Lecture 2 Flashcards by Rachel Kaplan

Definition: a measure of the degree of hotness or coldness, the thermal state of an object

temperature

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Definition: thermal energy

Heat

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quantitative measure of thermal energy

temperature

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Measurement scales for temperature:

Celcius
Fahrenheit
Kelvin

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Definition: Heat energy transfer from higher concentration or hotter to lower concentration or less hot

heat loss

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What physiologic mechanism prevents heat loss?

vasoconstriction

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What in anesthesia promotes heat loss?

vasodilation, induction of GA

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Definition: body’s increased heat loss due to vasodilating effects of volatile anesthetic agents and regional anesthetics

core temperature redistribution

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Blood flow redistribution to the body’s surface promotes heat loss by 4 processes:

– Radiation
– Conduction
– Convection
– evaporation

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Vasodilating effects of anesthetics can cause rapid temp reduction with greatest decrease in ____ (time frame)

1 hour

first hour

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Definition: In areas where blood flow is the highest there is a tendency for infrared electromagnetic heat transfer

radiation

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The greater the blood flow to _____ (body part) the greater the heat loss due to radiation

head

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Definition: Heat loss from one object to another by way of direct contact

conduction

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How do we mitigate heat loss via conduction in anesthesia?

warm blankets, Bair hugger

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Definition: Heat creates air currents. The body transfers kinetic energy to the circulating air molecules on the skin’s surface

Convection

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Definition: Along the skin’s surface a phase change occurs from liquid to gas (vapor) and the body losses heat for this reaction to occur

Evaporation

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Source of heat needed for evaporation comes from:

surrounding environment

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Which of the 4 processes of core temp redistribution is NOT a significant source of heat loss?

evaporation

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How to reduce evaporative heat loss?

HME

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when you exhale, you lose heat via which process?

evaporation

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Amount of heat energy per unit mass required to convert a liquid into the vapor phase

latent heat of vaporization

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How many joules are required to convert 1 gram H2O to vapor?

2500 J

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Identify the processes that produce the greatest heat loss (select two)

Evaporation
Convection
Conduction
Radiation

Radiation and convection

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The process of converting solids or liquids to vapor

requires heat energy

Vaporization

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Boiling point

At a given pressure the temp at which the bulk of a liquid turns to vapor

What happens to temperature after it reaches boiling point?

does not increase, but the additional heat energy is used for the phase change from liquid to gas.

What makes vapor pressure?

Gas that escapes the liquid

How are boiling point and vapor pressure related?

inversely

Liquids with high vapor pressures are called:

volatile liquids

VP of Iso at STP:

238 mmHg

VP of Sevo at STP:

160 mmHg

VP of Des at STP:

660 mmHg

What is STP?

standard temp and pressure | 273.15 K or 0C

What happens when sevoflurane is mistakenly added to the isoflurane vaporizer?

LHL | Output will be a lower concentration risk of awareness

What happens when Desflurane is mistakenly added to the sevoflurane vaporizer?

HLH Output will be a higher concentration risk HD instability, over sedation, hypotension, death

any substance that can flow and alter its shape continuously

fluids

fluid that resists compression:

liquid

fluid that compresses and expands:

gas

both liquid and gas are considered:

fluids

3 forces that affect fluid mechanics:

gravity pressure friction

Measures a fluids resistance to flow

viscosity

Highly viscous fluids flow:

NOT easily

Low viscosity fluids flow:

easily/readily

Where along a pipe/blood vessel do the molecules move the slowest?

the wall/edge

Where along the pipe do the molecules move the quickest

the center (less friction)

What is requiredto initiate and maintain flow of a fluid?

force

What is force due to? (in fluid mechanics)

a pressure difference along the length of pipe

Describe laminar flow:

- smooth and orderly - particles move parallel to the walls of the tube - flow is fastest in the center of the tube, where there is less friction.

