Oxygen Therapy 101

Are oxygenation and ventilation the same thing?

No

Oxygenation

• getting O2 from the alveoli to the blood

• assessed using SpO2/PaO2

• supplemental O2 can improve oxygenation

Ventilation

• moving air in and out of the lungs

• removes CO2

• assessed using PaCO2

The role of supplemental oxygen in terms of oxygenation and ventilation

Supplemental oxygen CAN improve oxygenation, but does NOT NECESSARILY correct inadequate ventilation

Oxygen Source

Where the oxygen comes from (ex. wall oxygen or portable cylinder)

Flow Rate

How quickly oxygen is flowing from the source

• measured in liters per minute (L/min)

Interface

What delivers the oxygen to the patient (ex. nasal cannula or mask)

FiO2 →fraction of inspired oxygen

The concentration of oxygen in the gas the patient breathes in

• as FiO2 increases, stability of the patient is lower

Flow rate is not the same as FiO2? Why?

Flow rate

• how much gas is flowing

• expressed in L/min

FiO2

• the concentration of oxygen in the gas the patient inspires

• expressed as a fraction or percent

*with many interfaces the patient breathes a mixture of: supplemental O2 and room air (therefore exact FiO2 may vary)

Lower FiO2

Lower oxygen flow (i.e. 2L/min)→more room air entrained

When does the delivered FiO2 get closer to the anticipated FiO2?

Higher oxygen flow (10L/min) →less room air entrained

Why is FiO2 variable?

The amount of room air mixed with the delivered oxygen depends on both the oxygen flow rate and the patient’s breathing pattern and inspiratory demands

What does the FiO2 actually mean for the patient?

• higher FiO2 increases the oxygen available in the alveoli for gas exchange

• a patient requiring 90% (0.9) FiO2 has a high supplemental oxygen requirement and may have significantly impaired oxygenation

• higher FiO2 foes not necessarily mean better SpO2 or adequate ventilation

*FiO2 tells us the oxygen concentration being delivered not how well the patients lungs are transferring oxygen into the blood

Two patients have an SpO2 of 94% at rest, patient A receives 30% FiO2 and patient B receives 90% FiO2.

1. Are these patients equally stable?

2. What does this suggest about their oxygen reserve?

3. What are the implications for mobilization?

1. No, patient B requires substantially more oxygen to maintain the same SpO2

2. Patient B likely has less oxygen reserve despite the same SpO2

3. Patient B is at greater risk of desaturation as oxygen demands increase. Assess stability and clarify with the team before mobilizing

Wall oxygen

• connected to an oxygen flowmeter

• flow set in L/min

• commonly 0.5 or 1L/min intervals, depending on the flow meter

Portable oxygen cylinder

• used for mobility and patient transport

• flow set at the regulator

• often uses a dial with a fixed flow setting (i.e. 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, 15)

****check how much oxygen is remaining before leaving the bedside

PT mobility considerations

• secure the cylinder in an appropriate holder (cart, wheelchair, or walker)

• check oxygen supply is sufficient for the planned activity

• plan equipment management: can one person safely assist the patient and manage the oxygen?

IMPORTANT: never carry or balance an unsecured oxygen cylinder on mobility equipment

For PTs, what are our concerns with the interfaces?

• mobility

• eating/talking

• tubing management

• equipment required

Variable FiO2

The amount of oxygen inhaled can vary with the patient’s breathing

Fixed/controlled FiO2

Designed to deliver a specified oxygen concentration

Nasal Cannula/Nasal Prongs

Flow: ~0.5-6L/min

FiO2: 24-44% (variable)

• oxygen delivered through nasal prongs mixes with room air →exact FiO2 varies

• comfortable; allows eating, talking, coughing, and mobility

PT perspective on nasal cannulas

• mobility-friendly

• extension tubing may be used with appropriate low-flow systems

• watch for tubing kinks, disconnection and trip hazards

Higher-Flow Nasal Prongs

Flow:~6-15L/min

FiO2: 24-60% (variable)

• larger-bore prongs/tubing delivers higher O2 flows

• room air mixing →variable FiO2

• humidification may be used to reduce airway drying and discomfort

How to recognize higher-flow nasal prongs

• larger prongs and thicker tubing than standard nasal cannula

• often green tubing (but colour varies by manufacturer)

PT perspective on higher-flow nasal prongs

• allows eating, talking, and mobility

• higher O2 requirement →assess stability and portable O2 supply

• do NOT add extension tubing unless approved for the specific system; added resistance may limit flow

Simple Face Mask

Flow: ~5-10L/min

FiO2: 35-60% (variable)

• covers nose and mouth; O2 mixes with room air

• FiO2 depends on breathing pattern and mask fit

• minimum flow ~5L/min to flush exhaled CO2 and reduce rebreathing

PT perspective on simple face mask

• more restrictive than nasal cannula; interferes with eating, drinking, and talking

