Physics of Gas Therapy

Question 1

What is the unit that pressure is measured in?

Answer 1

Pascal, Pa (N/m^2)

Question 2

What is barometric pressure?

Answer 2

The pressure that is exerted on us by the atmosphere (1atm at sea level)

Question 3

What is the equivalent of 1atm in the other units of pressure?

Answer 3

760 mmHg, 1034 cmH20, 101.3 kPa, 14.7 psi

Question 4

What unit of pressure is most often used on ventilators?

Answer 4

cmH2O

Question 5

What unit of pressure do the wall vacuums use?

Answer 5

mmHg

Question 6

What unit of pressure do medical air and oxygen outlets use?

Answer 6

psi

Question 7

What is vapour

Answer 7

The state between gas and liquid that can revert to a liquid if the pressure is increased below the critical temperature.

Question 8

What is the Ideal Alveolar Gas Equation?

Answer 8

PaO2 = (PB - 47) FiO2 - (PaCO2 / 0.8)

Question 9

What does the Ideal Alveolar Gas Equation Measure?

Answer 9

The PaO2, or the alveolar oxygen tension.

Question 10

What does Boyle’s law state?

Answer 10

There is an inverse proportion between the pressure exerted on the gas and the volume of its container. Larger container = less pressure.

Question 11

What is Boyle’s law?

Answer 11

V1P1 = V2P2

Question 12

What does Charles’s law state?

Answer 12

The volume of gas increases proportionately with increases in temperature at a constant pressure. Higher temp = more volume.

Question 13

What is Charles’s law?

Answer 13

V1/T1 = V2/T2

Question 14

What does Dalton’s law state?

Answer 14

The total pressure of the mixed gases is equal to the sum of the partial pressures.

Question 15

What is Dalton’s law?

Answer 15

Ptotal = P1 + P2 + P3…

Question 16

What does Gay-Lussac / Amonton’s law state?

Answer 16

At a constant volume, the pressure a gas exerts rises as the temperature of the gases rise. Higher temp = higher pressure exerted by gas.

Question 17

What is Gay-Lussac / Amonton’s law?

Answer 17

P1/T1 = P2/T2

Question 18

What is the ideal gas law?

Answer 18

PV = nRT

Question 19

What is the combined gas law?

Answer 19

P1V1/T1 = P2V2/T2

Question 20

What does Graham’s law state?

Answer 20

When two gases are at the same temperature and pressure their rates of diffusion are inversely proportional to the square root of their masses. Heavy gases diffuse more slowly.

Question 21

What is Graham’s law?

Answer 21

Rate 1/Rate 2 = (sqrt M2)/ M1

Question 22

What does Henry’s law state?

Answer 22

The amount of gas that can dissolve in a liquid is directly proportional to the partial pressure of the gas over the liquid.

Question 23

What does Fick’s law state?

Answer 23

The flow of gas across a semi-permeable membrane into a liquid is directly proportional to the surface area, pressure gradient, and solubility of the gas.

Question 24

What is Fick’s Law?

Answer 24

Vgas = (D(P1-P2)A)/T

Question 25

What is does Poisuille's law state?

Answer 25

The pressure driving the fluid through a tube and the resistance of the tube both affect the flow of the fluid or gas through the tube.

Question 26

What is the formula for resistance?

Answer 26

Resistance = (8nl)/(πr^4)

Question 27

How do we measure the pressure difference from beginning to end of tube?

Answer 27

ΔP = Q x R where Q is flow through the tube and R is the resistance to flow.

Question 28

What unit is airway resistance reported in?

Answer 28

cmH2O/L/sec

Question 29

What is the Bernoulli principle?

Answer 29

An increase in the speed of the fluid occurs with a decrease in pressure.

Question 30

What is the Venturi effect?

Answer 30

When a section of tubing narrows, the pressure in the narrowed section will be lower.

Question 31

What is the Coanda effect?

Answer 31

Fluid clings to areas of lower pressure such as preferentially flowing down one section of airway at a split or water sticking to the side of a pitcher.