Skin flap physiology from Cummings

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Skin Flap Physiology — Cummings Otolaryngology Head and Neck Surgery

Core Principle

The most important determinant of flap success is vascular supply. All flaps — pedicled or free tissue transfer — depend on maintaining adequate perfusion to meet the metabolic demands of mobilized tissue. The distal flap is both the most critical for defect coverage and the most likely to fail.

Physics of Flow

Flow (Q) in a vessel is governed by the Hagen-Poiseuille equation:

Q = πr⁴(ΔP) / 8ηl

r⁴ = fourth power of vessel radius (dominant factor)
ΔP = perfusion pressure = P_diastolic − P_tissue
η = dynamic viscosity
l = vessel/flap length

Perfusion pressure (PP) = Diastolic BP − Tissue pressure

All clinical efforts target two goals: maintain normal PP and minimize resistance to flow.

Factor	Clinical Action
Systemic BP	Avoid hypotension and vasoconstriction
Tissue pressure	Avoid excess tension, edema, fluid overload
Vessel radius	Base flaps on large named vessels; use flap delay; free tissue transfer
Blood viscosity	Maintain hydration; target low-normal hematocrit
Flap length	Longer flaps = more resistance = greater risk of distal necrosis

Critical Closing Pressure

Critical closing pressure is the point at which tissue pressure exceeds intracapillary pressure, causing capillary collapse and cessation of flow.

In rigid tubes, flow rises linearly with pressure (Hagen-Poiseuille)
In distensible blood vessels, flow rises exponentially with pressure (LaPlace's law)
When tissue pressure rises above capillary pressure → vessels collapse → flow stops

LaPlace's law also explains why wider vessels dilate preferentially and how collateral flow develops over time (rationale for flap delay).

Effect of Flap Length on Viability

Fig. 77.1 Effect of flap length and tissue pressure on flap blood flow

Fig. 77.1 — As flap length increases, perfusion pressure falls. Where it intersects the critical closing pressure threshold, the flap becomes "at risk," then "necrotic." Falling systemic BP or rising tissue pressure shifts this intersection proximally.

Key myth dispelled: A wider base in a random flap adds vessels with the same perfusion pressure — it does NOT change the relationship between perfusion pressure and critical closing pressure, and does NOT increase survival length.

Zones of Perfusion

Flap perfusion is conceptualized in three zones:

Zone	Compartment	Key Determinants
Zone I — Macrocirculatory	Large vessels, pedicle, anastomosis	Systemic BP, vessel patency
Zone II — Microcirculatory	Arterioles, capillaries, venules	Tissue pressure, sphincter tone, A-V shunts
Zone III — Interstitial	Extracellular matrix, lymphatics	Starling forces, edema, diffusion distances

Zone II — Microcirculation

Terminal arterioles → metarterioles → precapillary sphincters → capillary beds
Arteriovenous shunts allow direct arteriole→venule bypass (thermoregulation)
Preshunt sphincters: regulate thermoregulation & systemic BP via vasoactive substances
Precapillary sphincters: regulate nutritive (capillary) blood flow
Elevated interstitial pressure compresses capillaries → decreased flow
Autoregulation = normalization of capillary flow in response to pressure changes
Lymphatics run parallel to blood capillaries; impaired by inflammation and loss of pulsation

Zone III — Interstitial System

Filled with proteoglycans, collagen, hyaluronic acid filaments — high resistance to fluid movement in normal hydration
Fluid movement occurs by two mechanisms:
1. Diffusion — dominant for small molecules; distance increases with edema → ↓ nutrient delivery
2. Convective flow (bulk flow) — fluid swept along microchannels; large molecules use this route

Starling equation governs transcapillary flow:

Jv/A = Lp[(Pi − Pi) − σ(πi − πi)]

Where Lp = membrane water permeability, P = hydrostatic pressures, π = osmotic pressures, σ = osmotic (reflection) coefficient.

