Supplemental Oxygen

Placing patients on oxygen is one of the simplest and most effective interventions used to stabilize a vast number of medical complaints. This section will review the different devices used to deliver and transport oxygen and how you might choose one over the other based on patient presentation.

 

Portable Oxygen Cylinders

Portable oxygen cylinders are the most common form of oxygen available in the field. Become comfortable with the different types of cylinders and their operation.

SIZES:

Size D cylinders hold 350 liters of oxygen and last about 30 minutes at 10LPM, a common flow rate for non-rebreather facemasks.

Size E cylinders hold 625 liters and last about an hour at 10LPM.

Size G Tanks, which hold 5,300 liters, are generally found on board BLS and ACLS ambulances. They will generally hold enough oxygen for any call if they are refilled at appropriate intervals. 
 

REGULATOR: Each oxygen cylinder has a regulator that controls the flow of oxygen. The oxygen cylinders designed for medical use are designed to allow only medical-grade regulators to be attached--and only in one configuration. The indentations on the cylinder match up with pins on the regulator and allow for smooth and tight connection when secured to the cylinder

 

Connecting a Cylinder

To connect a regulator to a cylinder;

1. If present, remove the plastic cap on the cylinder.
2. Slide the regulator over the top of the cylinder.
3. Line up the pins and indentations present on the cylinder and regulator.
4. Secure the screw mechanism on the regulator until it is tight, and there is no movement between the regulator and cylinder.
5. Make sure the regulator is in the off position, take the oxygen-cylinder wrench and turn the cylinder on, then quickly turn it back off.

 

• If any escaping air is observed, the regulator should be checked for a secure fit on the cylinder; if the fit is questionable, it should be taken out of service for maintenance.
• If no escaping air is observed, turn the cylinder back on and test the regulator by turning it to a chosen flow rate. The pressure indicator on the regulator shows the internal pressure of the oxygen cylinder.
• A safe residual for operation is 200 psi, but this changes with each service, so check your local shop's manual of standards and regulations.

SAFETY: Always secure assembled oxygen cylinders at all times, and do not leave them unsupported in upright positions where they could fall. A significant impact can damage the regulator/tank assembly, leading to ineffective delivery or dangerous release of high-pressure gas. 

Oxygen is highly flammable and should never be used or stored near an open flame.

 

Calculating Oxygen Cylinder Duration:

To determine how long an oxygen cylinder will last, use this formula: Duration (minutes) = (Cylinder volume × Cylinder pressure) ÷ (Flow rate × 760)

Example: For an E cylinder with 622 L capacity at 2000 PSI with a flow rate of 4 LPM: Duration = (622 × 2000) ÷ (4 × 760) ≈ 408 minutes or about 6.8 hours

 

Oxygen Delivery

The main oxygen delivery devices that you will encounter are the nasal cannula, non-rebreather, venturi mask, and tracheostomy mask. Each has different uses and limitations, and the choice of which to use will heavily depend upon the nature of the patient you are caring for.

NASAL CANNULA (NC)

Nasal cannulas are used to administer supplemental oxygen to a responsive patient who could benefit from oxygen administration but may not be able to tolerate a non-rebreather (NRB) mask or does not need the large amount of oxygen it would provide.

NCs are used when SPO2 levels are relatively normal as demonstrated by a patient that is exhibiting only mildly abnormal breathing.

The NC should be placed on the patient with the prongs curving up into the nares, the tubing wrapped over the patient’s ears (or secured to the tubing holders on a C-collar), and then tightened up to the chin with the sliding mechanism. Connect the other end of the tubing to the oxygen regulator and set the desired flow rate.

The rate for NC oxygen administration in adults is usually 2 to 6 LPM and should not exceed 6 LPM.

Limitations of the NC include the inability to deliver a high FiO2 percentage compared to other modalities, the possibility of causing significant nasal discomfort, and an inability to accurately control oxygenation in patients that alternate between nose and mouth breathing.

The nasal cannula can also be used to administer Blow-By-Oxygen in very young patients. Infants and toddlers rarely tolerate a nasal cannula or lask even when reassured and calmed by their parents. One of the best ways to deliver oxygen to a conscious young patient is to set the nasal cannula to 10 - 15LPM and place it near the patient, blowing across their face but not directly on it. Enlisting the help of a parent or caregiver to hold the nasal cannula in the blow-by position is often the most time-effective method.

