Gas Delivery Devices

Requirements for an O2 Order

• FIO2 or flow rate

• Delivery device

• When the device must be worn (PRN or continuous)

• Protocols

Indications for O2

• Documented hypoxemia

• Acute situations in which hypoxemia/hypoxia is suspected

• Severe trauma

• Acute myocardial infarction (? But still common practice)

• Post anesthesia (short term)

• Fire or noxious gas exposure

Contraindications for O2

• NO specific contraindications if indications are present (ductal dependent heart lesions)

• Hazards and complications

What is the drawback of low flow systems?

The actual FIO2 delivered with any low flow system is variable and unpredictable

Types of Low Flow Devices

Nasal Cannula

Simple Mask

Partial-Rebreathing Mask

Non-Rebreather Mask

Increased respiratory rates and tidal volumes will result in....

a decrease in the delivered FIO2

Types of Reservoir Masks (low-flow)

Simple Mask

Partial-Rebreathing Mask

Non-Rebreather Mask

High Flow Systems

• A system that is capable of meeting the patient's entire inspiratory flow demand without the addition of room air

• Consistent and predictable

• The device (total) flow (not flowmeter flow rate) must exceed the flow demand of the patient

• Has to provide 60 lpm total flow - based on the fact that average adult peak inspiratory flow during tidal breathing is about 3x VE -20 lpm is close to the upper limit of sustainable VE for someone that is ill - works for most

• All high flow systems mix O2 and air - they deliver a PRECISE FIO2, not necessarily a high FIO2

Air: Oxygen ratio

• Determines the delivered FIO2 and total flow

• Recommended flow rates and FIO2 levels available will depend upon the brand of the mask - always familiarize yourself with the type you will be using

What defines a low flow oxygen delivery device?

A system that does not match or exceed the patient's inspiratory flow needs, requiring the patient to entrain room air.

What factors affect the FIO2 delivered by low flow systems?

1) Flow rate of gas

2) Size of the patient's upper anatomical reservoir

3) Reservoir of the equipment

4) Patient's Minute Ventilation (RR, TV, and pattern)

What is the most effective respiratory rate and tidal volume for low flow systems?

Respiratory rate < 25 and tidal volume between 350-700 mls

What is the FIO2 range delivered by a nasal cannula?

Approximately 0.24 to 0.44, depending on the flow rate (1-6 LPM)

What is the Rule of Fours for nasal cannula oxygen delivery?

The oxygen percentage increases by 4% for every liter of flow

(1 LPM = 24%, 2 LPM = 28%, etc.).

Which device and at which flow would require a humidifier?

Nasal cannula at equal to or greater than 4 LPM

What should be charted for low flow devices?

Patient response and flow rate (not FIO2!)

What is the maximum FIO2 for a nasal cannula according to AARC guidelines?

The maximum FIO2 for a nasal cannula is 40%.

What is the minimum flow rate for a simple mask? Maximum?

A minimum of 5 LPM is necessary to wash CO2 from the mask, with a maximum of 10 LPM.

What is the FIO2 range delivered by a simple mask?

Delivers an FIO2 of 0.35 to 0.50, depending on the fit of the mask.

What is a partial-rebreathing mask?

A mask with a reservoir bag and no one-way valves that may deliver an FIO2 > 0.50 depending on mask fit.

What is the function of a non-rebreather mask?

Prevents rebreathing with one-way valves and can deliver 100% O2 if fitted tightly.

What is the minimum flow rate for a non-rebreather mask?

A minimum of 10 LPM is required to keep the bag inflated during inspiration.

What defines a high flow oxygen delivery system?

A system capable of meeting the patient's entire inspiratory flow demand without the addition of room air.

What is the total flow requirement for high flow systems?

The total flow must exceed 60 LPM to meet the average adult peak inspiratory flow during tidal breathing.

How do air-entrainment systems work?

They direct a high-pressure O2 source through a jet surrounded by air entrainment ports, with the amount of air entrained depending on port size and gas velocity.

High Flow- Air Entrainment Systems:

1. What effect do larger intake ports or higher gas velocity have on FIO2?

2. What happens when intake ports are smaller or gas velocity is lower?

1. They entrain more air, resulting in a lower FIO2.

2. Less air is entrained, leading to a higher FIO2.

What factors can vary among different manufacturers of high-flow devices?

Port size, jet size, or a combination of both.

What is the purpose of the air/oxygen ratio in high-flow devices?

It determines the delivered FIO2 and total flow.

What is a Venti-mask?

An air-entrainment mask that delivers a specific FIO2, regulated by changing the size of the entrainment port.

What are the 2 types of Venti masks?

• Fixed orifice (jet stays the same) - FIO2 is regulated by changing the size of the entrainment port

• Variable orifice (jet size changes) - FIO2 is regulated by changing the size of the orifice

How does downstream resistance affect FIO2 in high-flow devices?

It decreases air entrainment and total flow, likely increasing FIO2.

What are large volume nebulizers used for?

They deliver an aerosol via a venturi device, bottle of water, aerosol tubing, and a delivery device.

What types of devices fall under aerosol delivery systems?

T-Bar, T-Piece, tracheostomy collar, aerosol mask, face tent, face shield, oxyhood, and croup tent.

1. What is the advantage of using tandem nebulizers?

2. Which O2 device can do this?

1. They can increase flow by combining two nebulizers.

2. Large volume nebulizers can combine 2 nebulizers via venti mask.

What is transtracheal oxygen?

