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Basic physics for Anaesthesiologists
The document discusses the importance of physics in anesthesiology, covering various topics such as the calculation and storage of N2O gas, alveolar gas exchange, and the principles of gas diffusion using Henry's Law. It explains key concepts like partial pressure, Dalton's law, and the function of pressure regulators, alongside practical applications such as the Venturi principle in medical devices. Overall, it highlights how understanding physics is essential for anesthesiologists in their daily practice.
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Basic physics for Anaesthesiologists
- 1. BASIC PHYSICS FORTHE ANAESTHESIOLOGISTS RATHER APPLIED PHYSICS dr.r.selvakumar. professor of anaesthesiology k.a.p.viswanatham govt medical college trichy
- 2. WE HATE PHYSICS… THAT’SWHY WE SELECTED MEDICINE CBE-SZ
- 3. BUT… THERE ISA LITTLE BIT OF PHYSICS IN ALLACTIVITIES OF OUR DAY TO DAY LIFE….
- 4. JUST NOW I’VEFITTED THE MACHINE WITH A NEW N2O CYLINDER…. HOW LONG WILL IT LAST…? CAN I TAKE A CASE WHICH MAY LAST FOR 6 HOURS….? How the physics knowledge helps the Anaesthesiologists?
- 5. 1.HOW TO CALCULATETHE AMOUNT OF N2O GAS IN A CYLINDER..? •STORAGE OF N2O IN A CYLINDER •PARTLY AS GAS ,PARTLY AS LIQUID STORY OF O2 – IDEAL GAS CBE-SZ
- 6. MOLECULAR WEIGHT ADDITION OFATOMIC WEIGHT ATOMIC WEIGHT OF NITROGEN – 14, OXYGEN – 16 MOLECULAR WEIGHTOF N2O – 14+14+16 = 44 CBE-SZ
- 7. GRAM MOLECULAR WEIGHT MOLECULARWEIGHT EXPRESSED IN GRAMS. AVAGADRO HYPOTHESIS: ONE GRAM MOLECUALR WEIGHT OF ALL GASES WILL CONTAIN THE SAME NUMBER OF MOLECULES AND OCCUPY THE SAME VOLUME ( 22.4 L) AT S.T.P 32 g OF O2 = 44 g OF N2O = 28 g OF N2 =22.4 LITERS CBE-SZ
- 8. AMOUNT OF N2OGAS IN A CYLINDER TARE WEIGHT OF THE CYLINDER = 12.5 K.G CYLINDER WEIGHT WITH N2O = 15 K.G SO.. WEIGHT OF THE N2O = 2.5 K.G = 2500G 44G OF N2O = 22.4 L THEREFORE 2500 G = 22.4/44 x 2500 = 1272 L CBE-SZ
- 9. 2. HOW DOESTHE ALVEOLAR GAS EXCHANGE OCCURS….? O2 AND CO2 MOVE IN OPPOSITE DIRECTION BECAUSE OF PARTIAL PRESSURE GRADIENT. CBE-SZ
- 10. WHAT DO YOUMEAN BY PARTIAL PRESSURE? @ @ @ @ @ $ $ $ @ @ @ @ @ $ $ IN A MIXTURE OF GASES,THE PRESSURE EXERTED BY EACH GAS IS THE SAME AS THAT WHICH IT WOULD EXERT IF IT ALONE OCCUPIED THE CONTAINER $ 5 PSI 3 PSI 8 PSI
- 11. DALTON’S LAW OFPARTIAL PRESSURE THE PROPORTION OF THE PRESSURE EXERTED BY A GAS IN THE TOTAL PRESSURE IS EQUATED WITH THE VOLUME IT OCCUPIES @ @ @ @ @ $ $ $ PRESSURE OF @ GAS = 5 PSI PRESSURE OF $ GAS = 3 PSI TOTAL PRESSURE = 8 PSI What is the % contribution of pressure of @ gas In the total pressure? 5/8 x 100 = 62.5% So, gas @ will occupy 62.5% of the total volume
- 12. THE % OFO2 IN THE ROOM AIR = 21% BY VOLUME THAT MEANS…IT CONTRIBUTES 21% OF THE TOTAL ATMOSPHERIC PRESSURE 21/100 X 760 = 159.6 mm of Hg. pO2 in room air = 159.6 CBE-SZ
- 13. Gaseous Component Percentage in Air % x760 (mm Hg) Partial Pressure exerted (mm Hg) Symbol Nitrogen 79.04 0.7904 x 760 600.7 PN Oxygen 20.93 0.2093 x 760 159.1 PO2 Carbon Dioxide 0.03 0.0003 x 760 0.228 PCO2 Total 100 760 Partial Pressure of Atmospheric Gases Calculation CBE-SZ
- 15. WHAT WILL HAPPENIN Mt EVEREST…? ATMOSPHERIC PRESSURE = 253 mm of Hg. PARTIAL PRESSURE OF O2 = 21/100 X 253 = 53 mm of Hg CBE-SZ
