Anesthesia Pharmacology Chapter 4:  Anesthesia Fundamentals

Page Back Page Forward
Table of Contents

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)

  • "The height of mercury is determined by the need to balance the weight of mercury lifted against the weight of the air above it.

  • The weight of air presses down uniformly on everything on the surface of the earth, including the surface of the pool of mercury in the beaker.

  • This pool transmits the pressure uniformly through its volume and therefore maintains the height of mercury in the glass tube.

  • The 76.0 mm of mercury has a weight equal to the weight of a column of air with the same cross-sectional area and a height of 150 km (roughly the height of our atmosphere)."

    • Figure and legend by Professor Larry Gladney, Ph.D. Dept. of Physics, University of Pennsylvania. 

 

Page Back

Page Forward

 

Regional anesthesia: Bier Block

 

 

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

 

Clinical Correlation

Bier block:  double tourniquet location7

 

Bier block:  elastic bandage wrapping to exsanguinate the arm7

 

 

Page Back

Page Forward

 

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

 

Boyle's Experimental Data2

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

 

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



 

Page Back

Page Forward

 

 

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

 

 

Charles' Experimental Data2

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

 

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
Page Back Page Forward