This document discusses various oxygen therapy devices: 1. It classifies devices as fixed or variable performance, patient dependent or independent, and low, reservoir, or high flow. Nasal prongs and Hudson masks are examples of low flow devices while venturi masks are high flow. 2. Nasal prongs deliver 1-6 L/min of oxygen but allow a large fraction of inspired volume from room air. Hudson masks deliver 5-10 L/min and have a maximum FiO2 of 60%. 3. Reservoir bags attached to masks can increase oxygen concentration delivered. Partial rebreathers allow some exhaled gas to re-enter the bag while non-rebreathers prevent inhaling room

1. Oxygen Therapy Devices
Dr. Swarnalingam Thangavelu M.D
Associate Professor
Department of Anaesthesiology,
Tagore Medical College & Hopsital

2. Basics

3. Peak Inspiratory flow- Importance
The flow at the peak of inspiration is called peak
inspiratory flow rate

4.  Respiratory rate: 10/minute
 Each respiratory cycle lasts for 6 seconds
I:E 1:2
Inspiratory time: 2 seconds
Tidal volume -500ml (Must be inspired during 2 seconds)
 0.25L/sec or 15L/minute---- Mean inspiratory flow

5. INSPIRATORYFLOW(L/min)
Start inspiration
Time 0
End inspiration
Time 2 sec
0
15
50

6. Air Entrainment
When a patient is being given Oxygen, there is a
flow below which a patient entrains air from the
atmosphere
Depends on the Oxygen therapy device and the
patient’s respiratory pattern

8. Classification of O2 Therapy Devices
Fixed/Variable Performance
Patient Dependent/Patient Independent
Low Flow/Resorvoir/High Flow

9. Fixed performance devices Variable performance devices
Fixed concentration of Oxygen
irrespective of the minute volume or
peak inspiratory flow rate of the
patient.
Variable oxygen concentration
depending on the minute volume or
peak inspiratory flow rate
Examples:
1. Venturi mask (Air entrainment mask)
2. Mask with reservoir bag and a non-
rebreathing valve
Examples:
1. Nasal prongs
2. Hudson mask ( Simple face mask)

10. Patient Dependent Device Patient Independent Device
Flow of gas delivered < Peak
inspiratory flow
Flow of gas delivered > Peak
inspiratory flow
Oxygen concentration is patient
dependent
Oxygen concentration is patient
independent

11. High flow devices Low flow devices
Capable of delivering Oxygen at a
flow rate greater than Peak
inspiratory flow rate by virtue of
air entrainment.
Based on Venturi principle ( Jet
mixing)
Deliver a flow rate only up to 15
L/min which is much lower than
PIFR of the patient (35L/min)

13. Nasal Prongs or Nasal Cannula
Standard device for
low flow O2 therapy
Delivers O2 into the
naopharynx at flow
rate of 1-6L/min
Large fraction of the
inspired volume is
drawn from room air

14. Flow rate(L/min) Approximate FiO2
1 24%
2 28%
3 32%
4 36%
5 40%
6 44%

15. Advantages
• Simplicity of use
• Patient acceptance
• Ability to eat and talk
Disadvantages
• Inability to achieve high concentration of inhaled O2
• Particularly in patients with increased ventilatory demands

17. Standard face mask (Hudson mask)
Considered a reservoir
system because the
mask encloses a
volume of 100-200ml
Deliver O2 at flow rate
5-10L/min
Minimum flow rate of
5L/min is needed to
clear exhaled gases
from the mask
Exhalation ports on the
side allows room air to
be inhaled
Maximum FiO2 of
about 60% during
quiet breathing

18. Advantages
• Slightly higher maximum FiO2 than low flow nasal prongs
Disadvantages
• Like nasal prongs, Fio2 varies with the ventilator demand of the
patient
• No oral feeding or conversation

20. Mask with reservoir bags
Addition of
reservoir bag to a
standard face
mask
Increases the
capacity of O2
reservoir by 600-
1000ml
If reservoir is
kept inflated, the
patient will draw
primarily from
the gas in the bag

21. Two types of Resorvoir bag
Partial Rebreather
Non-Rebreather

22. Partial Rebreather
Device allows the gas exhaled in the initial phase of expiration to return into
the reservoir bag
As exhalation proceeds and the expiratory flow rate declines
When expiratory flow rate falls below O2 flow rate, exhaled gas no
longer return to the reservoir bag
The patient can inhale room air through the exhalation ports on the mask
But the gas in the reservoir bag is under positive pressure and inhalation will draw
primarily from the gas in the bag. Maximum FiO2 of abourt 70%

23. Non- Rebreather
Expiratory ports
on the mask are
covered with
flaps that allow
exhaled to
escape but
prevent
inhalation of
room air gas
One way valve
situated between
the reservoir bag
and mask allows
inhalation of gas
from the bag but
prevents exhaled
gas from
entering the bag
Theoretically
achieve an FiO2
of 10O%.
But exactly
maximum FiO2
is closer to
80%(leaks
around the mask)

24. Advantage
• Ability to deliver higher concentration of inhaled O2
Disadvantages
• Same as for face mask
• Aerosolised bronchodilator therapy not possible

26. Air Entrainment Device
• High flow systems that deliver constant FiO2

27. End of O2 inlet port is narrowed that creates a high velocity stream of
gas
Creates a shearing force(viscous drag) which pulls room air into the
device through air entrainment ports
The greater the flow of O2 into the mask
The greater the volume of air that is entrained-keeps FiO2 constant
The final flow created by the device in excess of 60L/min. FiO2 can
be varied by changing the size of air entrainment port on the device

28. Mechanism of air entrainment is Jet mixing
Air entrainment was originally attributed to the venturi
effect( Pressure of a fluid decreases when the fluid
flows through the constricted section of the tube)
As a result masks were called venturi or venti
mask

29. Flow meter setting Total gas flow possible O2 Delivery
2-3L/min(Blue) 78L/min 24%
4-6L/min(White) 68L/min 28%
6-8L/min(Orange) 63L/min 31%
8-10L/min(Yellow) 56L/min 35%
12-15L/min(Green) 40L/min 60%

30. Advantages
• Ability to deliver a constant FiO2
• Desirable in patients with chronic CO2 retention( Inadvertent
increase in FiO2- further increase in arterial PCO2)
Disadvantages
• Inability to deliver higher concentration of inhaled O2

31. High Flow Nasal Oxygen
The newest technique of O2 delivery using heated (to body
temperature)and humidified gas(Supersaturated with water)
O2 flow rate up to 40-60 L/min can be delivered through wide
nasal prongs without discomfort and mucosal injury
Allows adjustment for flow rate 1-40L/min, FiO2 21-100%
Temperature 37 degree Celsius

32. Clinical Experience
Encouraging initial
experience
Significant
improvement in
measures of respiratory
distress along with
improved gas exchange
High flow nasal O2
creates positive
pressure in nasopharynx
It could act like PEEP
to prevent collapse of
alveoli at the end of
expiration
It avoids intubation and
mechanical ventilation

33. T
A
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34. YOU