Oxygenation - Advanced

Oxygenation is more than SpO₂—it’s about delivering O₂ to tissues (DO₂), ensuring content (CaO₂) is adequate, matching ventilation to perfusion, and avoiding harm from over- or under-oxygenation. This set covers advanced concepts and special situations not detailed in the basic respiratory or ABG notes.

Safety anchors: ABCs • Device fit & FiO₂ accuracy • Skin/pressure checks • Fire safety with O₂ • Reassess after every change (SpO₂, WOB, mentation)

Clinical judgment: Identify the failed link (air, lung, blood, pump, demand) → pick the lever (position, airway clear, O₂, PEEP/NIV, circulation) → trend response → escalate early

Use this pack: Scan tables • run the Quick Checks • try the NGN item

Policy note: Follow local targets for SpO₂/FiO₂, HFNC/NIV use, escalation/ICU transfer, and oxygen safety.

1) Oxygen Delivery: From Numbers to Tissues 🚚

1.1 Content & Delivery (why anemia matters even with “good” SpO₂)

Concept	Plain meaning	Bedside pearl
CaO₂ (arterial O₂ content)	How much O₂ is in each 100 mL of blood (mostly on hemoglobin)	Low Hgb = low CaO₂ even if SpO₂ is 100%
DO₂ (oxygen delivery)	O₂ sent to tissues each minute = Cardiac Output × CaO₂	Falls with anemia, low CO, or low SaO₂/PaO₂
VO₂ (oxygen use)	What tissues consume	Fever, sepsis, agitation ↑ VO₂ → desats faster

Memory aid — C.A.R.D.: Content • Afterload/CO • Respiratory (SpO₂/FiO₂) • Demand. Fix what’s lowest first.

2) Hemoglobin Pitfalls (when SpO₂ lies) 🩸

Issue	What happens	Clues	What to do
Anemia	CaO₂ low despite normal SpO₂	Pale, fatigue, tachycardic on exertion	Treat anemia per orders; pace activity; O₂ won’t fix CaO₂ alone
Carboxyhemoglobin (CO)	Pulse ox reads falsely high	Exposure (fires, garages), HA, cherry skin rare	High-flow O₂; consider co-oximetry if available
Methemoglobinemia (MetHb)	SpO₂ ~85% plateau; chocolate-brown blood	Nitrates, local anesthetics	High-flow O₂; notify provider; antidote per protocol
Poor perfusion/vasoconstriction	Erratic or low SpO₂	Cold, shock, weak waveform	Warm limb, reposition probe, correlate with patient

Glossary: FiO₂ = % O₂ you give • SaO₂/SpO₂ = % Hb carrying O₂ • Co-oximeter = lab tool that separates Hb species.

3) Oxygen Toxicity & Absorption Atelectasis ⚠️

Risk	What it is	When to worry	Nursing actions
Hyperoxia harms	High O₂ → oxidative injury	Prolonged high FiO₂ with minimal reassessment	Use lowest FiO₂ that meets target; wean with evidence
Absorption atelectasis	High O₂ washes out nitrogen → alveoli collapse	High FiO₂ with shallow breaths	Add PEEP/CPAP per order, upright, IS, mobilize
Retinopathy risk (neonates)	Over-oxygenation injury	Special population	Follow neonatal targets strictly (unit policy)

Memory aid — L.O.T.: Lowest O₂ • Often reassess • Titrate down.

4) High-Flow Nasal Cannula (HFNC) & Noninvasive Ventilation (NIV) 💨

4.1 HFNC — what you control

Knob	What it does	Tips
Flow (L/min)	Washout dead space; ↓WOB; tiny PEEP effect	Start moderate–high if distressed; ensure heated humidification
FiO₂ (%)	Changes PaO₂/SpO₂	Titrate to target; wean FiO₂ before flow once stable

ROX index = (SpO₂/FiO₂) ÷ RR. Lower = worse. Use as trend, not single truth.

4.2 NIV (CPAP/BiPAP) — basics

Mode	What it gives	Use it for	Avoid/Use caution
CPAP	One continuous pressure (PEEP)	Alveolar collapse, cardiogenic pulmonary edema	Vomiting risk, reduced consciousness, facial trauma
BiPAP	IPAP (ventilation) + EPAP (oxygenation/PEEP)	Hypercapnia (COPD), mixed hypoxemia/hypercapnia	Same cautions; ensure mask fit & leak check

Nursing responsibilities: Skin checks q2–4 h • mask fit/leak • patient coaching • hydration/humidification • escalation triggers ready.

Escalate if: persistent SpO₂ below target, tiring, rising CO₂/encephalopathy, hypotension, or ROX trending down despite optimization.

5) Awake Proning & Position Strategies 🤸‍♂️

Technique	When it helps	How to do it	Watch out for
Awake prone	Shunt/low V/Q (posterior atelectasis)	Rotate prone ↔ lateral ↔ upright 30–120 min cycles	Pressure areas, nausea, lines/tubes
Good lung down	Unilateral disease	Side-lying with healthy lung dependent	Hemodynamic tolerance; aspiration risk

Memory aid — R.O.L.L.: Rotate often • Observe skin • Lines secure • Lungs expand.

6) Humidification, Nebs & Airway Clearance 🌫️

Tool	Purpose	Nursing notes
Heated humidifier	Protect mucosa; improve comfort	Required for HFNC/NIV circuits
Nebulized bronchodilator	Open airways (wheeze/bronchospasm)	Pre/post breath sounds; spacer for MDIs when possible
Mucolytic/saline nebs	Thin secretions	Assess cough strength; suction PRN
PEP/OPEP devices	Back-pressure + oscillation to mobilize mucus	Teach technique; 10–20 breaths/set; rest between

Memory aid — C.L.E.A.R.: Coach technique • Limit fatigue • Evaluate sounds • Assist cough • Reassess SpO₂/WOB.

