Oxygen Therapy Guide

🏭 Oxygen Delivery Device Comparison

Device	Flow Rate	FiO₂ Range	Key Indication	Notes
Nasal Cannula (NC)	1–6 L/min	24–44%	Stable hypoxaemia, ambulatory patients	Comfortable; patient can eat & talk. Each 1 L/min ≈ +4% FiO₂ from baseline 20%
Simple Face Mask (SFM)	5–10 L/min	35–55%	Acute hypoxaemia, short-term use	Minimum 5 L/min to flush CO₂ from mask. Imprecise FiO₂ delivery
Non-Rebreather Mask (NRM)	10–15 L/min	60–80%	Emergency oxygen (anaphylaxis, major trauma, CO poisoning)	One-way valves limit CO₂ rebreathing. Reservoir bag must remain inflated
Venturi Mask (VMask)	2–15 L/min (colour-coded)	24 / 28 / 31 / 35 / 40 / 60%	COPD, precise FiO₂ needed	Jet-entrainment (Bernoulli). Blue=24%, White=28%, Yellow=35%, Red=40%, Green=60%
HFNC / Optiflow	Up to 60 L/min	21–100%	Hypoxaemic respiratory failure, pneumonia, COVID-19	Heated/humidified; generates low PEEP (~1 cmH₂O per 10 L/min); use ROX index at 2, 6, 12 h
CPAP	Continuous positive pressure	Variable (set FiO₂)	OSA, cardiogenic pulmonary oedema, mild–moderate ARDS	Single pressure throughout respiratory cycle. Reduces preload, recruits alveoli
BiPAP	IPAP + EPAP pressures	Variable (set FiO₂)	COPD exacerbation with CO₂ retention, NMJ disease, OHS	IPAP supports inspiration (reduces WOB); EPAP = PEEP. Contraindicated: vomiting, GCS <8
Invasive MV (ETT/Trach)	Ventilator-set	21–100%	Respiratory failure, airway protection, post-op	Requires ICU. FiO₂ titrated by ABG. Wean FiO₂ <60% as soon as possible

🔢 FiO₂ Estimator

Select Device

Flow Rate (L/min) or FiO₂ % for Venturi

Select device and enter flow rate.

📈 HFNC ROX Index

SpO₂ (%)

FiO₂ (decimal, e.g. 0.6 for 60%)

Respiratory Rate (breaths/min)

Enter SpO₂, FiO₂, and RR.

ROX = (SpO₂ / FiO₂) ÷ RR | >4.88 at 12 h → HFNC success likely

💡 Venturi Colour Codes

Colour	FiO₂	Minimum Flow	Total Gas Delivered
Blue	24%	2 L/min	~53 L/min
White	28%	4 L/min	~45 L/min
Yellow	35%	8 L/min	~34 L/min
Red	40%	10 L/min	~30 L/min
Green	60%	15 L/min	~30 L/min

🔍 ABCDE Airway-Focused Assessment

Step	Assessment	Key Actions
A — Airway	Patency: speaking, snoring, gurgling, stridor, silent obstruction	Head-tilt chin-lift / jaw thrust; suction; airway adjuncts (OP/NP); call anaesthetics
B — Breathing	RR, depth, symmetry, SpO₂, WOB, auscultation	Administer oxygen per prescription; position upright; ABG if SpO₂ <92%
C — Circulation	HR, BP, CRT, pallor, cyanosis (peripheral vs central)	IV access; fluids; monitor
D — Disability	GCS, AVPU, pupils; CO₂ narcosis (headache, drowsy)	ABG; escalate if GCS falling
E — Exposure	Chest wall movement, surgical emphysema, chest drain	Inspect chest; temperature; skin colour

📈 Respiratory Rate Reference

Normal 12–20 breaths/min (adult)
Tachypnoea >20/min — early sign of deterioration; most sensitive NEWS2 parameter
Severe tachypnoea >30/min — impending respiratory failure
Bradypnoea <12/min — opioid toxicity, CO₂ narcosis, cerebral event
Count manually for full 60 seconds (30 s × 2 is less accurate)
Document alongside depth and pattern (e.g. Kussmaul, Cheyne-Stokes)

