Physics for Anesthesiologists and Intensivists : From Daily Life to Clinical Practice

This book, now in its 2nd edition, discusses, explains and provides detailed, up-to-date information on physics applied to clinical practice in anesthesiology and critical care medicine, with the aid of simple examples from daily life. Almost everything that happens around us, including in the operating room and intensive care units, can be explained by physical laws. An awareness and understanding of relatively simple laws such as the Hagen-Poiseuille equation, or of slightly more complex topics such as harmonic motion and electromagnetism, to name just a few, offer anesthesiologists and intensivists fascinating insights into why they do what they do. After an introductory chapter that brushes up on all the (few) mathematics the reader will need to face the book, with many practical examples and clinical applications, each of the following 20 chapters deals with some everyday phenomena, explains them with one or more physical laws, and shows why these laws are important in anesthesia and critical care practice. Many illustrations are included for extra clarity. This enriched and updated edition of Physics for Anesthesiologists is intended for anesthesiologists, intensivists, anesthesia and intensive care medicine teachers and trainees, as well as medical students. Preface Preface to the First Edition Contents Part I: Before Starting 1: A Little Math we Will Need Throughout the Book and a Clinical Application Immediately 1.1 We Must “Speak Mathematics” (But Don’t Worry About It) 1.2 Playing with Equations 1.3 A Bit of Geometry and Trigonometry 1.3.1 Angles and Triangles 1.3.2 Pythagorean Theorem, Trigonometry, and Central Venous Catheters 1.4 One Last Little Effort: Functions, Limits, Derivatives, and Integrals 1.4.1 Limits and Derivatives: The “True” Definition of Velocity, Gradients, and Other Quantities 1.4.2 Integral Calculus: Distances, Areas, and Cardiac Output References Part II: Gases, Bubbles and Surroundings 2: Coffee, Popcorn, and Oxygen Cylinders: The Ideal Gas Law 2.1 Strange Associations 2.2 Delicious Scents and a Nauseating Stench 2.3 Ideal Gas Law 2.3.1 Boyle’s Law 2.3.2 First Law of Gay-Lussac (or Charles’s Law) 2.3.3 Second Law of Gay-Lussac (or, Simply, Gay-Lussac’s Law) 2.3.4 Avogadro’s Law 2.3.5 Dalton’s Law 2.4 Calculating the Duration of an Oxygen Cylinder 2.5 Decompression Illness and Hyperbaric Therapy 2.6 Gas Laws and the Tracheal Tube Cuff References 3: Boats, Balloons, and Air Bubbles: Archimedes’ Principle 3.1 Archimedes’ Principle: Gravity Not Always Makes You Fall 3.2 Anesthesiologists, Intensivists, and Archimedes’ Principle References 4: Dalton’s Law and Fick’s Law: Resorption Atelectasis, Membrane Oxygenators, and How an Air Bubble May Affect Blood Gas Analysis 4.1 Dalton’s Law: When You Do the Math, It All Adds Up! 4.2 Down the Slope: Fick’s Law 4.2.1 Fick’s Law and the Pathophysiology of Absorption Atelectasis 4.2.2 Fick’s Law and Extracorporeal Support Technology: Membrane Oxygenators 4.3 Air Bubbles and Blood Gas Analysis References 5: Cold, Sodas, and Blood Gas Analysis: Henry’s Law 5.1 The Physics in a Soda Bottle: Henry’s Law 5.2 Acid-Base Management During Cardiopulmonary Bypass 5.3 Pathophysiology and Treatment of Decompression Sickness References 6: Bubbles, Tracheal Tube Cuffs, and Reservoir Bags: Surface Tension and Laplace’s Law 6.1 Physics in a Soap Bubble: Surface Tension and Laplace’s Law 6.1.1 Also Liquids Care About Their “Appearance”: Surface Tension 6.1.2 Laplace’s Law 6.2 Reservoir Bags and Tracheal Tube Cuffs 6.2.1 Some Unexpected Help from the Reservoir Bag 6.2.2 Monitoring Tracheal Tube Cuff Pressure: We Cannot Trust Our Fingers 6.3 