Lecture 2

Question 1

What is the symbol of Volume?

Answer 1

V.

Question 2

What is the unit of volume?

Answer 2

mL or L.

Question 3

What is V dependent on ?

Answer 3

Temperature (T), barometric pressure (P), and water vapour pressure (PH2O). Sometimes necessity to correct to standard conditions.

Question 4

What is a capacity?

Answer 4

Some of two or more volumes.

Question 5

What is the standard temperature?

Answer 5

0 degrees celsius.

Question 6

What is the standard pressure?

Answer 6

101.3kPa or 760mmHg.

Question 7

What is the standard humidity?

Answer 7

Dry.

Question 8

What is tidal volume?

Answer 8

V .

It is the volume of air inspired during a single ventilatory cycle.

Question 9

How do you correct volume?

Answer 9

V(ST) = V(AT) x 273/(273+T).

Question 10

What is residual volume?

Answer 10

The volume that remains in your lungs after active expiration.

Question 11

What is total lung capacity?

Answer 11

The total amount of air that can be within your lungs. Combination of all lung volumes.

Question 12

What is vital capacity?

Answer 12

The maximum volume that your lung can breathe. It is the combination of expiratory reserve volume, inspiratory reserve volume and tidal volume.

Question 13

What is functional residual capacity?

Answer 13

The capacity of volume which remains in your lungs after quiet expiration. A combination of residual volume and expiratory reserve volume.

Question 14

How do you correct volume to standard pressure?

Answer 14

V(SP) = V(AP) x P / 760.

Question 15

How do you correct volume to standard temperature and pressure?

Answer 15

V(STP) = V(ATP) x 273/(273 + T) x P /760.

Question 16

How do you correct volume to standard temperature, pressure and humidity?

Answer 16

V(STPD) = V(ATPS) x 273/(273 + T) x

(P - P )/760

Question 17

What is expired air?

Answer 17

Water-saturated. The saturation pour of water is temperature-dependent.

Question 18

What happens when temperature increases?

Answer 18

Partial pressure of water increases so does kPa.

Question 19

What is the symbol of Flow?

Answer 19

V.

Question 20

What is the equation of flow?

Answer 20

V = dV/dt.

Question 21

What is the unit of flow?

Answer 21

Lmin-1.

Question 22

What is minute volume?

Answer 22

Tidal volume x frequency (breaths per minute).

Vt = 500mL and f = 15breaths per min

Minute volume =
7.5Lmin-1.

Question 23

What is the difference between alveolar ventilation and minute volume?

Answer 23

It is smaller due to Dead space e.g. 5.25Lmin-1.

Question 24

What is Anatomic Dead Space?

Answer 24

The volume of everything inspired before it gets to to the respiratory zone.

Question 25

What is the functional consequence of the anatomical dead space?

Answer 25

The first air into the alveoli is the old dead space air form the previous breath - not fresh air. Exchange 450mL and only 300mL makes it way down.

Question 26

What is the equation of dead space?

Answer 26

V = f x (V - V ).

Question 27

How do you measure anatomic dead space?

Answer 27

The total expired volume of Carbon dioxide is the alveolar volume of carbon dioxide plus the dead space volume of carbon dioxide. The volume of carbon dioxide is the total volume of air multiplied by the fractional component of the expired carbon dioxide. Alveolar air is the tidal volume - dead space volume - which you multiply by fractional component of carbon dioxide in alveolar air. The fraction of carbon dioxide is so low, that is pretty much zero. The dead space volume is just the tidal volume multiplied by the extent to which the alveolar air has been reduced by mixing with the dead space air.

Question 28

What are the approximations of measuring anatomic dead space?

Answer 28

Pressure of a gas is proportional to its fraction.
That the partial pressure of arterial carbon dioxide is the same as partial pressure in the alveoli. Carbon dioxide exchanges across the cell membrane very rapidly.

Question 29

What is the Bohr equation?

Answer 29

It is by expressing dead-space volume as a fraction of tidal volume.

Question 30

How do you get dead space in practice?

Answer 30

Exhale ovvero 1 breath, collect in a rectangular shaped vessel. The first thing that comes out is the dead space (no carbon dioxide). The air that follows alter, contains carbon dioxide from deep in the alveoli. Can look in a graph from carbon dioxide fraction (5% to 0% when we inhale and first exhale). The first bit of expired gas, contains negligible amount of carbon dioxide. The air air begins to get mixed as it arrives. The carbon dioxide fraction begins to rise. We exhale air, and hold the breath, we measure the carbon dioxide fraction instantaneously. The carbon dioxide fraction continues creeping up as you stop breathing (stop ventilating - blood brings carbon dioxide back to the lungs). A vertical line is put through the sigmoidal S shape, so that the area down is same as above = anatomical dead space.

Question 31

What is needed for flow to occur?

Answer 31

Gradient of pressure.
V = P/R.
Flow is inversely proportional to resistance and proportional to change in pressure.

Question 32

Describe distribution of air flow resistance in the lungs?

Answer 32

It is not uniform. As we descend from the trachea deep into the alveoli, the total cross sectional area for gas exchange, does’;t change much over the first 10 divisions however sky rockets around 15th division. Despite the fact that the vessels are getting smaller, there are a lot more of them, so the cross sectional area is bigger thus resistance decreases.

Question 33

Describe a topographical variation of air-flow in the lungs?

Answer 33

The lungs are a highly compliant ‘network’ structure suspended in a gravitational field. In consequence, ventilation varies with location from base (higher) to apex (lower). Ventilation is better at the lower zone compared to the higher zone.

Question 34

What is laminar flow?

Answer 34

Characterised by the flow being in laminae (in layers). The layering is such that you get a parabolic profile of the flow. Laminar flow is characterised by no velocity at the edges of the tube -> cylindrical tube. Flows at a velocity at given radius which gives us laminar flow: looks t flow end on, the highest velocity is at the centre most of the concentric rings.

Question 35

What is poiseuille-hagen law?

Answer 35

The laminar flow in which velocity is highest in the centre of the concentric rings.

Question 36

What is a quantitative comparison of laminar and turbulent flow?

Answer 36

If the flow is laminar the rate of change of volume is proportional to the change in pressure. Where as in turbulent you need to apply a greater pressure to get the same rate of flow.