Respiratory 2

Front 1

Lung volumes and capacities.

Back 1

Adding up certain divisions of lung volumes creates varying groups of lung capacities.

Front 2

Lung Volumes

Back 2

Tidal Volume (VT) - amount of air breathed in and out during one normal breath. ~15mL/kg for most domestic species.

Residual Volume (RV) - the volume of air that remains in the lungs after a complete and forceful expiration. You can't breathe it out no matter how hard you try to.

Front 3

Reserve Volumes

Back 3

Inspiratory Reserve Volume - amount of air that you can inspire beyond what you breathe in during a normal breath

Expiratory Reserve Volume - amount of air you can expire beyond what you breathe out during a normal breath

Front 4

Lung Capacities

Back 4

Vital Capacity - Maximum amount of air that can be inspired after the maximum amount of air has been expired (the most you can breathe in and out with max effort)

Total Lung Capacity = vital capacity + residual volume

Functional Residual Capacity = Residual volume + Expiratory Reserve Volume. The amount of air in the lung after a normal expiration. The lung volume that occurs when the chest wall and lung are in equilibrium. Affected by many diseases and conditions (diaphragmatic hernia, pneumothorax, etc)

Front 5

Why is energy used during breathing?

Back 5

1. Contraction of muscles expands the thorax and ventilates the lungs

2. Needs to overcome forces that would contract the lungs (recoil from elastic tissues, surface tension)

3. Needs to overcome resistance to air flow through the respiratory system. Everytime the airway forks, a little air turbulence is created

Front 6

Compliance

Back 6

Change in volume relating to a change in pressure. Measures how easy it is to distend the lung. Determined by measuring the change in lung volume as a result of a change in pressure.

Front 7

Where is compliance highest?

Back 7

In the mid-range of pressure, compliance is high. Change in volume is large with a small pressure change.

At higher pressures (at the end of inspiration), compliance is low and the curve flattens out. Lungs are less distensible.

Front 8

Surface Tension

Back 8

Attractive forces between atoms or molecules. Water molecules pull on each other. Surface tension needs to be overcome in the lung for breathing

Front 9

Which law does alveolar surface tension follow?

Back 9

Laplace's Law P=2T/r

P=the pressure inside the alveolus

T=the tension on its inner surface

r=the internal radius of the alveolus

P works to expand the alveolus

T works to contract the alveolus

Front 10

Why is Laplace's Law important?

Back 10

The smaller the radius of the alveolus, the more pressure you need to overcome that initial resistance/inner surface tension (just like starting to blow up a tight balloon. Once you get it started it's a lot easier).

It also means that at a given surface tension, small alveoli would have higher internal pressures. As a result, they would always empty into the larger alveoli. This is not a good thing because we would expend a lot of energy just to breathe and air wouldn't necessarily go where it needs to.

Front 11

How do we reduce the work of breathing?

Back 11

Surfactant: a substance that accumulates at the surface of the fluid in the alveoli to reduce surface tension, thereby reducing the work of breathing. It reduces the # of water molecules that can attract each other.

Front 12

Pulmonary Surfactant

Back 12

Lipoprotein Complex: 70% lipid, 30% protein.

Synthesized by type ll alveolar epithelial cells. Surfactant producing cells develop very late in gestation, so premature babies don't have these cells and their lungs can't function properly. Another surfactant-lacking syndrome is Respiratory Distress Syndrome.

Front 13

At the end of expiration...

Back 13

The alveolus is at its smallest size (r is low). Surfactant becomes more concentrated on the surface of the alveolus, greatly reducing surface tension (T).

Reducing surface tension also stabilizes the alveolus so that when it is small, it doesn't simply empty into larger alveoli and collapse.

Front 14

Surfactant Concentration vs. Alveolar size

Back 14

When the alveolus is small, like at the end of expiration, the surfactant is very concentrated so the surface tension is reduced (T). This counteracts the effects of the small radius so the 'opening' pressure at the start of inspiration is not prohibitively high, making it easier to start taking a breath.

As the lung inflates with inspiration, that same volume of surfactant needs to spread over the larger alveolar area so the concentration of surfactant goes down.

Front 15

At the end of Inspiration...

Back 15

The alveolus is at its largest size (r is high).

