low flow systems

Question 1

what is a low flow system

Answer 1

oxygen gas devices that does not meet or supply all of the patient’s inspiratory demand. a high flow system does meet all demand.

Question 2

FiO2 depends on :

Answer 2

reservoir size ( reservoir bag or nasal cavity)
patient's ventilatory pattern(RR or Vt) 
oxygen flow ( increase or decrease)

Question 3

low flow ( pro’s and con’s)

Answer 3

pro’s- easy to set up and can deliver low and high FiO2

con’s- FiO2 is a variable

Question 4

What’s the range for a low flow system

Answer 4

Vt 300-700mL

RR< 25

Question 5

when is a low system suitable

Answer 5

when the respiratory pattern is consistent and regular

when a consistent predictable FiO2 is no required.

Question 6

high flow system

Answer 6

meet or exceeds all the patient’s inspiratory flow demands.
-Enables delivery of a specific, or guaranteed FiO2
To determine your patient’s high flow requirements you need to know some of the following:
Minute Volume and Vt
Cycle Time
Inspiratory Time
Expiratory Time
Inspiratory Flow

Question 7

pros and cons of high flow system

Answer 7

pros- constant and predictable FiO2 
you can humidity and temperature of gas being delivered.
can deliver high/low FiO2
cons
expensive, time consuming to set up

Question 8

nasal catheter

Answer 8

024-0.44 (1-6)
Inserted through the nasal passage until the tip sits behind the uvula ; not visible in the oropharynx
Pros:
None, some use in the immediate post-op period
Cons:
uncomfortable, have a tendency to plug so need to be changed regularly

Question 9

nasal cannula

Answer 9

0.24-0.44
Flow:
Up to 6 lpm
Application:
Cannula sits just inside nares, while tubing rests over top of ears
Pros:
Uses the upper airway as a gas reservoir
Commonly used so all staff familiar with it
Cons:
Can be uncomfortable at higher flows due to dryness
Above 4LPM use humidifier as per AARC guidelines

Question 10

simple mask

Answer 10

FiO2’s: 
0.40 - 0.60
Flow:
5 - 10 lpm
Application:
Mask covers mouth and nose, with an adjustable metal tab that covers bridge of nose, and flexible straps behind the head

Question 11

simple mask pros and cons

Answer 11

Pros:
Higher FiO2’s possible because mask acts as an additional oxygen reservoir
Can attach to a nebulizer to deliver medications, humidity – not routinely done

Cons:
Patient unable to eat/ drink without removing the mask
Speech may be muffled
Flow must be > 5 lpm to avoid dangerous CO2 buildup
Patient compliance can be an issue – feelings of claustrophobia or “I can’t get enough air!”
Aspiration risk with emesis

Question 12

partial rebreathing mask

Answer 12

FiO2’s:
0.60-0.80 +
Flow:
Flow is set so the reservoir bag does not collapse on inspiration
In practice this is 6 - 15 LPM – commonly just set to 15 LPM*
At minimum 6 LPM to avoid collection and rebreathing of CO2 – there must be enough flow to wash out mask, aka 6 LPM!
Application:
Same as simple mask but with higher FiO2 capability
Variable FiO2 , as always, based on patient RR, Vt, therefore titrate to each patient and their reported lab/saturation values
“Titrate to effect”

Question 13

non rebreathing mask

Answer 13

FiO2’s:
> 0.80
Flow:
As with partial rebreather, flow is set to keep bag inflated at all times – peak inspiration and exhalation
Application:
Ca be packaged with 3 valves, be sure to remove one side valve
This removes suffocation risk with source gas failure
Exhaled air does not go into the bag because of one-way valve positioning, rather the bag is filled completely by the oxygen source
Also has a valve on mask that minimize entrainment of room air on inspiration
(not use in the edmonton region at all)