Oxygen Delivery System| FON | Nasal Cannula, Venturi Mask , Color code Of Cannula

Oxygen Delivery Systems – Fundamentals of Nursing | NORCET Notes 2025

🫁 Fundamentals of Nursing – NORCET 2025

Oxygen Delivery
Systems

Complete study notes on Low-flow & High-flow oxygen devices, FiO2 values, Venturi mask colour codes, cylinder colour codes, oxygen therapy complications and high-yield MCQs — ready for NORCET, AIIMS & State Nursing Exams.

💨 Low-flow & High-flow Devices

🎨 Venturi Colour Codes

🟢 Cylinder Colour Codes

❓ 14 MCQs Included

🧠 Mnemonics

💡 Introduction to Oxygen Therapy

Oxygen therapy is the administration of oxygen at concentrations greater than that in room air (21%) to treat or prevent hypoxia. It is one of the most commonly prescribed therapies in nursing practice. Correct selection of the oxygen delivery device is critical for patient safety and effective treatment.

🌬️

Room Air FiO₂

21%

Normal atmospheric O₂

💧

Normal SpO₂

95–100%

Pulse oximetry

⚠️

Hypoxia SpO₂

< 94%

Requires intervention

🚨

Critical Hypoxia

< 90%

Emergency oxygen

🎯

Max FiO₂ (NRM)

90–95%

Non-rebreather mask

🧠

Key Term – FiO₂ (Fraction of Inspired Oxygen)

FiO₂ = The fraction (proportion) of oxygen in the gas mixture being inhaled. Room air = FiO₂ 0.21 (21%). Pure oxygen = FiO₂ 1.0 (100%). Higher the flow rate → higher the FiO₂ delivered to the patient.

📊 Classification of Oxygen Delivery Systems

Oxygen delivery devices are classified into two main categories based on whether they can meet the patient's total inspiratory flow demand:

Feature	Low-Flow System	High-Flow System
Definition	Provides O₂ at flow rates LESS than patient's inspiratory demand — room air is entrained (mixed in)	Provides O₂ at flow rates that MEET or EXCEED patient's total inspiratory flow demand — no room air entrainment
FiO₂	Variable — depends on patient's breathing pattern (rate, depth, tidal volume)	Fixed, precise, predictable FiO₂
Examples	Nasal cannula, Simple face mask, Partial rebreather, Non-rebreather	Venturi mask, High-flow nasal cannula (HFNC), Aerosol mask, T-piece
Best For	Stable patients with mild hypoxia and normal breathing pattern	Patients needing precise O₂ control (COPD), critically ill
FiO₂ Predictability	❌ Unpredictable	✅ Predictable & precise

📈 FiO₂ Delivered by Each Device – Visual Comparison

Room Air

21%

Nasal Cannula (1L)

24%

Nasal Cannula (6L)

44%

Simple Face Mask

35–55%

Partial Rebreather

60–70%

Non-rebreather Mask

80–95%

Venturi Mask

24–60%

HFNC (High-flow NC)

21–100%

Up to 100%

🟢 Low-Flow Oxygen Delivery Devices

👃

Nasal Cannula (NC)

Low-Flow | Most Common

Flow Rate	1–6 L/min
FiO₂ Range	24% – 44%
FiO₂ Formula	FiO₂ = 20 + (4 × L/min)
Indication	Mild hypoxia, COPD, home O₂
Prongs	2 soft prongs sit in nostrils
Advantage	Patient can eat, talk, cough
Disadvantage	Mouth-breathing reduces FiO₂; nasal dryness

⚠️ Do NOT exceed 6 L/min — causes nasal mucosal drying & discomfort. For each 1 L/min increase, FiO₂ increases by ~4%.

😷

Simple Face Mask (SFM)

Low-Flow | Common

Flow Rate	5–10 L/min
FiO₂ Range	35% – 55%
Minimum Flow	5 L/min (to flush CO₂)
Indication	Moderate hypoxia, short-term use
Exhalation ports	Small holes on side of mask
Advantage	Higher FiO₂ than nasal cannula
Disadvantage	Cannot eat; claustrophobic; FiO₂ variable

⚠️ Minimum 5 L/min MUST be maintained — lower flow causes CO₂ rebreathing & CO₂ retention.