Surfactant spreads out (less concentrated) on the surface of the alveolus (surface tension, T, increases). This increased tension, along with elastin and collagen fibres, put an upper limit on the potential expansion of the lungs and provides some of the recoil necessary for making expiration a passive process.

Front 16

Airway Resistance

Back 16

Air flow follows the general principles of fluid flow through a rigid, smooth tube.

Flow of fluid follows "Poiseuille's Law"

n=viscosity of the fluid or gas

l=length of the tube

r=radius of the tube

Small changes in diameter have a huge change on resistance, like breathing through a straw

Front 17

Why is airway resistance important to consider?

Back 17

If the length of a tube is doubled, resistance will double and you need to double the force you apply in order to maintain a constant air flow.

However, if the radius is halved, the force must be increased 16X in order to maintain a constant flow.

Airway diameter has the greatest effect on resistance to air flow

Front 18

Where in the airway is resistance highest?

Back 18

Greatest resistance is around the 4th-5th branches (lots of turbulence as airways divide).

Front 19

As you move down the respiratory tree, the branches get smaller and smaller. Why does airway resistance go down if the radius of the airways gets progressively smaller?

Back 19

There are many more tubes as you get smaller and smaller, so there is a higher overall surface area. Higher surface area means less airway resistance as the surface area for gas exchange has increased.

Front 20

How does airflow resistance between the 2 zones compare?

Back 20

Resistance to airflow is lower in the respiratory zone than in the conducting zone, making it easier to breathe.

Front 21

Which gases are important for breathing?

Back 21

Oxygen

Carbon Dioxide

Nitrogen

Water Vapour

Front 22

Gas Laws

Back 22

Volume = constant/Pressure

volume of gas is inversely proportionate to pressure. As you dive deeper, volume decreases and pressure increases. Density also increases, making it harder to breathe

Volume = constant x Temperature

Volume is proportional to temperature. Heat up air tank, pressure goes up

Dissolved amount of a gas = pressure x solubility coefficient

Gas must dissolve in order to enter the bloodstream

Front 23

Partial Pressure

Back 23

The pressure exerted by a specific gas when it is in a mixture of gases (its contribution to the total pressure).

Identified by the symbol "P"

Calgary = 670 mmHG. 21% is oxygen

Front 24

Dalton's Law

Back 24

the pressure exerted by one gas is independent of the pressures exerted by the other gases in a mixture.

The sums of all the individual gas pressures in a mixture is equal to the "total gas pressure"

Front 25

How do you find the partial pressure of a gas?

Back 25

the P of a gas is found by multiplying its fraction concentration (%) by the total gas pressure:

Oxygen is 21% of the air we breathe. Total atmospheric pressure is 760mmHg. So the partial pressure of oxygen is

PO2 = 0.21 x 760mmHg = ~160 mmHg

Front 26

How do we name the body's partial pressures?

Back 26

Pa = arterial pressure of a gas (amount that is dissolved in the plasma). The concentration of CO2 in the arteries is the same as in the lungs. It doesn't change because capillaries are required for a concentration change.

Pv = venous pressure of a gas (amount dissolved in the plasma). The pulmonary artery is the best place to measure overall body venous pressure. Usually the jugular is used though because of easier access, but the reading won't be quite correct.

PA = alveolar pressure (the air in the lung). The driving force to push oxygen across the membrane or to bring CO2 back across the membrane.

Front 27

Gas Movement

Back 27

Gases move by simple diffusion from areas of high pressure to areas of low pressure.

Regardless of the total pressure of a gas mixture, individual gases diffuse in response to their own gradients (from areas of high partial pressure to low partial pressure). Each gas follows its own gradient rules.

Front 28

Fick's Law

Back 28

Front 29

What conditions favour optimal gas exchange in mammals?

Back 29

Large surface area

Fast diffusion coefficient

Large difference between the 2 partial pressures

Thin membrane thickness (single layer of simple squamous epithelium without significant cytoplasm or basement membrane)

Front 30

What can affect single layer membrane O2 and CO2 diffusion?

Back 30

pneumonia or pulmonary edema can thicken the layer by forming fluid overtop of it. This can affect diffusion and limit O2 and CO2 exchange.