Heart, Lungs, and Vessels (or Catheters) 6.3.1 Left Ventricular Hypertrophy and Dilated Cardiomyopathy 6.3.2 Aortic Aneurysm 6.3.3 Pulmonary alveoli Are Not a House of Cards 6.3.4 Air Embolism and Catheter Obstruction References Part III: Fluids in Motion or at Rest: Masks, Tubes, Invasive Pressure Monitoring, and Hemodynamics 7: Continuity Equation and Bernoulli’s Theorem: Airplanes, Venturi Masks, and Other Interesting Things (for Anesthesiologists and Intensivists) 7.1 Garden Hoses and Echocardiographic Assessment of Heart Valve Stenosis: Continuity Equation 7.2 How Does an Airplane Fly? Bernoulli’s Theorem 7.2.1 And Now...Let’s Fly This Airplane! 7.2.2 Bernoulli’s Theorem and Echocardiography 7.3 Continuity Equation and Bernoulli’s Theorem Work Together in a Venturi mask 7.4 Continuity Equation and Bernoulli’s Theorem Work Together Again: The Pathophysiology of Systolic Anterior Motion References 8: From Tubes and Catheters to the Basis of Hemodynamics: Viscosity and Hagen–Poiseuille Equation 8.1 Real Fluids Flow in a Different Way: Viscosity and Hagen–Poiseuille Equation 8.1.1 Viscosity 8.1.2 Hagen–Poiseuille Equation 8.2 Tubes, Cannulae, and Catheters: Some Implications of Hagen–Poiseuille Equation 8.2.1 Endotracheal Tubes, Tracheotomy Cannulae, and Work of Breathing 8.2.2 Cannulae for Extracorporeal Membrane Oxygenation: Hagen–Poiseuille Equation and the Pseudoplastic Behavior of Blood 8.3 Hagen–Poiseuille Equation and Hemodynamics References 9: Toothpaste, Sea Deeps, and Invasive Pressure Monitoring: Stevin’s Law and Pascal’s Principle 9.1 Fluids at Rest: Stevin’s Law and Pascal’s Principle 9.1.1 Density and Pressure of Fluids 9.1.2 Under the Sea: Stevin’s Law 9.1.3 Push, Squeeze, and Lift: Pascal’s Principle 9.2 Invasive Pressure Monitoring 9.2.1 Leveling: How Important Is the Difference? 9.2.2 Differences that Matter and Really Insignificant Differences: Zeroing References Part IV: Heat, Temperature, and Electricity: Hemodynamic Monitoring and Much More 10: Heat, Cardiac Output, and What Is the Future: The Laws of Thermodynamics 10.1 Temperature, Heat, and Energy: The Laws of Thermodynamics 10.1.1 Temperature and Thermometers: The Zeroth Law of Thermodynamics 10.1.2 The First Law of Thermodynamics: It All Adds Up! 10.1.3 In which Direction, Please? The Second Law of Thermodynamics 10.1.3.1 Second Law of Thermodynamics, Metabolic Heat Dissipation, and the Zero-Heat-Flux Thermometer 10.1.4 There Is Also a Third Law of Thermodynamics (Just to Know) 10.2 More or Less “Greedy”: Specific Heat 10.3 Measuring Cardiac Output by Thermodilution 10.3.1 It’s Just Thermodynamics, Beauty! References 11: Electric Current, Resistance, Circuits, Thermoelectric Effect: Platelet Aggregometry, Pressure Transducers, and Temperature Monitoring 11.1 Electricity: A (Very) Concise Introduction 11.1.1 Charge 11.1.2 Electric Field 11.1.3 Electric Potential 11.2 Electric Current, Resistance, and Circuits 11.2.1 Electrical Resistance and Platelet Aggregometry 11.2.2 Electrical Resistance and Invasive Pressure Monitoring: The Wheatstone Bridge 11.2.3 Electrical Resistance and Temperature Measurement: Thermistors 11.3 Other Temperature Probes: Thermoelectric Effect and Thermocouples References 12: Spark plugs, Computer Keyboards, and Defibrillators: Capacitors 12.1 Storing Electric Energy: Capacitors 12.2 Computer Keyboards, Smartphones, and Defibrillators References Part V: Forces in Action 13: Doors, Steering Wheels, Laryngoscopes, and Central Venous Catheters: The Moment of a Force 13.1 Vectors, Vector Sum, and Components of a Force 13.2 Pliers, Nutcrackers, Tweezers (and so on): Moment of a Force and the Levers 13.3 Bend a Guidewire or Blow up a Tooth: Matter of a Moment! References 14: Friction, Trigonometry, and