Diffrent types of oxygen therapy - give table
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I now have comprehensive data from the textbooks. Let me compile the full table.
Types of Oxygen Therapy
Based on Roberts and Hedges' Clinical Procedures in Emergency Medicine and Rosen's Emergency Medicine.
Low-Flow Devices (Variable FiO₂)
These deliver O₂ at a flow less than the patient's inspiratory flow rate; room air is entrained to make up the difference, so FiO₂ varies with the patient's breathing pattern.
| Device | Flow Rate | FiO₂ Delivered | Key Features / Notes |
|---|---|---|---|
| Nasal Cannula | 1-6 L/min | ~24-44% | Comfortable, well-tolerated; FiO₂ rises ~4% per L/min; nasopharynx acts as reservoir; fire risk if patient smokes |
| Simple Face Mask | 5-10 L/min | ~35-55% (up to 80-90% at 30 L/min) | Mask volume (~200 mL) acts as reservoir; vent holes allow room air entrainment; min 5 L/min to flush CO₂ |
| Partial Non-Rebreather Mask | 6-15 L/min | ~50-70% | Reservoir bag adds oxygen reserve; no one-way valves; some exhaled gas re-enters bag |
| Non-Rebreather Mask (NRM) | 10-15 L/min (standard); up to 45+ L/min | ~70% at 15 L/min; ~90%+ at 45 L/min | One-way valves prevent exhaled gas entering reservoir + room air entering mask; commonly misunderstood to deliver near 100% - in practice ~70% at standard settings |
High-Flow / Fixed FiO₂ Devices
These deliver total gas flow that meets or exceeds the patient's inspiratory demand, minimizing room air entrainment and providing more consistent FiO₂.
| Device | Flow Rate | FiO₂ Delivered | Key Features / Notes |
|---|---|---|---|
| Venturi Mask (Air-Entrainment Mask) | 2-15 L/min O₂ source (total gas flow ~30 L/min) | 24%, 28%, 31%, 35%, 40%, 60% (color-coded jets) | Precise, titratable FiO₂; preferred in COPD patients; cannot reliably exceed 35% FiO₂; FiO₂ drops in respiratory distress if inspiratory flow >30 L/min |
| High-Flow Nasal Cannula (HFNC) | 5-60 L/min (heated, humidified) | 70-80% at 15 L/min; ~90%+ at 45 L/min; up to ~100% | Wide-bore nasal prongs; requires humidifier; provides ~5 cmH₂O PEEP effect; better tolerated than face mask/NPPV; suitable for hypoxemic respiratory failure |
Positive Pressure / Ventilatory Support Devices
| Device | FiO₂ | Key Features / Notes |
|---|---|---|
| Non-Invasive Positive Pressure Ventilation (NPPV/NIV) - includes CPAP & BiPAP | 21-100% (titrated) | Tight-fitting mask; delivers set pressures; used in COPD exacerbation, pulmonary edema, OSA; avoids intubation |
| Bag-Valve-Mask (BVM / Ambu bag) | ~40-60% without O₂ reservoir; ~90-100% with reservoir + 15 L/min O₂ | Manual ventilation for apneic patients; rescue device after failed intubation; tidal volume ~500 mL over 1-1.5 sec to minimize gastric inflation |
| Invasive Mechanical Ventilation (Endotracheal Tube / ETT) | 21-100% (precisely set) | Full control of FiO₂, PEEP, tidal volume, rate; used for respiratory failure, airway protection, apnea; gold standard for most critical patients |
Hyperbaric / Specialized Devices
| Device | FiO₂ / Pressure | Key Features / Notes |
|---|---|---|
| Hyperbaric Oxygen Chamber | 100% O₂ at >1 atm (2-3 ATA) | Used for CO poisoning, decompression sickness, gas gangrene, wound healing; CO half-life cut from ~4-5 hr (room air) to ~20 min |
| Portable Hyperbaric Chamber (Gamow bag) | Simulates descent by pressurization | Used in wilderness/altitude medicine for high-altitude illness when descent is impossible |
| Transtracheal Oxygen (TTO) | Low flow (0.5-2 L/min) | Catheter inserted percutaneously into trachea; used for long-term home O₂; more efficient than nasal cannula, cosmetically preferred |
Quick Reference: FiO₂ by Device
| Device | Min FiO₂ | Max FiO₂ |
|---|---|---|
| Nasal cannula | ~24% | ~44% |
| Simple mask | ~35% | ~90% (high flow) |
| Non-rebreather mask | ~60% | ~90% (high flow) |
| Venturi mask | 24% | ~60% (but unreliable >35%) |
| HFNC | ~30% | ~100% |
| NPPV/NIV | 21% | 100% |
| Mechanical ventilation | 21% | 100% |
| Hyperbaric chamber | 100% | 100% at elevated pressure |
Key clinical points:
- Never withhold O₂ from a hypoxemic patient out of fear of complications; CO₂ retention is a reason for caution, not a contraindication
- Target SpO₂ 94-98% in most patients; 88-92% in COPD (to avoid blunting hypoxic drive)
- In STEMI, O₂ is only indicated if SpO₂ <90%; routine O₂ in normoxic MI patients increases infarct size
- At 100% FiO₂, CO-poisoning carboxyhemoglobin half-life drops from ~5 hours to ~1 hour
Sources: Roberts and Hedges' Clinical Procedures in Emergency Medicine; Rosen's Emergency Medicine, 10e
High flow , low flow
Here is a focused comparison of High-Flow vs Low-Flow Oxygen Systems:
Low-Flow vs High-Flow Oxygen Systems
The key distinction is not the liter-per-minute rate but whether the device meets the patient's total inspiratory demand.