⚠ Work of Breathing Signs

Accessory muscle use — sternocleidomastoid, scalenes, trapezius active at rest
Intercostal recession — inward draw of intercostal spaces
Sub-costal recession — visible below costal margin
Nasal flaring — alae nasi dilating on inspiration
Tracheal tug — downward laryngeal movement on inspiration
Paradoxical breathing — abdomen moves in while chest moves out (respiratory muscle fatigue)
Pursed-lip breathing — auto-PEEP in COPD

🔴 Pulse Oximetry — Interpretation & Limitations

SpO₂ Interpretation

≥94% Normal (non-COPD adult)
88–92% Acceptable in COPD (target range)
88–93% Borderline — assess clinically
<88% Hypoxaemia — escalate, review oxygen

SpO₂ is a peripheral measure of haemoglobin saturation — it does NOT measure PaO₂ or ventilation (PaCO₂). A patient can have normal SpO₂ with rising CO₂ (type 2 RF).

Limitations (False Readings)

Carbon monoxide poisoning — COHb reads as OxyHb → falsely high SpO₂
Methaemoglobinaemia — SpO₂ tends toward 85% regardless of true saturation
Severe anaemia — SpO₂ may appear normal despite low O₂ content (low Hb)
Poor perfusion — vasoconstriction, hypotension, hypothermia → poor signal
Dark nail varnish (dark blue/black/green) — may underestimate; remove or use alternative site
Skin pigmentation — studies show SpO₂ may overestimate by ~1–3% in darker skin tones
Motion artefact — shivering, movement; use forehead or earlobe probe

📊 NEWS2 Respiratory Components

Parameter	Score 3	Score 2	Score 1	Score 0	Score 1	Score 2	Score 3
Respiratory Rate	≤8	—	9–11	12–20	—	21–24	≥25
SpO₂ Scale 1 (standard)	≤91	92–93	94–95	≥96	—	—	—
SpO₂ Scale 2 (COPD/hypercapnic)	≤83	84–85	86–87	88–92 on air ≥93 on air	93–94 on O₂	95–96 on O₂	≥97 on O₂

Scale 2 is used for patients with a confirmed diagnosis of hypercapnic respiratory failure (usually COPD). Higher SpO₂ on supplemental oxygen scores higher in Scale 2 — reflecting the risk of over-oxygenation.

🎤 Auscultation Guide

Sound	Character	Common Cause
Vesicular (normal)	Soft, low-pitched, heard throughout inspiration, short expiration	Normal lung parenchyma
Bronchial breathing	Loud, high-pitched, equal inspiration & expiration with gap; heard normally over trachea only	Consolidation (pneumonia), lung collapse
Wheeze (rhonchi)	Musical, continuous; expiratory usually; may be inspiratory in fixed obstruction	Bronchospasm (asthma, COPD), secretions, tumour
Crackles (crepitations)	Fine: high-pitched, end-inspiratory. Coarse: low-pitched, throughout	Fine: pulmonary oedema, fibrosis, early pneumonia. Coarse: secretions, bronchiectasis
Pleural rub	Leathery, creaking sound; heard on inspiration & expiration; does not clear on coughing	Pleuritis, pulmonary embolism
Absent breath sounds	No sound in area	Pneumothorax, pleural effusion, mucus plug

💨 Sputum Assessment

Colour / Type	Likely Significance
Clear / White	Viral infection, COPD, asthma (mucoid)
Yellow / Green	Bacterial infection (purulent); culture & sensitivity if new
Pink frothy	Pulmonary oedema — urgent escalation
Rust-coloured	Pneumococcal (Streptococcus pneumoniae) pneumonia
Frank haemoptysis	TB, lung cancer, PE with infarction, bronchiectasis — urgent review
Black / dark grey	Coal dust, heavy smoking (melanoptysis)

Document: colour, consistency (watery/thick/tenacious), approximate amount (scant/moderate/copious), odour if present.

