Oxygen Therapy

Oxygen Therapy – Different oxygen delivery methods (nasal cannula, face mask, non-rebreather mask), adjusting flow rates, and monitoring oxygen saturation levels.

Oxygen Therapy

Oxygen therapy is used to treat patients with hypoxemia (low blood oxygen levels) and ensure adequate oxygen delivery to tissues. Different oxygen delivery methods are available depending on the patient’s oxygen needs. Proper adjustment of flow rates and monitoring of oxygen saturation (SpO₂) levels are crucial for effective therapy.

1. Oxygen Delivery Methods

a. Nasal Cannula (Low-flow Device)

• Description: The nasal cannula consists of two small prongs that are inserted into the nostrils.
• Flow Rate: 1-6 liters per minute (L/min).
• Oxygen Concentration: Delivers approximately 24-44% oxygen, depending on the flow rate.
• Use: Suitable for patients with mild hypoxemia who require low to moderate oxygen concentrations. It is commonly used for long-term oxygen therapy and is generally well-tolerated.
• Advantages: Comfortable, allows the patient to talk and eat while receiving oxygen.
• Disadvantages: Oxygen concentration is variable due to the patient’s breathing pattern, and it can dry out nasal passages.

b. Simple Face Mask

• Description: A plastic mask that covers the nose and mouth.
• Flow Rate: 6-10 L/min.
• Oxygen Concentration: Delivers approximately 40-60% oxygen.
• Use: Suitable for short-term oxygen therapy for patients who need moderate concentrations of oxygen but not a precise percentage.
• Advantages: Provides higher oxygen concentration than a nasal cannula.
• Disadvantages: Requires a higher flow rate to avoid CO₂ rebreathing; can be uncomfortable and restricts eating and talking.

c. Non-Rebreather Mask (High-flow Device)

• Description: A face mask with a reservoir bag attached, which delivers nearly 100% oxygen. The mask has one-way valves to prevent room air and exhaled air from entering the bag.
• Flow Rate: 10-15 L/min.
• Oxygen Concentration: Delivers approximately 60-100% oxygen.
• Use: Suitable for patients with severe hypoxemia, such as those in respiratory distress or shock, who require high oxygen concentrations.
• Advantages: Delivers high concentrations of oxygen, often used in emergency situations.
• Disadvantages: Can cause discomfort with prolonged use, does not allow for rebreathing of exhaled air.

d. Venturi Mask

• Description: A mask with interchangeable adapters that provide precise oxygen concentrations.
• Flow Rate: Depends on the adapter; usually between 4-12 L/min.
• Oxygen Concentration: Delivers a precise concentration of oxygen, from 24% to 50%.
• Use: Ideal for patients who require specific oxygen concentrations, such as those with chronic obstructive pulmonary disease (COPD).
• Advantages: Provides controlled oxygen concentration regardless of the patient’s breathing pattern.
• Disadvantages: May be less comfortable for patients over long periods.

2. Adjusting Flow Rates

• Flow Rate Control: The oxygen flow rate is adjusted using a flow meter attached to the oxygen supply source. Each delivery device has a recommended flow rate range that corresponds to the amount of oxygen it delivers.
• Low-flow Devices: Nasal cannula and simple masks provide low-flow oxygen, which mixes with room air, so the actual inspired oxygen concentration can vary.
• High-flow Devices: Non-rebreather masks and Venturi masks deliver more precise oxygen concentrations and are used when a specific oxygen level is required.
• Monitoring and Adjustment: The flow rate is adjusted based on the patient’s oxygen saturation levels and clinical status. It is important not to administer excessive oxygen, especially in patients with conditions like COPD, where high oxygen levels can suppress the respiratory drive.

3. Monitoring Oxygen Saturation (SpO₂) Levels

• Pulse Oximetry: A pulse oximeter is used to monitor oxygen saturation levels (SpO₂). It provides a non-invasive method of measuring the percentage of hemoglobin saturated with oxygen in the blood.
• Normal Range:
  • A normal SpO₂ level is generally 95-100% in healthy individuals.
  • 88-92% may be acceptable for patients with chronic lung conditions like COPD.
• Indications for Oxygen Therapy:
  • SpO₂ < 90%: Indicates significant hypoxemia, usually requiring oxygen therapy.
  • SpO₂ < 85%: Represents a more severe hypoxemia and often warrants high-flow oxygen.
• Reassessing Oxygen Therapy: It is important to continually monitor SpO₂ levels to assess the effectiveness of oxygen therapy. If SpO₂ levels improve, the oxygen flow rate can often be decreased.

4. Precautions and Considerations

a. Oxygen Toxicity

• Prolonged exposure to high oxygen concentrations (greater than 60% for more than 24 hours) can cause oxygen toxicity, leading to lung damage, decreased lung compliance, and difficulty in oxygen exchange.
• Use the lowest effective concentration of oxygen to achieve target SpO₂ levels.

b. CO₂ Retention (Hypercapnia)

• In patients with COPD, high concentrations of oxygen can lead to hypercapnia (CO₂ retention) because they rely on hypoxemia to stimulate breathing. In such patients, aim for an SpO₂ of 88-92%.

c. Humidification

• Long-term oxygen therapy, especially with high flow rates, can dry out mucous membranes, leading to discomfort. Adding humidification to the oxygen can prevent this and improve patient comfort.

Summary of Key Points:

• Nasal cannula: Low-flow device (1-6 L/min), delivers 24-44% oxygen.
• Simple face mask: Moderate oxygen delivery (6-10 L/min), 40-60% oxygen.
• Non-rebreather mask: High-flow device (10-15 L/min), delivers 60-100% oxygen, used for severe hypoxemia.
• Venturi mask: Provides precise oxygen concentration, commonly used in patients with COPD.
• Monitor SpO₂ with a pulse oximeter, aiming for 95-100% in most patients but 88-92% in those with COPD.

By choosing the correct delivery method and adjusting the flow rate appropriately, oxygen therapy can effectively manage hypoxemia while minimizing the risks of oxygen toxicity and other complications.