Classification of Flaps by Vascular Supply

Fig. 77.5 Classification of skin flaps based on vascular supply

Fig. 77.5 — (A) Random, (B) Arterial cutaneous (axial), (C) Fasciocutaneous, (D) Musculocutaneous

Flap Type	Blood Supply	Plane of Dissection	Notes
Random cutaneous	Subdermal plexus from unnamed musculocutaneous perforators	Subcutaneous fat	Survival = function of PP, NOT length:width ratio
Arterial (axial) cutaneous	Named septocutaneous artery along longitudinal axis	Must include septocutaneous vessel	Better survival than random; distal extension = random territory
Fasciocutaneous	Septocutaneous vessels → deep fascial plexus → subdermal plexus	Deep fascia included	Relies on skin vascular territories; 4 subtypes based on fascial supply pattern
Musculocutaneous / Myocutaneous	Segmental vessels to muscle → musculocutaneous perforators	Muscle incorporated	Best survival; leaves local perforators intact; named for donor muscle

Examples in H&N:

Deltopectoral flap — anterior perforators of internal mammary artery
Paramedian forehead flap — supratrochlear vessels
Pectoralis myocutaneous flap — pectoral branch of thoracoacromial artery
Latissimus dorsi flap

Flap Failure

Failure is most detectable by the time it is irreversible — hence early monitoring is critical in at-risk cases.

Monitoring and salvage by zone:

Zone	Monitoring	Salvage
Zone I (macrocirculatory)	Doppler, near-infrared spectroscopy, temperature	Explore pedicle/anastomosis; thrombosis treatment
Zone II (microcirculatory)	Doppler, tissue oxygenation, tissue pressure	Vascular washout; reduce edema
Zone III (interstitial)	Clinical assessment	Address Starling forces, reduce edema

Risk factors for failure: diabetes, prior irradiation, hypotension, excess tension, edema.

Methods to Augment Flap Survival

Flap Delay

Creates collateral flow by preliminary interruption of part of the blood supply
Dilates remaining vessels via LaPlace's law over time
Extends viable flap length

Hyperbaric Oxygen (HBO)

Increases blood oxygen-carrying capacity by ~20% (oxygen dissolved in plasma)
Greater benefit when hematocrit is low
Also increases oxygen diffusion from perfused surrounding tissue into ischemic zones
Beneficial effects: ↓ leukocyte adherence, ↓ edema (vasoconstriction effect), ↑ neovascularization in irradiated tissue
Must be given early — little benefit if >24 hours after flap elevation
HBO challenge test: transcutaneous O₂ rise ≥50 mmHg predicts successful outcome
Not cost-effective for every flap; reserve for high-risk cases

Source: Cummings Otolaryngology Head and Neck Surgery, Chapter 77 — Skin Flap Physiology (pp. 1388–1395)

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mkdir -p /home/daytona/workspace/skin-flap-ppt && node /home/daytona/skills/shar…

Writing File

~/skin-flap-ppt/generate.js

const pptxgen = require("pptxgenjs");
const { execSync } = require("child_process");

// Fetch images
const images = JSON.parse(execSync(
  `node /home/daytona/skills/shared/scripts/fetch_images.js ` +
  `"https://cdn.orris.care/cdss_images/d0a512d589cd28d792911d65f39b832f4c28f68db7b1f5c791afa3e2267bd9bc.png" ` +
  `"https://cdn.orris.care/cdss_images/4849dcb2ef6c4152e12631aca3798c9760b67d2a3336332ed02be715a1ece884.png"`
).toString());

const imgFlap = images[0].base64;
const imgClass = images[1].base64;

// Color palette — deep surgical blue & warm anatomical tones
const C = {
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  panel:     "162436",   // slightly lighter navy for cards
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  gold:      "F4A261",   // warm gold for highlights
  teal:      "2EC4B6",   // teal for sub-accents
  white:     "FFFFFF",
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  grey:      "8FA3B1",
  lightblue: "A8DADC",
};

let pres = new pptxgen();
pres.layout = "LAYOUT_16x9";
pres.title = "Skin Flap Physiology";
pres.author = "Cummings Otolaryngology";

