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94 Cards in this Set
- Front
- Back
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Give 4 equivalent values, using different units of measurement, for 1 atm of pressure?
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760 torr, 1030cmH2O
100kPa, 29.92in Hg 1 bar, 1.013bar 14.7psi, 1kg/cm2 |
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How do you convert mmhg to cmH2o of pressure?
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Mercury is 13.6 x denser than water
pressure exerted by 7.5mmhg= 13.6 x 7.5mmhg=10.2cm H2O |
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Define gauge and absolute pressures?
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Gauge pressure= reading gauge
Absoulute pressure= pressure on gauge + atm pressure |
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What is Entonox?
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*Premix of Nitrous and Oxygen in a 50:50 mixture
*The Nitrous is all in gas form Used in emergency vehicles |
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What is 1 Newton?
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Unit of force (F= M x A)
1 N being the force that will give a mass of 1 kg an acceleration of 1 meter per second 1N= 102g wt |
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What is the difference between 1 kg mass and 1 kg weight?
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Wt= force
1 kg mass placed on a scale, earth exerts a force= 1kg of wt= force |
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How many N= 1kg wt?
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9.81 N= 1kg weight
1N= 102gram |
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What is the relationship between resistance and diameter of the ETT during laminar flow?
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Halving the diameter reduces the flow to one-sixteenth of its original value.
Flow is proportional tothe fourth power of the diameter |
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What effect does Helium have on gas flow resistance?
To which flow? |
*Resistance in turbulent flow pertains to density
resistance in laminar flow pertains to viscosity Reduces density by 33% and improves flow by 60% *Decreases resistance for turbulent flow |
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Define critical flow velocity?
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onset of turbulent flow
Reynolds #= onset of turbulent flow in cylindrical tubes > 2000 |
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What is the CFV for a 9mm ETT?
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Its about equal to the tube size
9mm ETT= becomes turbulent when flow exceeds about 9 L/min |
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What is the law of Laplace for a sphere?
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2 x tension/ R
small radius= high pressure |
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What is surfactant's significance for pulmonary function?
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If you didnt have surfactant in the lungs all of the small alveoli would collapse
Surfactant reduces tension on the smaller alveoli |
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Describe how one reads the gas flow on a spherical vs a bullet shaped bobbin?
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Read it across the narrowest point
Spherical-read at upper surface Bobbin- read in the middle of the ball |
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What is the "fail safe" mechanism on an anesthesia machine, and how would you test whether it is working?
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Chain linking the oxygen & Nitrous Oxide flowmeter controls. (inability to adm. hypoxic mixture)
Test it by opening both flows then shut O2 off and see if Nitrous turns off as well |
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What about a gas changes as it passes through a venturi?
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As the flow velocity increases, the pressure drops
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What about a gas changes as it passes through a venturi?
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As the flow velocity increases, the pressure drops
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Describe the changes in gas bubble volume with pressure if the temp is held constant?
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The pressure increases the size of the bubble decreases.
Double the volume of the balloon, the pressure inside decreases |
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What is Dalton's Law of partial pressure?
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States that in a mixture of gases the pressure exerted by each gas is the same as that which it would exert if it alone occupied the container
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What is Avogadro's Law?
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A gram molecular wt of anything has the same # of molecules 6.022 x 1023
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Define a gram molecular wt?
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1 mole of any gas at STP occupies 22.4L
1 mole= 6.022 x 1023=Avogadro's number |
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Define the critical temperature for a gas?
What is it for N2O? |
The temp. above which a substance cannot be liquefied however much pressure is applied
*Nitrous-36.5 |
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When does a liquid boil?
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when VP = atmospheric pressure
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List 4 factors that determine the solubility of a gas in a liquid?
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PP
Temp Gas Liquid |
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Define Ostwald solubility coefficient?
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Volume of gas dissolves in a Liter of liquid at a specified temp.
does NOT relate to pressure |
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Arrange the following anesthetics in the order of increasing bld solubility: N2O, Halothane, Des, Iso, Sevo, Ether?
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Des, Nitrous, Sevo, Iso, Halo, Ether
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Which anesthetics are more sensitive to ventilation during gas induction?
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Soluble
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What is the relationship of the Myer-Overton Theory to anesthetic MAC?
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Potency correlates directly with lipid solubility
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Name 4 factors that determine the diffusion of a gas across a membrane?
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solubility
size area of membrane thickness of membrane |
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Describe what happens to trapped gas pockets during N2O inhalation and how one determines the extent of change?
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Pressure or volume goes up or both go up
The extent of change in 50%N2O: 5cc air in a cuff (1/2=2x5=10cc) volume=5cc n2o + 5cc air 66% n2o= (2/3=3x5=15cc) have 5cc air+ 10cc N2O |
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Define Osmolarity?
