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Gas Laws and Physics
CRNA:Gas Laws and Physics (christina's)
| Question | Answer |
|---|---|
| What is a mole? | It is used to express the gram molecular weight of a substance. |
| 1 mole = What is Avagadro's number? | 1 mole = 6.022 x 10 to the 23rd power 6.022 x 10 to the 23rd power |
| What does Avagadro's number express? | It is the number of molecules in one mole of a substance. |
| What is the Avagadro hypothesis? | The hypothesis is that one mole of a gas at standard temperature 0C and standard pressure 1 atm occupies a volume of 22.4 L |
| If 1 mole of gas at a standard temperature 0C and standard pressure 1 atm how much volume does it occupy? | 22.4 L (ideally) In reality, 1 mole of gass may take up less volume depending on the atmospheric pressure exerted on it. |
| As atmospheric pressure increases, What happens to the volume of a gas according to Avagadro's number? | It decreases. |
| As atmospheric pressure decreases, what happens to the volume of gas according to Avagadro's number? | It increases. |
| What does Fick's law have to do with? | Rate of diffusion |
| What is Fick's Law of Diffusion? And what does it take into account? | Rate of diffusion = KA(P2-P1)/D A = Surface Area K= Constant of gas at a given temperature (P2-P1)= difference in partial pressures across a membrane D= thickness of membrane (distance across membrane) |
| According to Fick's Law of Diffusion, what happens to the rate of diffusion if I increase the thickness of the membrane? | The rate of diffusion will decrease. |
| According to Fick's Law of diffusion, what is the relationship between surface area and the rate of diffusion? | The rate of diffusion is directly proportional to the surface area. As the surface area increases, the rate of diffusion increases and as the rate of diffusion decreases, the surface area decreases. |
| According to Fick's Law of diffusion, what is the relationship between partial pressure across the membrane and the rate of diffusion? | The difference in partial pressures of a gas across a membrane is directly proportional to the rate of diffusion. (as the (P2-P1) increases, the rate of diffusion increases and vice versa. |
| According to Fick's law of diffusion, what is the relationship between rate of diffusion and distance? | The rate of diffusion is inversely proportional to the distance across the membrane/membrane thickness. As the thickness of the membrane increases (distance increases), rate of diffusion decreases. |
| According to Fick's law of diffusion, what is the relationship between the concentration of a substance and the rate of diffusion? | The rate of diffusion is directly proportional to the concentration gradient. As the concentration increases, the rate of diffusion increases. |
| According to Fick's law of diffusion, if I have a patient with asbestosis, what happens to the rate of diffusion of oxygen and the capillary in the alveolar membrane. | Because asbestosis causes scarring in the lungs, it increases the membrane thickness, therefore, it increases the distance. The rate of diffusion would decrease. Same thing occurs with pneumonia. |
| What is Graham's Law and what does it take into consideration? | KE = 1/2mv2 also V=1/√m m1v1 = m2v2 Average kinetic energy of the molecules of two samples of different gases at the same temperature is identical. KE= kinetic energy m= mass of the particle v= average velocity of the particles |
| According to Graham's Law, what is the relationship between the rate of diffusion of a gas and the mass of it's particles? | the rate of diffusion of gas is inversely proportional to the square root of the mass of its particles. rate1/rate2 = √m2/m1 |
| In a concentration of mixed gases, will the gas with the largest molar mass take diffuse faster or slower across the same membrane as a gas with a smaller molar mass? | It will take longer to diffuse across the same membrane. example: Rate H2/Rate O2 = √32/√2 =√16/√1 = 4/1 or hydrogen will diffuse across the membrane at a rate of 4 to 1 when compared to oxygen. Why? because Oxygen is has a larger molecular mass than |
| What are 3 characteristics of the ideal gas law? | 1. an equation of state of an ideal gas 2. combines the three primitive gas laws 3. roughly accurate for gases and becomes increasingly inaccurate at HIGHER PRESSURES and LOWER TEMPERATURES |
