Lecture 2 Flashcards

Question

What is the functional consequence of the anatomical dead space?

Answer 1

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.

Answer 2

V = f x (V - V ).

Answer 3

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.

Answer 4

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.

Answer 5

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

Answer 6

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.

Answer 7

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

Answer 8

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.

Answer 9

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.

Answer 10

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.

Answer 11

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

Answer 12

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.