Oxygen Therapy and Noninvasive Ventilation Concepts

1. Oxygen therapy and FiO2

Oxygen therapy is the prescribed administration of oxygen above room air to treat or prevent hypoxemia. It is a treatment, not a comfort measure, so it is ordered, monitored, and titrated. FiO2 — the fraction of inspired oxygen — expresses how much of each breath is oxygen; room air is about 0.21, and delivered oxygen raises this fraction. The goal is enough oxygen to meet tissue needs without excess, since excessive oxygen can harm some individuals.

2. Delivery devices

• Nasal cannula — two prongs in the nostrils; a low-to-moderate concentration that is comfortable and allows eating and talking.
• Simple face mask — a mask over the nose and mouth; a moderate step up.
• Partial rebreather mask — a mask with a reservoir bag that lets some exhaled air return, raising the concentration further.
• Non-rebreather mask — a mask with a reservoir bag and one-way valves that delivers a high concentration for higher-need situations.
• Venturi mask — uses a venturi mechanism to entrain a precise, predictable concentration, useful when the exact FiO2 matters.

Device selection balances the needed concentration against comfort, breathing pattern, skin tolerance, and the ability to keep the device in place; exact flows and concentrations are ordered and titrated by qualified clinicians per policy. Humidification adds moisture to delivered oxygen to protect airway tissues.

3. Oxygen safety and noninvasive ventilation

Oxygen safety is critical because oxygen supports combustion: fire risk rises near flames, sparks, and petroleum-based products, and policies restrict smoking and ignition sources. Noninvasive ventilation (NIV) delivers positive airway pressure through a mask instead of an artificial airway: CPAP (continuous positive airway pressure) delivers one steady pressure through the cycle, while BiPAP (bilevel positive airway pressure) delivers a higher pressure on inspiration and a lower one on expiration. NIV monitoring includes SpO2, breathing effort, and tolerance; skin integrity is protected by well-fitted, padded interfaces and skin checks; and comfort and anxiety management improve adherence. Respiratory-therapy collaboration is essential for device selection, settings, and troubleshooting.

How it works

1. Oxygen is prescribed to raise the fraction of inspired oxygen (FiO2) above room air when the body cannot maintain adequate oxygenation.
2. A device is selected to provide the needed concentration while preserving comfort and function.
3. Humidification protects airway tissues, and safety rules prevent fire risk near the oxygen source.
4. When positive pressure is needed, CPAP or BiPAP props the airway open without an artificial airway.
5. Throughout, the nurse monitors oxygenation, protects skin, supports comfort, and collaborates with respiratory therapy, adjusting settings only as ordered.

Common confusions

Memory aids

For the mask devices in order of increasing oxygen concentration: "Simple People Never Ventilate" — Simple mask, Partial rebreather, Non-rebreather, Venturi (precise). And CPAP = Continuous pressure; BiPAP = two (Bi) levels.

Quick review

Topic Recap

• Oxygen therapy raises the fraction of inspired oxygen (FiO2) above room air to treat or prevent hypoxemia and is always ordered and monitored.
• Devices — nasal cannula, simple, partial-rebreather, non-rebreather, and Venturi masks — differ in concentration and precision.
• Oxygen safety and fire risk are paramount; humidification protects airway tissues.
• Noninvasive ventilation (CPAP and BiPAP) provides positive pressure without an artificial airway and requires monitoring, skin protection, and comfort support.
• Respiratory-therapy collaboration is central to device choice, settings, and troubleshooting.

Knowledge Check

1. What does FiO2 represent, and what is its approximate value in room air?
2. Which device delivers the highest oxygen concentration among the mask options, and which delivers the most precise concentration?
3. Why is fire risk a major concern with oxygen therapy?
4. How do CPAP and BiPAP differ?
5. Why must oxygen settings be ordered and titrated by a qualified clinician rather than chosen independently by the nurse?

Answers and Rationales

1. Answer: FiO2 is the fraction of inspired oxygen; room air is about 0.21 (21%). Why: It is the measure of how much of each breath is oxygen.
2. Answer: The non-rebreather delivers the highest concentration; the Venturi mask delivers the most precise, predictable concentration. Why: The non-rebreather's valves and bag concentrate oxygen; the Venturi entrains an exact mixture.
3. Answer: Oxygen supports combustion, so flames, sparks, and smoking near oxygen can cause serious fire and burns. Why: Safety precautions and signage are essential around any oxygen source.
4. Answer: CPAP delivers one continuous pressure; BiPAP delivers two — higher on inspiration, lower on expiration. Why: This distinction guides device selection for different breathing needs.
5. Answer: Oxygen is a prescribed treatment, and the correct concentration and flow depend on the individual's condition; too much or too little oxygen can harm. Why: Nurses administer oxygen as ordered and monitor its effects.