| What is the Ideal Gas Law and what does it take into consideration? | PV = nRT P= pressure V= volume T= temperature R= molar gas constant n = number of moles of gas |
| According to the ideal gas law, why do gas molecules not interact with each other? | Because they are spread out and do not collide. |
| What is Boyle's Law and what does it take into account? | PV=k P=pressure V=volume k=temperature constant |
| According to Boyle's law, what relationship does the volume have with pressure? | Volume is inversely proportional to Pressure If the volume increases, the pressure decreases at a constant temperature. |
| Boyle's law can also be used when a gas is added to a container. How do you express this using an equation? | P1V1=P2V2 examples: compressed air in a cylinder Ambu bag |
| According to Boyle's law, what happens to a gas when the volume is halved? | The Pressure doubles. |
| In a full E cylinder, what is the pressure of O2? What is the volume an E cylinder tank? | 2200 psi, 4.46 L = small volume of gas under high pressure |
| What are some examples of Boyle's law? | 1. squeezing an ambu bag 2. during inspiration when breathing spontaneously, intrapulmonary pressure falls and volume increases, during expiration, intrapulmonary pressure increases and volume decreases. |
| What is Charles' Law? and What does it take into account? | T/V = k T=temperature V=volume k=pressure constant can also be expressed as? T1/V1 = T2/V2 or T2/T1 = V1/V2 |
| According to Charles' Law, what is the relationship between volume and temperature? | Volume is directly proportional to Temperature at a constant pressure. As temperature increases, volume increases and as temperature decreases, volume decreases. |
| What is an example of Charles' Law? And why does it occur? | The inflatable cuff of laryngeal mask airway (LMA) expands when placed into an autoclave. Why does it occur? It occurs b/c autoclave is very hot, as the temperature inside the autoclave increases the LMA volume increases |
| What is Gay-Lussac's law and what does it take into account? | P=Tk P=pressure T=temperature k=volume constant |
| According to Gay-Lussac's law, what is the relationship between pressure and temperature at a constant volume? | Pressure is directly proportional to temperature at a constant volume. |
| What is Gay-Lussac's law? | Pressure is directly proportional to absolute temperature (K) if volume is constant. |
| According to Gay-Lussac's law, what happens to the pressure when the temperature increases? What happens to the pressure when the temperature decreases? | When volume is constant and the temperature increases, the pressure increases. If the temperature decreases, the pressure decreases. They are directly proportional. |
| As a N2O cylinder empties, the temperature decreases,the pressure in the tank decreases even. What law explains this? | Gay-Lussac's law. As the temperature at a constant volume in the cylinder decreases, the pressure of the gas in the cylinder decreases as well. |
| When a full cylinder of gas is moved from the loading dock where the temperature is 0C to the operating room where the temperature is 20C, what happens to the pressure in the cylinder/tank? What law explains this? | The pressure in the tank/cylinder increases because the temperature increases. Particles are moving faster= increased number of collisions against cylinder = greater pressure in the cylinder. Gay-Lussac's law. |
| What is Dalton's law and what does it take into account? | Dalton's law of partial pressure. PTotal= P1+P2+P3... PTotal = 760 mmHg total pressure P1=partial pressure 1 P2=partial pressure 2 P3=partial pressure 3 etc. |
| What is Dalton's Law of Partial Pressures? How do you calculate partial pressure? | The total pressure in a mixture of gases is equal to the sum of the pressures of the individual gases (each gas is said to exert a partial pressure). Partial pressure = %concentration x atmospheric pressure (760 mmHg)or Total pressure |
| What law explains the pressure of a certain gas in a mixture? | Dalton's law |
| Example: If the atmospheric pressure on a mountain is 550mmHg, what is the partial pressure of oxygen? | Concentration of Oxygen of room air = 21% Atm pressure on mountain = 550mmHg=total pressure 21%x550mmHg=115.5 mmHg for O2 |
| Example: What are the partial pressures of N2O and O2 if they are delivered to a patient in a 70%/30% N2O/O2 mixture? What law explains this? | Dalton's law of partial pressures. Total pressure= 760mmHg atmospheric pressure Concentration N2O=70% Concentration O2= 30% Partial pressure of N2O= 70%x760mmHg=532mmHg Partial pressure of O2=30%x760mmHg= 228mmHg |
