Separate lasting injury history from the active burden that can recover. Follow brain pressure, oxygen delivery and changing vascular tone together.
The lasting, high-water injury grade. It sets the patient's remaining cerebrovascular and autonomic reserve and the pressure requirements for recovery. Severe and critical structural injury remain vulnerable after acute symptoms settle.
The current secondary injury burden. It can rise with new insults and fall when oxygen delivery, ventilation, ICP and perfusion improve. Stable mild or moderate TBI can resolve toward zero, subject to any herniation injury floor.
A concussion can remain in the history without continuing to generate ICP, unconsciousness or deterioration. As acute burden resolves, the ICP target returns toward the normal 10 mmHg baseline, rather than zero.
Both severity values use a 0–1 scale. A fresh injury initializes both. Repeat impact or blast compares incoming severity with the current acute value, while structural severity preserves the greater historical injury grade. A previously resolved injury can therefore become active again.
Head impact and blast exposure can enter the TBI system. A visible head wound is not required for blast related TBI.
| Finding | Meaning in the examination |
|---|---|
Equal and reactive / PERRL | No abnormal pupil state and ICP below the early warning threshold |
Both equal but slow | ICP at least 18 mmHg by default, or a Cushing state |
One larger and slower / anisocoria | Asymmetric pupil state, with the affected side recorded by the injury |
One fixed and dilated | Impending herniation can produce this finding while the other pupil still reacts |
Both fixed and dilated | Can accompany established or terminal herniation; assess the complete patient |
Nystagmus / rapidly moving eyes | Separate ketamine finding; review the sedation explanation linked below |
For ketamine sedation and pupil findings, see Ventilator Settings & Tips.
Intracranial pressure opposes the pressure supplying the brain. The recovery calculation uses effective brain MAP:
Head elevation subtracts a default 6 mmHg from the MAP used by this calculation. The debug overlay currently subtracts ICP from systemic MAP instead, so displayed CPP can differ from the recovery calculation when the head is elevated.
In gameWhat raises ICP
Active injury burden, poor ventilation, altered cerebral blood volume, fluid overload, positive pressure and ventilator dyssynchrony can raise ICP. The burden component uses the greater of baseline ICP and 40 × acute severity; 40 mmHg is not an absolute cap on combined effects. Structural history alone no longer sustains the old severity driven ICP burden.
The base injury rise coefficient is 0.015 per second, scaled by acute severity. The maximum configured CO₂ coefficient is 0.12 per second, scaled by the ventilation disturbance. The ordinary global rise cap is 0.025 mmHg per second and the fall cap is 0.04 mmHg per second. These are coefficients and limits, not a guaranteed patient slope. Procedure effects can be applied separately.
There is no longer a universal MAP below 85 means ongoing TBI injury rule. Structural grade sets the pressure requirement. Mild and moderate injury can recover within the normal MAP recovery band.
| Structural grade | Severity | Direct hypotension floor | Recovery MAP minimum | Additional CPP minimum |
|---|---|---|---|---|
Mild | Up to 0.35 | 60 mmHg | 65 mmHg | No fixed CPP floor |
Moderate | Above 0.35 to 0.60 | 60–65 mmHg | 65 mmHg | No fixed CPP floor |
Severe | Above 0.60 to 0.80 | 65–75 mmHg | Same rising floor | 55 mmHg |
Critical | Above 0.80 to 1.00 | 75–85 mmHg | Same rising floor | 60 mmHg |
Read the recovery ranges
Ranges show linear scaling within each grade, not a choice of targets. The recovery minimum is the greater of 65 mmHg and the structural hypotension floor. All MAP values above mean effective brain MAP. The lower mild hypotension floor does not make MAP 60 sufficient for recovery: below the recovery MAP gate, the separate low CPP injury path can still add acute burden.
CautionRecovery gates act together
All conditions must be met together. Oxygen delivery deficit starts below 70% of the model reference and, once active, clears at 78% or more. The higher clearing threshold prevents repeated switching near the boundary. A 45-second reperfusion window limits renewed delivery related injury after recovery, but does not bypass the recovery gates.
Effective MAP 70, ICP 10, CPP 60: the pressure gate passes. With adequate oxygen delivery and ventilation, acute burden can resolve. CPP 70 is not required.
Structural 0.75 gives a MAP floor of 72.5. Effective MAP 80 and ICP 14 give CPP 66, passing the 55 minimum. Recovery can occur while reduced reserve remains.
Structural 0.90 gives a MAP floor of 80. At effective MAP 80 and ICP 25, CPP is only 55. MAP and ICP pass, but the critical CPP minimum of 60 does not.
The legacy CPP 70 target and debug CPP warning colors are not universal healing gates. PerfOK reports the pressure predicate only; it does not confirm oxygen delivery, SpO₂ or ventilation. See the debug field reference.
Cerebral autoregulatory integrity describes how well brain vessels adjust to pressure. Mild TBI retains essentially normal control, moderate injury only mild impairment, and severe or critical structural injury progressively less reserve. Secondary injury, exhausted compensation and herniation can reduce it further.
Impaired autoregulation makes low CPP more damaging. High CPP becomes increasingly pressure passive: excessive pressure can add to ICP. Raising pressure indefinitely is not always protective.