7) Special Populations & Situations 👩‍🦳🤰⚖️

Group	Targeted pearls	What to avoid
COPD/OHS (CO₂ retainers)	Use unit target range; focus on WOB relief & secretion clearance; consider BiPAP for hypercapnia	Large rapid FiO₂ jumps without monitoring
Obesity/OSA	Upright, ramped positioning; early CPAP	Supine only; sedation without monitoring
Pregnancy	Higher O₂ demand; left tilt; early O₂ if hypoxemic	Hypotension from aortocaval compression
Heart failure/edema	CPAP/PEEP reduces preload/afterload; strict I&O	Flat position
Palliative/hospice	Treat dyspnea, not the number; fan, opioids per orders	Device escalation that conflicts with goals of care

8) Oxygen Troubleshooting & Safety 🛠️🔒

Problem	Likely cause	Quick fix
Reservoir bag on NRB collapses	Flow too low	Increase to keep bag 1/3–1/2 full on inspiration
Nasal cannula dry nose/epistaxis	No humidification ≥4 L/min	Add humidifier; assess skin; saline gel
Mask leaks/low SpO₂	Poor seal, beard, fit	Refit/change interface; consider HFNC/NIV
No improvement with higher FiO₂	Shunt/atelectasis	Positioning, PEEP/CPAP, recruit lungs; treat cause
Fire risk (home/ward)	O₂ near flame/smoking	Strict No Smoking, signage, education, tubing check

Memory aid — S.A.F.E. O₂: Seal & Skin • Adequate Flow • Fire precautions • Escalate if no response.

9) Device Selection & Weaning Map 🗺️

If SpO₂ below target but breathing effort OK:→ Cannula → Venturi (need precise FiO₂) → NRB if acute drop while arranging escalation.

If high WOB or persistent hypoxemia:→ HFNC (humidified, high flow) → add positioning/airway clearance → NIV if hypercapnia or ongoing distress → call for higher level of care if failing.

Wean order (when stable): FiO₂ ↓ to safe target → then flow/PEEP ↓ → reassess after each change.

10) Home & Transport Oxygen 🏠🚑

Context	Key checks	Teach points
Home O₂	Flow at rest/exertion • safe storage • backup power	No smoking/flame • tubing trip hazards • when to call
Ambulatory/transport	Cylinder level • portable settings • mask vs cannula	Keep O₂ on during exertion if ordered • bring extra cylinder

Quick Checks (Retrieval) 🧠✅

1. Your patient’s SpO₂ is 99% on 6 L cannula but Hgb is 7 g/dL and they’re dizzy on ambulation. Which link of C.A.R.D. is failing and what’s your first nursing priority?

2. Name two signs that pulse ox may be unreliable and what you’ll check next.

3. On HFNC, which do you usually wean first once stable: FiO₂ or flow? Why?

4. List two reasons for worsening SpO₂ despite rising FiO₂ and one escalated intervention for each.

5. What are two contraindications/cautions for NIV you must screen before applying a mask?

Answer Key (for review):

1. Content (CaO₂) via anemia; support safety/pace activity and notify for anemia mgmt (O₂ alone won’t fix).

2. Poor waveform/cold extremities; exposure to CO. Check waveform/site, warm limb, correlate clinically; consider co-ox.

3. FiO₂ first—minimize hyperoxia; keep flow for comfort and dead-space washout.

4. Shunt/atelectasis → PEEP/CPAP & positioning. Secretions → airway clearance/suction.

5. Vomiting risk/aspiration, reduced consciousness, facial trauma/poor fit (plus hemodynamic instability).

NGN-Style Mini-Item 🧩

Scenario: 64-year-old with pneumonia on HFNC 50 L/min, FiO₂ 0.60. RR 30, SpO₂ 90%, speaking short phrases, coarse crackles posteriorly. After coached prone/lateral cycles and airway clearance, SpO₂ stays 90%; ROX index trends down.

Select all priority actions:

• ☐ Reduce flow to 20 L/min to improve comfort

• ☐ Increase FiO₂ to 0.80 without other changes

• ☐ Trial NIV (CPAP/BiPAP) per protocol; close monitoring

• ☐ Call provider/RT for escalation and ICU criteria check

• ☐ Maintain strict prone/lateral rotation and continue clearance while preparing NIV

• ☐ Delay escalation because SpO₂ is 90%

Correct: ✅ Trial NIV • ✅ Call for escalation (ICU criteria) • ✅ Maintain position/clearance while preparing NIVWhy: Persistent hypoxemia + ROX falling despite optimized HFNC & recruitment suggests failure of HFNC → escalate to NIV/ICU. Comfort changes alone won’t fix shunt.

Closing Practice Pearls ✨

• Treat the weakest link. Numbers improve fastest when you fix the true bottleneck (airway, alveoli, Hb, pump, demand).

• O₂ is a drug. Use the lowest effective FiO₂, reassess often, and add PEEP/positioning when shunt dominates.

• Pulse ox can deceive. Anemia, CO, MetHb, and poor perfusion mislead—trust the patient + waveform.

• Position is therapy. Rotate, prone, and put the good lung down.

• Document the story. Device/FiO₂, WOB, positions tried, ROX, response, and your escalation plan.