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    { n: "03", title: "Zones of Perfusion", sub: "Macrocirculation · Microcirculation · Interstitium", col: C.teal },
    { n: "04", title: "Flap Classification", sub: "Random · Axial · Fasciocutaneous · Myocutaneous", col: C.lightblue },
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// ─── SLIDE 3: PHYSICS OF FLOW ─────────────────────────────────────────────
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    { icon: "↓", label: "Minimize tissue pressure", detail: "No excess tension, edema or fluid overload" },
    { icon: "⊕", label: "Maximize vessel radius", detail: "Base on named vessels; use delay or free transfer" },
    { icon: "↓", label: "Lower blood viscosity", detail: "Hydration · Low-normal hematocrit" },
    { icon: "↓", label: "Minimize flap length", detail: "Longer flap = more resistance = distal risk" },
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// ─── SLIDE 4: CRITICAL CLOSING PRESSURE ──────────────────────────────────
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      title: "Critical Closing Pressure",
      body: "When tissue pressure exceeds intracapillary pressure → capillary collapse → flow ceases. This threshold defines the necrotic zone."
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      title: "Width ≠ Safety",
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// ─── SLIDE 5: ZONES OF PERFUSION ─────────────────────────────────────────
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// ─── SLIDE 6: STARLING EQUATION ──────────────────────────────────────────
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    { sym: "πc − πi", def: "Osmotic pressure gradient (capillary − interstitium)" },
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  const mechs = [
    { t: "Diffusion", d: "Dominant for SMALL molecules under normal conditions. Edema ↑ diffusion distances → ↓ nutrient delivery to cells." },
    { t: "Convective Flow", d: "Bulk flow sweeps molecules along microchannels regardless of concentration gradient. Important for LARGE molecules." },
  ];
  mechs.forEach((m, i) => {
    card(s, 0.4 + i * 4.8, 4.55, 4.6, 0.82);
    s.addShape(pres.shapes.RECTANGLE, {
      x: 0.4 + i * 4.8, y: 4.55, w: 0.06, h: 0.82,
      fill: { color: i === 0 ? C.accent : C.gold },
      line: { color: i === 0 ? C.accent : C.gold }
    });
    s.addText(m.t, {
      x: 0.6 + i * 4.8, y: 4.58, w: 4.2, h: 0.3,
      fontSize: 13, bold: true, color: i === 0 ? C.accent : C.gold, margin: 0
    });
    s.addText(m.d, {
      x: 0.6 + i * 4.8, y: 4.88, w: 4.2, h: 0.44,
      fontSize: 9.5, color: C.offwhite, margin: 0
    });
  });
}

// ─── SLIDE 7: FLAP CLASSIFICATION ────────────────────────────────────────
{
  let s = pres.addSlide();
  addBg(s);
  addTopBar(s, C.lightblue);

  pill(s, "FLAP CLASSIFICATION", 0.4, 0.18, 2.4, "2A7D8A");

  s.addText("Classification by Vascular Supply", {
    x: 0.4, y: 0.6, w: 9, h: 0.65,
    fontSize: 28, bold: true, color: C.white
  });

  // Image right
  if (imgClass) {
    s.addImage({ data: imgClass, x: 5.2, y: 1.3, w: 4.5, h: 3.8 });
  }

  const flaps = [
    {
      type: "Random Cutaneous",
      supply: "Subdermal plexus from unnamed musculocutaneous perforators",
      plane: "Subcutaneous fat",
      note: "Survival = perfusion pressure, NOT length:width ratio",
      col: C.accent
    },
    {
      type: "Arterial (Axial)",
      supply: "Named septocutaneous artery along flap axis",
      plane: "Must include septocutaneous vessel",
      note: "Distal extension beyond named artery = random territory",
      col: C.gold
    },
    {
      type: "Fasciocutaneous",
      supply: "Septocutaneous vessels → deep fascial plexus → subdermal plexus",
      plane: "Deep fascia included",
      note: "4 subtypes; relies on skin vascular territories",
      col: C.teal
    },
    {
      type: "Musculocutaneous",
      supply: "Segmental vessels to muscle → musculocutaneous perforators",
      plane: "Muscle incorporated",
      note: "Best survival; leaves local perforators intact",
      col: C.lightblue
    },
  ];

  flaps.forEach((f, i) => {
    card(s, 0.25, 1.3 + i * 1.0, 4.75, 0.88);
    s.addShape(pres.shapes.RECTANGLE, {
      x: 0.25, y: 1.3 + i * 1.0, w: 0.06, h: 0.88,
      fill: { color: f.col }, line: { color: f.col }
    });
    s.addText(f.type, {
      x: 0.4, y: 1.33 + i * 1.0, w: 4.4, h: 0.28,
      fontSize: 12, bold: true, color: f.col, margin: 0
    });
    s.addText(`Supply: ${f.supply}`, {
      x: 0.4, y: 1.6 + i * 1.0, w: 4.4, h: 0.24,
      fontSize: 8.5, color: C.offwhite, margin: 0
    });
    s.addText(`▶ ${f.note}`, {
      x: 0.4, y: 1.84 + i * 1.0, w: 4.4, h: 0.24,
      fontSize: 8.5, color: C.grey, italic: true, margin: 0
    });
  });

  s.addText("Fig. 77.5 — Vascular supply patterns for each flap type", {
    x: 5.2, y: 5.12, w: 4.5, h: 0.25,
    fontSize: 8, italic: true, color: C.grey, align: "center"
  });
}

