Source: https://guthlabs.ai/docs/instruments/cardiac-output-related-hemodynamics/mechanism/

instrument mechanism / verified-clean

# Cardiac Output & Related Hemodynamics mechanism

The inspectable method record for Cardiac Output & Related Hemodynamics, kept separate from implementation and qualification.

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

## Model scope

The exact ambiguity requiring review is the unit of SV: the specification does not state whether SV is mL/beat or L/beat, yet the stated CO output is L/min. Retain the educational, not-medical-advice label; also label CO, CI, and MAP as estimates and document the MAP approximation limits.

- CO=HR×SV is dimensionally correct for CO in L/min only if SV is supplied in L/beat; the common clinical unit mL/beat requires CO=(HR×SV)/1000.

- The specification claims to compute stroke volume, but no stroke-volume formula is provided; SV is listed only as an input. A defined independent formula such as SV=EDV−ESV is required, or the claim must be removed.

- CI=CO/BSA is standard when CO is in L/min and BSA is in m², but the missing CO unit conversion can propagate an error into CI.

- MAP=DBP+1/3(SBP−DBP) is the standard resting approximation, not an exact formula for all heart rates or rhythms.

## Units and conventions

- HR is in beats/min.

- SV test inputs are in mL/beat; therefore HR×SV is divided by 1000 to obtain CO in L/min. Alternatively, the implementation must require SV in L/beat and document that unit explicitly.

- BSA is in m² and must be greater than zero.

- CO is in L/min, CI is in L/min/m², and SBP, DBP, and MAP are in mmHg.

- The MAP one-third pulse-pressure weighting assumes a typical resting cardiac cycle and may be less accurate at substantially elevated heart rates or with irregular rhythms.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "HR_bpm": 70,
    "SV_mL_per_beat": 70,
    "BSA_m2": 1.8,
    "SBP_mmHg": 120,
    "DBP_mmHg": 80
  },
  "expected_outputs": {
    "CO_L_per_min": 4.9,
    "CI_L_per_min_per_m2": 2.7222222222,
    "MAP_mmHg": 93.3333333333
  },
  "working": "CO=(70 beats/min×70 mL/beat)÷1000=4900 mL/min÷1000=4.9 L/min. CI=4.9÷1.8=2.7222222222 L/min/m². MAP=80+1/3×(120−80)=80+40/3=93.3333333333 mmHg."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

BSA=0 makes CI undefined by division by zero, so the instrument must reject that input. The specification also leaves SV units implicit; interpreting SV as mL/beat requires an unstated conversion to produce CO in L/min.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/cardiac-output-related-hemodynamics/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/cardiac-output-related-hemodynamics/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/cardiac-output-related-hemodynamics/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-tranche4/tranche4-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`