📈 ICP Waveform

Interpretation of intracranial pressure waveforms and compliance changes

Waveforms often change BEFORE ICP rises → early warning system.

icpWaveforms = {
  const { initializeApp, getApps, getApp } = await import("https://www.gstatic.com/firebasejs/10.14.1/firebase-app.js");
  const { getFirestore, collection, onSnapshot } = await import("https://www.gstatic.com/firebasejs/10.14.1/firebase-firestore.js");

  const firebaseConfig = {
    apiKey: "AIzaSyD1FLnIrd86qOsFPLi5y1q_EIU0lhL5gxc",
    authDomain: "evdtoolkit.firebaseapp.com",
    projectId: "evdtoolkit",
    storageBucket: "evdtoolkit.firebasestorage.app",
    messagingSenderId: "1002374431151",
    appId: "1:1002374431151:web:fe3724bb1f39eb4744af5a"
  };

  const app = getApps().length ? getApp() : initializeApp(firebaseConfig);
  const db = getFirestore(app);

  return Generators.observe(notify => {
    const unsubscribe = onSnapshot(collection(db, "ICPWaveforms"), snapshot => {
      notify(snapshot.docs.map(d => d.data()).sort((a, b) => (a.order ?? 0) - (b.order ?? 0)));
    });
    return unsubscribe;
  });
}

function waveformGrid(category) {
  const items = icpWaveforms.filter(w => w.category === category);
  return items.length === 0
    ? html`<div class="fs-empty">Loading…</div>`
    : html`<div class="fs-grid">${items.map(w => `
        <div class="fs-card">
          <img class="fs-card-image" src="${w.imageURL ?? ""}" onerror="this.style.display='none'" onclick="fsOpenLightbox(this.src)" onload="fsClassifyImage(this)" />
          <div class="fs-card-body">
            <h4 class="fs-card-title">${w.title ?? "Untitled"}</h4>
            <p class="fs-card-desc">${w.description ?? ""}</p>
            ${w.source ? `<span class="fs-source">📎 ${w.source}</span>` : ""}
          </div>
        </div>
      `).join("")}</div>`
}

Normal ICP Waveform

waveformGrid("Normal")

Normal: P1 > P2 > P3 → intact intracranial compliance.

• P1 (percussion wave): Arterial pulsation transmitted through the elastic walls of the cerebral arteries as arterial systolic pressure rises.
• P2 (tidal wave): Reflects intracranial compliance – its amplitude rises as compliance falls, tracking changes in cerebral blood volume.
• P3 (dicrotic wave): Follows closure of the aortic valve; associated with venous outflow.

Takeaway: P2 should NEVER exceed P1.

Note

Source: Cardoso ER, Rowan JO, Galbraith S. Analysis of the cerebrospinal fluid pulse wave in intracranial pressure. Journal of Neurosurgery. 1983 Nov. PMID: 6619934

Abnormal ICP Waveform

waveformGrid("Abnormal")

Abnormal: P2 > P1 → reduced intracranial compliance.

• Early intracranial hypertension
• Loss of compensatory reserve
• Precedes ICP elevation

Warning

Early Warning: Waveform changes occur BEFORE ICP rises.

How to Examine ICP Waveform

Watch how to interpret ICP waveform at the bedside:

Tip

Think: Is P2 higher than P1? What does that imply about compliance?