NON-REBREATHER MASKS (NRB)

Non-rebreather masks deliver high-flow oxygen to patients without the possibility of them rebreathing expired carbon dioxide. They have the advantage of delivering nearly 100% FiO2, but this is often lower due to the mask's variable fit on the patient's face.

NRB’s are used in patients that have critically low SPO2 levels. The patient must be able to breathe unassisted, that is, have adequate tidal volume. 

To place an NRB on a patient, first, connect the tubing to the oxygen regulator and turn up the flow to the desired rate (at a minimum of 10 LPM). Allow the bag at the mask of the NRB to inflate fully and then place the mask over the patient's mouth and nose, securing with the strap that goes behind the head and manipulating the metal nose clip to fit snugly around the nose.

RATE: The rate for NRB oxygen administration in adults is between 10 and 15 Lpm, and should not be lower than 10 LPM. Values below this do not provide enough oxygen to fully inflate the bag before each breath and can restrict the patient's breathing. NRB oxygen administration is limited by the respiration rate, depth, and quality of the patient.

PARTIAL NON-REBREATHER MASKS (NRB)

As expected from the name, a partial NRB mask is an NRB that has had one or more of its one-way valves removed. This is a way of creating an intermediate delivery method between the NRB and the nasal cannula in ambulances that do not carry facemasks alone.

The indications and contraindications are otherwise the same as for NRB masks, as are the complications. The procedure for placing a partial NRB is the same as the placing of an NRB, with the removal of one of the inner flaps which allows for exhalation of expired CO2.

While it is theoretically possible to run this setup with less than 10 LPM of O2 it is not recommended, as there is no way to know how much "fresh air" the patient is getting with oxygen inputs below 10 LPM.

VENTURI MASKS

The Venturi mask is similar to a partial NRB mask but is far more precise. Venturi masks can be targeted to a specific FIO2 through selectable settings on the device itself. Small plastic inserts will instruct you to set a specific flow rate from the oxygen tank and name a specific FiO2 that results from using that specific insert at that specific flow rate. This allows for more precise control over the actual FIO2 delivered. Venturi masks are indicated in patients who need precision control over FIO2. This often means that patients with known medical conditions or alternative airways may require venturi maks.

CONTRAINDICATIONS TO VENTURI MASKS: include the need for extremely high flow oxygen, an unstable airway, and not knowing the correct rate the patient requires. Venturi masks are rarely used in the pre-hospital environment but may be present during interfacility transfers.

COMPLICATIONS OF VENTURI MASKS: Complications generally result from discomfort from a high airflow rate and errors in the device's setup.

To place a Venturi mask,

1. first, determine the amount of FIO2 the patient requires (respiratory therapists often perform this),
2. connect the tubing to the regulator, then
3. select the correct plastic insert for the desired FiO2 and set the oxygen flow rate from the regulator accordingly. Next,
4. remove one of the straps from the mask and secure it around the posterior neck of the patient connecting it back to the side it belongs.
5. Place the mask over the airway and secure the mask snuggly to the patient.

TRACHEOSTOMY MASKS

Tracheostomy masks are used to deliver high-flow oxygen to patients with a tracheostomy in place—consider this the same thing as an NRB just for patients who have a tracheostomy--and are indicated in patients with a tracheostomy who require supplemental oxygen.

CONTRAINDICATIONS: include patients who are known to retain CO2, such as those with advanced COPD. 

POSSIBLE COMPLICATIONS of tracheostomy masks include irritation of the tracheostomy site, dryness of the mucous membranes, and retention of CO2.

To place a tracheostomy mask

1. Remove the strap from one side and place the mask over the stoma.
2. Secure the strap around the patient’s posterior neck and reconnect to the other side of the mask.
3. Connect the opposite end of the tubing to the oxygen regulator.
4. Set the desired flow rate.

HUMIDIFIERS

Humidifiers are often used in pediatric patients and patients who require long-term oxygen therapy. This is due to the drying effect of blowing oxygen on the mucous membranes.

CONTRAINDICATIONS: Humidified oxygen is contraindicated for patients with pulmonary edema, heart attack, suspected drowning, or intolerance of humidified oxygen.

COMPLICATIONS are generally limited to cough, rhinorrhea, and water retention in the lungs.

To use a humidifier,

1. Connect it to the oxygen regulator directly.
2. Connect the tubing of the oxygen delivery device to the humidifier—this places the humidifier in-line so that any oxygen coming through the delivery device is humidified.
3. Don’t forget to turn on the regulator to the desired flow rate.