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63 Cards in this Set

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Airway resistance influences what?
Influences rate of airflow.
Give the eqn for Flow Rate.
F = ^P / R

F = flow rate

^P = pressure gradient

R = resistance (influences rate of airflow in and out)

(F and ^P are directly proportional)

(F and R are inversely proportional)
What leads to increased airflow?
Increased difference between atmospheric and intra-alveolar pressures (^P).

(remember F and ^P are directly proportional)
What leads to decreased airflow?
Increased resistance (R).

(F and R are inversely proportional)
What is a major determinant of airway resistance?
RADIUS of conducting airways. (R ~ 1/r^4)

R = airway resistance

r = radius

note, r is to the 4th power so any small change in radius has a big impact on airflow.
What controls the contraction of smooth muscle in walls of bronchioles?
Autonomic nervous system controls contraction of smooth muscle in walls of bronchioles.
List three aspects of how the ANS controls the contraction of smooth muscle in walls of bronchioles.
1. ANS can change conducting airway radii

2. Sympathetic stimulation and epinephrine: bronchodilation (related to asthma)

3. Parasympathetic stimulation (at rest) : bronchoconstriction (...demand for airflow is low)
COPD stands for what?
Chronic Obstructive Pulmonary Disorder
What does COPD to airway resistance?
There is increased airway resistance with copd.
COPD is essentially what?
Group of 2 chronic diseases.

1. Chronic Bronchitis

2. Asthma Emphysema
What two properties allow the lungs to behave like balloons?
Stretching and recessing is due to:

1. Elastic Recoil

2. Compliance
What is elastic recoil?
How readily the lungs rebound if stretched. This allows the lungs to return to preinspiratory volume when inspiratory muscles relax at end of inspiration.
What is compliance?
The effort required to stretch (distend) the lungs. How much effort does it take.
Compliance is analogous to what?
Analagous to the effort required to blow up a balloon. A thin balloon is more compliant than a thick balloon.
A highly compliant lung does what?
A highly-compliant lung stretches further for a given increase in P than less compliant lung.
What happens to compliance in fibrotic lungs?
There is decreased lung compliance in fibrotic lungs.
Pulmonary elastic behavior depends upon what 2 things?
(structural elements)

1. Pulmonary elastic connective tissue

2. Alveolar surface tension
What is Pulmonary Elastic Connective Tissue?
Lots of elastin fibers arranged to enhance elasticity.
What is Alveolar Surface Tension?
Tension determined by thin liquid film lining each alveolus. This film allows alveolus to resist expansion. Film also squeezes alveolus, producing recoil. Coating of pulmonary surfactant prevents alveolus from collapsing from this surface tension.
What is pulmonary surfactant?
Mixture of proteins and lipids secreted by type II alveolar cells.
Where is pulmonary surfactant found?
Found between H2O molecules in fluid lining alveolus.
What does pulmonary surfactant reduce? What is the benefit to this?
Pulmonary surfactant reduces alveolar tension, with important benefits:

1. Increases pulmonary compliance, reducing work reqd to inflate lung

2. Reduces lungs tendency to recoil, so they do not readily collapse.
The work of breathing normally requires how much energy expenditure?
Normally reqs 3% of total energy expenditure.
What 4 situations INCREASE the amount of work necessary to breath?
1. Decreased pulmonary compliance : pulmonary fibrosis

2. Increased airway resistance : COPD

3. Decreased elastic recoil : Emphysema

4. Need for increased ventilation : exercise
How much are is inspired and expired during each quiet breathing cycle?
~500 ml
Do the lungs completely empty after each expiration?
Lungs do not completely empty after each expiration.
What is the total lung capacity at max inflation?
5,700 mL
What is the variation in lung volume with normal, quiet breathing?
Volume of lungs at end of normal inspiration = ave 2700 mL

Volume of lungs at end of normal expiration = ave 2200 mL
What is the minimum lung volume (residual volume) at maximum deflation?
1200 mL
What is tidal volume?
The difference between end-expiratory and end-inspiratory volume. So it is the air entering or leaving lungs in a single breath.

Ave = 500 mL

(2700 - 2200 mL)
How are lung volumes and capacities measured?
Measured using spirometers.
What is pulmonary ventilation aka? What is it?
Pulmonary ventilation = Minute ventilation.

Volume of air breathed in and out in one minute.
What is the respiratory rate?
Number of breaths / minute
What is the eqn for pulmonary ventilation?
Pulmonary ventilation = Tidal volume (mL / breath) X Respiratory rate (breaths / min)
What is the avg value of pulmonary ventilation?
6000 mL (6 L)

Because: 500 mL/breath X 12 breaths/min = 6000 mL
What is anatomic dead space?
Not all inspired air reaches alveoli, where gas exchange can occur, some in conducting airways.
Alveolar ventilation is ? ? pulmonary ventilation because of anatomic dead space.
Alveolar ventilation is less than pulmonary ventilation because of anatomic dead space.
What is the eqn for alveolar ventilation?
Alveolar ventilation =
((tidal volume - dead space volume) / breath) X respiratory rate
What is the avg alveolar ventilation?
Avg alveolar ventilation = (500 mL - 150 mL)/breath X 12 breaths/min = 4200 mL/min

So dead space is about 150 mL.
What patterns can affect alveolar ventilation? Explain.
Breathing patterns (eg. deep and slow) can affect alveolar ventilation.

