3.2a Nasal Cannula

Instructions for Using a Nasal Cannula in Oxygen Therapy

1. Connect the nasal cannula to an oxygen flowmeter and place it in your nose and set the flow rate to one liter, then three liters, and then six liters per minute (lpm).
2. Observe the prong positioning and note any differences in your comfort at various flow rates.
3. Use a humidifier (bubbler) when administering oxygen at flow rates greater than 4 lpm to maintain moisture and comfort for the patient.
4. Apply the nasal cannula properly:
   • Position the prongs to face downward into the nostrils.
   • Secure the tubing behind the ears and under the chin, allowing for easy removal.
   • Ensure the fit minimizes the risk of strangulation or discomfort.
5. Understand normal flow rates: The standard flow range for a nasal cannula is 0-6 lpm. To estimate the approximate FiO2, multiply the flow rate by 4% per lpm. For example, an oxygen flow rate of 3 lpm will deliver an approximate FiO2 of 30-33%.
6. Consider patient-specific factors. Keep in mind that the actual delivered FiO2 can vary based on the patient’s depth of respiration and breathing pattern.
7. Once you have completed the nasal cannula activity, take the Nasal Cannula Quiz.

3.2b Simple Mask

Instructions for Using a Simple Mask in Oxygen Therapy

1. Connect the simple mask to an oxygen flowmeter and place the mask on your face and set the flow rate to five liters, then eight liters, and then ten liters.
2. When using a simple mask, it is important to ensure adequate oxygen flow. Apply the mask to the patient in a way that creates a secure seal without causing discomfort. The normal flow rate for a simple mask is 6-10 lpm (liters per minute), and the anticipated FiO2 (fraction of inspired oxygen) range is typically 35-50%. Ensuring the correct flow rate and mask fit helps maintain patient safety and optimal oxygen delivery.

3.2c Non-Rebreather

Instructions for Using a Non-Rebreather in Oxygen Therapy

1. Connect the non-rebreather mask to an oxygen flowmeter. Set the flow rate between ten and fifteen liters, ensuring that the reservoir bag inflates. Then, place the mask on your face.
2. To determine if the device is set accurately, observe the patient breathing at the prescribed flow rate and ensure that the reservoir bag deflates during inspiration. The FiO2 (fraction of inspired oxygen) typically ranges between 60-80%, though some sources may extend this range to 70-90%.
3. A non-rebreathing mask provides the highest FiO2 available without the use of a mechanical device. This mask features two one-way valves: one on the reservoir bag and another on the side of the mask. These valves help ensure the highest possible FiO2 by allowing oxygen to flow in while preventing room air from diluting it and stopping exhaled air from reentering the bag.

3.2d Venturi Mask

Instructions for Using a Venturi Mask in Oxygen Therapy

1. Connect the Venturi port to the aerosol mask and set the port to 50%. Set the flow rate that aligns with 50% and then place the mask on your face. You will need to use the manufacturer’s flow range to determine the appropriate flow for the device.
2. Determine the total flow for the device based on the flow from the flowmeter and the FIO2 utilizing the air/O2 entrainment ratio.
3. The Venturi mask is different from the other oxygen masks. It is a high-flow oxygen mask that utilizes the Venturi principle. The FIO2 ranges from 24-50%. The mask features an adjustable setting to control the amount of air entrained, while other designs use variable-sized Venturi adapters for this purpose.

3.2e Humidity and Heated High Flow

Utilizing the humidity definitions for Absolute Humidity, Relative Humidity, Body Humidity and Humidity deficit stated below, the above Water Vapor Pressure and Content table and the corresponding equations you should answer the following questions:

Absolute Humidity (AH) – the actual amount of moisture “or content” contained in a gas.

AH = RH x Capacity

Relative Humidity (RH) – the ratio of the moisture a gas is actually holding to what it can hold when saturated at a given temperature. This is represented by the formula: absolute humidity (content) / moisture capacity (according to charts) x 100. This value is expressed as a percentage.

RH = AH/Capacity x 100

Body Humidity (BH) – the relative humidity of a gas at body temperature (37° C). This is represented by the formula: absolute humidity (content) / moisture capacity at body temperature x 100. This value is expressed as a percentage.

BH = AH/44mg/L x 100

Humidity Deficit (HD) – the actual amount of moisture deficit between the inspired air and the needs of the body. This is represented by the formula: capacity at body temperature – absolute humidity = humidity deficit.

HD = 44mg/L – AH