| What is Henry's Law? And what does it take into account? | P=kC P=pressure k=Henry's law constant C=Concentration |
| What is Henry's law? What is an application of henry's law? | The mass of a gas that dissolves in a definite volume of liquid is directly proportional to the pressure of the gas. ex. Permits calculation of the amount of O2 dissolved in blood and the amount of CO2 dissolved in blood. |
| What is the relationship between pressure and concentration according to Henry's law? | Pressure is directly proportional to Concentration. As the concentration increases, the pressure increases = # of molecules increases = increases number of collisions = increases pressure. |
| According to Henry's law how much oxygen will dissolve in arterial blood if the alveolar partial pressure of oxygen is doubles? | Twice as much O2 will dissolve/it will double too. Because it is directly proportional to the pressure. |
| According to Henry's law, what is the relationship between solubility of a gas in a liquid and the pressure of the gas overlying the liquid? | Solubility of the gas is directly proportional to the pressure overlying the liquid. |
| Which is more soluble CO2 or O2? | CO2 is 22 times more soluble than O2. |
| What is the law of LaPlace? And what does it take into account? | T=(PxR)/M T=tension P=the pressure difference across the membrane/wall R=radius of the cylinder M=is the thickness of the wall |
| According to the Law of LaPlace, what is the relationship between pressure and wall tension? | Pressure is directly proportional to wall tension. As the pressure increases, the wall tension increases. |
| According to the Law of LaPlace, what is the relationship between the radius of the cylinder and wall tension? | The radius directly proportional to the wall tension. As the radius increases, the wall tension increases. |
| According to the Law of LaPlace what is the relationship between the wall thickness and wall tension? | Wall thickness is inversely proportional to wall tension. As the thickness of the wall increases, the wall tension decreases. Ex. balloon thicker wall=less tension. Thinner the wall/more blown up=more tension. |
| What is an example of the Law of LaPlace? | Dilated cardiomyopathy. The radius increases, and the tension increases. |
| According to the Law of LaPlace, a blood vessel with an aneurysm will have a _______wall tension? | Greater |
| According to the Law of LaPlace, when ventricular filling increases during diastole, there is a _________tension in the wall at end-diastole. | Greater |
| According to the Law of LaPlace, in ARDS, smaller alveoli empty into larger alveoli (atelectasis). true of false | True. Due to the absence of surfactant, As the radius decreases, the tension decreases and the cells collapse. As the radius decreases, the pressure increases. The volume will then travel from an area of high pressure to an area of low pressure. Small alv |
| What is starling's law? What does it take into account? | The principle of stretch in the ventricle creating a maximal contraction of the heart muscle and chamber. force of contraction +HR=SV |
| What changes when increase IV bag height? | Increase pressure gradient. |
| What is Pouiseulle's Law? What does it take into account? | Explains how pressure, tube radius, tube length, and fluid viscosity contribute to laminar flow. Volume flow rate= F = P1-P2/R =π(pressure difference)(radius)4/8(viscosity)(length) Resistance=R= 8nL/πr4 |
| According to Pouiseulle's Law, What happens to the flow when the radius of the IV/gauge increases? | It increases. |
| According to Pouiseulle's law, what happens to the flow when the length of the needle increases? | it decreases (slows down) |
| According to Pouiseulle's law, that happens to the flow if the IV bag is raised? | The flow increases because increase pressure gradient. |
| According to Pouiselle's law, does blood flow slower or faster in anemic patients and why? | Faster because, decreased blood cells, therefore decreased resistance. |
| For IV administration, according to pouiselle's law, what increases flow? | 1. increasing diameter of needle 2. decreasing length of needle 3. Raising the IV bag to a greater height |
| According to Pouiseulle's law, what happens to the flow in a polycythmic patient? | It is slower because increased turbulence/resistance to flow. |
