Oxygen Therapy Flashcards
How easy is it for the first oxygen molecules to bind to Hb?
- very hard
- needs to be saturated
How easy is it for the second oxygen molecule to bind to Hb?
- co-operative binding via confirmational change
- easy for 2nd one to bind
- same for 3rd and 4th
What does the oxygen-Hb dissociation curve show you?
- O2 sat % against change in PO2
- sigmoid shape due to co-operative binding
What factor shifts the ox-Hb curve right?
- CO2 increase (Bohr Shift)
- pH decrease
- Temp
- exercise
- 2-3 DPG
What happens to oxygen release when you move the curve to the right?
- easier
Supply of oxygen forms in hospital
- wall
- cylinder
BTS Guideliness
- above 94% sats target
- 88-92% target if at risk of T2 resp failure
- COPD use venture mask
BTS Critical Illness Ox advnce
High levels of oxygen supplementation
15L of high flow
BTS Stable Patients Ox advice
- nasal cannulae low dose
Harmful effects of oxygen
- free radicalisation = toxicity
- flammable = explosion risk
- can cause vasoconstriction of pulmonary circulation
- loss of hypoxic drive
Oxygen delivery devices
- venturi = fixed conc.
- simple face mask
- non rebreathe reservoir bag
- nasal cannulae
Nasal cannulae
- 2-5L/min
- conc between 25-50%
- resp failure
- for stable patients
- over face mask as more comfortable
- low cost
- no-rebreathing
- easily tolerated
Simple face Mask
- medium conc
- variable performance
- type 1 resp failure
- 5-10L/min
- variable conc 35-60%
- flow at least 5L/min to avoid CO2 build up
Humidification purpose and how
- done normally by nasal cavities
- stops airways becoming dry so less thick secretions
- if giving medium to high flow oxygen for more than 24 hours should be humidified
High Conc Reservoir Mask
- non-rebreathe
- trauma/critical illness
- post-cardiac or resp arrest
- ST treatment
- 70-80% conc
High Flow Nasal Cannulae
- critical illness
- flows up to 60L/mind
- humified and warm
- LT use if higher conc required
- can provide PEEP 7.4cm H20 at 60L/min
Define PEEP
Positive End Expiratory Pressure
- normally 5cm of water
- keeps alveoli open when expire
- prevents alveoli collapsing
Venturi or Fixed Peformance Masks
- colour coded
- deliver constant ox conc
- fixed performance device
- increasing flow does not increase ox conc.
- fixed sized air slots allowing fixed size concentration of air
- conc depends on size of air slot
Blue venturi mask
24%
2L min
White venturi mask
28%
4L min
Yellow venturi mask
35%
8L min
Red venturi mask
40%
8L min
Green venturi mask
60%
5L min
What is the worry with COPD patients?
- some are CO2 retainers (5-15%)
- hypercapnic state is what induces oxygen drive
- if give oxygen = wont have drive to breathe = hypercapnia