Core Concept
| Parameter | Low-Flow System | High-Flow System |
|---|---|---|
| Definition | O₂ flow is LESS than patient's inspiratory flow rate | O₂ flow MEETS or EXCEEDS patient's inspiratory flow rate |
| Room air entrainment | YES - variable amount entrained to make up the deficit | MINIMAL to NONE |
| FiO₂ | Variable - changes with patient's breathing pattern | Fixed / predictable |
| Effect of tachypnoea | FiO₂ drops as respiratory rate/depth increases | FiO₂ remains stable |
| Patient's inspiratory flow | Typically 30-100 L/min in distress | Device matches or exceeds this |
Low-Flow Devices
| Device | O₂ Flow (L/min) | Approx FiO₂ | Notes |
|---|---|---|---|
| Nasal Cannula | 1 | ~24% | +4% per extra L/min (rough rule) |
| 2 | ~28% | ||
| 3 | ~32% | ||
| 4 | ~36% | ||
| 5 | ~40% | ||
| 6 | ~44% | Max for standard nasal cannula | |
| Simple Face Mask | 5-6 | ~35-40% | Min 5 L/min to wash out CO₂ |
| 8-10 | ~45-55% | ||
| Partial Rebreather Mask | 6-10 | ~40-70% | Reservoir bag, no one-way valves |
| Non-Rebreather Mask | 10-15 | ~60-80% | One-way valves; commonly thought to give 100% but actually ~70% at 15 L/min |
Limitation: In a distressed, tachypnoeic patient, all low-flow devices deliver LESS FiO₂ than predicted because more room air is entrained.
High-Flow Devices
| Device | O₂ Flow (L/min) | FiO₂ | Notes |
|---|---|---|---|
| Venturi Mask | 2 | 24% | Color-coded jets (blue = 24%) |
| 4 | 28% | White jet | |
| 6 | 31% | Yellow jet | |
| 8 | 35% | Red jet | |
| 10 | 40% | Green jet | |
| 15 | 60% | Pink jet (unreliable >35% in distress) | |
| High-Flow Nasal Cannula (HFNC) | 15 | ~70-80% | Heated, humidified; wide-bore prongs |
| 30-40 | ~90% | ||
| 40-60 | ~95-100% | Provides ~5 cmH₂O PEEP effect | |
| NRM at flush flow | 40-45+ | ~90%+ | Standard flowmeter opened to flush |
Side-by-Side Summary
| Feature | Low-Flow | High-Flow |
|---|---|---|
| Examples | Nasal cannula, simple mask, NRM (standard) | Venturi mask, HFNC, NRM at flush |
| FiO₂ precision | Poor - variable | Good - predictable |
| FiO₂ range | 24-80% | 24-100% |
| Affected by breathing pattern? | YES | Minimally (Venturi) / No (HFNC at high flows) |
| Humidification needed? | Not usually (up to 4 L/min nasal cannula) | YES for HFNC (nearly 100% humidity required) |
| PEEP effect | None | Small (~3-5 cmH₂O with HFNC) |
| Equipment complexity | Simple, cheap | More complex (HFNC needs special setup) |
| Patient comfort | High (cannula) / Moderate (mask) | High (HFNC) / Moderate (Venturi mask) |
| Best for | Mild-moderate hypoxia, stable breathing | Severe hypoxia, respiratory distress, COPD (Venturi) |
| Use in COPD | Risky without titration | Venturi preferred (precise low FiO₂) |
Clinical Decision Guide
SpO₂ < 90%, stable breathing → Nasal cannula 2-4 L/min (low-flow)
SpO₂ < 90%, COPD → Venturi mask 24-28% (high-flow, controlled)
Moderate hypoxia, distress → Simple mask / NRM 10-15 L/min
Severe hypoxia, avoid intubation → HFNC 30-60 L/min
CO poisoning → NRM at flush / 100% O₂
Apnoea / arrest → BVM + 100% O₂ → Intubation
Key rule to remember: A Venturi mask running at only 2 L/min source O₂ is classified as high-flow because its total delivered gas (O₂ + entrained air) = ~30 L/min, matching the patient's inspiratory demand. A non-rebreather at 15 L/min is technically low-flow because 15 L/min still falls short of a distressed patient's 50-100 L/min inspiratory demand.
Source: Roberts and Hedges' Clinical Procedures in Emergency Medicine
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