Describe turbulent flow:

- disorderly - Particles do NOT move parallel to the walls of the tube - flow rate is the same across the diameter of the tube

In which flow is the flow rate the same across the diameter of the tube?

turbulent

Which flow contains Eddies?

Turbulent flow

what are eddies?

composed of | particles moving across or opposite the general direction of flow

Which law describes laminar flow mathematically?

Poiseuille's law

According to Poiseuilles law, what has the most dramatic effect on flow?

radius

In Poiseuille's law, rate of flow is ______ proportional to the length of the tube and viscosity

inversely

According to Poiseuilles law, doubling the radius will increase the flow:

16 fold

According to Poiseuilles law, if viscosity increases, what happens to flow?

decreases

How is Poiseuilles law used in blood administration?

large bore IV (increase radius) pressure bag/taller IV pole (increase pressure gradient) dilute with NaCl/run through warmer (decrease viscosity) short tubing (decrease length)

Formula for Poiseuilles law

Q = [pi x R^4 x changeP] / 8 x n x L

What flow is common in medium to large airways?

turbulent flow

What flow is common in small bronchial tubes?

laminar

Reynolds number less than 2000 indicates:

laminar flow

Reynolds number greater than 4000 indicates:

turbulent flow

Reynolds number 2000-4000 indicates:

transitional flow

Which law describes laminar flow?

Poiseuilles law

Which law describes turbulent flow?

Graham's law

laminar flow is dependent on what quality of fluid?

viscosity

Definition: As flow of fluid passes through a narrowing in a tube, the velocity of flow increases and there is a decrease in pressure at the narrowed area

Bernoulli's principle

Definition: As airflow in a tube moves past a point of constriction, the pressure at the constriction drops and if it falls bellow atmospheric pressure then air is entrained into the tube

Venturi effect

What principles does the Venturi mask combine?

Bernoulli and Venturi

The amount of room air drawn in to dilute oxygen in a Venturi mask/system is determined by:

the size of the orifice

When a pipe is contracted, what happens to velocity and pressure?

increase in velocity, decrease in pressure

Definition: Describes the tendency of fluid flow to follow the curved surface when emerging from a constriction.

Coanda effect

At the widening of the tube beyond the constriction, pressure _____ and flow _____

pressure increases and flow decreases/slows

Which principle/effect? If there is a bifurcation that delays the higher pressure it will attract the greater percentage of total flow and higher volume of liquid or gas toward its path

Coanda effect

Describes turbulent flow mathematically

Graham's law

Definition: Turbulent flow rate is directly proportional to the pressure gradient on either side of the tube and inversely proportional of the fluid to the density

Graham's law

The number of molecules within a given volume

Density

Measurement of intermolecular forces (friction that dictate flow)

Viscosity

Low FGF in a Thorpe tube favors which flow pattern?

laminar

High FGF in a Thorpe tube favors which flow pattern?

turbulent

Turbulent flow is dependent on what quality of fluid?

density

Describes relationship of wall tension (T) to pressure and radius in spheres and cylinders

Law of LaPlace

Increasing radius leads to what change in tension?

increase

Increasing pressure leads to what change in tension?

increase

What law explains why larger blood vessels and aneurysms may burst under extreme increases in BP and capillaries do not.

Law of LaPlace

How does increased wall thickness impact tension?

increasing wall thickness REDUCES tension

Why do ventricles get hypertrophic/remodel in hypertensive patients?

Law of Laplace, ventricles constantly need to overcome afterload, the tension in the ventricle needs to be greater, so ventricle develops wall tension ventricle increases wall thickness over time to try to reduce the stress on ventricle wall

T/F: Large alveoli have more surfactant

false. all alveoli have same amount of surfactant

Large alveoli have ____ concentration of surfactant

less/lower

small alveoli have ______ concentration of surfactant

more/greater

Peak surfactant development at what gestation?

35-36 weeks

Which Law describes why we are more concerned with large vessels rupturing with changes in BP?

Law of Laplace

Pushing force:

pressure

Pulling force:

tension