EASy Hypoxia Protocol
Educational framework: this combines validated EASy components; the complete EASy Hypoxia pathway has not yet undergone protocol-specific validation.
Clear the airway → acquire the focused exam → identify the predominant mechanism of hypoxaemia → act on it.
🎓 Train in the EASy module →Airway-first POCUS for the desaturating patient in the post-anaesthesia care unit
What is EASy Hypoxia?
EASy Hypoxia extends the EASy MAP framework to the desaturating perioperative patient — the one who is frequently not breathless, but sedated, blocked, or splinted.
The order is fixed: airway, then ventilation, then the probe. Ultrasound is step three because a blocked airway and a blocked tube both kill faster than you can find a lung point — and both are invisible on the lung profile that would otherwise send you down the wrong branch.
Key Principles
- Airway before the probe — An occluded tube reads as a clean A-profile and an endobronchial tube reads as absent sliding — an airway problem can route a lung-first pathway to the wrong branch
- Acquire like MAP, report lungs first — Same subcostal-anchored sweep as EASy MAP; the lung profile is what branches a hypoxia differential
- Oxygen response supports the mechanism — V/Q mismatch usually improves substantially with oxygen; a large right-to-left shunt responds incompletely. Mixed post-operative physiology is common, so the response supports rather than proves the mechanism
- A normal scan is a result — Residual block, upper airway obstruction, shunt and shivering all scan clean — and several are the most reversible causes in recovery
- Name the predominant mechanism — Peri-operative hypoxia is often multifactorial; treat the predominant driver, then reassess
When to Use EASy Hypoxia
- SpO₂ < 90% in the PACU
- Desaturation on the ventilator, with or without rising pressures
- Hypoxia after extubation
- Sudden desaturation with a haemodynamic change
- Unexplained hypoxia with a clean chest film
The EASy Hypoxia examination
Acquired in the EASy MAP sequence — subcostal 4-chamber, IVC, then four lung zones. Reported lungs first, because the lung profile branches the differential; on the ventilator, the pressure loop leads.
Airway — before the probe
Patent and ventilating, or not. If intubated: confirmed, patent, correctly sited.
Pressure loop — if ventilated
Ppeak − Pplat is resistance; Pplat − total PEEP is driving pressure. Measured passively, values around or above 15 flag rising respiratory-system stress — reassess, not an isolated target. Three patterns split the differential before the probe touches skin.
Subcostal 4-chamber
RV:LV ratio and septal shape before LV function. Scored on the same 12-point scale as EASy MAP.
IVC
Venous pressure and filling, sampled just distal to the hepatic vein. Integrated with the cardiac and lung findings it helps distinguish hydrostatic congestion from a permeability process — it does not determine the cause of B-lines on its own.
Lung — four zones
One overall profile: A/A, B/B, A/B, consolidation, effusion, or absent sliding.
The differential, marked first
Seven mechanisms, each marked present or excluded before scanning. The exam names which is predominant and shows where your pre-scan impression held.
Thirteen phenotypes, seven mechanisms
Each phenotype names the predominant physiology causing the hypoxaemia at the moment you scanned — not every abnormality present, and dynamic. Two mechanisms have no phenotype because the probe cannot see them: low inspired oxygen and diffusion limitation, both excluded off-screen.
| Phenotype | Mechanism | EASy pattern | First move |
|---|---|---|---|
| H1 Upper airway obstruction | Hypoventilation | Normal or reduced excursion | Open the airway — do not scan first |
| H2 Hypoventilation | Hypoventilation | Clear; rising EtCO₂ | Support ventilation; reverse block to TOF ≥ 0.9 |
| H3 High-pressure oedema | Shunt | B/B, plethoric IVC, dilated LA | Sit up, CPAP; stop fluids; 12-lead + troponin |
| H4 Low-pressure oedema | Shunt | A/B patchy, normal IVC | Treat the trigger, CPAP; don't diurese a euvolaemic patient |
| H5 Atelectasis / collapse | Shunt | C, static bronchograms, lung pulse | Recruit + PEEP, analgesia; withdraw a mainstem tube |
| H6 Pneumonia / aspiration | Shunt | C, dynamic bronchograms | Head-up, suction, PEEP; antibiotics only if infected |
| H7 Pneumothorax | V/Q → obstructive | No sliding, no lung pulse; lung point | Decompress if tensioning, before imaging further |
| H8 Obstructive airway | V/Q mismatch | A/A, wheeze, ↑Ppeak − Pplat | Bronchodilator, lengthen expiration; watch for stacking |
| H9 Acute RV failure — embolic | Dead space | A/A, dilated RV, plethoric IVC, ↓EtCO₂ | Noradrenaline early; don't fluid-load; correct hypoxia/CO₂ |
| H10 Effusion / haemothorax | Shunt (compressive) | E, spine sign, jellyfish | Drain what compresses; if bleeding, call surgery |
| H11 Extrapulmonary hypoxia | ↓ Content / delivery | Clean scan | Blood gas + co-oximetry, haemoglobin, lactate — the off-screen causes |
| H12 Tube displacement | Airway / circuit | No EtCO₂; bilateral no sliding | If in doubt, take it out and bag-mask |
| H13 Tube / circuit obstruction | Airway / circuit | ↑Ppeak, normal Pplat | Disconnect, hand-bag, pass a suction catheter |
Oxygen response supports the read, it does not prove it: V/Q mismatch usually improves substantially with oxygen; a large shunt responds incompletely; mixed physiology is common.
Findings that mislead
Each of these looks like one thing and is another
Absent sliding WITH a lung pulse
Not a pneumothorax — the pleura are still touching. Endobronchial tube, mucus plug, or apnoea.
Bilateral absent sliding just after intubation
Check the tube before the pleura. An oesophageal tube mimics bilateral pneumothorax.
Normal peak pressure with profound hypotension
Auto-PEEP. Disconnect for fifteen seconds — if the blood pressure returns, you were stacking.
Bilateral B-lines with a flat IVC
Discordant for hydrostatic oedema. Reconsider a permeability cause before you reach for a diuretic.
Normal scan, unassessable cardiac window
The RV has not been excluded, so embolism has not been excluded. A poor image is not a diagnosis.
Hypoxia and hypotension together
They often share one cause — tension pneumothorax, massive PE, anaphylaxis, cardiogenic oedema. Hunt those first and treat the shock in parallel.
Free bedside cards
Print and laminate for your own machines — letter landscape, no sign-up. They render from the same content as the tool, so they cannot drift apart.
EASy Hypoxia
The fixed order, the lung-profile branches with their discriminators, the off-screen causes, and the findings that mislead.
Mechanical Ventilation Hypoxia
DOPES and the disconnect test, the two gaps and their targets, and the three pressure patterns for the ventilated patient.
Work a live patient through the pathway
Take a real desaturation through the EASy Hypoxia tool
Every EASy application is one loop of the same pathway. See the next step in the pathway