Oxygen therapy is indicated for patients with low blood oxygen levels and is commonly provided after surgery. Supplemental oxygen can be administered through a nasal cannula, which provides oxygen through prongs in the nose and is comfortable for patients. The amount of oxygen received depends on factors like flow rate and breathing. A flow of 6L/min provides about 44% inhaled oxygen. Different types of face masks provide varying oxygen concentrations depending on their design and flow rates, such as whether they include reservoirs or valves. Air-entrainment masks use the Venturi effect to mix oxygen and room air for stable oxygen levels.

1. Oxygen therapy
Oxygen therapy administered as increased
inhaled concentration of oxygen is indicated
for a PaO2 lower than 60 mmHg.
Supplemental inspired oxygen is often routinely
provided in the post operative period
regardless of the duration or type of surgery.

2. In the presence of chronic obstructive
pulmonary disease associated with carbon
dioxide retention, graded doses of
supplemental oxygen administered via an air
entrainment (Venturi) mask increase the
patient’s PaO2 to acceptable level

3. Nasal Cannula
Supplemental oxygen can be administered
through a nasal cannula with minimal patient
discomfort.
A nasal cannula incorporates two prongs that
extend about 1 cm into the patient’s nares
and is held in place by an adjustable elastic
head strap

5. Inspired oxygen concentrations achieved with
nasal cannula depends on:
1. The flow rate of oxygen through the flow
meter (L/min)
2. Patient’s tidal volume
3. breathing frequency
4. Volume of nasopharynx

7. Oxygen flow rate 6L/min gives inhaled oxygen
concentrations about 44%
Excessive flow rates of oxygen may result in air
swallowing and gastric distension without increasing
inhaled oxygen concentration
Mouth breathing does not decrease the effectiveness
of oxygen therapy delivered by nasal cannula
because inspiratory airflow through the posterior
pharynx entrains oxygen from the nose

10. Face Mask
Face masks used for oxygen therapy are
categorised as:
• Simple
• Partial rebreathing
• Nonrebreathing
• Air-entrainment

12. Simple Face mask
• It does not include a valve or oxygen reservoir
bag
• can provide inhaled concentration of oxygen
between 35% and 50% with O2 flow rate of 5-
8 L/min
• Provides little advantage over nasal cannula in
term of delivering constant inhaled
concentrations of oxygen

14. Partial Rebreathing
Its valveless system that includes an O2 resrvoir
bag
With O2 flow10L/min the inhaled concentration
of oxygen are between 50-60%

16. Non rebreathing
It includes a unidirectional valve plus an oxygen
reservoir bag
Inhaled concentration of O2 can reach 100% if
the mask was fixed tight on the patient face to
completely eliminate entrainment of room air
The flow rate of oxygen into this system should
be sufficient to maintain an inflated reservoir
bag

18. Air-Entrainment (Ventimask)
Venturi Face mask
It employs the Bernolli principle to entrain large
volumes of room air to mix with oxygen flowing
through an injector the resultant mixture of gases
produces stable inhaled concentrations of
oxygen(24-50%) depending on the bore of the O2
injector
The high flow of gas into the face mask result in
constant inhaled concentrations of O2 despite of
changes in the patient ventilation