilation and don’t change metabolism
O2 increases and CO2 decreases
what happens if decrease alveolar ventilation and don’t change metabolism
decrease O2 and increase CO2
what happens if increase metabolism and don’t change alveolar ventilation
increase CO2 and decrease O2
what happens if decrease metabolism and don’t change alveolar ventilation
decrease CO2 and increase O2
what happens to alveolar O2 and CO2 when proportional increases in metabolism and alveolar ventilation occur
no change in either CO2 or O2
what happens with hypoventilation
decrease alveolar PO2 because ventilation is decreased
increase CO2 because not releasing CO2 through expiration as much
hyperventilation
ventilation is increased relative to metabolism
DECREASE in alveolar CO2 because expiring too much
(causes disturbance in pH, increases pH or makes more basic)
increase in alveolar O2
what happens during exercise and why is it not termed hyperventilation
in exercise
- increase respiration rate
- increase tissue metabolism
breathing faster so losing CO2 by air being expired but does not disrupt pH because tissue metabolism produces CO2 to compensate
therefore it is not termed hyperventilation
solubility of gases (O2 and CO2)
CO2 is more soluble in water than O2
O2 will diffuse slower from air to blood
what is large safety factor in capillaries
the capillaries are much longer than you need for oxygen to be diffused into blood
usually first 20-30% of capillary length is needed to reach appropriate concentration of O2 (100 mmHg)
In a diseased lung- capillary does not pick up Oxygen as fast but can still pick up enough for survival by using the additional length of the capillary
why is it so hard for oxygen to diffuse in disease and strenuous exercise when the walls of the alveoli are thickened
O2 is not very soluble to begin with so very affected by a thicker wall to diffuse across
CO2 is not as affected (more soluble)
how is ventilation perfusion inequality corrected by LOCAL FACTORS (2 pathways)
decrease airflow–>decrease alveolar PO2–>decrease blood PO2–>vasconstriction–>decrease blood flow
- vasoconstriction is needed when have reduced airflow because need to slow down blood to allow more time for diffusion of O2
- also diverts blood to healthy parts of the lung that can serve function
decrease blood flow–>decrease alveolar PCO2–>bronchoconstriction–>decreased air flow
-bronchoconstriction is used to divert air to other parts of the lung where blood supply is functional (divert to healthy alveoli)
in pulmonary edema (fluid filled alveoli) and diffuse interstitial fibrosis (thickening of alveolar walls) why is oxygen more affected than CO2
O2 is less soluble and has more difficulty diffusing through the thick walls and fluid
how does gravity and flow rate of fluid create perfusion inequalities in PO2
gravity causes the blood to flow to the bottom of the lung more readily so there is greater perfusion at the base of the lung
but the blood flow is too fast for the O2 to diffuse fully (O2 not very soluble, diffuses slow) so the P02 of the blood is about 5 mmHg lower than PO2 in the alveoli
LOCAL response to decreased airflow in the lung
vasconstriction
LOCAL response to decrease blood flow in the lung
bronchoconstriction
what is the PO2 in pulmonary arteries going back to the lung
40 mmHg
what is the PO2 in pulmonary veins that leaves the lung
why is it not in equilibrium with the PO2 in the alveoli?
100 mmHg
diffusion cannot happen as fast as the flow rate of the blood so not all the oxygen diffuses into the blood
also the physiological dead space plays a role; gravity causes less blood to perfuse the top of the lung
what is the PCO2 in pulmonary veins that leaves the lungs
40 mmHg
what is the PCO2 in pulmonary arteries heading back to the lung after tissue diffusion
46 mmHg
