Physics for the Nurse Anesthetist~Quiz 3 Flashcards Preview

2nd Quarter > Physics for the Nurse Anesthetist~Quiz 3 > Flashcards

Flashcards in Physics for the Nurse Anesthetist~Quiz 3 Deck (65)
Loading flashcards...

What is solubility?

Solubility the maximum amount of one substance(solute) that is able to dissolve into another(solvent).


What are three factors that may affect the solubility of solutes in solvents.

The intermolecular interactions between substances, temperature and pressure.

*pressure exhorts little to no influence on solubility of solids and liquids. But GAS solubility in a liquid is directly proportional to pressure.


What does the phrase "like dissolves like", mean?

Solubility is enhanced by intermolecular interactions between substances that have similar electron configurations. For example, H2O and salts(NaCL) have similar polarity.


What is the difference between endothermic versus exothermic reactions?

Define endothermic reactions!

Endothermic(into)- consumes heat rather produces heat, with endothermic reactions, solubility is increased with increased temperature. Energy is required to break the chemical bonds of substances that are dissolving. Most often this is an endothermic reactions which means it requires more energy than it produces.


What is the difference between endothermic versus exothermic reactions?

Define exothermic reactions!

Exothermic(out)- Occasionally the process may be exothermic, meaning energy is released in excess of the energy required to break the bonds of the solute.


How is gas solubility in gases altered by temperature?

-Gas solubility in liquids is inversely related to temperature.
-as temperature increases, less gas is able to dissolve into the liquid.
-Lower temperature slows the kinetic energy of gas molecules, allowing them to dissolve into liquids.


What is a clinical example of temp affecting solubility?

The slower emergence of a hypothermic patient receiving general anesthesia. The hypothermic patient retains anesthetic gases in the blood due to increased solubility related to temperature.


What is Henry's Law?

At a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas at equilibrium above the gas-liquid interface.


What happens to the amount of salt that dissolves in whiter with increasing temperature? What happens to the amount of gas that dissolves in liquid with increasing temperature? What principle applies?

-The solubility of a salt increase with increasing temperature. More salt dissolves in water when temperature increases.
-The solubility of a gas decreases with increasing temperature.
-Less gas dissolves in water when temperature increase.
-LeCatelier's principle applies to both situations.


If you heat a solvent, what happens to the solubility of a non-gaseous solute such as sodium chloride?

The solubility of a non-gaseous solute increases when the liquid is heated.


What effect does hypothermia have on gas solubility?

As a liquid is cooled, more gas dissolves in the liquid; therefore, hypothermia will cause an increase in gas solubility.


Is the blood solubility and the tissue solubility of an inhaled volatile agent increased or decreased in the hypothermic patient?

-the amount of gas that dissolves in solution is inversely proportional to temperature.
-the lower the temperature, the greater the amount of gas dissolved in solution.
-in the hypothermic patient, therefore, the solubility of an inhaled volatile agent in blood and in tissue increased.


What is the Ostwald Solubility Coefficient?

The higher the blood gas partition coefficient(also called Ostwald Solubility Coefficient), the longer it takes to induce anesthesia and the longer it takes to emerge from anesthesia.

For example: Desflurane at 0.42, is the quickest on and the quickest off while Isoflurane at 1.4 is the slowest on and the slowest off


What are the anesthetic Blood Gas Coefficients for Des, N2O, Sevo and Iso?

Anesthetic Blood/Gas Partition Coefficient
DES 0.42
N2O 0.47
SEVO 0.6
ISO 1.4


The agent follows what series of partial pressure gradients to reach its target the brain?

delivered--->inspired--->alveolar--->arterial--->brain & tissue


The Ostwald solubility coefficient is a measure of what?

It is a measure of the solubility of a gas in a fluid.


What is the definition of the Ostwald solubility coefficient? What is the significance of the Ostwald solubility coefficient in anesthesia?

-the Ostwald solubility coefficient is defined as the ratio of the concentration of gas dissolved in solution to the concentration of gas in the gas phase at equilibrium at 37 degrees.
-Blood-gas partition coefficient for inhalational anesthetics are derived from Ostwald solubilities.


What is the formula associated with Henry's Law?

p = k * c

Where p is the partial pressure of the solute above the solution, k is Henry's constant, and c is the concentration of the solute in the solution.


As stated by Henry's law, what will happen to the solubility of gas as the partial pressure of a gas increases?

Increasing the partial pressure of a gas above a liquid will increase the amount of gas that dissolves in the liquid.


What are two clinical examples that reflect the direct relationship of pressure and solubility described by Henry's Law?

1. Increasing delivery of oxygen to patients to increase arterial oxygenation
2. and over pressuring(high concentration) of anesthetics to increase the end tidal of the volatile agent upon induction


Describe what "Overpressuring" is referring.

It is the process of significantly increasing a volatile anesthetic concentration(partial pressure) delivered to a patient to increase the alveolar concentration, and therefore the amount dissolved in the blood, to speed uptake.


What is the solubility coefficient of O2 and of Co2 that is related to Henry's Law?

O2=0.003 ml/100 ml blood/mmHg of Ox
C)2=0.067 ml/100 ml blood/mmHg of CO2


What is Henry's Law?

Henry's law states that the amount of gas that will dissolve in solution is proportional to the partial pressure of the gas in contact with the solution.


Henry's Law is used for what two purposes?

Henry's Law is used to calculate:
1. the amount of oxygen dissolved in blood(O2 dissolved= PO2 X 0.003
2. the amount of carbon dioxide dissolved in blood(CO2 dissolved = 0.067 X PCO2)


If the oxygen partial pressure in arterial blood increases from 50 mmHg to 350 mmHg, the amount of dissolved oxygen increases by how much?

at 50 mmHg(X 0.003)--->0.15 ml O2/100 ml blood
at 350 mmHg(X 0.003)--->1.05 ml O2/100 ml blood
The increase in dissolved O2 is 1.05 - 0.15 = 0.90 ml O2/100 ml blood


How much O2 is dissolved in arterial blood when the PaO2 is 300 mmHg?

0.9 ml O2 are dissolved in 100 ml blood


How much does dissolved O2 increase in blood when PaO2 increases from 100 mmHg to 500 mmHg?

1.2 ml O2/100 ml blood


How much O2 is dissolved if the FiO2 is 40%?

if the inspired O2 is given, estimate the PaO2 by multiplying the inspired concentration by 5.

so the answer would be 200 mmHg X 0.003 = 0.6 ml O2/100 ml blood


How much CO2 is dissolved in blood when the CO2 is 59 mmHg?

3.35 ml CO2 are dissolved per 100 ml blood


What is diffusion?

 Diffusion is the process of net movement of one type of
molecule through space as a result of random motion
intended to minimize a concentration gradient.
 Kinetic energy allows molecules to move freely in a fluid,
and therefore mixtures of fluids tend to evenly distribute
 Molecules with smaller mass will diffuse faster