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Chemistry Physics
Class Notes

Do study questions for quiz

Density – r’ship between wt and vol of substance

- D = M/V expressed in in gm/L

Densities – Room air is 1.3 gm/L

- H is .09

- H2O 1.0 gm/cc

- ice .92gm/cc, which is why it floats

Vander Waals forces (VDW f) these forces occur when the shape and pattern of their charges are aligned so 1 end is relatively + and the other end is relatively - a 2 pole system

VDWf must be overcome to have change from a a liquid to a vapor

GMW not really related to anesthesia but its taught anyway

Its expressed in gm per gm/L,

so O2 is expressed as 32gm per 1.429gm/L = 22.4L

Avagadro's hypothesis says 1 mol of any gas will = 22.4L, and real gasses can be calculated to = 22.4L, 1 mol of O2 weighs 32gm and fills a 22.4L container

Diffusion rate is proportional to differences in PaP

A way to figure out the PaO2 is to multiply 5 x %O2 administered, this is approximate, as the A-a gradient, N, H2O vapor in lungs and CO2 contribute their own Pa P which alter the #’s. It is possible to figure an approximate PaO2 if it is known that a person receiving 100% O2 should have a sat of 500%, we’ll learn it later

We need to know pressure volume for ventilator patients as RT shheres and ARDs

Face mask O2 delivers @ 4% O2 / L, and venturi masks entrain some RA to adjust O2 delivery

Need to know about full cylinder containers – pressure & volume

Anesthesia bag – requires flow in order to maintain size, so if the bag is flat then there is 1) no flow or 2) a poor seal

Page 11 - vapor pressure – flask with 100% O2 + desflorane and Halo(243vp)at 273 C and 1 atm

Also think of how to calc the numbers when a % is given, and calc mmHg from % derived or given

Need to know what vp is because it exerts mmHg – Dalton says all the pressures will add up to 760mmhg

Problems that will be asked – at STP there is a flask of O2 and halo is added. What is the PaO2 in the flask. When Pa P are asked for the answer is in mmHg

Think of 760 as 100%, and 243 as 32% Pa Halo

243/760 == .32 = 32% of halo in flask, there are 2 ways to figure it out

1. 100% - 32% = 68%, 68% of 760mmHg(mult .68 x 760) = 517mmHg

    1. 760mmHg – 243mmHg = 517mmHg

just think of adding enough halo to exert a pressure which will change the PaO2

Critical pressure is the pressure needed to liquefy a gas at its critical temp.

Adiabatic deals with expansion or compression of gasses

Gasses cool with adiabatic expansion and heat with adiabatic compression

When cylinder is opened into a vacuum and no heat loss or gain is noted this is considered to be adiabatic???????????????

When opening a cylinder of compressed gas into free air, the gas molecules expand into the free air so the heat can dissipate into the air around it. Condensation is seen on the valve, and this is good. Joules-Thompsons effect condensation occurs because the molecules that come out cool the molecules just around the valve which causes condensation. ??????????????

If gas is released from a pipe thru a small orifice and there is no room for those molecules to go, and there is a potential for a large temp increase in the container (pipe), therefore it can heat and explode. This would happen if the temp raises over the combustibility of the gas. (BOOM)

HUMIDIFICATION – refers to the presence of water molec in the gaseous state in a mixture of gas. Gas water molec are considered vapors at temps < the critical temp of water

Humidity – absolute – the water content of gas expressed as the wt of water per volume of gas, which is usually expressed as x mg of water / L air

At a given temp and pressure

Ambient temp is the air temperature of the air around us. Ie the ambient temp of a frig is considered when keeping milk form souring

Humidification helps prevent drying and heat loss. Causes are:

Cascades not used in OR because they're cumbersome and they promote bacterial growth

Hypothermia – physio effect causes

Cool and warm patient effects the Av dissociation curve

Cold – shifts to the left causing: hbg to hold onto O2(hbg has inc affinity for O2) and wont release it ti the tissues –

A-a gradient: A= alveolar a= arterial gradient means the difference between the two. Partial pr of inspired O2 is PiO2, which is 760 mmhg – 47 mmHg

Formula PaO2 = FIO2 { PiO2 - (paCO2 / RQ) } RQ = .8

Alveolar PaO2 of the A-a gradient of O2 = .21{(760-47) – (40/.8)} is @100

Medical gas cylinders handout chap 99

CO2 is used for insufflations during lap, and tourniquet placement

Helium is used to get laminar flow movement. – ENT cases use it in cuff so when laser is used the tracheal burns wont occur, or can fill balloon with NS or water and a blue dye, which alerts if the cuff is broken

And helio-ox good for asthma pts who need laminar flow to dec turbulance on airways

The testing of tanks is to 5/3 of capacity , so O2 is tested at nearly double to ensure tank integrity.


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