Rest, quiet : alveolar ventilation ~ 4200 mL/min

Deep, slow breaths (increased TV, decreased respiratory rate): alveolar vent ~ 5250 mL/min
Alveolar dead space exist but is usually what?
Alveolar dead space is usually small.
The resistance of individual alveoli can be what?
The resistance of individual alveoli can be adjusted independently.
Local controls on the resistance of individual alveoli act on what?
Local controls act on the SMOOTH MUSCLE of the airways.
How do local controls act on smooth muscle of the airways?
(opposite effects)

1. Accumulation of CO2 in alveoli : decreases airway resistance by causing airway supplying alveoli to relax

2. Decreased CO2 has opposite effects : increased contraction of airways supplying alveoli, reduced airflow
Concerning local controls on resistance what should match?
Ventilation and perfusion should match.
List 4 stages for the transfer of gases.
1. Breathing movements (muscles) : supplies air to respiratory surface

2. Diffusion of O2 and CO2 across respiratory epithelium (alveoli)

3. Transport of gases (blood)

4. Diffusion of O2 and CO2 across capillary walls between blood and tissue cells.
What is the key to gas exchange?
Partial pressure gradients
O2 and CO2 exchange at pulmonary and tissue capillaries via what?
O2 and CO2 exchange at pulmonary and tissue capillaries via SIMPLE DIFFUSION.
Air is basically what?
A mixture of gases.
What does the partial pressure of each gas in the air depend on? Explain using Nitrogen as an example.
The partial pressure of each gas depends on its percentage in total atmospheric pressure (760 mmHg).

For example, air is 79% nitrogen. Nitrogen partial pressure: 0.79 X 760 = 600.4 mmHg.

O2: 21% in air; 0.21 X 760 = 160 mmHg.
What is a partial pressure gradient?
Two partial pressures for a gas in different regions of the body.
Describe the partial pressure of oxygen (Po2) as it relates to oxygen and carbon dioxide exchange in the lungs.
Partial Pressure of Oxygen (Po2) =

Greater in alveoli (100 mm Hg) verses in blood of pulmonary capillaries (40 mm Hg).

O2 diffuses from alveoli into capillaries.
Describe the partial pressure of carbon dioxide (Pco2) as it relates to oxygen and carbond dioxide exchange in the lungs.
Partial pressure of carbon dioxide (Pco2):

Greater in blood of pulmonary capillaries (46 mm Hg) verses in alveoli (40 mm Hg).

CO2 diffues into alveoli from capillaries.
Describe the partial pressure of O2 as it relates to oxygen and carbon dioxide exchange in tissue cells.
Partial pressure of oxygen (Po2):

Greater in blood (100 mm Hg) verses in tissue cells (40 mm Hg0.

O2 diffuses from blood into tissue cells.
Describe the partial pressure of carbon dioxide as it relates to oxygen and carbon dioxide exchange in the tissue cells?
Partial pressure of carbon dioxide (Pco2):

Greater in tissue cells (46 mm Hg) verse in blood (40 mm Hg).

CO2 diffuses into blood from tissue cells.
What is the O2 partial pressure gradient from ALVEOLI to BLOOD?
(so across pulmonary capillaries)
60 mm Hg (100-->40). So O2 enters blood.
What is the CO2 partial pressure gradient from BLOOD to ALVEOLI?
(so across pulmonary capillaries)
6 mm Hg (46-->40). So CO2 released from blood to alveoli.
What is the O2 partial pressure gradient from BLOOD to TISSUE CELLS?
(so across systemic capillaries)
60 mm Hg (100-->40). So O2 enters tissue cells.
What is the CO2 partial pressure gradient from TISSUE CELLS to BLOOD?
(so across systemic capillaries)
6 mm Hg (46-->40). So CO2 released from tissue cells to blood.
How does surface area affect the rate of gas transfer?
Increased SA leads to an increased rate of gas exchange.

The alveoli collectively have a tremendous surface area.

Increased pulmonary blood pressure, from an increased cardiac output, increases SA.
How does 'distance' affect the rate of gas transfer?
Thin walls lead rapid gas exchange.

The alveolar and pulmonary capillary walls are thin.
What conditions might thicken the areas for gas exchange?
1. Pulmonary edema

2. Pulmonary fibrosis

3. Pneumonia

(all thicken the areas for gas exchange)
How does the gas diffusion coefficient (fick's law) affect the rate of gas transfer?
Exchange is directly proportional to diffusion coefficient for a gas.

The coefficient for CO2 is 20X that of O2 (so CO2 is more soluble). This is why it is only 6 mm Hg (compared to 60 of O2)