Oxygen Therapy & Humidification (Wk1)

Question 1

what is O2 therapy used for?

Answer 1

• hypoxaemia ( low concentration of oxygen in the blood)
• some cardiac conditions

Question 2

what is O2 therapy titrated to meet?

Answer 2

target SpO2/ PaO2 which depends on the patient’s:
- age
- clinical condition
- risk factors for receiving supplemental O2

Question 3

Target SaO2 for acutely ill patients

Answer 3

94-98%

Question 4

Target SaO2 for those at risk of hypercapnic respiratory failure

Answer 4

88-92%

Question 5

medical management to improve PaO2

Answer 5

• increase FiO2 via oxygen therapy
• increase SA (FRC) for gas exchangeh

Question 6

how does increasing the FiO2 via O2 therapy increase PaO2

Answer 6

increases PAO2 (in alveoli), and therefore by diffusion, increases PaO2 in arteries (arteries surround the capillaries; oxygen diffuses across the alv cap membrane into artieries)

Question 7

physio strategies to increase PaO2 in hypoxaemic patients

Answer 7

increase SA (FRC) for gas exchange (e.g. via positioning, DB with IH)

Question 8

how much O2 is in room air?

Answer 8

21%

Question 9

how much CO2 is in room air?

Answer 9

0.03%

Question 10

how much N2 is in room air?

Answer 10

79%

Question 11

PO2 journey through body

Answer 11

air –> upper airways –> alveoli –> interstitium –> blood –> tissues/cells

Question 12

is the PO2 in the air the same as the Po2 in the blood?

Answer 12

no

Question 13

factors that contribute to the difference in the partial pressure of the O2 in air vs in blood

Answer 13

• humidification of inspired gas
• gas mixing in airways
• gas exchange across the alveoli-capillary unit

Question 14

PO2 in air

Answer 14

21% x 760 mmHg = 159 mmHg

Question 15

what reduces the PO2 in the upper airway?

Answer 15

air is warmed and humidified, introducing significant water vapor, reducing the PO2

Question 16

PO2 in the upper airway

Answer 16

21% x (760-47) = 149 mmHg

Question 17

why is the PO2 in the alveoli < than the PO2 in the upper airway?

Answer 17

gas mixing occurs (alveolar & dead space) so that the PO2 in the alveoli is less than in the upper AW

Question 18

what is the PaO2 in the blood vs to PAO2 in alveoli?

Answer 18

lower

Question 19

what is the difference between PaO2 and PAO2 known as?

Answer 19

A-a gradient (alveolus-arterial blood supply)

Question 20

what is a normal A-a gradient for a young adult smoker on room air?

Answer 20

5-10 mmHg

Question 21

does the A-a gradient increase or decrease with age?

Answer 21

increase (range 5-25mmHg)

Question 22

normal PaO2

Answer 22

80-100 mmHg

Question 23

OXYGEN TRANSPORT SYSTEM
what is external air affected by?

Answer 23

• FiO2
• Barometric pressure
• amount of fresh gas inspired

Question 24

OXYGEN TRANSPORT SYSTEM
what are alveoli affected by?

Answer 24

decreased surface area for gas exchange

Question 25

OXYGEN TRANSPORT SYSTEM what are the interstitium affected by?

Answer 25

decreased diffusion

Question 26

OXYGEN TRANSPORT SYSTEM what is PaO2 in blood affected by?

Answer 26

- decreased lung perfusion - decreased cardiac output

Question 27

OXYGEN TRANSPORT SYSTEM what is O2 in the tissues/ cells affected by?

Answer 27

decreased oxygen extraction & utilisation

Question 28

options for oxygen therapy delivery?

Answer 28

- piped system (through the wall) (cold & dry) - O2 cylinder (cold & dry) - O2 concentrator (at room temp & humidity)

Question 29

what 2 factors determine how much O2 the patient receives on O2 therapy?

Answer 29

1. FLOW from the O2 therapy device 2. the patient's demand for FLOW

Question 30

what is the definition of the the FLOW from the O2 therapy device?

Answer 30

the flow rate of the O2 that's being delivered to the patient (e.g. in L/min)

Question 31

are O2 delivery systems/ devices classified as high/ low flow?

Answer 31

either

Question 32

what is the patient's demand for FLOW?

Answer 32

ptnt's own camera inspiratory flow rate (PIFR)

Question 33

can patient's have a normal / higher than normal IFR?

Answer 33

both