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Osmoles per liter in solution; concentration of particles(molecules) per liter
-1 Osmolar/L = 1 mole of solute dissolved per liter -1 mOsmol/L = 1 millimole of solute dissolved per liter (1 mEq/L) |
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How does osmolarity differ from osmolality?
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Osmolarity: osmoles per Liter of solution
Osmolality: osmoles per Kilogram of water |
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What is osmotic pressure?
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the hydrostatic pressure produced by a solution in a space divided by a semipermeable membrane due to a differential in the concentrations of solute.
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How does osmotic pressure differ from oncotic pressure?
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Oncotic pressure in the circulatory system is a form of osmotic pressure exerted by proteins in blood plasma that normally tends to pull water into the circulatory system.The difference between the osmotic pressure exerted by plasma proteins (colloidal osmotic pressure) in blood plasma and that exerted by tissue fluid proteins is the oncotic pressure.
Osmotic pressure-built up by an increase in solutes that causes solvent to pass through a semi-permeable membrane to achieve equilibrium |
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Describe the forces determining fluid flow in and out of the capillary?
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Ions are free to move across the capillary membrane. They do not contribute to the plasma osmotic pressure. It’s the protein, b/c proteins do not move out of the capillaries under normal conditions. Hydrostatic pressure is greater in the capillaries than the plasma oncontic pressure so water can move out. Venous side of capillaries have a lower hydrostatic pressure in capillaries lower than plasma oncotic pressure and pulls water back in on the venous side, which helps bring nutrients in.
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Define work and power
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*work is a mechanical form of energy (heat & chemical energy)
*Power- energy consumed over a period of time (*rate of working and is measured in watts) Forced exerted through a distance 1J=1Nmeter |
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How could one calculate the amount of work during the respiratory cycle from spirometry?
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Work= P x V (pressure applied x volume of gas moved)
Area contained in the volume pressure loop,that represents the total work performed during the resp. cycle *Area of the VP curve |
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What energy/ power changes occur when gas flow changes from laminar to turbulent?
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P=FxR
*Power required for laminar flow is proportional to the square of gas *Power required for turbulent flow is proportional to the cube of gas flow |
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How much energy/ sec does the adult human consume/ produce at rest?
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50W/m2
80W total |
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Name 4 sources of heat loss in pts
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conduction
convection radiation evaporation |
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Name 3 determinants of myocardial O2 consumption (power requirement)
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HTN (pressure)
increase HR (chronotropy) increase inotrop |
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What percentage of total heat loss occurs from respiration?
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10%
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Describe 4 methods of warming pt's in the OR?
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*warming of IV fluids
*forced air warmer(bairhugger) *raise OR temp. *minimize exposure of the pt *infant surgery in infrared warmer *thermal blanket *heating and humidifying inspired gases (closed system) |
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Define dewpoint
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Temperature at which air becomes 100% humidified/ saturated
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Define a kilocalorie
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a unit of heat equal to the amount of heat required to raise the temp. of one kilogram of water by one degree at one atmosphere pressure
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What is the heat capacity of H2O?
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4.18kJ kg-1C-1/ 1kcal kg-1C-1
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What are the relative contributions to heat loss of mass transfer vs evaporation during respiration?
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about 90% due to evaporation and respiration about 10%
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What is the energy cost of rewarming 1 deg C in the PACU following anesthesia?
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In order to rewarm the body by 1 degree C, you have to increase O2 consumption 4x's causing shivering.Shivering causes an incr. in basal heat production x 4.
(basal heat production= 80W) KJ to raise 1 deg C= 245J Will take 17min to get temp. up to 1 degree Celsius |
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What is the difference b/w absolute and relative humidity?
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Absolute- the mass of water vapor present in a given volume of air
Relative: ratio fo the mass of water vapor in a given vol. of air to the mass required to saturate that given volume, at the same temp. expressed as a percentage |
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Describe 4 benefits of closed system anesthesia?
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*Heat & moisture from exhaled air retained within the system
*heating and humidification of gas by CO2 absorption *conservation of anesthetic gases *reduction in environmental pollution *decrease cost of anesthetic adm. |
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Describe the conditions within a Desflurane vaporizer
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VP at room temp 700mmhg
boils at 22.6 deg C liquid held in pressurized chamber at 39 deg C Des vapor added under pressure to gas flow to maintain fixed concentration as set on calibrated dial |
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What is correlation b/w the percentage of anesthetic administered and its pharmacologic effect?