🔄

Partial Rebreather Mask (PRM)

Low-Flow | Reservoir Bag

Flow Rate	6–10 L/min
FiO₂ Range	60% – 70%
Reservoir Bag	Bag must stay ½–⅔ inflated
Valve	NO one-way valve between mask & bag
Rebreathing	First 1/3 expired air re-inhaled (less CO₂)
Indication	Moderate-severe hypoxia
Disadvantage	CO₂ rebreathing possible if flow too low

🔄 The bag should NOT fully deflate during inspiration — increase flow rate if it does.

🚫

Non-Rebreather Mask (NRM)

Low-Flow | Highest FiO₂

Flow Rate	10–15 L/min
FiO₂ Range	80% – 95%
Valve	One-way valve between mask & bag
Exhalation valves	1-way valves on exhalation ports
Rebreathing	NO exhaled air re-enters bag (valve prevents it)
Indication	Severe hypoxia, CO poisoning, trauma, code situations
Disadvantage	FiO₂ still not 100%; uncomfortable

🚨 Highest FiO₂ of any mask (up to 95%). Used in emergencies. Bag must NEVER fully deflate.

🚨

Key Difference! Partial Rebreather (PRM) has NO valve between mask and reservoir bag — first ⅓ of exhaled air re-enters bag. Non-Rebreather (NRM) has a ONE-WAY VALVE — no exhaled air enters bag. NRM gives higher FiO₂.

🔵 High-Flow Oxygen Delivery Devices

🎭

Venturi Mask (Air-Entrainment Mask)

High-Flow | Precise FiO₂

Principle	Bernoulli's principle / Jet mixing (Venturi effect)
FiO₂ Range	24%, 28%, 31%, 35%, 40%, 60%
FiO₂ Control	Colour-coded adapters (diluters)
Best For	COPD patients (precise low FiO₂ needed)
Advantage	Most accurate, fixed FiO₂ regardless of breathing
Disadvantage	Noisy, uncomfortable, limits mobility

✅ GOLD STANDARD for COPD patients — prevents hypoxic drive depression. Colour-coded diluter = easy identification!

💨

High-Flow Nasal Cannula (HFNC)

High-Flow | Modern Device

Flow Rate	Up to 60–70 L/min
FiO₂ Range	21% – 100%
Humidification	Heated and humidified gas
Indication	Severe hypoxia, COVID-19, post-extubation, ARDS
Advantage	Comfortable, reduces work of breathing, provides PEEP
Disadvantage	Expensive, specialised equipment needed

✅ Increasingly used in ICU as alternative to non-invasive ventilation. Provides a small degree of CPAP effect.

🧪

Aerosol Mask / Tracheostomy Mask

High-Flow | With Nebulizer

Flow Rate	10–15 L/min
FiO₂ Range	Variable (set by Venturi)
Humidification	Always humidified via nebulizer
Used With	Tracheostomy patients
T-piece	Used with endotracheal tube / tracheostomy tube
Advantage	Provides moisture and O₂ simultaneously

💧 Always used with humidification. T-piece connects directly to ETT for ventilated patients being weaned off ventilator.

🤿

CPAP / BiPAP (Non-Invasive)

High-Flow | Non-Invasive Ventilation

CPAP	Continuous Positive Airway Pressure — one pressure level
BiPAP	Two pressure levels: IPAP (inspiratory) + EPAP (expiratory)
FiO₂	21–100% (adjustable)
Indication (CPAP)	Sleep apnea, pulmonary edema, mild ARDS
Indication (BiPAP)	COPD exacerbation, hypercapnic respiratory failure
Contraindication	Apnea, facial trauma, inability to protect airway

✅ BiPAP preferred over CPAP for COPD as it assists both inhalation & exhalation. Avoids intubation in many cases.

🎨 Venturi Mask – Colour Code of Adapters (HIGH YIELD!)

🚨

Most Frequently Asked in NORCET! The Venturi mask colour-coded adapters are one of the MOST tested topics. Memorise all 6 colours with their FiO₂ % and flow rates.

