oxygen supply

Question 1

what is venturi mask?

Answer 1

•this has a jet adapater placed between the mask & the tubing of the oxygen source.
•the jet adapter comes in various sizes (& are often color coded)coressponding to various Fi02 values 
-blue 24%
-white 28%
-orange 31%
-yellow 35%
-red 40%
-green 60%

• it operates on bernoulli principle of air entrainment.
• as gas flow under pressure at a rapid flow rate through the narrow orifice of the jet adapter
• an area of subatmospheric pressure develop lateral to the small opening.
• this create a “jet drag” that leads to entrainment of room air through side ports located on the adapter.
• the fio2 modified by either by altering the size of side ports or by the altering the jet orcifice diameter , both of which affect the amount of air entrained. the appropriate flow rate is usually inscribed on the jet adapter

Question 2

advantage in venturi mask?

Answer 2

• delivery of very predictable Fi02

- useful in hypoxemic copd pt. where delivery of excessive oxygen could depress the respiratory rate

Question 3

what are disadvantages in venturi mask?

Answer 3

• claustrophobic feeling generated by mask
• limited access to mouth eating , drinking, expectorating
• eye irritation from high flow rates of oxygen & improper fit at the nose

Question 4

what is partial re breathing mask?

Answer 4

• mask alongwith on oxygen reservior bag
• increasing the oxygen reservior beyond the size of the anatomic reservoir allows the delivery of an fi02 greater than 0.60

Question 5

what is the mechanism of partial re breathing mask?

Answer 5

during inspiration , pt draws air from the mask,bag & through the holes in side of the mask

•during exhalation , the first third of exhaled gases flows back into the reservoir bag
•the position of exhaled gas comes from the anatomic dead space & is thus reach in oxygen
,humidified and warmed and contains little carbon di oxide
•if oxygen flows is high enough to keep the bag from deflating more than 1/3rd its volume during inhalation , the exhaled co2 does not accumulate in the reservoir bag
•on the next breath the pt. inspire part of previously exhaled gases alongwith 100% oxygen from the source

Question 6

ada vantage in partial re breather mask?

Answer 6

-fi02>0.60 is delivered in moderate to severe hypoxemia

•exhaled oxygen from the anatomic dead space is conserved

Question 7

disadvantages in partial re breather mask?

Answer 7

•insufficient flow rate may lead to rebreathing of co2
•mask over mouth may lead to feeling of claustrophobic
•limited access to mouth eating , drinking, expectorating
-eye irritation from high flow rates of oxygen & improper fit at the nose