| What is Ohm's Law? What does it take into account? | Allows the calculation of resistance R of flow through a tube. R= (Pin-Pout)/flow ex. allows the calculation of SVR=80(MAP-CVP)/CO |
| Which law explains or allows for the calculation of Systemic Vascular Resistance? | Ohm's Law Allows the calculation of resistance R of flow through a tube. R=(pin-pout) SVR= 80(MAP-CVP) |
| What is the Venturi Effect? And what does it take into account? | When fluid flows through a constricted region of a tube (venturi tube) the velocity of flow increases and the lateral pressure decreases(bernolli's principle) |
| Flow become turbulent if? | 1. velocity of flow is high 2. Tube wall is rough 3. There are kinks or bends, narrowing or branches in the tube 4. fluid flows through an orifice/opening |
| At what angle does laminar flow become turbulent? | Greater than an angle of 25 degrees |
| According to the venturi effect, what is the relationship between resistance and turbulence? | Resistance to flow increases when flow becomes turbulent. Ventilating patients is more difficult when flow is turbulent, either in thte tubing or the airway. |
| Venturi effect requires what value/number? | Reynolds number. |
| What is the Reynolds equation? And what effect does it explain? | Re=(vdp)/n Re=reynolds number v=fluid velocity p=fluid density d=tube diameter n=fluid viscocity Predicts when flow through a cylindrical tube changes from laminar to turbulent. Explains venturi effect |
| According to the Venturi effect, what is the relationship between reynolds number and fluid velocity, fluid density, tube diameter? what is the relationship between Reynolds number and fluid viscosity? | Reynolds number is directly proportional to fluid velocity, fluid density, and tube diameter. Reynold's number is inversely proportional to fluid viscosity. |
| Reynolds number tells us what? | that flow will become turbulent if velocity gets high enough. |
| At what reynolds number does flow change from laminar to turbulent? | Greater than 2000 |
| When flow is turbulent what determines flow? | Density,not viscosity Flow is inversely proportional to density |
| What is an example of the venturi effect? | ex. Helium (He) is a gas with low density; helium/oxygen gas mixtures are used medically for upper airway obstruction (the obstruction causes flow to be turbulent, so a low density gas mixture makes breathing easier). |
| Describe venturi's effect and bernoulli's principle. | When fluid flows through a constricted region (venturi effect), the velocity of flow increases (visualize a narrowing in a stream), and the lateral pressure (the pressure exerted by the fluid on the walls of the tube) decreases (bernolli's principle) |
| According to the Bernoulli principle, what happens when velocity increases? | Pressure decreases simultaneously |
| What occurs when passing air through a venturi tube? | It creates a low pressure and picks up gas as it passes over an area of higher pressure. |
| According to the Bernoulli principle, what happens to the lateral pressure (the pressure exerted by the fluid on the walls of the tube) when velocity of flow increases? | The lateral pressure decreases |
| What is Critical Temperature | The temperature in which a gas will liquify if sufficient pressure is applied. |
| At what temperature will a gas liquify when a sufficient temperature is applied? | Critical temperature |
| What is the critical temperature for N2O? For O2? | N2O=39.5C Therefore N2O can be compressed and stored as a liquid at room temperture O2 is -199C. Therefore no matter how much pressure is applied, O2 cannot be stored as a liquid at room temperature. |
| At what pressure does N2O vaporize? | At pressures below 750 psi. |
| What is the Joule-Thompson Effect? | Explains when a compressed gas is allowed to escape freely into space, the process uses heat from the system and cooling occurs. Explains why a cylinder cools (and condensation forms) after opening the valve. |
| According to the Joule-Thompson effect, what happens to an N2O cylinder when gas escapes? | As gas escapes from a N2O cylinder, the liquid N2O in the cylinder vaporizes. Heat is lost as a liquid vaporizes (latent heat of vaporization) and the temperature in the cylinder falls (Joule-Thompson Effect). As the cylinder temperature falls, the pressu |
| What volume of N2O does an full E cylinder contain? | 1,590 L |