// ─── SLIDE 8: HEAD & NECK EXAMPLES ───────────────────────────────────────
{
  let s = pres.addSlide();
  addBg(s);
  addTopBar(s, C.gold);

  pill(s, "H&N EXAMPLES", 0.4, 0.18, 1.8, C.gold);

  s.addText("Common Head & Neck Flaps", {
    x: 0.4, y: 0.6, w: 9, h: 0.65,
    fontSize: 28, bold: true, color: C.white
  });

  const examples = [
    { flap: "Deltopectoral Flap", type: "Arterial (Axial)", vessel: "Anterior perforators of internal mammary artery", col: C.gold },
    { flap: "Paramedian Forehead Flap", type: "Arterial (Axial)", vessel: "Supratrochlear vessels", col: C.gold },
    { flap: "Pectoralis Major Myocutaneous", type: "Musculocutaneous", vessel: "Pectoral branch of thoracoacromial artery", col: C.lightblue },
    { flap: "Latissimus Dorsi Flap", type: "Musculocutaneous", vessel: "Thoracodorsal artery (segmental supply)", col: C.lightblue },
    { flap: "Radial Forearm Free Flap", type: "Free Tissue Transfer", vessel: "Radial artery", col: C.teal },
    { flap: "Fibula Free Flap", type: "Osteocutaneous Free Flap", vessel: "Peroneal artery", col: C.teal },
  ];

  examples.forEach((e, i) => {
    const col = i % 2 === 0 ? 0.3 : 5.1;
    const row = Math.floor(i / 2);
    card(s, col, 1.5 + row * 1.25, 4.55, 1.1);
    s.addShape(pres.shapes.RECTANGLE, {
      x: col, y: 1.5 + row * 1.25, w: 0.06, h: 1.1,
      fill: { color: e.col }, line: { color: e.col }
    });
    s.addText(e.flap, {
      x: col + 0.18, y: 1.54 + row * 1.25, w: 4.2, h: 0.32,
      fontSize: 13, bold: true, color: C.white, margin: 0
    });
    s.addText(e.type, {
      x: col + 0.18, y: 1.85 + row * 1.25, w: 4.2, h: 0.25,
      fontSize: 10, color: e.col, italic: true, margin: 0
    });
    s.addText(`Vessel: ${e.vessel}`, {
      x: col + 0.18, y: 2.1 + row * 1.25, w: 4.2, h: 0.38,
      fontSize: 9.5, color: C.grey, margin: 0
    });
  });
}

// ─── SLIDE 9: FLAP FAILURE & MONITORING ──────────────────────────────────
{
  let s = pres.addSlide();
  addBg(s);
  addTopBar(s, C.accent);

  pill(s, "FLAP FAILURE & MONITORING", 0.4, 0.18, 2.8, C.accent);

  s.addText("Recognition, Monitoring & Salvage", {
    x: 0.4, y: 0.6, w: 9, h: 0.65,
    fontSize: 28, bold: true, color: C.white
  });

  // Risk factors
  card(s, 0.3, 1.35, 9.4, 0.72);
  s.addText("⚠  Key Risk Factors:", {
    x: 0.5, y: 1.38, w: 2, h: 0.35,
    fontSize: 11, bold: true, color: C.accent, margin: 0
  });
  s.addText("Diabetes   ·   Prior irradiation   ·   Hypotension   ·   Excess tension on closure   ·   Tissue edema   ·   High hematocrit   ·   Vasoconstriction", {
    x: 2.4, y: 1.38, w: 7.1, h: 0.6,
    fontSize: 10, color: C.offwhite, valign: "middle", margin: 0
  });

  // Monitoring / salvage table
  const rows = [
    { zone: "Zone I\n(Macro)", monitor: "Doppler · Near-infrared spectroscopy · Temperature", salvage: "Explore pedicle / anastomosis · Thrombectomy", col: C.accent },
    { zone: "Zone II\n(Micro)", monitor: "Doppler · Tissue oxygenation · Tissue pressure", salvage: "Vascular washout · Reduce edema", col: C.gold },
    { zone: "Zone III\n(Interstitium)", monitor: "Clinical assessment · Fluid balance", salvage: "Optimize Starling forces · Manage edema", col: C.teal },
  ];