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The depth of anesthesia is dependent on the PP of anesthetic vapor rather than on its percentage, an anesthetic vaporizer can normally be used with the usual settings at different atmospheric pressures
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What would be the pharmacologic significance of administering 1% isoflurane (dial setting) in a hyperbaric chamber?
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you really dont have to change the vaporizer setting very much but there is a little bit of a difference & conc. gets stronger at higher altitudes & a little weaker at hyperbaric condtions
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Name 4 precautions to observe in the use of a portable vaporizer?
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*Do not tip b/c if spill liquid into bypass area can have a very high concentration
*may not be accurate at low flows *check for agent specific fill port *close dial before using O2 flush |
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Depression of the VP of a solvent, is proportional to the molar concentration of the solute in the solvent
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Raoult's Law
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Some large solute molecules of a substance reduces the surface area available for the escape of the smaller solvent molecules. This solute therefore reduces the vapor pressure of the solvent
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Depression of the freezing point
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Force x Distance that the force acts through =
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Work
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Flow of energy, rate of working measured in Watts
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Power
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Flow x Resistance=
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Power it takes to flow a gas
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Low compliance vent. settings
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High RR, low TV
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High Resistance vent. settings
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Low RR, high TV
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How do you calculate work of Myocardial contraction?
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Work = PxV
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Pressure x Flow
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Power
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Can transfer heat energy b/w two objects which are not in contact
The rate of transfer depending on the relative temp. and the surface characteristics of the objects |
Radiation
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A rise in warm air away from the body.
The air layer adjacent to the surface of the body is warmed by conduction and, as it is heated, it expands and becomes less dense and so rises |
Convection
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Heat loss due to the loss of latent heat of vaporization of moisture on the skins surface.
The loss of heat by this route is dependent on the water vapor pressure gradient from the skin to the air and on the total area of moist skin exposed to the atm. |
Surface evaporation
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unit of work
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Joule
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unit of power
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Watts
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The amount of heat required to raise the temp. of a given object by 1 deg C
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Heat capacity
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The heat required to convert 1 Kg of a substance from one phase to another at a given temp.
When a substance changes from a liquid to a vapor or from a solid to a liquid, heat must be supplied even though this change of state takes place at a constant temp |
Latent Heat
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What is the latent heat of vaporization
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liquid to vapor
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What is the latent heat of fusion
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solid to liquid
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Force applied to a surface
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Pressure
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Pressure applied to small airways and alveoli and is measured during an inspiratory pause on the vent
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Plateau Pressure
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Predicts the change of flow from laminar to turbular flow
>2000= turbulent <2000= Laminar |
Reynolds #
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pressure gradient across the wall of a tube=
Tension/ Radius |
La Place's Law
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2 x Tension/ Radius
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La Place's Law for a spherical shape
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Critical closing pressure
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alveoli, bld vessels, veins= not enough pressure, will collapse
*Delta P at which cylinder collapses |
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Explain kinetic energy and potential energy flowing through a narrow tube
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Narrow neck of tube, flow increases (kinetic energy) and pressure drops (potential energy)so total energy is conserved all the way through flow of gas (conservation of energy)
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States that at constant temperature, the volume of a given mass of gas varies inversely with the absolute pressure
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Boyle's Law
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States that at constant pressure, the volume of a given mass of gas varies directly with the absolute temperature
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Charle's Law/ Gay Lussac's Law
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States that at constant volume, the absolute pressure of a given mass of gas varies directly with the absolute temperature
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The third perfect gas law
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The state of a gas can also be altered without allowing the gas to exchange heat energy with its surroundings
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Adiabatic changes
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Hagen-Poiseuille
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resistance, diameter,and length are imp. variables
*describes laminar flow through a tube |
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States that at a particular temperature, the amount of a given gas dissolved in a given liquid is directly proportional to the partial pressure of the gas in equilibrium with the liquid
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Henry's Law
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Defined as the ratio of the amount of substance present in one phase compared with another, the two phases being of equal volume and in equilibrium
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Partition Coefficient
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States that the rate of diffusion of a substance across unit area (such as a surface or membrane), is proportional to the concentration gradient
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Fick's Law
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Rate of diffusion of a gas is inversely proportional to the square root of its molecular weight
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Graham's Law
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Defined as the amt of heat required to raise the temp. of 1 Kg of a substance by 1 kelvin
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Specific Heat capacity
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That which changes or tends to change the state of rest/ motion of an object
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Force
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Force is measured in?
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Newtons
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Force that will give a mass of 1 kg/ms2
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a Newton
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The force of gravity acting on any object will give the object an acceleration of
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9.81m s-2
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Force applied or distributed over a surface, and is expressed as force per unit area
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Pressure
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