• maintain mask position and manage tubing during mobility

OxyMask

Flow: ~1-15L/min

FiO2: ~24-90% (variable)

• open mask design allows room air entry

• delivers a wide range of O2 concentrations depending on flow and patient factors

• often better tolerated than enclosed masks (less claustrophobic)

PT perspective on OxyMask

• mobility possible; ensure correct mask position and tubing management

• eating/drinking may require temporary removal or adjustment

Venturi Mask

Flow: device specific

FiO2:~24-60% (fixed/controlled)

It delivers fixed O2 by:

• oxygen passes through a specially desinged adapter

• the adapter draws in a controlled amount of room air to mix with the oxygen

• each adapter setting produces a specific oxygen concentration (FiO2) when the prescribed flow is used

**unlike nasal prongs, the delivered FiO2 remains relatively constant despite changes in breathing pattern, provided total flow meets the patients inspiratory demands (they are breathing what is controlled, no room air)

PT perspective on venturi mask

• allows mobilization with an appropriate portable oxygen supply

• maintain the prescribed adapter setting and oxygen flow

• DO NOT block air-entrainment ports or change oxygen flow arbitrarily

Heated High-Flow Nasal Cannula (HFNC)

Flow: up to ~60L/min

FiO2: 21-100% (controlled)

• delivers heated, humidified gas at high flow rates

• flow and FiO2 are set independently

• high flow minimizes room-air mixing →delivered FiO2 closely matches the set FiO2

• mouth breathing or high inspiratory demands may increase room-air mixing

common systems: AIRVO/Optiflow

PT perspective on heated high-flow nasal cannula (HFNC)

• mobilization may be possible if clinically stable (typically only EOB and maybe not even then)

• assess oxygen requirements (flow/FiO2) and SpO2 response

• plan for equipment, tubing length, and oxygen supply

• coordinate with RT and follow local procedures

Non-rebreather mask

Flow: ~10-15L/min

FiO2:~60-90% (variable)

• reservoir bag: stores oxygen to deliver high concentrations during inspiration

• one-way valves: limit room-air entry and prevent rebreathing of exhaled gas

so why is FiO2 variable?

• depends on mask fit, oxygen flow rate and patient’s inspiratory demands

Important: reservoir bag must remain adequately inflated during inspiration

PT perspective on non-rebreather mask

• high oxygen requirement → assess clinical stability before activity

• determine whether oxygen needs are stable or increasing

• prioritize positioning, respiratory care, ROM and bed mobility, as appropriate

• more advanced mobilization requires careful assessment and monitoring

Oxygen is a medication:

It should have a reason, dose, and target

Before treating a patient receiving oxygen, know:

• why are they receiving it?

• what interface are they using?

• what flow rate/ FiO2?

• what is their prescribed SpO2 target?

• is this their usual oxygen requirements?

• has their oxygen requirement increased?

Important precautions for working with a patient receiving oxygen

• oxygen supports combustion: no smoking or open flames

• use oxygen to achieve the prescribed SpO2 target

• excessive oxygen can be harmful

• some patients require lower SpO2 targets

Can a PT adjust oxygen?

In Nova Scotia, YES, under specific conditions

• PTs may titrate, with typical nasal cannulas, low-flow oxygen (0-6L/min) during treatment when:

  • there is a written physical prescription with a target SpO2/range

  • the PT has required knowledge and competence

  • changes are communicated and documented

  • employer policies/procedures are followed

What don’t PTs have authority to do

• do NOT adjust high-flow oxygen

• changing the oxygen delivery device

What should you do before mobilizing a patient who is using supplemental oxygen?

Check the oxygen prescription an oxygen equipment

Check the oxygen prescription

• interface and flow rate/FiO2

• prescribed SpO2 target

• baseline versus current oxygen requirement

Check the oxygen equipment

• correct connections and flow settings

• adequate tubing length and safe positioning

• portable oxygen available and sufficient for activity

• equipment secured and manageable during mobility

Why is it important to monitor oxygen delivery during mobility?

A drop in SpO2 may reflect a problem with oxygen delivery, not necessarily deterioration in the patient’s respiratory condition

• is SpO2 within the prescribed target during activity?

• does the patient require more oxygen during activity than at rest?

• has the mask or cannula become displaced?

• is tubing kinked, disconnected or creating a trip hazard?

• is the portable oxygen supply adequate?

Key PT considerations for each oxygen interface:

1. Nasal cannula→ manage tubing; extension tubing may be used

2. Higher-flow nasal prongs → avoid extension tubing; check humidification

3. Simple face mask: maintain >/= 5L/min to minimize CO2 rebreathing

4. OxyMask →maintain correct mask position

5. Venturi mask → keep entrainment ports clear; maintain prescribed settings

6. Non-rebreather → ensure reservoir bag remains inflated; assess stability

7. Heated HFNC → specialized equipment; coordinate mobility with RT

**know the interface, oxygen requirements and prescribed SpO2 target. Ensure safe oxygen delivery throughout mobility