  // Table header
  ["Zone", "Monitoring Method", "Salvage Method"].forEach((h, i) => {
    const xs = [0.3, 2.0, 6.0];
    const ws = [1.55, 3.8, 3.75];
    s.addShape(pres.shapes.RECTANGLE, {
      x: xs[i], y: 2.18, w: ws[i], h: 0.4,
      fill: { color: "1E3A50" }, line: { color: "1E3A50" }
    });
    s.addText(h, {
      x: xs[i] + 0.1, y: 2.18, w: ws[i] - 0.1, h: 0.4,
      fontSize: 11, bold: true, color: C.offwhite, valign: "middle", margin: 0
    });
  });

  rows.forEach((r, i) => {
    const y = 2.65 + i * 0.88;
    card(s, 0.3, y, 1.55, 0.82, "0A1520");
    s.addShape(pres.shapes.RECTANGLE, {
      x: 0.3, y, w: 0.06, h: 0.82,
      fill: { color: r.col }, line: { color: r.col }
    });
    s.addText(r.zone, {
      x: 0.42, y: y + 0.04, w: 1.35, h: 0.74,
      fontSize: 10, bold: true, color: r.col, valign: "middle", margin: 0
    });

    card(s, 2.0, y, 3.8, 0.82);
    s.addText(r.monitor, {
      x: 2.15, y: y + 0.08, w: 3.5, h: 0.66,
      fontSize: 10, color: C.offwhite, valign: "middle", margin: 0
    });

    card(s, 6.0, y, 3.75, 0.82);
    s.addText(r.salvage, {
      x: 6.15, y: y + 0.08, w: 3.45, h: 0.66,
      fontSize: 10, color: C.offwhite, valign: "middle", margin: 0
    });
  });
}

// ─── SLIDE 10: AUGMENTING FLAP SURVIVAL ──────────────────────────────────
{
  let s = pres.addSlide();
  addBg(s);
  addTopBar(s, C.teal);

  pill(s, "AUGMENTING SURVIVAL", 0.4, 0.18, 2.4, C.teal);

  s.addText("Flap Delay  &  Hyperbaric Oxygen", {
    x: 0.4, y: 0.6, w: 9, h: 0.65,
    fontSize: 28, bold: true, color: C.white
  });

  // Flap Delay card
  card(s, 0.3, 1.38, 4.6, 3.9);
  s.addShape(pres.shapes.RECTANGLE, {
    x: 0.3, y: 1.38, w: 4.6, h: 0.5,
    fill: { color: C.teal }, line: { color: C.teal }
  });
  s.addText("FLAP DELAY", {
    x: 0.3, y: 1.38, w: 4.6, h: 0.5,
    fontSize: 15, bold: true, color: C.bg, align: "center", valign: "middle", margin: 0
  });
  const delayPts = [
    "Preliminary interruption of part of flap's blood supply",
    "Triggers collateral vessel dilation via LaPlace's Law",
    "Allows time for neovascularization",
    "Effectively extends safe flap length",
    "Used when large or borderline flap is planned",
    "Interval of 1–3 weeks typically required",
  ];
  delayPts.forEach((p, i) => {
    s.addShape(pres.shapes.ROUNDED_RECTANGLE, {
      x: 0.52, y: 2.02 + i * 0.52, w: 0.22, h: 0.22,
      fill: { color: C.teal }, line: { color: C.teal }, rectRadius: 0.04
    });
    s.addText(p, {
      x: 0.82, y: 1.98 + i * 0.52, w: 3.9, h: 0.44,
      fontSize: 10, color: C.offwhite, margin: 0, valign: "middle"
    });
  });

  // HBO card
  card(s, 5.1, 1.38, 4.6, 3.9);
  s.addShape(pres.shapes.RECTANGLE, {
    x: 5.1, y: 1.38, w: 4.6, h: 0.5,
    fill: { color: C.gold }, line: { color: C.gold }
  });
  s.addText("HYPERBARIC OXYGEN (HBO)", {
    x: 5.1, y: 1.38, w: 4.6, h: 0.5,
    fontSize: 15, bold: true, color: C.bg, align: "center", valign: "middle", margin: 0
  });
  const hboPts = [
    "↑ O₂ carrying capacity by ~20% (plasma-dissolved O₂)",
    "Greater effect with low hematocrit",
    "↑ O₂ diffusion from perfused → ischemic zone",
    "↓ Leukocyte adherence · ↓ Edema · ↑ Neovascularization",
    "Must be given EARLY — little benefit after 24h",
    "Challenge test: TcO₂ rise ≥50 mmHg = favorable",
    "Reserve for high-risk flaps (not cost-effective for all)",
  ];
  hboPts.forEach((p, i) => {
    s.addShape(pres.shapes.ROUNDED_RECTANGLE, {
      x: 5.32, y: 2.02 + i * 0.44, w: 0.22, h: 0.22,
      fill: { color: C.gold }, line: { color: C.gold }, rectRadius: 0.04
    });
    s.addText(p, {
      x: 5.62, y: 1.98 + i * 0.44, w: 3.9, h: 0.38,
      fontSize: 9.5, color: C.offwhite, margin: 0, valign: "middle"
    });
  });
}