🎯 Oxygen Target SpO₂ Ranges

Clinical Scenario	SpO₂ Target	Guideline / Rationale
Acutely ill — non-COPD	94–98%	BTS 2017; avoid hyperoxia in stable patients
COPD / hypercapnic risk	88–92%	BTS 2017 — hypoxic drive + Haldane effect (see below)
Post-cardiac arrest (ROSC)	94–98%	AHA/ERC — avoid hyperoxia → reactive oxygen species damage
Sickle cell crisis	≥95%	Hypoxia triggers sickling; liberal oxygen target
Neonates (term)	91–95%	Avoid retinopathy of prematurity; adjust per gestational age
Anaphylaxis	Max (15 L NRM)	High-flow O₂ immediately; part of ABCDE resuscitation
CO poisoning	100% O₂ (NRM)	SpO₂ falsely normal in CO poisoning — DO NOT use SpO₂ to guide; give 100% regardless
Cluster headache	100% O₂ 15 min	High-flow O₂ aborts acute attack; 12–15 L/min NRM

💥 COPD Oxygen Prescribing

Key principle: Oxygen is a drug in COPD. Uncontrolled high-flow O₂ can cause life-threatening hypercapnia.

Why 88–92%?

Hypoxic drive: some COPD patients with chronic CO₂ retention lose chemosensitivity to CO₂ and rely on hypoxia to stimulate breathing
Haldane effect: O₂ displaces CO₂ from haemoglobin (right-shift), raising dissolved CO₂
V/Q mismatch: O₂ causes vasodilation in poorly-ventilated lung → worsens V/Q

Controlled O₂ Protocol

Start Venturi 24% or 28% mask (never NC for precise delivery)
Titrate to SpO₂ 88–92%
ABG within 30–60 min of oxygen change; check pH & PaCO₂
If PaCO₂ rising or pH falling → consider NIV (BiPAP)
Do NOT withhold oxygen if SpO₂ <88% — hypoxia is still dangerous

❤ Cardiogenic Pulmonary Oedema

Upright / high Fowler positioning immediately — reduces venous return
SpO₂ target ≥94%; CPAP reduces preload and improves oxygenation
CPAP 5–10 cmH₂O → recruits alveoli, reduces pulmonary oedema
BiPAP if concurrent hypercapnia or respiratory fatigue
Pink frothy sputum = severe → escalate urgently
Diuretics (IV furosemide) + GTN (if SBP >110 mmHg) alongside NIV

🚫 CO Poisoning Warning

SpO₂ reads falsely normal in carbon monoxide poisoning because pulse oximetry cannot distinguish COHb from OxyHb.

Give 100% oxygen via tight-fitting NRM (15 L/min) regardless of SpO₂. Diagnosis confirmed by co-oximetry ABG (COHb %).

⚡ Anaphylaxis — Immediate Oxygen

Step 1: Remove trigger | Step 2: Call for help | Step 3: IM Adrenaline 0.5 mg (thigh) | Step 4: High-flow O₂ 15 L/min NRM immediately | Step 5: IV access + fluids

Oxygen supports airway oedema management and tissue perfusion during anaphylactic shock. Do not delay for SpO₂ reading.

🔧 NIV (CPAP / BiPAP) Setup & Management

Mask Types

Mask	Pros	Cons
Full face	Best seal, most common	Claustrophobic, aspiration risk
Nasal only	More comfortable, can speak/eat	Leak via mouth, less effective
Helmet (hood)	Well tolerated, less skin risk	CO₂ rebreathing risk, noise, complex fitting

Leak Monitoring

Acceptable leak <30–40 L/min on most devices
Excessive leak → refit mask; try different size or type
Check strap tension: 1–2 fingers between mask and face

Pressure Settings

CPAP: 5–12 cmH₂O — single continuous pressure
Start 5–7 cmH₂O; titrate by 1–2 cmH₂O every 15–30 min

BiPAP:
IPAP: 10–20 cmH₂O (inspiratory support)
EPAP: 4–8 cmH₂O (PEEP equivalent)
PS = IPAP − EPAP (aim 4–10 cmH₂O)
Typical start: IPAP 12 / EPAP 4

