{
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  "capturedAt": "2026-10-29T10:31:13.619Z",
  "sha256": "de6b6091f60244404dd90d26b766e58a82d5f98ad91de2173ed752aba0652566",
  "work": {
    "id": "TAP-RDN-0018",
    "type": "RDN",
    "kind": "note",
    "key": "billman-2013",
    "locale": "en",
    "path": "/research/billman-2013/",
    "title": "TAP reading note: The LF/HF ratio does not accurately measure cardiac sympatho-vagal balance",
    "description": "Billman examines the assumptions needed to interpret LF/HF as cardiac sympathetic–vagal balance. LF is not a purely sympathetic signal, HF is influenced by respiration and mechanical effects, and autonomic branches do not always vary reciprocally or linearly. Similar ratios can therefore arise from different physiological processes.",
    "rights": "© The Allostasis Project. All rights reserved. Reproduction or adaptation requires separate permission, subject to applicable legal exceptions.",
    "version": "0.3",
    "updatedAt": "2026-10-29",
    "editorial": {
      "contentType": "evidence-review",
      "reviewState": "draft",
      "reviewedAt": null,
      "reviewedVersion": null,
      "updatedAt": "2026-10-29",
      "version": "0.3",
      "author": null,
      "reviewer": null,
      "workflow": {
        "ai": {
          "usage": "used",
          "system": "OpenAI Codex",
          "scope": "Assisted source comparison, evidence extraction and bilingual research-note preparation. The materials consulted and unresolved scientific issues are specified in each note.",
          "version": "0.3",
          "tasks": [
            "Source comparison and evidence extraction",
            "Bilingual research-note drafting and editorial comparison"
          ]
        }
      },
      "revisions": [
        {
          "date": "2026-10-27",
          "version": "0.2",
          "description": "Reframed scope in terms of study design, population, outcomes and observation window."
        },
        {
          "date": "2026-10-29",
          "version": "0.3",
          "description": "Added physiological assumptions and the specific scope of the LF/HF critique."
        }
      ]
    },
    "original": {
      "id": "billman-2013",
      "title": "The LF/HF ratio does not accurately measure cardiac sympatho-vagal balance",
      "authors": "George E. Billman",
      "journal": "Frontiers in Physiology",
      "year": "2013",
      "url": "https://doi.org/10.3389/fphys.2013.00026",
      "doi": "10.3389/fphys.2013.00026",
      "pmid": "23431279"
    },
    "references": [
      {
        "id": "billman-2013",
        "title": "The LF/HF ratio does not accurately measure cardiac sympatho-vagal balance",
        "authors": "George E. Billman",
        "journal": "Frontiers in Physiology",
        "year": "2013",
        "url": "https://doi.org/10.3389/fphys.2013.00026",
        "doi": "10.3389/fphys.2013.00026",
        "pmid": "23431279"
      }
    ],
    "sections": [
      {
        "id": "finding",
        "title": "What the study found",
        "paragraphs": [
          "Billman examines the assumptions needed to interpret LF/HF as cardiac sympathetic–vagal balance. LF is not a purely sympathetic signal, HF is influenced by respiration and mechanical effects, and autonomic branches do not always vary reciprocally or linearly. Similar ratios can therefore arise from different physiological processes."
        ]
      },
      {
        "id": "limits",
        "title": "Scope & limitations",
        "paragraphs": [
          "Existing physiological experiments and mathematical arguments; no new patient cohort.",
          "The critique targets this particular interpretation of LF/HF, not all information carried by HRV. Other measures require assessment of their own physiological basis, breathing, heart rate and recording conditions."
        ]
      },
      {
        "id": "sample",
        "title": "Population & sample",
        "paragraphs": [
          "Existing physiological experiments and mathematical arguments; no new patient cohort."
        ]
      },
      {
        "id": "exposure",
        "title": "Exposure or intervention",
        "paragraphs": [
          "Assumptions behind LF, HF and their ratio, drawing on blockade, denervation and respiration studies."
        ]
      },
      {
        "id": "outcomes",
        "title": "Outcomes",
        "paragraphs": [
          "Mechanisms and assumptions of autonomic interpretation; no new diagnostic-accuracy estimate."
        ]
      },
      {
        "id": "duration",
        "title": "Time frame",
        "paragraphs": [
          "Different experimental and model time scales; no common follow-up."
        ]
      },
      {
        "id": "funding",
        "title": "Research funding",
        "paragraphs": [
          "Not yet verified against the full text."
        ]
      },
      {
        "id": "conflicts",
        "title": "Research conflicts of interest",
        "paragraphs": [
          "Not yet verified against the full text."
        ]
      },
      {
        "id": "basis",
        "title": "Reading scope",
        "paragraphs": [
          "Full-text four assumptions, respiratory/heart-rate influences and conclusion. All cited original experiments have not been individually traced."
        ],
        "links": [
          {
            "label": "Full text in PubMed Central",
            "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC3576706/"
          }
        ]
      }
    ]
  }
}