A low flow oxygen delivery method using a 16-gauge catheter inserted directly into the trachea.

What are the advantages of transtracheal oxygen delivery?

It is comfortable, cosmetically acceptable, and allows for normal activities like eating and washing.

What complications can arise from transtracheal oxygen use?

Accidental removal, irritation and infection of the site, and blockage of the catheter.

What is the function of reservoir systems in oxygen delivery?

They gather and store O2, decreasing room air entrainment and increasing inspired FIO2.

What is the formula used to estimate flow needs in high-flow systems?

VE x 3

What are air/O2 blenders used for?

They mix air and oxygen to deliver a precise FIO2, with alarms for source failure.

How often should FIO2 be confirmed with an analyzer in blended systems?

At least once per shift.

What are demand flow and pulse dose systems designed to do?

They synchronize gas delivery with inspiration to extend the duration of tanks.

What is the indication for using high-flow oxygen therapy?

For patients with respiratory insufficiency who do not respond to traditional oxygen methods.

High-flow nasal cannula (HFNC)

1. What is this device?

2. Function?

1. Heated, humidified O2 that may be delivered at flows up to 60 lpm - up to 90% O2 via a specialized NC (Vaoptherm, Airvo, Opti-Flow)

2. Provide undetermined amount of positive pressure, reduces anatomical deadspace

What are the indications for using high-flow nasal cannula (HFNC)?

• Hypoxemic and Hypercapneic Respiratory Failure

• Reduction of Reintubation risk

• DNI or Hospice patients

• Inability to tolerate other devices

What factors should be considered when deciding on an oxygen delivery device?

Severity of hypoxemia, patient characteristics, and the device's purpose and performance.

What should be done if tissue hypoxia is suspected?

Always use the highest FIO2 possible

What type of patients require a reservoir or high flow system for oxygen therapy?

Critically ill patients with moderate to severe hypoxemia.

What oxygen delivery method is suitable for patients with mild to moderate hypoxemia?

A low flow device

What is the oxygen requirement for patients with COPD and acute-on-chronic hypoxemia?

They need adequate oxygen but not too much to avoid depression of drive; typically low flow nasal cannula or low FIO2 air entrainment mask.

1. What is the primary type of oxygen analyzer in use today?

2. What are the 2 types of this O2 analyzer?

1. Electrochemical analyzers

2. Galvanic Fuel Cell and Polarographic

How does a Galvanic Fuel Cell oxygen analyzer work?

It consumes O2 to generate a low electric current, which is measured to determine FIO2, and requires no power source.

What is the function of a Polarographic oxygen analyzer? Drawbacks?

It uses a Clark electrode and a battery to speed up the reaction, but its accuracy can be affected by altitude, positive pressure, and humidity.

What are common issues that can affect the accuracy of oxygen analyzers?

Low batteries, sensor depletion, and electronic failure.

What should be analyzed on your NBRC exam regarding oxygen?

Almost all oxygen delivered should be analyzed

What are the indications for using Heliox therapy?

Upper airway obstructions, post-extubation stridor, acute severe asthma, and croup.

Why is Heliox so useful for obstructions?

Helium is light, allowing it to flow around the obstruction.

What is the technique for administering Heliox therapy?

Using a well-fitting non-rebreather mask or endotracheal tube with cuff.

1. How do you calculate the actual flow of Heliox from an oxygen flowmeter for an 80:20 mixture?

2. How do you calculate the actual flow of Heliox from an oxygen flowmeter for a 70:30 mixture?

1. Multiply the displayed flow by a factor of 1.8

2. Multiply the displayed flow by a factor of 1.6

Why are the O2 flowmeters not accurate for heliox?

Low density of helium will result in a LOWER than actual reading on the O2 flowmeter.

What are some issues associated with Heliox therapy?

Altered pitch of voice, poor humidity and aerosol carrying, less effective coughing, and high cost.

What is Hyperbaric Oxygen Therapy?

The use of oxygen pressures greater than one atmosphere.

What are the two methods of administering Hyperbaric Oxygen Therapy?

Multiplace chamber- holds multiple patients

Monoplace chamber- holds one patient only

What are the physiological effects of Hyperbaric Oxygen Therapy?

• Bubble Reduction - high pressure decreases size (Boyle's Law)

• Hyperoxygenation of blood and tissue (Henry's Law)

• Vasoconstriction - offset by increase in O2 content, but beneficial for some problems

• Enhanced host immune function - increases PO2 of tissues

• Neovascularization - mechanism unknown

What are some indications for Hyperbaric Oxygen Therapy?

• Air Embolism, Decompression Sickness

• Carbon Monoxide or Cyanide Poisoning

• Traumatic ischemia

• Peripheral arterial insufficiency

• Intracranial abscess

• Tissue infections/Gangrene

• Ischemic skin grafts

• Osteomyelitis

• Any non-healing wound

• Actinomycosis

• Radiation necrosis

What are potential complications of Hyperbaric Oxygen Therapy?

• Ear and sinus trauma

• O2 Toxicity

• Reversible visual changes

• Claustrophobia

• Avoiding fires and sudden decompression are the major safety concerns

What safety precautions must be taken during Hyperbaric Oxygen Therapy?

Avoiding fires and sudden decompression.

• Patients must wear 100% cotton (no static)

• No alcohol or petroleum based products

• No hairspray or cologne, no make-up, no deodorant