Recommended Terms
| Oxygen Device | Oxygen Flow Rate | FiO2 | Description |
| Nasal Cannula | 1 ~ 6 lpm | 0.24 ~ 0.44* | ≤ 6 lpm |
| Simple Mask | 6 ~ 10 lpm | 0.35 ~ 0.55* | ≥ 5 lpm |
| Reservoir Mask | 10 ~ 15 lpm | 0.60 ~ 0.80* | Reservoir must not collapse |
| Venturi Mask | 3 lpm | 0.24, 0.26, 0.31* | Read instructions |
| 6 lpm | 0.35, 0.40, 0.50* | ||
| Anesthesia Bag Mask | 12 ~ 15 lpm | 1 | ≥ 12 lpm |
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Main Text
Common Oxygen Devices
Nasal Cannula:
Advantages: Easy to use, constant oxygen flow. Well tolerated by patients, allows freedom of activity, convenient for eating and talking. However, when using a nasal cannula, it is important to clear the patient’s nasal passage to keep it unobstructed. If the nasal cavity is filled with mucus or other secretions, it becomes ineffective.
Disadvantages: Patients with high minute ventilation find it difficult to achieve higher inspired oxygen concentration (< 0.40). Not suitable for patients with complete nasal obstruction. May also cause headache or mucosal dryness.
Precautions: Maximum oxygen flow of 5 to 6 liters per minute; if > 5 lpm is needed, another oxygen device should be used. Using a nasal cannula at 10 lpm does not provide any benefit besides damaging the respiratory tract.
Simple Mask
Simple masks are common oxygen devices in many primary hospitals. They have poor seal and large ventilation holes, allowing air to enter; they contain a reservoir section, so FiO2 is higher than nasal cannula but not fixed, FiO2 ≤ 0.60. In low ventilation patients, CO2 may accumulate in the reservoir, causing hypercapnia. Even if hospital wall oxygen is set to maximum, only about 50% oxygen is inhaled, so oxygen toxicity is not a concern.
Precautions: Oxygen flow should be at least 6 lpm (compared to nasal cannula) to “flush” exhaled CO2 and prevent rebreathing of CO2; humidifiers should not be used.
Reservoir Mask (Partial Rebreathing)
Structurally similar to a simple mask plus an oxygen reservoir bag; looks like a non-rebreather mask but without one-way valves between the reservoir bag and mask. The reservoir bag is filled with oxygen to increase FiO2; exhaled gas mixes with oxygen in the bag. When expiratory flow exceeds oxygen flow, a one-way valve on the mask allows exhalation, but air is less likely to enter during inhalation, enabling higher FiO2. Patients are at higher risk of CO2 retention.
Reservoir Mask (Non-Rebreathing)
This is a simple mask plus an oxygen reservoir bag. Similar in appearance to the partial rebreathing reservoir mask but with one-way valves between the mask and the reservoir bag and also on the mask. The advantage is better control of FiO2. This mask provides the highest FiO2 under non-intubated and non-mechanical ventilation conditions (an aspect highly desired by many doctors and patient families). It is effective for short-term use and does not dry the nasal mucosa.
Disadvantages: Requires a good seal, which is often overlooked by doctors and nurses. Edge leakage is “fatal” to oxygen delivery. It may also cause discomfort, skin irritation, interfere with eating and talking, and prevents nebulization therapy.
Precautions: The reservoir bag must always remain inflated. If the bag is deflated, it indicates inadequate nursing care. Prevent bag “kinking,” maintain free expansion of the bag, ensure good mask-to-face fit, and proper function of one-way valves. Humidifiers should not be used.
In summary, the above low-flow oxygen devices are suitable for patients with stable conditions, normal breathing patterns, minute ventilation < 10 lpm, respiratory rate < 20-25 breaths/min, and tidal volume < 700-800 ml.
High-Flow Oxygen Devices
Provide oxygen flow greater than three times the patient’s minute ventilation, can reach 40 lpm, ensuring inhaled oxygen is not diluted by air and FiO2 remains constant (the major difference between low and high flow).
Anesthesia Bag Mask
Equipped with a large bag below the mask to store oxygen; during inhalation, oxygen is supplied from the bag without air mixing. FiO2 is fixed. To understand anesthesia bags well, anesthesiologists are the best reference due to their expertise in airway opening techniques and squeezing the bag. For other department doctors, knowing that the anesthesia bag is a high-flow oxygen device is sufficient.
Venturi Mask
Many large hospitals have this mask, but unfortunately, its effectiveness is not ideal. It uses the mechanical Venturi principle to increase oxygen flow to the mask and limit air inflow, thus maintaining fixed FiO2. Different Venturi mask types provide different FiO2 values (FiO2: 24% ~ 28% at 4 lpm, 35% ~ 40% at 8 lpm).
Advantages: Provides consistent FiO2, suitable for COPD patients.
Disadvantages: Cannot provide high FiO2 (despite being a high-flow oxygen device, it cannot deliver high FiO2; however, it isolates ambient air from breathing, ensuring constant FiO2, thus classified as high-flow).
Precautions: The most important is to ensure oxygen flow matches the Venturi device markings to guarantee FiO2 accuracy. Refer to the mask instructions, usually indicated by color coding.
Anesthesia Machine and Ventilator
Both require endotracheal intubation or tracheostomy and can provide 100% FiO2. Their setup and adjustment are professional and specialized.
High-flow oxygen device indications:
- Need for fixed FiO2: for example, emphysema patients—now you know which mask to use.
- Need for high concentration FiO2: for conditions like ARDS; many options exist except Venturi masks.
In conclusion, a summary of the effects of different oxygen devices described above.