Nursing Field Notes / Respiratory · Oxygenation & Airway I · Fundamentals of Nursing

Hypoxia & O₂ Devices 🫁

Low oxygen — how to spot it, and what to put on the face

NG-006 RESPIRATORY ADHD-friendly visual edition

Hypoxemia = low oxygen levels in the blood. Hypoxia = low oxygen supply in the body tissues. Hypoxemia dominoes into hypoxia — low oxygen in the blood means low oxygen delivery to the tissues. Then you pick the device that fixes it.

📄 Simple Nursing original — opens in Drive →

🩸 emia = blood · ia = tissueHypoxemia is the lab. Hypoxia is the patient.

🧠 Restlessness is FIRSTBrain first: restless → agitated → confused. Cyanosis is LATE.

📈 Early vitals go UP↑RR ↑HR ↑BP. Bradycardia & hypotension are LATE and BAD.

🎈 Deflated NRB bag?INCREASE the oxygen flow. Don't open the valves. Don't tighten the straps first.

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HYPOXEMIA → HYPOXIA

STEP 1 · TWO WORDS, ONE DOMINO

Get the two words straight first — half the exam questions are just testing the vocabulary.

🩸 The domino — blood first, tissue second

🧠 “-EMIA is in the blood (an-emia, hyperglyc-emia). -IA is the whole person.” The blood number falls first; the tissues suffer second.

🧯 Why the oxygen is low — 4 reasons

Not enough air in — hypoventilation, opioid oversedation, airway obstruction
Membrane too thick — pulmonary edema, pneumonia, fibrosis
Blood bypassing air — shunt from atelectasis or consolidation
Air bypassing blood — dead space, as in a pulmonary embolism

Also: low hemoglobin (anemia) means fewer carriers, and poor perfusion (shock) means the loaded blood never arrives.

🧠 “Can't get air in · can't cross over · wrong place · no truck.” Four failure points on the same delivery route.

🚩 Who is at risk right now on your unit

🛌Post-opanesthesia + pain + flat

💊Opioidssedation → ↓RR

🫁COPD/asthmachronic disease

💓Heart failurepulmonary edema

🦠Pneumoniaconsolidation

🧓Immobilityatelectasis

🧠 The post-op client on opioids lying flat is the classic exam setup. Sit them up and assess before anything else.

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SIGNS

STEP 2 · EARLY vs LATE

The brain complains first. If you wait for blue lips you waited too long.

🧠 Head-to-toe — early signs (act) vs late signs (emergency)

ATI QUESTION “Which of the following are early indications that the client is developing hypoxemia? Select all that apply.” ✅ Restlessness · Confusion · Hypertension · Tachypnea. ❌ Bradycardia — that is a LATE finding.

🧠 “Everything goes UP before it goes DOWN.” Rate up, pressure up, agitation up. When the numbers finally fall, the client is crashing.

⭐ Restless is the first word

Answer first: the earliest sign of hypoxia is a change in mental status — restlessness. The brain is the most oxygen-hungry organ in the body, so it complains first.

❌ Never medicate new restlessness or agitation as “anxiety” before you have checked oxygenation.

🧠 “A restless patient is a hypoxic patient until proven otherwise.” Sedating them is the classic wrong answer.

🚨 Paradoxical breathing — what it looks like

Normally the abdomen rises on inspiration. In paradoxical breathing the chest and abdomen move in opposite directions — the abdomen sinks in as the chest rises. It signals diaphragmatic fatigue or flail chest and is a sign of impending respiratory failure.

🧠 “See-saw belly = call for help.” This is not a “watch and see” finding.

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THE DEVICES

STEP 3 · WHAT GOES ON THE FACE

Low flow first, then the masks, then the precision device. Learn the picture and the numbers follow.

👃 Low-flow & simple: nasal cannula · simple face mask · Venturi

🧠 V · V — Venturi Mask = Very Accurate O₂. The color-coded barrel mixes a fixed amount of room air with the oxygen, so the FiO₂ stays exactly where you set it.

