Physics of Anesthesiology Nursing NGR 6401 Physics of Anesthesiology Nursing

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Physics of Anesthesiology Nursing NGR 6401 Physics of Anesthesiology Nursing. Jeffrey Groom, PhD, CRNA, ARNP Clinical Associate Professor & Program Director Anesthesiology Nursing Program College of Nursing and Health Sciences Florida International University Miami, Florida.

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## Physics of Anesthesiology Nursing NGR 6401 Physics of Anesthesiology Nursing

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### Physics of Anesthesiology NursingNGR 6401 Physics of Anesthesiology Nursing

Jeffrey Groom, PhD, CRNA, ARNPClinical Associate Professor & Program DirectorAnesthesiology Nursing Program College of Nursing and Health SciencesFlorida International University Miami, Florida

### Applied Physics for Anesthesia

Pressure – Volume – TemperatureRelationships

States of Matter
• SOLID
• LIQUID
• VAPOR
• GAS

Scales: Kelvin – Celsius - Fahrenheit

(Cx1.8) + 32=F

(F-32)/1.8=C

• Evaporation
• Convection
• Conduction

Pressure – Volume – TemperatureRelationships

Gaseous State
• ALL gases obey certain “Gas Laws” with four physical quantifiable characteristics
• Pressure (P)
• Volume (V)
• Temperature (T)
• Amount [moles] (n)

Kinetic theory of gases

Pressure

• A cylinder is never “empty”, the atmospheric pressure inside matches that outside the cylinder
• A full E cylinder of Oxygen contains 2200 PSIG
• A full E cylinder of Nitrous Oxide contains 745 PSIG
CYLINDERS
• Gases liquify if sufficient pressure is applied and the temperature is below critical temperature.
• The critical temperature of N2O is 39.5C and thus is compressed and stored as a liquid at room temperature.
• The critical temperature of O2 is –119C and thus cannot be liquified at room temperature, no matter how much pressure is applied.
CYLINDERS
• ADIABATIC Processes – if a cylinder of compressed gas is opened into a closed space, the pressure in the closed space will rapidly rise as will the temperature.
• Because the change in pressure/temperature occurs quickly, the heat generated cannot be dissipated.
• Rapid rise in temperature presents potential explosive hazard.

CYLINDER SAFETY

• Cylinder
• Valve
• Regulator
• Contents
CYLINDERS

Joule-Thompson Effect

• When a compressed gas is allowed to escape freely into an open space, cooling occurs.
• Condensation of water or frost may accumulate on the cylinder valve.
• A cycloprobe operates on the Joule-Thompson effect.
N2O CYLINDERS
• As gas escapes from a N2O cylinder, the liquid N2O in the cylinder vaporizes.
• Heat is lost as the liquid vaporizes (latent heat of vaporization) and the temperature in the cylinder falls (Joule-Thompson Effect)
• As the cylinder temperature falls, the pressure of the gas in the cylinder decreases.

750

PSI

400

0

60

120

MIN

N2O CYLINDERS
• N2O is exiting cylinder at 5 L/min
• If the cylinder is turned off, the pressure is restored as the cylinder regains heat from room air.
• If the liquid runs out, the pressure in the cylinder will fall.
• A full N2O cylinder contains 1,590 L
O2 CYLINDERS
• At 20 C, a full E cylinder of O2 shows a pressure of about 2200 psi and contains approximately 625 L.
• How long will a fill O2 E cylinder last at a flow rate of 10 L/min ?
O2 CYLINDERS

(625 L) / (10 L / min) =

62.5 min or ~ 1 hr.

O2 CYLINDERS

How long will an O2 cylinder last at 5 L/min flow and starting at a gauge pressure of 1,100 psi ?

