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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

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

Applied Physics for Anesthesia

Pressure – Volume – TemperatureRelationships

states of matter
States of Matter
  • SOLID
  • LIQUID
  • VAPOR
  • GAS
slide5

Scales: Kelvin – Celsius - Fahrenheit

(Cx1.8) + 32=F

(F-32)/1.8=C

  • Radiation
  • Evaporation
  • Convection
  • Conduction

Pressure – Volume – TemperatureRelationships

gaseous state
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

slide7

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
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.
cylinders11
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.
slide12

CYLINDER SAFETY

  • Cylinder
  • Valve
  • Regulator
  • Contents
cylinders14
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
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.
n2o cylinders16

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
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 cylinders18
O2 CYLINDERS

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

62.5 min or ~ 1 hr.

o2 cylinders19
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 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
slide21

Pressure P= f/a

_____ mm

800 mm

pressure p f a22
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 a23
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?

slide24

20ml

2ml

Bier Block

slide27

Pressure P= f/a

Head 20kg=20kPa > BP 120mmHg=16kPa

pressure p f a28
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
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 pressures32
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 pressures34
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 temperature relationships
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 temperature relationships36
Pressure-Volume-TemperatureRelationships

Charles’ Law (Temperature-Volume Law)

Gas volume varies directly with temperature at a constant pressure

pressure volume temperature relationships37
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 temperature relationships38
Pressure-Volume-TemperatureRelationships

Gay-Lussac Law (Temperature-Pressure Law)

Gas pressure varies directly with temperature at a constant volume

slide39

Pressure-Volume-TemperatureRelationships

Universal Gas Law (Ideal Gas Law)

PV=nrT

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

slide40

Pressure-Volume-TemperatureRelationships

Universal Gas Law (Ideal Gas Law)

PV=nrT

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

slide41

Pressure-Volume-TemperatureRelationships

“Pay TV Can Be Good”

Pay- T - V -

Can Be Good

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

slide42

Applied Physics for Anesthesia

Pressure – Volume – TemperatureRelationships