24%

2 L/min

BLUE

Lowest FiO₂

28%

4 L/min

WHITE

Mild hypoxia

31%

6 L/min

ORANGE

Moderate

35%

8 L/min

YELLOW

Moderate

40%

10 L/min

RED

High hypoxia

60%

15 L/min

GREEN

Highest FiO₂

🧠

Mnemonic – Venturi Colour Order (Low → High FiO₂)

"Beautiful White Oranges Yield Real Goodness"

Blue = 24%

White = 28%

Orange = 31%

Yellow = 35%

Red = 40%

Green = 60%

Flow rates: 2 – 4 – 6 – 8 – 10 – 15 L/min (increases by 2 till Red, then jumps to 15 for Green)

🟢 Oxygen Cylinder – Colour Codes

Medical gases are colour-coded worldwide to prevent confusion and ensure safety. Nurses must know the colour coding for oxygen and other common medical gases.

O₂

Oxygen (O₂)

Body: Black, Shoulder: White
International (ISO) standard

🇮🇳

Oxygen – India (BIS)

Full Black cylinder
Indian Standard (BIS 7468)

N₂O

Nitrous Oxide (N₂O)

Body: Blue, Shoulder: Blue
Used in anaesthesia

CO₂

Carbon Dioxide (CO₂)

Body: Black, Shoulder: Grey
Used in laparoscopy

E/N₂

Entonox (50% O₂ + 50% N₂O)

Body: White & Blue quartered
Pain relief in labour

Air

Medical Air

Body: White & Black quartered
Used in ventilators

Helium (He)

Body: Brown, Shoulder: Brown
Used with O₂ in airway obstruction

He/O₂

Heliox (He + O₂)

Body: Brown, Shoulder: White & Brown
Upper airway obstruction

🧠

Oxygen Cylinder Colour – Most Tested (India vs International)

🌍 International (ISO) O₂ = Black body + White shoulder

🇮🇳 India (BIS) O₂ = Full Black cylinder

🔵 N₂O = Full Blue

⚪ Entonox = Blue & White quarters

👉 Remember: In India, oxygen cylinders are painted completely BLACK (BIS 7468 standard). International ISO standard = black body with white shoulder (collar).

⚠️ Complications of Oxygen Therapy

Complication	Description	Prevention / Management
Oxygen Toxicity	High FiO₂ (>60%) for prolonged time → lung damage, ARDS-like picture, absorption atelectasis	Use lowest effective FiO₂; monitor regularly
Hypercapnic Drive Suppression (COPD)	COPD patients rely on low O₂ as breathing drive. High O₂ → removes hypoxic drive → respiratory depression, CO₂ retention	Target SpO₂ 88–92% for COPD. Use Venturi mask for precise FiO₂
Absorption Atelectasis	High O₂ replaces nitrogen in alveoli → alveoli collapse when O₂ absorbed rapidly	Use humidified O₂; avoid 100% O₂ unless necessary
Retinopathy of Prematurity (ROP)	High O₂ in premature neonates → retinal blood vessel damage → blindness	Strict SpO₂ targeting in preterm infants (90–95%)
Nasal Dryness / Mucosal Damage	Dry, unhumidified O₂ at high flow dries nasal mucosa	Use humidifier with O₂ at rates > 4 L/min
Fire Hazard	O₂ supports combustion — naked flame near O₂ = fire risk	No smoking, no open flame near O₂ cylinders
Infection	Contaminated humidifiers/nebulizers → respiratory infection	Change humidifier water every 24 hrs; sterile technique

🚨

COPD Warning – Most Important! Never give high-flow oxygen to COPD patients without a specific target. Use Venturi mask at 24–28% FiO₂. Target SpO₂ = 88–92% (NOT 94–98% as in normal patients). High O₂ suppresses hypoxic drive!

👩‍⚕️ Nursing Care During Oxygen Therapy

Verify the Order

Check physician's prescription — flow rate, device, target SpO₂, duration. Oxygen is a DRUG — requires prescription.

Assess the Patient

Check SpO₂, respiratory rate, ABG (if ordered), level of consciousness, skin colour (cyanosis?), and signs of respiratory distress before starting O₂.

Select Correct Device

Choose appropriate device based on required FiO₂, patient condition, and ability to tolerate mask/cannula. COPD → Venturi. Emergency → NRM.

Set Flow Rate Correctly

Attach to O₂ source, set prescribed flow rate, confirm adequate gas flow before applying to patient.

Apply Device Correctly

Ensure proper fit (no leaks). Adjust mask straps. Position nasal cannula prongs curved downward into nostrils. Secure tubing comfortably.