🎈 Reservoir devices & the special cases: partial rebreather · non-rebreather · face tent

🧠 “Partial has holes. Non-rebreather has flaps.” The flutter valves are the whole difference — they stop room air (and exhaled air) from diluting the oxygen, which is why the NRB gets the highest percentage.

🚨 Don't let the EXAMS trick you — the non-rebreather rules

Answer first: if the reservoir bag is fully deflated on inspiration → INCREASE the oxygen flow rate. The bag must stay at least partly inflated so the client always has a full breath of oxygen waiting.

❌ Do NOT open the flutter valves
❌ Do NOT tighten the face mask straps first
✅ Turn the flow up first, then reassess the bag with each breath
✅ Used for medical emergencies and for carbon monoxide poisoning — CO binds hemoglobin far more tightly than O₂, so you flood the system with the highest FiO₂ available

TRAP In carbon monoxide poisoning the pulse oximeter can read falsely normal — it cannot tell oxygen from carbon monoxide on the hemoglobin. Treat the client and the history, not the number.

🧠 “Flat bag = more gas.” Three words. It is the single most repeated NRB question on every exam.

📏 FiO₂ comparison — line them all up

🌡️ Face tent is not on the scale because its delivered FiO₂ is variable and imprecise — it is chosen for humidity and comfort (facial trauma, burns), not for a specific percentage.

🧠 Order of climbing: cannula → simple mask → partial rebreather → non-rebreather. Venturi steps out of the ladder — it is for precision, not for maximum.

📋 All of it in one table

Device	Flow	FiO₂	Use it when / watch for
Nasal cannula	1–6 L/min	~24–44%	Short-term low oxygenation after surgery. Long-term use dries the nasal mucous membranes → humidify. Client can eat & talk.
Simple face mask	6–10 L/min	40–60%	The step between cannula and the rebreathers. Never run it below the minimum flow — exhaled CO₂ gets rebreathed.
Partial rebreather	6–11 L/min	~60–75%	Looks very similar to the NRB. Key difference = the flutter valves (the partial rebreather's ports are open).
Non-rebreather	10–15 L/min	60–100%	Medical emergencies & carbon monoxide poisoning. Bag deflated on inspiration → increase the flow.
Venturi mask	4–10 L/min	precise, set	⭐ Most precise delivery. Unstable COPD who cannot tolerate changes in oxygen concentration.
Face tent	high, humidified	variable	Facial trauma & burns. High humidification, nothing pressing on injured skin.
High-flow nasal cannula	very high	up to 100%	Heated, humidified, high flow; provides some airway pressure and is better tolerated than a mask.

⚠️ These flow rates and FiO₂ percentages are typical, approximate values — published ranges differ between textbooks, and the FiO₂ a client actually receives varies with mask fit, respiratory rate and depth. Learn the order and the indication; check specific numbers against your own course materials and always follow the prescribed order.

🧠 Read the stem for the WORD, not the number: “precise / COPD” → Venturi. “Emergency / carbon monoxide” → non-rebreather. “Facial burn” → face tent. “After surgery, mild” → nasal cannula.

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SAFETY & NURSING CARE

STEP 4 · OXYGEN IS A DRUG

It needs an order, it has a dose, it has side effects, and it can start a fire.

🔥 Fire safety — non-negotiable

🚭NO smokingpost the sign, in the room & on the door

🕯️No open flamecandles, lighters, matches

🧴No petroleum productsuse water-soluble lubricant

🔌Check electricalsno frayed cords, no static-prone blankets

🧯Know the extinguisherand the shut-off valve

🛢️Secure cylindersupright, chained, away from heat

❌ Oxygen does not burn — it makes everything else burn faster and hotter. That is why a single spark matters.

🧠 “Oxygen is the accelerant, not the flame.”

