Lecture 2 Flashcards
What is the symbol of Volume?
V.
What is the unit of volume?
mL or L.
What is V dependent on ?
Temperature (T), barometric pressure (P), and water vapour pressure (PH2O). Sometimes necessity to correct to standard conditions.
What is a capacity?
Some of two or more volumes.
What is the standard temperature?
0 degrees celsius.
What is the standard pressure?
101.3kPa or 760mmHg.
What is the standard humidity?
Dry.
What is tidal volume?
V .
It is the volume of air inspired during a single ventilatory cycle.
How do you correct volume?
V(ST) = V(AT) x 273/(273+T).
What is residual volume?
The volume that remains in your lungs after active expiration.
What is total lung capacity?
The total amount of air that can be within your lungs. Combination of all lung volumes.
What is vital capacity?
The maximum volume that your lung can breathe. It is the combination of expiratory reserve volume, inspiratory reserve volume and tidal volume.
What is functional residual capacity?
The capacity of volume which remains in your lungs after quiet expiration. A combination of residual volume and expiratory reserve volume.
How do you correct volume to standard pressure?
V(SP) = V(AP) x P / 760.
How do you correct volume to standard temperature and pressure?
V(STP) = V(ATP) x 273/(273 + T) x P /760.
How do you correct volume to standard temperature, pressure and humidity?
V(STPD) = V(ATPS) x 273/(273 + T) x
(P - P )/760
What is expired air?
Water-saturated. The saturation pour of water is temperature-dependent.
What happens when temperature increases?
Partial pressure of water increases so does kPa.
What is the symbol of Flow?
V.
What is the equation of flow?
V = dV/dt.
What is the unit of flow?
Lmin-1.
What is minute volume?
Tidal volume x frequency (breaths per minute).
Vt = 500mL and f = 15breaths per min
Minute volume =
7.5Lmin-1.
What is the difference between alveolar ventilation and minute volume?
It is smaller due to Dead space e.g. 5.25Lmin-1.
What is Anatomic Dead Space?
The volume of everything inspired before it gets to to the respiratory zone.
What is the functional consequence of the anatomical dead space?
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.
What is the equation of dead space?
V = f x (V - V ).
How do you measure anatomic dead space?
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.
What are the approximations of measuring anatomic dead space?
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.
What is the Bohr equation?
It is by expressing dead-space volume as a fraction of tidal volume.
How do you get dead space in practice?
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.
What is needed for flow to occur?
Gradient of pressure.
V = P/R.
Flow is inversely proportional to resistance and proportional to change in pressure.
Describe distribution of air flow resistance in the lungs?
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.
Describe a topographical variation of air-flow in the lungs?
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.
What is laminar flow?
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.
What is poiseuille-hagen law?
The laminar flow in which velocity is highest in the centre of the concentric rings.
What is a quantitative comparison of laminar and turbulent flow?
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.