Humidification

Add humidifier if flow rate >4 L/min or for prolonged therapy. Prevents mucosal dryness. Change humidifier water every 24 hours.

Monitor Continuously

Check SpO₂ every 15–30 min initially, then hourly. Watch for signs of O₂ toxicity, CO₂ retention in COPD, skin breakdown under mask straps.

Safety Measures

NO smoking within 3 metres of O₂. No petroleum-based products (Vaseline) near O₂ face — fire risk. Post "No Smoking / Oxygen in Use" sign.

Skin Care

Check behind ears and around face for pressure sores from mask/cannula straps. Apply padding as needed. Reposition mask periodically.

Documentation

Record: flow rate, device used, SpO₂ before & after, time started, patient response, ABG values, any complications observed.

📋 Complete Comparison – All Oxygen Devices at a Glance

Device	Type	Flow Rate	FiO₂	Key Feature
Nasal Cannula	Low-flow	1–6 L/min	24–44%	Most comfortable; can eat/talk; FiO₂ = 20+(4×L)
Simple Face Mask	Low-flow	5–10 L/min	35–55%	Min 5L/min; side ports allow CO₂ escape
Partial Rebreather	Low-flow	6–10 L/min	60–70%	NO valve; 1st 1/3 exhaled air re-inhaled
Non-Rebreather	Low-flow	10–15 L/min	80–95%	ONE-WAY valve; no exhaled air re-enters bag
Venturi Mask	High-flow	2–15 L/min	24–60%	Colour-coded adapters; most precise FiO₂; COPD choice
HFNC	High-flow	Up to 60 L/min	21–100%	Heated + humidified; provides mild PEEP effect
CPAP	High-flow	Variable	21–100%	One pressure level; sleep apnea, pulmonary oedema
BiPAP	High-flow	Variable	21–100%	Two pressures (IPAP+EPAP); COPD exacerbation

🧠

Nasal Cannula FiO₂ Calculation – Easy Formula

FiO₂ (%) = 20 + (4 × Flow Rate in L/min)

1 L/min = 24%

2 L/min = 28%

3 L/min = 32%

4 L/min = 36%

5 L/min = 40%

6 L/min = 44%

📝 High-Yield MCQs – Oxygen Delivery Systems (NORCET 2025)

Q1. The fraction of oxygen in room air (atmospheric air) is?

A) 16%
B) 18%
C) 21%
D) 24%

💡 Tip: Room air FiO₂ = 21%. Nitrogen = 78%, Oxygen = 21%, other gases = 1%. Any O₂ therapy above 21% is therapeutic oxygen. Always remember this baseline value.

Q2. A nasal cannula running at 4 L/min delivers what FiO₂?

A) 28%
B) 32%
C) 36%
D) 40%

💡 Formula: FiO₂ = 20 + (4 × L/min) = 20 + (4×4) = 20 + 16 = 36%. Learn this formula — it's tested frequently in NORCET!

Q3. The BLUE adapter on a Venturi mask delivers which FiO₂?

A) 24% at 2 L/min
B) 28% at 4 L/min
C) 31% at 6 L/min
D) 35% at 8 L/min

💡 Tip: Blue = 24% at 2 L/min (lowest). White = 28%. Orange = 31%. Yellow = 35%. Red = 40%. Green = 60% (highest). Mnemonic: "Beautiful White Oranges Yield Real Goodness".

Q4. Which oxygen delivery device is the GOLD STANDARD for COPD patients?

A) Non-rebreather mask
B) Nasal cannula
C) Venturi mask
D) Simple face mask

💡 Tip: Venturi mask delivers precise, fixed FiO₂ regardless of breathing pattern. COPD patients need controlled O₂ (target SpO₂ 88–92%) to avoid suppressing their hypoxic drive. Venturi = precision.

Q5. The HIGHEST FiO₂ that can be delivered by a simple face mask is?

A) 35%
B) 44%
C) 55%
D) 70%

💡 Tip: Simple face mask = 35–55% FiO₂ at 5–10 L/min. Minimum 5 L/min is mandatory to flush CO₂ from mask. Below 5 L/min → CO₂ rebreathing → dangerous!

Q6. The key difference between a Partial Rebreather and a Non-Rebreather mask is?

