PHYSICS IN ANESTHESIA.pptx
- 2. Introduction WHY • Anesthesiologist dealing with many of the gases which are delivering through the anesthesia work station • A sound knowledge about the application of gas laws are essential for every anesthesiologist for safe use of anesthesia practice
- 3. GAS LAWS Boyle’ law Charle’s law Gay lussac’ law AVAGAADRO’S HYPOTHESIS Dalton’s aw Universal gas law Hagen poiseulle’s law Graham’s law Reynold’s number Graham’s law of diffusion
- 4. Bernoulli’s law Ventury’s effect Coanda effect Critical temperature Poynting effect Henry’s law Raoult’s law
- 5. Boyle’s law At constant temperature Volume of a given mass of a gas is inversely proportional to absolute pressure V 1/P Or PV= Constant( temp is constant) Application To know the volume of oxygen in a cylinder available for use at15psig (pressure at common gas outlet) Physics in spontaneous respiration
- 6. P1V1 =P2V2 V1 Is the volume of an E type cylinder 5L P1 is 2000 psig P2 is 15 psig V2 = 2000 X5/15 =665L If we use 3L OF Oxygen last for about 220min
- 7. Charle’s law At constant pressure Volume of gas is directly proportional to temperature V T Or V/T is constant
- 8. Gay lussac’law At constant volume Pressure is directly proportional to temperature P T P/ T is constant Application :oxygen cylinder should be stored in a cool place
- 9. Avagadro’s hypothesis Equal volume of gases contain equal number of molecules at standard temperature and pressure (STP) OR 1 mole of any gas at STP occupies 22.4 L of volume Standard temperature is 273 K Standard pressure is 760mm of Hg Application ;to know how much of N2O is present in a E type of cylinder for use
- 10. At STP (273K temp and 760mmHG Pressure) 44gm N2O give 22.4L Weight of N2O in cylinder equals weight of cylinder – tare weight of cylinder =3.3 Kg 3300gm N2O will give 3300 X 22.4/44 =1680L As per Charle’s law V T Aat room temperature T= 273 +20 = 293K V =1680 X 293/273 = 1803 L
- 11. Dalton’s law of partial pressure
- 13. Reynold’s number Is proportional to velocity, density and diameter Inversely proportional to viscosity Re = vρd/ Ƞ If Re is more than 2000 the flow is turbulent < 2000 flow is laminar Anesthesia equipments do nnot use connectors with sharp curves
- 15. Graham’s law
- 16. Bernoulli’s principle Whengas flowing through a tube encounters a constriction ‘at that point the pressure drops and velocity increases; i.e,kinetic energy increases and potential energy dicreases VENTURY’S EFFECT; Entrainment of air from surrounding due to fall in pressure at the point of constriction Checking the integrity of inner tube of Bain’s circuit( pethick’s test)
- 18. Venturi masks uses for oxygen therapy Sander's jet injector Nebulisation chambees Modern vaporizers.
- 20. Critical temperature Temperature above which gas can not be compressed to its liquid state with any amount of pressure. Critical temperature of oxygen is -118 degree C For N2O is 37 degree C POYNTING effect When two gases of one with higher critical temp. and another of low critical temp. Are mixedin a container,critical temperature of of gas with higher critical temp, will decrease to a lower level ( pseudo critical temp.)
- 21. In cold climate Entonox should thoroughly shaken before use Because when O2 and N2O are in mixture
- 22. Principle adopted in construction of pressure regulator Force = pressure X area High pressured gases from cylinders exposed to larger area of diaphragm of the regulator output pressure decreases from pressure regulators at constant force