CAALaw

Category: Focused Concept Reviews

  • Dead Space Fraction (Vd/Vt): Measuring Wasted Ventilation

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    Bryan Rogers
    in ,

    Dead Space Fraction (Vd/Vt): Measuring Wasted Ventilation The Bohr/Enghoff equation, the ETCO₂ gradient, and tracking lung perfusion Capnography  ·  Airway Management  ·  Cardiovascular Physiology Background: Dead Space Fraction (Vd/Vt): the proportion of a tidal volume breath (Vt) that does not participate in gas exchange because it remains in the conducting airways or reaches unperfused alveoli.…

  • Fick Principle

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    Bryan Rogers
    in ,

    Fick Principle Arteriovenous Extraction, Cardiac Output, and the Shift from Direct to Indirect Measurement Cardiovascular Physiology  ·  Capnography  ·  Case Analysis Background: Fick Principle: the physiological rule stating that the total uptake or release of a substance by the peripheral tissues is equal to the product of the blood flow to the peripheral tissues and…

  • The Neuromuscular Junction

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    Bryan Rogers
    in ,

    The neuromuscular junction relies on nicotinic receptors and a built-in safety margin, so fade only appears once about 75% of those receptors are blocked.

  • Train of Four Ratio: Quantifying Paralysis

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    Bryan Rogers
    in ,

    Train-of-Four ratio explained: T4:T1 fade, depth-of-block staging, and why ≥0.9 is the threshold defining adequate recovery from neuromuscular blockade.

  • Cardiac Output: Quantification of Heart Performance

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    Bryan Rogers
    in ,

    Cardiac Output: Quantification of Heart Performance Stroke Volume vs. Heart Rate, and the Four Determinants That Make or Break Perfusion Cardiovascular Physiology  ·  Hemodynamics  ·  Preload & Afterload  ·  Anesthetic Management Background: The concept of measuring blood flow as a product of the heart’s rate and ejection volume traces back to Adolf Fick in 1870,…

  • Capnography & ETCO₂: Visualizing Ventilation

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    Bryan Rogers
    in ,

    Capnography & ETCO₂: Visualizing Ventilation The Waveform, the Number, and What Each Phase Actually Tells You Respiratory Monitoring  ·  CO₂ Transport  ·  Waveform Analysis  ·  Airway Safety TL;DR In practice, ETCO₂ is best understood as a real-time window into three coupled physiologic systems: metabolism, circulation, and ventilation, all read through the imperfect lens of a…

  • MAC: How Anesthetic Potency is Defined

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    Bryan Rogers
    in ,

    MAC: How Anesthetic Potency is Defined MAC-awake vs. MAC-intubation, and the Patient Factors That Shift the Curve Pharmacokinetics  ·  Volatile Agents  ·  Anesthetic Potency  ·  Dose-Response Background: Minimum Alveolar Concentration (MAC): the end-tidal concentration of an inhaled anesthetic that prevents purposeful movement to a standardized surgical stimulus in 50% of unpremedicated subjects. It can be…

  • Bispectral Index (BIS): Monitoring the Brain Under Anesthesia

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    Bryan Rogers
    in ,

    Bispectral Index (BIS): Monitoring the Brain Under Anesthesia EEG Signal Processing, Spectral Analysis, and the 0–100 Scale as a Proxy for Hypnotic Depth M&I  ·  Neuromonitoring  ·  EEG  ·  Anesthetic Depth Background: The Bispectral Index is a processed EEG-derived algorithm that attempts to quantify hypnotic depth on a dimensionless 0–100 scale. Raw EEG is captured…