Source: https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/implementation/

instrument implementation / implementation-contract

# Lung Capacity Predicted Values (Spirometry Reference) implementation

A source-bound implementation contract for Lung Capacity Predicted Values (Spirometry Reference); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t7-025

**Effect**: Computation or source lookup only

## Input and validation requirements

The specification cannot produce numerical predicted FVC, FEV1, or ratio outputs because the required GLI-2012 coefficient tables and exact validity/switch definitions are missing. In addition, measured FEV1/FVC with measured FVC = 0 creates an undefined 0/0 result that must be explicitly rejected or reported as undefined.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "age_years": 25,
    "height_cm": 180,
    "sex": "male",
    "ethnicity": "Caucasian",
    "measured_FVC_L": 5,
    "measured_FEV1_L": 4
  },
  "expected_outputs": {
    "predicted_FVC_L": 5.5,
    "predicted_FEV1_L": 4.4,
    "predicted_FEV1_FVC_ratio": 0.8,
    "FVC_percent_predicted": 90.91,
    "FEV1_percent_predicted": 90.91
  },
  "reference_data": {
    "predicted_FVC_L": 5.5,
    "predicted_FEV1_L": 4.4,
    "source_convention": "GLI-2012 spirometry reference convention; provisional arithmetic test fixture, not an official coefficient-table extract"
  },
  "working": "Predicted ratio = predicted FEV1 / predicted FVC = 4.4 / 5.5 = 0.800000. FVC %predicted = 5.0 / 5.5 x 100 = 0.9090909 x 100 = 90.91%. FEV1 %predicted = 4.0 / 4.4 x 100 = 0.9090909 x 100 = 90.91%."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/lung-capacity-predicted-values-spirometry-reference/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-tranche7/tranche7-results.json`