| How much pressure does a full E cylinder of O2 have? How many Liters does it hold? | 2200 psi, 660L |
| Problem, if the flow of O2 from an E-size cylinder is 5L/min, how long will it take a full O2 cylinder to empty? | Pressure of O2 in E cylinder=2200 psi Volume of gas/O2 in a full E cylinder=660L (660L)/(5L/min)=132min, or about 2 hours. |
| Problem if the pressure in an O2 E cylinder is 1,100 psi and the flow is 5L/min, how long will it take the cylinder to finish emptying? | Tank is half full, 2200psi/2=1100 and 660L/2=330 5L/min x 330/time=66min or just over 1 hour |
| The venturi effect and bernoulli principle explain which phenomenons in practice? | nebulizer (pneumatic and jet) Venturi oxygen mask Jet ventilator Injector Anterior Leaflet in IHSS |
| What is Saturated Vapor Pressure? What happens to the saturated vapor pressure when temperature increases? | IN A CLOSED CONTAINER At any given temperature there is a pressure at which the vapor of that substance is in equilibrium with its liquid or solid forms=saturated vapor pressure the Saturated vapor pressure also increases |
| What is Partial Vapor pressure? | Vapor pressure in an OPEN CONATINER/when gases are mixed |
| What is the relationship between boiling point and vapor pressure? | Boiling point=atmospheric pressure Increase atmospheric pressure=Increase boiling point |
| What happens to the boiling point at high elevations? | The boiling point will decrease at higher elevations (decrease in atmospheric pressure) |
| What is air composed of? | Nitrogen (N2)= 78.08% PP=593.4 Oxygen (O2)=20.95% PP=159.2 Argon (Ar)= 0.93% PP=7.1 Carbon Dioxide (CO2)= 0.03% PP=0.2 Total =99.99% and PP=760 |
| What is the vapor pressure of Enflurane at 20C? What is the Minimal Alveolar Concentration of that gas (MAC)? | Enflurane = 175 mmHg MAC=1.68% |
| What is the vapor pressure of Halothane at 20C? What is the MAC? | Halothane=243 mmHg MAC=0.75% |
| What is the Vapor pressure at 20C of Isoflurane? MAC? | Isoflurane=239 mmHg MAC=1.15% |
| What is the Vapor pressure at 20C of Sevoflurane? MAC? | Sevolflurane= 170 mmHg MAC=2.1% |
| What is the Vapor pressure at 20C of Desflurane? MAC? | Desflurane=669 mmHg MAC=6.0% |
| What is MAC? | the Minimal Alveolar Concentration |
| The Minimal Alveolar Concentration is ? | 1 MAC=the minimal alveolar concentration of an inhalation agent at which 50% of the patients will not respond to surgical stimulation. |
| What is the minimum standard O2 concentration patients can receive during anesthesia? | 30% O2 |
| Problem: If Isoflurane is added to a flask of oxygen, what is the % oxygen and % isoflurane in the flask above the liquid? | Vapor pressure is 239 mmHg, Partial pressure of after Isoflurane is added = (760-239 mmHg)=521 mmHg %O2=521/760 x100 = 68.6% Isoflurane=239/760 x100=31.4% |
| Problem: If enflurane is added to a flask of oxygen, what is the % enflurane and the % oxygen in the flask above the liquid? | 760mmHg-175mmHg= 585 mmHg oxygen 175/760=.230 x 100=23% Enflurane 585/760=.769 x 100=76.9 % Oxygen |
| Problem: If desflurane is added to a flask of oxygen, what is the % desflurane and the % oxygen in the flask above the liquid? | PP of desflurane=669mmHg 669/760=.88 x 100= 88%= desflurane 760-669= 91mmHg O2 91/760=.119 x 100= 12%=oxygen |
| What are the dimensions of an E cylinder of Oxygen? | Dimensions: 2 feet long and 4 inches in diameter |
| When do you need to replace your Oxygen E cylinder? At what pressure? | 200 psi |
| What are the dimensions of an H cylinder of Oxygen? | Dimensions: 4 feet long and 9 inches in diameter |
| What is the purpose of the E cylinder? | Most often used for portable oxygen sources for transport. |
| What is the purpose of the H cylinder? | Sources of gas for small or infrequently used pipeline "gas-bank" systems |
| what is the pressure in a full E cylinder of oxygen, how much volume is in a full E cylinder? | 2200 psi. 660L |
| If your E cylinder of oxygen is 2/3 full how much oxygen do you have left? | 660Lx2/3=440L |
| How much volume is in a full H cylinder? | 6900L Still at 2200 psi for oxygen in H tank |
| What color is an oxygen tank? | Green |
| What color is a CO2 tank? | Gray |
| What color is a N2O tank? | Blue |
| What color is a cyclopropane tank? | orange |
| what color is a helium tank? | Brown |
| What color is nitrogen? | Black |
| What color is medical air? | Yellow |
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