CRNA BOARDS EXAM SCRIPT
COMPREHENSIVE STUDY GUIDE
●● From greatest to least, what are the vapor pressures of the inhaled
anesthetic agents?
Answer: Nitrous Oxide - XDesflurane - 669 mmHgHalothane - 244
mmHgIsoflurane - 240 mmHgEnflurane - 172 mmHgSevoflurane - 170
mmHDenise Has Intercourse Every Sunday
●● What is Dalton's Law of Partial Pressures?Why do we care?
Answer: The total pressure exerted by a mixture of gases is equal to the
sum of the partial pressures of each individual gas.This means you can
calculate the final percent concentration of a mixture of gas if you know
the pressure of Oxygen at sea level and the partial pressure of the other
gases.
●● What is the partial pressure of oxygen at sea level?
Answer: 14.7 PSI760 mm Hg760 torr1 atm101 kPa
●● If isoflurane is added to a flask of oxygen what is the percentage
concentration of both isoflurane and oxygen?
Answer: Oxygen Partial Pressure = 760Isoflurane Partial Pressure =
240After adding Isoflurane to the flask, the partial pressure of oxygen is
now 520 mmHg.% Oxygen = (520/760) = 69%% Isoflurane = (240/760)
= 31%It really is just that easy.
,●● If you add Desflurane to a flask of Oxygen, what is the percentage
concentration of both Desflurane and oxygen?
Answer: Oxygen Partial Pressure = 760 mmHgDesflurane Partial
Pressure = 669 mmHgAfter adding Isoflurane to the flask, the partial
pressure of oxygen is now 91 mmHg% Oxygen = () = 11%%
Desflurane = () = 89%It really is just that easy.
●● What happens if a volatile agent with a higher vapor pressure is
added to a vaporizer calibrated for a lower vapor pressure?
Answer: The concentration delivered will be higher than normal.Higher
Lower High - HLH
●● What happens if a volatile agent with a lower vapor pressure is
added to a vaporizer calibrated for a higher vapor pressure?
Answer: The concentration delivered will be lower than normal.Lower
Higher Low - LHL
●● What is unique about the deslflurane vaporizer?
Answer: It is heated to approxmiately 39 degrees celsius which creates a
vapor pressure of nearly 1500 mmHg (two atmospheres).This drives"
desflurane to the gas outlet"
●● 1 mmHg = (X) cm H2O1 atm = (X) mmHg = (X) psi = (X) kPa =
(X) bar1 psi = (X) mmHg
, Answer: 1 mmHg = 1.36 cm H2O1 atm = 760 mmHg = 14.7 psi = 101
kPa = 1 bar1 psi = 54 mmHg
●● How do Bourdon gauges work?What does it mean when the
Bourdon gauge on a cylinder reads zero?
Answer: They measure high (cylinder) pressure relative to atmospheric
pressure.That the cylinder pressure is equal to atmospheric pressure and
there is no 'drive' to the gas.
●● What is the Law of Laplace?What structures within the body does
this apply to?
Answer: Tension = (Pressure) x (radius)This is try for cylinder
structures, such as blood vessels and the left ventricle.It means that as
the structure expands (radius increases) the tension (force) of the
structure increases as well.
●● How does the Law of LaPlace help understand why aneurysms are
more likely to rupture than healthy blood vessel?
Answer: Tension = (Pressure) x (Radius)So, the tension on the wall is
proportional to the radius. The larger the radius (anyeursm) more
likely the vessel will rupture as the tension increases.
●● How does the Law of LaPlace help understand why capillaries are
more likely to withstand high pressures than larger blood vessels?
Answer: Tension = (Pressure) x (Radius)Because the radius in a
capillary is so much smaller (perhaps 1/100th of a larger vessel) it can
COMPREHENSIVE STUDY GUIDE
●● From greatest to least, what are the vapor pressures of the inhaled
anesthetic agents?
Answer: Nitrous Oxide - XDesflurane - 669 mmHgHalothane - 244
mmHgIsoflurane - 240 mmHgEnflurane - 172 mmHgSevoflurane - 170
mmHDenise Has Intercourse Every Sunday
●● What is Dalton's Law of Partial Pressures?Why do we care?
Answer: The total pressure exerted by a mixture of gases is equal to the
sum of the partial pressures of each individual gas.This means you can
calculate the final percent concentration of a mixture of gas if you know
the pressure of Oxygen at sea level and the partial pressure of the other
gases.
●● What is the partial pressure of oxygen at sea level?
Answer: 14.7 PSI760 mm Hg760 torr1 atm101 kPa
●● If isoflurane is added to a flask of oxygen what is the percentage
concentration of both isoflurane and oxygen?
Answer: Oxygen Partial Pressure = 760Isoflurane Partial Pressure =
240After adding Isoflurane to the flask, the partial pressure of oxygen is
now 520 mmHg.% Oxygen = (520/760) = 69%% Isoflurane = (240/760)
= 31%It really is just that easy.
,●● If you add Desflurane to a flask of Oxygen, what is the percentage
concentration of both Desflurane and oxygen?
Answer: Oxygen Partial Pressure = 760 mmHgDesflurane Partial
Pressure = 669 mmHgAfter adding Isoflurane to the flask, the partial
pressure of oxygen is now 91 mmHg% Oxygen = () = 11%%
Desflurane = () = 89%It really is just that easy.
●● What happens if a volatile agent with a higher vapor pressure is
added to a vaporizer calibrated for a lower vapor pressure?
Answer: The concentration delivered will be higher than normal.Higher
Lower High - HLH
●● What happens if a volatile agent with a lower vapor pressure is
added to a vaporizer calibrated for a higher vapor pressure?
Answer: The concentration delivered will be lower than normal.Lower
Higher Low - LHL
●● What is unique about the deslflurane vaporizer?
Answer: It is heated to approxmiately 39 degrees celsius which creates a
vapor pressure of nearly 1500 mmHg (two atmospheres).This drives"
desflurane to the gas outlet"
●● 1 mmHg = (X) cm H2O1 atm = (X) mmHg = (X) psi = (X) kPa =
(X) bar1 psi = (X) mmHg
, Answer: 1 mmHg = 1.36 cm H2O1 atm = 760 mmHg = 14.7 psi = 101
kPa = 1 bar1 psi = 54 mmHg
●● How do Bourdon gauges work?What does it mean when the
Bourdon gauge on a cylinder reads zero?
Answer: They measure high (cylinder) pressure relative to atmospheric
pressure.That the cylinder pressure is equal to atmospheric pressure and
there is no 'drive' to the gas.
●● What is the Law of Laplace?What structures within the body does
this apply to?
Answer: Tension = (Pressure) x (radius)This is try for cylinder
structures, such as blood vessels and the left ventricle.It means that as
the structure expands (radius increases) the tension (force) of the
structure increases as well.
●● How does the Law of LaPlace help understand why aneurysms are
more likely to rupture than healthy blood vessel?
Answer: Tension = (Pressure) x (Radius)So, the tension on the wall is
proportional to the radius. The larger the radius (anyeursm) more
likely the vessel will rupture as the tension increases.
●● How does the Law of LaPlace help understand why capillaries are
more likely to withstand high pressures than larger blood vessels?
Answer: Tension = (Pressure) x (Radius)Because the radius in a
capillary is so much smaller (perhaps 1/100th of a larger vessel) it can