Autonomic integrity is the remaining ability to regulate systemic vascular tone. Signed tone shows the direction: positive means vasoconstriction, zero neutral, and negative vasodilation. Tone ranges from −1 to +1 and changes progressively over time.
These are separate integrity states. A historical severe injury can have stable acute symptoms while both retain reduced reserve.
Vascular failure can appear without the full Cushing pattern. Once autonomic reserve is exhausted, the separate vascular path can alter peripheral resistance without imposing Cushing bradycardia, abnormal breathing or a hypertensive target. Do not wait for all three vital signs to change before reassessing.
Structural autoregulation baselines are 1.00 through mild injury, then interpolate to 0.95 at moderate, 0.70 at severe and 0.35 at critical maximum severity. Autonomic baselines interpolate from 1.00 to 0.97, 0.80 and 0.55 respectively. Acute burden, compensation exhaustion and herniation can push the live values below these baselines; both live integrities are bounded between 0.05 and 1.
With impaired autoregulation, the pressure passive component begins above CPP 70 and scales to its full fraction at 100 mmHg, weighted by lost integrity. Its configured maximum contribution is 8 mmHg. These are internal model thresholds, not an instruction to target CPP 100.
The default compensation budget is 600 seconds. It accumulates only when the pressure predicate fails and the injury is eligible: structural severity at least 0.60, acute severity at least 0.65, or ICP at least 25. Otherwise the budget recovers. A stable, well perfused mild or moderate injury does not exhaust a timer simply because its history remains.
The interaction runs through circulation rather than a fixed TBI bleeding multiplier. These directions describe the custom junctional channel with other inputs held equal; changing MAP, volume, wound control and coagulation still affect actual loss.
Positive sympathetic tone increases peripheral resistance, tending to reduce junctional flow. This temporary protection does not close the wound.
Negative tone lowers resistance, tending to increase junctional flow. Lost autonomic integrity also weakens the vessel's temporary spasm and compensation.
25% + (75% × autonomic integrity)
Integrity 1.00 preserves 100% of ordinary compensation. At the equation's zero-integrity endpoint, 25% remains. The current controller stops at 0.05, corresponding to 28.75%.
In gameHow compensation is counted
This scales the existing compensation mechanism, not total blood loss. Signed tone is already carried by systemic peripheral resistance and is not applied a second time in the junctional equation. The combined circulation update debits the blood compartment once. See Hemorrhage & shock for wound control and other loss factors.
In this game implementation, elevated head positioning blocks new herniation progression and allows the cascade to recede. It also lowers effective brain MAP by 6 mmHg, so reassess pressure gates after positioning.
Hypertonic saline and mannitol can reduce pressure through osmotherapy. Address inadequate circulating volume and perfusion as well. Excessive ventilation can lower ICP while adding ischemic injury; pressure support and ventilation need reassessment rather than indefinite escalation.
CautionWhat vehicle evacuation changes
When the vehicle evacuation option is enabled, entering a vehicle marks the patient as evacuated for the herniation calculation and pauses cascade progression. This does not erase structural history, established injury or other physiological problems. Vehicle evacuation does not stop an already active stage 3 terminal arrest timer. Continue monitoring during transport.
Rate of recovery
When all recovery conditions hold, acute severity falls by a default 0.0025 per second toward its injury floor. This is an uninterrupted model rate, not a guaranteed recovery time. Recent hypertonic saline or mannitol can double the rate for 120 seconds; the physiology gates still apply.
| Furthest herniation stage | Acute recovery limit | Practical meaning |
|---|---|---|
Never reached stage 1 | Can recover toward zero | Structural injury history remains. Its grade still determines reserve and pressure requirements. |
Stage 1: impending | Floor of 0.01–0.30, scaled to the depth of the impending episode | Can stabilize in the field. The TBI evacuation requirement can clear after the impending state resolves and acute severity returns close to its floor. |
Stage 2 or beyond | Persistent default floor of 0.85 | Established injury requires evacuation. Reducing ICP does not erase this damage. |
Stage 3: terminal | Dedicated arrest timer defaults to 20 seconds | Other causes, including hemorrhage or hypoxia, can cause arrest before this stage. |
The full TBI vital-pattern controller retains nonterminal limits on its HR, MAP and breathing targets. Those limits are not a survival guarantee: the separate vascular path and simultaneous blood loss or hypoxia still matter.
In gameHerniation timing
At default settings, ICP at or above 30 mmHg accumulates time toward a 600-second herniation gate while the head is not elevated. Below that pressure, or with the head elevated, accumulated time falls at half speed. Once the gate is open, progression uses 360-second stage intervals. Pressure control, elevated head positioning and evacuation can interrupt or pause progression. This herniation clock is separate from the compensation budget.
TBI behavior checked against ACM Extended B119 on dev, revision 98d18bb (14 September 2026). The supplied patch reports source and model checks; in-engine physiology and multiplayer staging remain pending. These are game defaults and mission settings can change them. Recovery and pressure gates · Defaults · Vascular and vital responses · Junctional coupling · Debug display · Unchanged pupil assessment.