✅ Ongoing nursing care

Oxygen requires an order — flow rate, device, and target saturation (unless it's an emergency, where you act and then obtain the order)
Titrate to the prescribed target SpO₂, then reassess
Humidify for higher flows and long-term use — dry gas cracks the mucosa and causes nosebleeds
Skin checks: behind the ears, over the cheekbones, the bridge of the nose, and the nares — pad the pressure points
Oral & nasal care — masks dry everything out
Reassess after every change: LOC, RR, work of breathing, SpO₂, color

🧠 “Order · device · target · skin.” Four checks every shift.

⚠️ COPD — say this carefully

Clients with chronic CO₂ retention are usually given controlled, low-flow oxygen titrated to a lower target saturation prescribed by the provider, and the Venturi mask is preferred because the FiO₂ does not drift.

❌ Never withhold oxygen from a client who is acutely hypoxic. Treat the hypoxia, then titrate down and monitor for rising drowsiness or a falling respiratory rate.

🧠 “Low and precise, not none.” The wrong answer is refusing to oxygenate a blue patient.

🪜 Priority action when you find a hypoxic client

Stay with the client and position upright — high Fowler's, or tripod if that is what they are already doing. Gravity is free oxygen.

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Assess airway & breathing — patency, rate, effort, breath sounds, SpO₂, color, level of consciousness.

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Apply / increase oxygen per the order or protocol; step up to a higher-delivery device if the target is not met.

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Call for help — rapid response or provider — and prepare for an ABG, chest X-ray and further treatment.

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Treat the cause — suction secretions, reverse oversedation as prescribed, coach deep breathing / incentive spirometry, ambulate when stable.

👉 Lung anatomy and breath sounds are on NG-004 — Anatomy of the Lungs.

🧠 “Sit them up before you look anything up.” Positioning is the fastest intervention you own.

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QUICK RECALL

SAY IT OUT LOUD

🩸 Hypoxemia = bloodPaO₂ less than 80 mmHg (typical adult reference range — verify against your lab). Hypoxia = tissues.

🧠 Restless firstThen agitated, then confused. Cyanosis is LATE.

V = Very AccurateVenturi = the most precise device · unstable COPD.

🎈 Deflated bag → ↑ flowNRB 10–15 L/min · 60–100% · emergencies & CO poisoning.

🎯 Cover & check — 7 rapid-fire questions

Q1: Define hypoxemia and hypoxia, and state the link.

Hypoxemia = low oxygen levels in the blood. Hypoxia = low oxygen supply in the body tissues. Hypoxemia dominoes into hypoxia, because low oxygen in the blood means low oxygen delivery to the tissues.

Q2: Which findings are EARLY indications of hypoxemia?

Restlessness, agitation/irritability, confusion, tachypnea (RR over 20), tachycardia (HR over 100), and hypertension (systolic over 140). Bradycardia, hypotension and cyanosis are LATE.

Q3: A client on a non-rebreather has a reservoir bag that fully deflates with each breath. What do you do?

Increase the oxygen flow rate. Do NOT open the flutter valves, and do NOT tighten the face mask straps first.

Q4: Which device is the most precise, and who is it for?

The Venturi mask — V for Very Accurate O₂. Typically used for clients with unstable COPD who cannot tolerate changes in oxygen concentration from other devices.

Q5: A client has facial burns. Which device and why?

A face tent — used for facial trauma and burns because it provides high humidification without anything strapped against the injured skin. F = Face Tent, F = Face Trauma.

Q6: How do you tell a partial rebreather from a non-rebreather at a glance?

They look very similar. The key difference is the flutter valves — the non-rebreather has one-way flutter valves on the sides (and between the bag and the mask) so exhaled and room air can't dilute the oxygen. That's why the NRB reaches roughly 60–100% while the partial rebreather sits around 60–75%.

Q7: Give the flow and FiO₂ for a nasal cannula, and the one long-term teaching point.

1–6 L/min, about 24–44% oxygen. Short-term it is used for low oxygenation after surgery. Long-term it dries out the mucous membranes in the nose, so humidification is added.