SS Physics Intro - Fall23.pptx

Intro to Physics Clay Freeman, DNP, CRNA Science in Anesthesia 1 Objectives Readings: Nagelhout: Chap. 15 Davis: Chap. 1 & 8 • List Units of Measurement • Describe Force • Describe Pressure • Identify types of Energy • Describe Work & how it is measured 2 International System of Units • Com...

Intro to Physics Clay Freeman, DNP, CRNA Science in Anesthesia 1 Objectives Readings: Nagelhout: Chap. 15 Davis: Chap. 1 & 8 • List Units of Measurement • Describe Force • Describe Pressure • Identify types of Energy • Describe Work & how it is measured 2 International System of Units • Common units of Measurement: mass – grams (g) length – meters (m) volume – liters (l) time – seconds (sec) 3 Units of Significance 4 Newtonian Physics Newton’s FIRST Law: An object in motion (or at rest) will tend to stay in Law of Inertia motion (or at rest) unless acted upon by another, outside force. Newton’s SECOND Law: Acceleration (a) of an object is in the direction of and Law of Acceleration proportional to force (F) and is inverse to the mass (m) of the object (F = m∙a). Newton’s THIRD Law: For every action, there is an equal and opposite Law of Reciprocal Action reaction. [Gravity] 5 Force (F) The amount of energy required to change an object from a state of rest to a state of motion. F = mass (m) x acceleration (a) F = m·a 6 Force (F) • Mass: sum of all matter contained within an object • Weight = Mass x Force of Gravity • Mass does NOT equal Weight • Acceleration: rate of change in velocity over time • Acceleration = Velocity / Time • Most commonly expressed as Meters/Second/Second (m/s2) 7 Unit of Force Newton (N) • How force is quantified • Force required to accelerate 1 kg of mass by 1 meter per second per second (N = kg/m/sec/sec) 8 Units of Force Dyne (dynes/sec/ cm-5) Dyne = g/cm/sec/sec • Force required to accelerate 1 g mass by 1 cm per second per second • Dyne is standardized fraction of a Newton (1/1000) • Used to measure Force in medicine – systemic vascular resistance (SVR) & Pulmonary Vascular Resistance (PVR) 9 Gravity • Universal force that attracts all objects with mass to one another • Mathematic expression: force of gravity (Fg) = G · (m1 · m2) / r2 • m = mass of object, r = distance between objects, G = gravitational constant • Force of Gravity = 9.8 m/sec/sec 10 Clinical Application Gravity exerts a force on fluids which creates a pressure gradient This hydrostatic effect is measurable and crucial to appreciate as part of surgical position and perfusion to desired tissue The standard reference point of blood pressure is the right atrium • Hydrostatic pressure is subsequently altered depending upon gravity and how distal the location is from the heart 11 Pressure Force applied per unit area P = f/a f = force, a = area Pascal (Pa) is the standard unit   Pressure exerted by a force of 1 newton over 1 square meter of area 1N / m2 = 1 Pa Kilopascal (kPa)   Pressure exerted by a force of 1000 newtons over 1 square meter of area 1000N / m2 = 1 kPa 12 Pressure Measurement Manometer: • U-shaped tube filled with liquid of known density • One end connected to closed system you want to measure & the opposite end open to atmosphere • Calibration of tube into precise units allows for measurement of differential pressure 13 Pressure Measurement Bourdon Gauge: • Commonly used for compressed gas cylinders • Pressure applied inside hollow tube causes expansion of metal coil and corresponding movement of pointer 14 Atmospheric Pressure • Gravitational forces on gases in a given area • Atmospheric gases are more concentrated/dense at sea level and less concentrated/dense at altitude • At sea level, Atmospheric Pressure = 100 kPa, or 1 atm 100 kPa = 1 atm = 760 mmHg = 760 torr = 1 bar = 1020 cmH2O = 14.7 psi 15 Absolute vs Gauge Pressure Absolute pressure is Atmospheric pressure plus Gauge pressure Gauge pressure is Absolute pressure minus Atmospheric pressure Pgauge = Pabsolute – Patmosphere Area for Variability Pabsolute = Patmosphere + Pgauge Therefore… Gauge pressure is zero referenced at atmospheric pressure 16 Anesthesia Applications Blood pressure (sphygmomanometer) Manual ventilation • Adjustable pressure limiting (APL) valve Mechanical ventilators • Pressure Relief Valve • Unidirectional Valve • Oxygen failure warning device (older machine) Compressed gas cylinders Syringe injection pressures (Regional & IV) • TB vs 10 cc syringe vs 30 cc syringe Tourniquet pressure Pressure-reducing valve 17 Airway Pressure Peak Inspiratory Pressure measured from the distal end of the ventilatory circuit • Used as a means to approximate alveolar pressures, differentiate ventilatory issues (mechanical or physiological), & avoid barotrauma 18 Energy Joule (J) 1 J = 0.239 cal The capacity to do WORK (Potential) calorie (cal) 1 cal = 4.184 J or the exertion of force (Kinetic) Can be expressed as thermal, mechanical, or chemical energy 19 Measurement of Energy Joule (J) is the standard unit of Energy Amount of Energy used to accelerate 1 kg of mass at 1 m/sec2 over a distance of 1 m 1 J = 1 N · Distance (1 kg · 1 m/sec2) · (1 m) = 1 kg · m2/sec2 20 Kinetic Energy KE = ½ mv2 Kinetic Energy Work = F·d WORK 𝑘𝑔× 𝑚 𝑠2 Energy of Motion • m = mass and v = velocity Result of force acting on an object to displace it • F = Force, d = distance 2 Kinetic Energy & Work are used 21 Clinical Application The work of the heart is directly affected by mean blood pressure and cardiac output Additional energy requirements over time can result in altered metabolic states and eventual heart failure 1 ventricular contraction = ~1 joule of work ~60 joules / minute (if HR = 60)22 Potential Energy Energy stored to be converted into work PE = m·g·h m = mass, g = gravity, h = difference in height Potential Energy is situational so therefore expressed in various formulas (thermal, chemical, light) 23 Conservation of Energy Law of Energy Conservation The amount of energy is constant and converted but not destroyed/created 24 Conservation of Energy Max Potenti al 25 Additional Resources Physics of Anaesthesia Made Easy: • https://lupinepublishers.com/anesthesia-pain-medicine-j ournal/pdf/GJAPM.MS.ID.000107.pdf 26