Source: https://guthlabs.ai/docs/instruments/mean-arterial-pressure-pulse-pressure/mechanism/

instrument mechanism / verified-clean

# Mean Arterial Pressure & Pulse Pressure mechanism

The inspectable method record for Mean Arterial Pressure & Pulse Pressure, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The two arithmetic formulas are standard under the stated approximation, but the instrument cannot be fully verified until the exact AHA threshold table, adult-population scope, unit contract, category-selection rule, and invalid-input policy are specified. The category labels in these test vectors are conditional on the standard adult AHA thresholds stated above.

- MAP=DBP+(SBP−DBP)/3 is the standard approximate resting MAP formula, not an exact formula for all heart rates or cardiac cycle timings; heart rate or systolic/diastolic time fractions would be needed for a more general calculation.

- PP=SBP−DBP is correct.

- The output category label has no formula or explicit threshold table in the spec. AHA adult blood-pressure categories classify the higher applicable SBP or DBP category, but the exact AHA edition and threshold rules are unspecified.

## Units and conventions

- SBP and DBP are numeric blood-pressure readings in mmHg unless an explicit unit-conversion layer is added.

- MAP and PP are reported in mmHg when the inputs are in mmHg; the arithmetic itself preserves the input unit.

- AHA category examples below assume standard adult categories: normal SBP <120 and DBP <80; elevated SBP 120–129 with DBP <80; stage 1 SBP 130–139 or DBP 80–89; stage 2 SBP >=140 or DBP >=90.

- AHA categorization requires adult context and normally should not be interpreted from one isolated reading.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "systolic": 118,
    "diastolic": 76,
    "unit": "mmHg"
  },
  "expected_outputs": {
    "MAP": 90,
    "PP": 42,
    "category_label": "Normal (assuming standard adult AHA thresholds)"
  },
  "working": "PP = SBP − DBP = 118 − 76 = 42 mmHg. MAP = DBP + (SBP − DBP)/3 = 76 + (118 − 76)/3 = 76 + 42/3 = 76 + 14 = 90 mmHg. Both SBP 118 and DBP 76 are below the normal-category boundaries, so the assumed AHA label is Normal."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

Extreme finite-number inputs overflow the plain-JavaScript subtraction to Infinity, and zero or reversed/nonphysical pressures can produce arithmetic outputs even though they should be rejected. Category behavior for invalid values is not defined by the specification.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/mean-arterial-pressure-pulse-pressure/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/mean-arterial-pressure-pulse-pressure/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/mean-arterial-pressure-pulse-pressure/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`