Newton’s Laws: All About Trendelenburg Position 14.1 Forces and Motion: Newton’s Laws 14.1.1 Newton’s First Law 14.1.2 Newton’s Second Law 14.1.3 Newton’s Third Law 14.2 Forces Against Motion: Normal Force and Friction 14.2.1 Normal Force: Physics of the English Course 14.2.2 Why Your Car Needs an Engine: Friction 14.3 Gravity Vs. Friction: Safety in the Trendelenburg Position References Part VI: Thermology and Inhalational Anesthesia: The Physics of Vaporizers 15: Physics in a Vaporizer: Saturated Vapor Pressure, Heat of Vaporization, and Thermal Expansion 15.1 Why a Vaporizer Is Not Exactly a “Vaporizer”: Saturated Vapor Pressure and Volatility 15.1.1 Saturated Vapor Pressure and Boiling Point 15.1.2 Volatility of Halogenated Anesthetics and the “Trick” of the Variable-Bypass Vaporizer 15.1.3 Why Desflurane Needs a Special Kind of Vaporizer 15.2 Why Vaporizers Are So Heavy: Heat of Transformation and the Need for Temperature Stabilization 15.2.1 Some Notes About the State Changes of Matter 15.2.2 Evaporative Cooling and Accuracy of Vaporizers 15.2.3 Temperature Stabilization (Heat Sink): Specific Heat and Thermal Conductivity 15.3 Thermal Expansion: Train Tracks, Thermostats and Temperature Compensation in Vaporizers References Part VII: Electromagnetic Waves and Optics 16: Light, Air Pollution, and Pulse Oximetry: The Beer–Lambert Law 16.1 A Journey Through the Waves 16.2 What is Light 16.2.1 Light as a Wave 16.2.2 The Electromagnetic Spectrum 16.3 Blue Oceans and Sea Deeps: Beer–Lambert Law 16.4 The Beer–Lambert Law in Anesthesia and Critical Care 16.4.1 Pulse Oximetry 16.4.2 Capnography and Anesthetic Analyzers References 17: Scattering of Electromagnetic Waves: Blue Skies, Cerebral Oximetry, and Some Reassurance About X-Rays 17.1 Electromagnetic Waves Encounter Matter: Scattering 17.2 Electromagnetic Scattering, Cerebral Oximetry, and Why the Sky Is Blue 17.2.1 The Unknown of Cerebral Near-Infrared Spectroscopy 17.3 Catch Me If You Can: X-Rays, Compton Scattering, and the Inverse Square Law 17.3.1 X-Rays ... from a Different Angle: Compton Scattering 17.3.2 Far Enough Away: The Inverse Square Law 17.4 Electromagnetic Scattering and Gas Analyzers: Raman Spectroscopy 17.5 Scattering and Absorption of Light Which Crosses the Skin: Why Veins Look Blue References 18: Sunsets and Optical Fibers: A Bit of Geometrical Optics 18.1 Light as a Set of “Rays”: Reflection and Refraction 18.1.1 The Law of Reflection 18.1.2 The Law of Refraction (Snell’s Law) 18.2 Total Internal Reflection and Optical Fibers References Part VIII: Sound Waves, Resonance, Ultrasonography 19: Oscillations and Resonance: Origin and Propagation of Sound, Children on the Swing, and Invasive Pressure Monitoring 19.1 Origin and Propagation of Sound 19.1.1 A Monster in the Operating Room 19.2 Children on the Swing and Invasive Pressure Monitoring: Oscillations, Natural Frequency, and Resonance 19.2.1 Simple Harmonic Motion 19.2.2 Natural Frequency and Resonance of an Invasive Pressure Monitoring System: Possible Causes of Underdamping References 20: Ultrasounds and Doppler Effect: Echocardiography and Minimally Invasive Cardiac Output Monitoring 20.1 A Few Notes on Ultrasonography 20.2 Bats, Speeding Fines, Echocardiography, and Cardiac Output Monitoring: The Doppler Effect 20.2.1 Cardiac Doppler Ultrasound 20.2.2 Doppler-Based Minimally Invasive or Noninvasive Monitoring Devices References Part IX: And Finally... 21: Activated Clotting Time and A Brief Look at Relativity 21.1 Surgeons are Always in a Hurry 21.2 How to Get the Result of ACT Faster 21.2.1 The “Relativity” and the “Speed of Light” Postulates 21.2.2 How Fast Should the Cardiac Surgeon Run 21.3 After All, It was Just for Fun References Index