At 1,100 psi, the cylinder is half full so half of 625 L is 312 L

With 312 L at 5 L/min-(312 L) / (5 L/min) = 62 min or ~ 1 hr

Pressure P= f/a
• PRESSURE = Force per amount of Area
• Units of measure for pressure
• Pascal (Pa):  1 Pa = 1 Newton/m2 or 1N/m2
• The Pascal is the Standard International Unit of pressure
• The Newton is the Standard International Unit of force
• Atmosphere (atm): one atm  =101325 Pa
• Pounds per sq inch (psi): one atm = 14.7 psi or lbs/in2
• Torricelli (torr): one atm = 760 torr
• mmHg: 1 mmHg = 1 torr
• Millimeters Hg: one atm = 760 mmHg

Pressure P= f/a

_____ mm

800 mm

Pressure P= f/a
• PRESSURE = Force per Unit Areaair is matter, has mass, and exerts force
• At sea level – Air Pressure = 14.7 psi or 760 mmHg
• 1 Standard Atmosphere1 atm = 14.7 psi = 760 mmHg = 101 kPa
Pressure P= f/a
• Pressure is inversely proportional to area

a

Force/area = 500 kPa

2 ml

4a

Force/area = 100 kPa

20 ml

Clinical ReferenceSystolic BP = 120 mmHg or 16 kPaWhat’s the clinical implications?

20ml

2ml

Bier Block

Pressure P= f/a

Pressure P= f/a

Anesthesia Machine Examples

• Pressure Relief Valve
• Expiratory Valve
• Pressure-reducing valve AKA pressure regulator
• Oxygen Failure warning device
Dalton’s Law of Partial Pressures

The total pressure exerted by a mixture of gases is the sum of their individual partial pressures.

Ptotal = Pa + Pb + Pc + etc.

Dalton’s Law of Partial Pressures

In a mixture of gases, each gas exerts a partial pressure. The PP of a gas is calculated by multiplying the percent times the atmospheric pressure

Atmosphere @ sea level

O2 = (21% X 760 mmHg) = 160 mmHg

N2 = (79% X 760 mmHg)=600 mmHg

Total 760 mmHg

Dalton’s Law of Partial Pressures
• What is the partial pressures of O2 and N2O if you are administering a ratio of 70/30?
• N20 70% X 760 mmHg = 532 mmHgO2 30% X 760 mmHg = 228 mmHg 760 mmHg
• Would this differ if you were administering anesthesia at Denver General Hospital?
• N20 70% X 630 mmHg = 441 mmHgO2 30% X 630 mmHg = 189 mmHg 630 mmHg

Miami = 14.7 psi Denver = 12.2 psi

Miami = 760mmHg Denver = 630mmHg

Pressure-Volume-TemperatureRelationships
• The product of the P and V of a gas divided by T is a constant
• The V of a gas varies inversely with its P at a constant T
• Robert BoyleP is inversely proportional to V
• P µ 1/V or P1V1 = P2V2
Pressure-Volume-TemperatureRelationships

Charles’ Law (Temperature-Volume Law)

Gas volume varies directly with temperature at a constant pressure

Pressure-Volume-TemperatureRelationships

Boyle’s Law (Pressure – Volume Law)

The volume of a given amount of gas at a constant temperature varies inversely with the pressure

Pressure-Volume-TemperatureRelationships

Gay-Lussac Law (Temperature-Pressure Law)

Gas pressure varies directly with temperature at a constant volume

Pressure-Volume-TemperatureRelationships

Universal Gas Law (Ideal Gas Law)

PV=nrT

P= Pressure V=Volume n = number moles of gas r = constant T= Temperature

Pressure-Volume-TemperatureRelationships

Universal Gas Law (Ideal Gas Law)

PV=nrT

PV=nrT P=T/VT=P/V V=T/P

Pressure-Volume-TemperatureRelationships

“Pay TV Can Be Good”

Pay- T - V -

Can Be Good

Pressure constant-Charles Temperature constant-Boyles Volume constant- GayLussac

Applied Physics for Anesthesia

Pressure – Volume – TemperatureRelationships