{
  "abstract": "BackgroundVideolaryngoscopy still requires adjuncts or hyperangulated rescue in a clinically important minority, and bedside screening discriminates modestly. Point-of-care ultrasound (POCUS) of the anterior airway is a promising alternative, but existing prediction models are opaque or assume a pre-specified functional form. We developed and internally validated a parsimonious, fully disclosed POCUS risk equation whose form is recovered from data and whose structural properties are machine-checked by formal proof -- to our knowledge the first formally verified clinical risk predictor -- following TRIPOD+AI 2024.\n\nMethodsIn a prospective single-centre, single-operator cohort of 259 adults undergoing elective videolaryngoscopy (no-Easy airway 68/259, 26.3%), Sequentially Thresholded Least Squares with bootstrap stability selection (B = 300) screened a 71-term library of nine POCUS features and retained a seven-term logistic equation; a two-term bootstrap-stable model was pre-specified as robustness analysis. Internal validation used 5 x 10 repeated cross-validation plus temporal and device hold-outs, with pre-specified overfitting and optimism assessments. Five behavioural properties of the deployed equation were machine-checked in Lean 4.\n\nResultsTwo interactions met the |c|/{sigma}c > 2 stability criterion: skin-to-epiglottis x skin-to-hyoid-bone distance and tongue volume x sagittal tongue area. The seven-term equation reached a 5 x 10 cross-validated C-statistic of 0.966 (optimism-corrected 0.968) and held across temporal and device hold-outs (0.94-0.97). Calibration-in-the-large matched prevalence, with cross-validated slope 0.90 attenuating to 0.625 out-of-time; standard recalibration restored 0.92 without loss of discrimination. The pre-specified two-term robustness model reproduced this performance (C-statistic 0.964-0.968; events-per-parameter 34; shrinkage 0.99), confirming the result is not an artefact of the screening stage. Net benefit over a clinical baseline was positive across 10-50% thresholds. All five Lean 4 theorems compiled without sorry.\n\nConclusionsA sparse, formally verified POCUS equation predicts difficult videolaryngoscopy with high internally validated discrimination and quantified, modest overfitting. Because the equation was developed in a single-operator cohort and its inputs are operator-dependent, external validation requires prior harmonisation of the measurement protocol and operator credentialing.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 4,
  "authors": [
    {
      "name": "R. A. Oyarzun-Silva"
    },
    {
      "name": "P. Hernandez-Hernandez"
    },
    {
      "name": "M. A. Fernandez-Vaquero"
    },
    {
      "name": "N. De Luis-Cabezon"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/dt4mp2wb04zcz.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.08.28.26361621",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.08.28.26361621v1.full",
  "id": "dt4mp2wb04zcz",
  "issns": [],
  "landing_url": "https://www.medrxiv.org/content/10.64898/2026.08.28.26361621v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "medrxiv",
      "anesthesia"
    ],
    [
      "openalex",
      "2703|Airway Management and Intubation Techniques"
    ]
  ],
  "openalex": "W7206173711",
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.08.28.26361621v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-08-28",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/dt4mp2wb04zcz.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:34Z",
      "native_id": "10.64898/2026.08.28.26361621",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.08.28.26361621v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:anesthesia",
      "subfield": "surgery"
    }
  ],
  "title": "An interpretable, formally verified point-of-care ultrasound risk equation for difficult videolaryngoscopy: development and internal validation",
  "title_text": "An interpretable, formally verified point-of-care ultrasound risk equation for difficult videolaryngoscopy: development and internal validation",
  "type": "preprint",
  "updated_at": "2026-10-30T12:17:34Z",
  "url": "https://research.draconitic.com/paper/dt4mp2wb04zcz",
  "venue": "medRxiv",
  "versions": []
}