🩺 Fundamentals, Fast · Lesson 5 of 5 · 6 min
Oxygen Devices in One Table
🎭 A simple face mask at 3 liters is not a gentle setting. It is a bag over a client's face that traps their own carbon dioxide. Every device has a floor, a ceiling and a trap. Here they all are.
💡 Key idea
Each device has a minimum flow and a maximum percentage. Simple masks need at least 5 L/min, non-rebreathers need an inflated bag, and Venturi masks give exact percentages for COPD.
🧠 Why it matters
NASAL CANNULA: 1 to 6 L/min, about 24 to 44% oxygen; humidify at 4 L/min and above; check the skin behind the ears and the nares. SIMPLE FACE MASK: 5 to 8 L/min, about 40 to 60%; never below 5 L/min or exhaled carbon dioxide accumulates in the mask. PARTIAL REBREATHER: 6 to 10 L/min, about 60 to 75%. NON-REBREATHER: 10 to 15 L/min, up to about 90%; the reservoir bag must stay inflated and the one-way valves intact. VENTURI MASK: precise percentages from 24 to 50% through color-coded adapters, the choice for COPD when exact delivery matters. HIGH-FLOW NASAL CANNULA delivers heated, humidified oxygen at much higher flows. Early hypoxia shows as restlessness, anxiety and tachycardia; late hypoxia as cyanosis, bradycardia and a falling level of consciousness. In COPD, aim for a saturation of 88 to 92% and titrate rather than withholding oxygen from a hypoxic client.
🏥 In the real world
😰 A post-op client becomes restless and keeps pulling at the sheets. The night nurse assumes pain and reaches for the opioid. The saturation reads 87%. Restlessness is the first sign of hypoxia, and an opioid would have deepened it. Oxygen first, then reassess, then treat pain if it is still there.
📌 Takeaways
- Cannula 1–6 L; simple mask at least 5 L; non-rebreather 10–15 L with an inflated bag
- Venturi for precise percentages in COPD; target saturation 88–92%
- Restlessness and tachycardia are early hypoxia; cyanosis is late
📖 Terms in this lesson
Non-rebreather mask: A mask with a reservoir bag that delivers up to about 90% oxygen at 10 to 15 L/min, as long as the bag stays inflated.
Venturi mask: A mask with color-coded adapters that deliver exact oxygen percentages, preferred for COPD.
✅ Test yourself
A client's simple face mask is set at 3 L/min. What should the nurse do?
- Switch to a non-rebreather mask at the same 3 L/min flow
- Increase the flow to at least 5 L/min to flush carbon dioxide
- Remove the oxygen
- Nothing; the setting is appropriate for a simple mask
Answer: B · Increase the flow to at least 5 L/min to flush carbon dioxide
A simple mask needs at least 5 L/min to flush exhaled carbon dioxide from the mask.
The reservoir bag on a non-rebreather mask collapses completely with each breath. What does this indicate?
- The flow is too low or there is a leak; the bag must stay inflated
- The device is working correctly and needs no adjustment
- The client no longer needs oxygen
- The mask should be changed to a nasal cannula at 6 L/min
Answer: A · The flow is too low or there is a leak; the bag must stay inflated
The bag must remain at least partially inflated so the client draws from a reservoir of oxygen, not room air.
Which early sign suggests a client is becoming hypoxic?
- Unresponsiveness to voice
- Cyanosis of the lips
- Restlessness and tachycardia
- Bradycardia and hypotension
Answer: C · Restlessness and tachycardia
Restlessness, anxiety and tachycardia appear first. Cyanosis, bradycardia and decreased consciousness are late and ominous.
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