// ─── SLIDE 11: SUMMARY ───────────────────────────────────────────────────
{
  let s = pres.addSlide();
  addBg(s);
  addTopBar(s, C.accent);

  // Background accent block
  s.addShape(pres.shapes.RECTANGLE, {
    x: 0, y: 0, w: 0.18, h: 5.625,
    fill: { color: C.accent }, line: { color: C.accent }
  });

  s.addText("Key Takeaways", {
    x: 0.5, y: 0.25, w: 9, h: 0.65,
    fontSize: 30, bold: true, color: C.white
  });

  const takeaways = [
    { n: "1", text: "Vascular supply is THE most critical factor in flap planning — perfusion pressure (DBP − tissue pressure) drives all zones.", col: C.accent },
    { n: "2", text: "Hagen-Poiseuille: vessel radius (r⁴) dominates flow. Choose large named vessels, minimize length, and maintain BP.", col: C.gold },
    { n: "3", text: "Critical closing pressure determines viable vs. at-risk vs. necrotic zones. Wider base does NOT increase survival length.", col: C.teal },
    { n: "4", text: "Three zones of perfusion (macro → micro → interstitial) each have distinct monitoring and salvage strategies.", col: C.lightblue },
    { n: "5", text: "Flap type dictates vascular anatomy: Random < Axial < Fasciocutaneous < Musculocutaneous in terms of reliability.", col: C.gold },
    { n: "6", text: "Flap delay (collateral development) and HBO (early, high-risk cases only) are the main methods to augment survival.", col: C.accent },
  ];

  takeaways.forEach((t, i) => {
    const y = 1.05 + i * 0.72;
    card(s, 0.5, y, 9.2, 0.62);
    s.addShape(pres.shapes.ROUNDED_RECTANGLE, {
      x: 0.62, y: y + 0.1, w: 0.38, h: 0.38,
      fill: { color: t.col }, line: { color: t.col }, rectRadius: 0.06
    });
    s.addText(t.n, {
      x: 0.62, y: y + 0.1, w: 0.38, h: 0.38,
      fontSize: 14, bold: true, color: C.bg, align: "center", valign: "middle", margin: 0
    });
    s.addText(t.text, {
      x: 1.12, y: y + 0.06, w: 8.4, h: 0.5,
      fontSize: 10.5, color: C.offwhite, valign: "middle", margin: 0
    });
  });

  s.addText("Cummings Otolaryngology Head & Neck Surgery  ·  Chapter 77: Skin Flap Physiology", {
    x: 0.5, y: 5.3, w: 9.2, h: 0.25,
    fontSize: 8.5, italic: true, color: C.grey, align: "center"
  });
}

// ─── WRITE FILE ───────────────────────────────────────────────────────────
pres.writeFile({ fileName: "/home/daytona/workspace/skin-flap-ppt/Skin_Flap_Physiology.pptx" })
  .then(() => console.log("✅ Done: /home/daytona/workspace/skin-flap-ppt/Skin_Flap_Physiology.pptx"))
  .catch(e => { console.error("❌ Error:", e); process.exit(1); });

Running Command

cd /home/daytona/workspace/skin-flap-ppt && node generate.js 2>&1

Your presentation is ready:

Skin Flap Physiology

Presentation · PPTX

11 slides with a deep navy + surgical red palette:

Slide	Content
1	Title
2	Overview / Agenda
3	Physics of Flow — Hagen-Poiseuille, clinical goals
4	Critical Closing Pressure — flap length graph (Fig. 77.1)
5	Three Zones of Perfusion (macro/micro/interstitial)
6	Starling Forces & Capillary Exchange (Zone III)
7	Flap Classification — with the 4-type vascular diagram (Fig. 77.5)
8	H&N Flap Examples (deltopectoral, forehead, pec major, LD, radial forearm, fibula)
9	Flap Failure — risk factors, monitoring & salvage table by zone
10	Augmenting Survival — Flap Delay vs. HBO side-by-side
11	Key Takeaways + source citation

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