Oxygen Therapy

Question 1

What does oxygen cause?

Answer 1

Systemic vasoconstriction in the small arteriolar thereby decreasing capillary surface area available for oxygen entry into tissues?

Question 2

What is ironic about hypoxia and aerobic metabolism?

Answer 2

Aerobic metabolism is not affected by oxygen flow

Question 3

How much FiO2 can low flow nasal cannula provide?

Answer 3

24-40%

Question 4

How much flow does low flow NC provide?

Answer 4

1-6 L/min

Question 5

How much flow happens during quiet breathing?

Answer 5

15L/min

Question 6

What doesn’t low flow nasal cannula achieve a high FiO2?

Answer 6

Because you have to inhale room air to reach your normal 15L/min since NC only provides 1-6L/min

Question 7

What are the flows and FiO2 provided on face masks?

Answer 7

5-10L/min (have to have minimum flow rate of 5 to clear the exhaled gas)
Fio2 of 60%

Question 8

How does a partial rebreather work?

Answer 8

Allows gas exhaled to return to the reservoir bag until the flow rate falls below the oxygen flow rate so that the air in the bag is rich in oxygen.

The air in the bag is under positive pressure so the patient breaths in mostly oxygen.

Also, the initial expired air that goes back into the bag is rich in oxygen because that is the air from the upper airways (anatomic dead space)

Question 9

How much FiO2 can be delivered by a partial rebreather?

Answer 9

70%

Question 10

What is the difference between a partial rebreather and a nonrebreather?

Answer 10

1. The expiratory ports on the mask of the non rebreather do not allow any room air to be taken in
2. There is a one way valve on the mask to the bag, that does not allow exhaled gas to go into the bag

Question 11

How much FiO2 can a nonrebreather give?

Answer 11

80% (theoretically 100%)

Question 12

What is the mechanism of a Venturi mask?

Answer 12

Uses viscous drag (high velocity stream to pull room air into the device)
Size of the port determines the FiO2
Flow is in excess of 60 L/min

Question 13

How much FiO2 is delivered thru the venti mask?

Answer 13

24-50%

Question 14

What is the advantage of a Venti mask?

Answer 14

The ability to deliver constant FiO2

Question 15

What patient is a venti mask used best in?

Answer 15

A chronic CO2 retained

Question 16

What is high flow nasal cannula?

Answer 16

Uses humidified and warmed oxygen so it can be delivered in rate of 40-60L/min

Question 17

What is selenium important for?

Answer 17

Glutathione synthesis

It is essential to glutathione peroxidase which is the enzyme that catalyzes the reduction of hydrogen peroxide to water

Question 18

What is the highest daily dose of selenium?

Answer 18

200 micrograms

Question 19

How does vitamin E work?

Answer 19

It stops the progression of lipid peroxidation in the cell membrane by donating an electron to the free radical intermediate and becoming an inert free radical itself

Question 20

What is the blood level for a vitamin E deficiency?

Answer 20

Less than 0.5 mg/dl

Question 21

How does vitamin C work?

Answer 21

It is a scavenger for superoxide and hydroxyl radicals in the extra cellular space

Question 22

Which 2 molecules account for most of the antioxidant activity in plasma?

Answer 22

Ceruplasmin

Transferrin

Question 23

How do ceruloplasmin and transferrin work as antioxidants

Answer 23

They limit free iron in the reduced form thereby limiting the production of hydroxyl

Ceruloplasmin oxidizes iron to Fe3+ and then transfer in binds iron

Question 24

What is the threshold FiO2 for inflammatory lung injury?

Answer 24

60%

Question 25

What is the definition of hypoxemia?

Answer 25

PaO2 less than 60

O2 sat less than 90%