Skin Breakdown Prevention

Foam dressings (Mepilex) to nasal bridge and forehead before fitting
30-min breaks every 2–4 h if tolerated (depends on severity)
Inspect skin at every break; document
Rotate mask type if persistent redness

🚨 When to Escalate — NIV Failing Criteria

Consider intubation / escalation to ICU if any of the following:

SpO₂ not improving or deteriorating despite NIV / HFNC at maximal settings
pH <7.25 and worsening (or <7.20 on BiPAP) — acidaemia not correcting
Respiratory rate rising despite NIV — patient tiring, respiratory arrest imminent
Haemodynamic instability — SBP <90 mmHg despite resuscitation
Reduced consciousness — GCS <8 or rapidly falling (aspiration risk, airway unsafe)
Patient unable to tolerate mask / excessive secretions not manageable
Cardiac arrest / respiratory arrest — immediate intubation

Early senior review and anaesthetics involvement is essential before the patient deteriorates to the point of emergency intubation.

📝 Oxygen Prescription Requirements

Oxygen is a drug — must be prescribed by a doctor (or authorised non-medical prescriber) before administration in most GCC institutions, except emergencies.

Prescription Must Include:

Delivery device (e.g. Venturi 28%, nasal cannula)
Flow rate (L/min) or FiO₂ setting
Target SpO₂ range
Duration / review schedule
Indication

Nurse Responsibilities:

Administer as prescribed; document administration
Monitor response (SpO₂, RR, clinical signs) within 5 min of change
Titrate within prescribed range; escalate if outside range
Do not increase beyond prescription without medical review

📄 Observation Documentation Standards

At every oxygen observation, document ALL of the following:

Device — exact device name (e.g. "Venturi 28%" not just "mask")
Flow rate — L/min as set
FiO₂ — percentage delivered (or set)
SpO₂ — value and whether on air or O₂
Respiratory rate — manually counted
Work of breathing — document accessory muscle use if present
Patient response — comfortable, distressed, tolerating device
Time of change and reason for any titration

⚠ Oxygen Toxicity

Absorption Atelectasis

High FiO₂ washes out nitrogen from alveoli
Nitrogen normally splints alveoli open; without it, alveoli collapse
Results in new atelectasis, worsening V/Q mismatch, reduced lung compliance
Especially problematic post-operatively

Free Radical / Oxidative Damage

Prolonged FiO₂ >60% for >24–48 h generates reactive oxygen species (ROS)
ROS damage alveolar epithelium, capillary endothelium
Can progress to ARDS-like picture (diffuse alveolar damage)
Wean FiO₂ <60% as soon as SpO₂ target achieved and maintained

🍥 Nebuliser Therapy & Oxygen

COPD patients: Use air-driven nebulisers (medical air cylinder or wall air) — do NOT nebulise on high-flow oxygen as it will raise their FiO₂ above target and risk CO₂ retention.

Standard nebuliser driven at 6–8 L/min gas flow
COPD with target 88–92%: use medical air at 6–8 L/min; if only O₂ available, add nasal cannula at 1–2 L/min to maintain SpO₂ during nebulisation
Non-COPD: can drive with oxygen at 6–8 L/min (monitor SpO₂)
Document driving gas used (O₂ or air) in medication administration record
Nebuliser duration typically 10–15 min; monitor throughout

📌 Quick Reference Card — Device FiO₂ Summary

Nasal Cannula 1 L/min~24%

Nasal Cannula 2 L/min~28%

Nasal Cannula 4 L/min~36%

Nasal Cannula 6 L/min~44%

Simple Face Mask 5–6 L/min~35–40%

Simple Face Mask 8–10 L/min~45–55%

Non-Rebreather Mask 10–15 L/min~60–80%

Venturi Blue (24%)24%

Venturi White (28%)28%

Venturi Yellow (35%)35%

Venturi Red (40%)40%

Venturi Green (60%)60%

HFNC (titrated)21–100%

CPAP / BiPAP21–100% (set)

Invasive MV21–100% (set)