A) Size of the reservoir bag
B) Flow rate used
C) Presence of a one-way valve between mask and reservoir bag
D) Color of the mask

💡 Tip: Non-Rebreather has a one-way valve preventing exhaled air from entering reservoir bag = higher FiO₂ (80–95%). Partial Rebreather has NO valve = 1/3 exhaled air re-enters = lower FiO₂ (60–70%).

Q7. The target SpO₂ for a COPD patient on oxygen therapy is?

A) 95–100%
B) 94–98%
C) 88–92%
D) 80–85%

💡 Tip: COPD patients rely on hypoxic drive (low O₂) to breathe. Target SpO₂ = 88–92%. Normal patients target 94–98%. Giving high O₂ to COPD removes their breathing drive → CO₂ narcosis → respiratory arrest!

Q8. What is the colour of an oxygen cylinder in India (as per BIS standards)?

A) Green
B) Blue
C) Black
D) White with black shoulder

💡 Tip: In India (BIS 7468) oxygen cylinder = completely BLACK. Internationally (ISO), oxygen = black body with white shoulder. In USA, oxygen = GREEN. Know the difference for your exam!

Q9. The Venturi principle (Bernoulli effect) used in Venturi mask involves?

A) Compression of gas under high pressure
B) High-velocity jet of O₂ that entrains (draws in) room air to give fixed FiO₂
C) Absorption of CO₂ by soda lime
D) Positive pressure ventilation

💡 Tip: The Venturi effect = high-speed O₂ jet creates low pressure → draws in (entrains) room air in a fixed ratio → produces a precise, predictable FiO₂. Changing the diluter changes the ratio = different FiO₂.

Q10. Which complication of oxygen therapy is specifically seen in PREMATURE neonates?

A) Oxygen toxicity
B) Absorption atelectasis
C) Hypercapnia
D) Retinopathy of Prematurity (ROP)

💡 Tip: High O₂ in premature babies causes retinal blood vessel damage = Retinopathy of Prematurity (ROP) = can cause blindness. Target SpO₂ for premature babies is strictly 90–95%. Very important pediatric point!

Q11. The minimum flow rate for a simple face mask is 5 L/min because?

A) To maintain adequate FiO₂
B) To flush carbon dioxide (CO₂) out of the mask
C) To prevent the reservoir bag from collapsing
D) To activate the Venturi mechanism

💡 Tip: Below 5 L/min in simple face mask → CO₂ accumulates in the mask dead space → patient rebreathes CO₂ → hypercapnia. Always maintain minimum 5 L/min for simple face mask.

Q12. The GREEN Venturi mask adapter delivers which FiO₂?

A) 35%
B) 40%
C) 50%
D) 60%

💡 Tip: Green = 60% at 15 L/min (highest of all Venturi adapters). Red = 40% at 10 L/min. Remember — colours go Blue, White, Orange, Yellow, Red, Green (increasing FiO₂).

Q13. Which device delivers the HIGHEST FiO₂ among the low-flow systems?

A) Nasal cannula at 6 L/min
B) Simple face mask at 10 L/min
C) Partial rebreather mask
D) Non-rebreather mask

💡 Tip: NRM (Non-Rebreather Mask) delivers 80–95% FiO₂ — highest of all LOW-FLOW devices. HFNC can deliver up to 100% but it is a HIGH-FLOW device. In emergencies (CO poisoning, trauma) = always use NRM.

Q14. A nurse notices the reservoir bag of a non-rebreather mask is completely deflating with each breath. The nurse should?

A) Change the mask to nasal cannula
B) Remove the one-way valve
C) Increase the oxygen flow rate
D) Ask the patient to breathe slower

💡 Tip: The reservoir bag should remain at least 1/3 to 2/3 full at all times. If it deflates completely → patient is not getting adequate O₂. Solution = increase flow rate. This applies to both NRM and Partial Rebreather masks.

⚡ Quick Reference – Oxygen Delivery Systems

Room Air FiO₂

21%

Nasal Cannula

1–6 L/min, 24–44%

NC Formula

20 + (4 × L/min)

Simple Mask Min

5 L/min (flush CO₂)

NRM FiO₂

80–95% (highest low-flow)

Venturi – Blue

24% at 2 L/min

Venturi – Green

60% at 15 L/min

COPD Target SpO₂

88–92%

O₂ Cylinder – India

Black (BIS std.)

O₂ Cylinder – ISO

Black + White shoulder

COPD Best Device