Anesthesia Fundamentals

Chapter 4:  Anesthesia Fundamentals

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Practice Questions

*(question attribution, Ira Rampil, M.D., 1995)

 

 Gases

"We live submerged at the bottom of an ocean of air - Torricelli, 1644"

3Lift Pump

 note rod "C" that lifts movable piston which contains a valve "B".  Also, note the valve A. When rod  C is lifted, valve B closes and valve C opens.  Then the water from below the piston will flow to the chamber and the water above the piston will flow out concurrently.  Now when rod C is pushed down, valve A closes and valve B opens which permits water to flow above the piston.

 

 

In the Torricellian tube, the atmospheric pressure supports, mercury 760 mm tall (Figure 12.2, reference 4)

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Regional anesthesia: Bier Block

 

Pressure "Bed" sore secondary to loss of blood flow with subsequent tissue necrosis

Clinical Correlation

7Bier block -- double tourniquet location

7Bier block -- elastic bandage wrapping to exsanguinate the arm

at

 

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Gas Laws

Abbreviations

atm (atmosphere)

mmHg (millimeters of mercury)

torr (same as mmHg)

Pa (Pascal; kPa = kiloPascal)

K (Kelvin)

oC = degrees Celsius

 

Conversions

K  =  C  +  273

1 cm3 (cubic centimeter)  =  1 mL (milliliter)

1 dm3 (cubic decimeter)  =  1 L (liter)  =  1000 mL

0.00 C  =  273 K

1.00 atm  =  760.0 mm Hg  =  101.325 kPa  =  101,325 Pa

 

 

 

 

Variables allowed to change

Variables held constant

Resulting relationship

Formal designation

pressure and volume

number of molecules and temperature

P1V1 = P2V2

Boyle's Law

 

2Boyle's Experimental Data

Volume (ml)

Pressure (Torr)

 PV (ml*Torr)

10

760.0

7.60 x 103

20

379.6

7.59 x 103

30

253.2

7.60 x 103

40

191.0

7.64 x 103

-- as noted from the data above the volume is inversely proportional to the pressure, recalling that everything else that might influence is held constant.  Since pressure may be defined in terms of the frequency of molecular collisions which result in momentum transfer, reducing the volume while retaining the same number of molecules increases the number of molecular collisions and therefore from the kinetic theory of gases point of view the pressure must increase

4Another graph of pressure vs. volume for a gas enclosed in a cylinder at constant temperature (Boyle's law requires that P*V is constant)--Fgire 12.4 from reference 4

In this figure, the gas is enclosed in the cylinder at constant temperature.  The volume of the gas in the gauge may be neglected.  (figure 12.5 from reference 4)



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Variables allowed to change

Variables held constant

Resulting relationship

Formal designation

volume and temperature

number of molecules and pressure

V1/T1=V2/T2

Charles' Law

 

2Charles' Experimental Data

ml

Temperature (oC)

Temperature (oK)

ml/oK

40.0

0.0

273.2

0.146

44.0

25.0

298.2

0.148

47.7

50.0

323.2

0.148

51.3

75.0

348.2

0.147

55.3

100.0

373.2

0.148

80.0

273.2

546.3

0.146

 The top case represents a lower temperature case; note that the weight exerting the downward force is the same in both cases.  The volume & temperature must change in a coordinated matter to ensure that the relationship  "V / T =constant" is maintained [volume is directly proportional to temperature]. Figure 12.6 from reference 4.

Ideal Gas Law

 

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2Comparison of Variables & Constants in Gas Laws
Variables allowed to change Variables held constant Resulting relationship Formal designation
pressure and volume number of molecules and temperature P1V1 = P2V2 Boyle's Law
volume and temperature number of molecules and pressure V1/T1=V2/T2 Charles' Law
pressure and temperature number of molecules and volume P1/T1=P2/T2 Amonton's Law
number molecules and volume pressure and temperature V1/n1=V2/n2 Avogadro's Law
pressure, volume, & temperature number of molecules P1V1/T1=P2V2/T2 Combined Gas Law
pressure, volume, temperature & number of molecules

--

P1V1/n1T1=P2V2/n2T2 Ideal Gas Law

2Gaseous Equation of State Calculator 

(courtesy of Dr. Fred Senese, General Chemistry OnLine : http://antoine.fsu.umd.edu/chem/senese/101/gases/)

Dependent
Variable
UnitsIdeal Gasvan der
Waals Gas
Dieterici
Gas
Pressure
Volume
Temperature
Moles mol

Gas van der Waals
Parameters
Dieterici
Parameters
PC (atm) a (SI units)
VC (L/mol) b (SI units)
TC (K) TBoyle/TC
ZC (K) ZC (calc)

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