- 16. * * ** ** ***** *** * * * * * * ** 3. DIFFUSION OF GAS IN A LIQUID GAS GOES INTO SOLUTION SATURATION POINT THE PRESSURE EXERTED BY THE GAS IN THE LIQUID IS CALLED AS “TENSION” CBE-SZ
- 17. DIFFFUSION OF GASIN A LIQUID 100 PSI 200 PSI * * * * * * * * * * * * ** * ** ** *** *** **** ** *** *** * * * THE AMOUNT OF GAS DISSOLVED IN A GIVEN LIQUID IS DIRECTLY PROPORTIONAL TO THE PARTIAL PRESSURE OF THE GAS IN EQUILIBRIUM WITH THE LIQUID HENRY’S LAW CBE-SZ
- 18. DIFFUSION OF GASIN A LIQUID PARTIAL PRESSURE OF THE GAS TEMPERATURE NATURE OF THE GAS TYPE OF LIQUID CBE-SZ
- 19. PARTITION COEFFICIENT 1 litreof BLOOD 1 litre N2O 0.47 L N2O RATIO OF THE AMOUNT OF SUBSTANCE PRESENT IN ONE PHASE COMPARED WITH ANOTHER,THE TWO PHASES BEING OF EQUAL VOLUME AND IN EQUILIBRIUM CBE-SZ
- 20. PARTITION CO-EFFICIENT THE AMOUNTOF DISSOLVED GAS TO RAISE THE SAME PARTIAL PRESSURE AS IN THE CONTAINER MAY NOT BE THE SAME…… CBE-SZ
- 21. ++++ ++++ +++ ******* ******* **** *** *** # ## # # ## # # ## ## ++ + + ******* **** **** # # ### ## ##### #### ######## N2O 0.47 HALOTHANE 2.3 ETHER 12 SOLUBILITY OF ANAESTHETICS IN BLOOD CBE-SZ
- 22. THATS WHY, INDUCTIONWITH ETHER IS SLOW…… Partial pressure in the alveoli builds up very slowly as most of the ether goes into solution in the blood. Only when blood gets fully saturated, the Partial pressure in the alveoli and then brain rises….. CBE-SZ
- 23. BOURDON PRESSURE GAUGE CBE-SZ 4. WHICHPART OF THE BOYLE’S MACHINE UTILISES THE SAME PRINCIPLE AS THIS TOY…?
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- 25. IN A CONTAINER,PRESSUREEXERTED BYA COMPRESSED GAS EXERTS ITS EFFECT EQUALLY ON ALL SIDES OF THE CONTAINER. IF THE CONTAINER IS MADE SUCH A WAY THAT IT CAN EXPAND OR STRAIGHTEN OUT IN A DIRECTION, IT WILL DO SO AS LONG AS THE PRESSURE IS MAINTAINED INSIDE. ONCE THE PRESSURE IS RELEASED, THE CONTAINER WILL RETAIN ITS ORIGINAL SHAPE PRINCIPLE OF BOURDON PRESSURE GAUGE CBE-SZ
- 26. ------------------------ --------------------------------------- BASIC PRINCIPLE OFPRESSURE REGULATORS TALL CONTAINER PRESSURE = P AREA OF ACTING FORCE = a SHORT, WIDE CONTAINER Pressure = p Area = A P a p A CBE-SZ 5. HOW THE CYLINDER PRESSURE IS REDUCED TO LOWER LEVEL IN THE BOYLE’S MACHINE…?
- 27. BASIC PRINCIPLE OFPRESSURE REGULATOR AT EQUILIBRIUM FORCE ACTING IN THE TALL CONTAINER = FORCE ACTING IN THE SHORT,WIDE CONTAINER P x a = p x A CBE-SZ
- 28. A LARGE FORCEACTING ON A SMALL SURFACE AREA CAN BE BALANCED BY A SMALL FORCE ACTING ON A LARGE SURFACE AREA BASIC PRINCIPLE OF PRESSURE REGULATORS CBE-SZ
- 29. CYLINDER PRESSURE = P SMALLDIAPHRAGM AREA = a LARGE DIAPHRAGM AREA = A REDUCED PRESSURE = p FLOW METER SCHEME OF A SIMPLE PRESSURE REGULATOR CBE-SZ
- 30. SIMPLE PRESSURE REGULATOR FORCEACTING TO OPEN THE SMALL DIAPHRAGM = P x a AT EQUILIBRIUM…. FORCE ACTING TO CLOSE THE SMALL DIAPHRAGM = p x A BALANCED BY CBE-SZ
- 31. EXAMPLE: CYLINDER PRESSURE =2000 psi SURFACE AREA OF SMALL DIAPHRAGM = 10 mm PRESSURE OF THE GAS IN THE REGULATOR = p SURFACE AREA OF LARGE DIAPHRAGM = 100 mm 2000 X 10 = p X 100 p = 2000 X 10 /100 p = 200 psi SO, IF THE CYLINDER PRESSURE IS 2000, THE REGULATOR WILL REDUCE IT TO 200 psi. CBE-SZ
- 32. 2000 X 10= p X 100 p = 2000 X 10 /100 p = 200 psi IN OTHER WORDS, THE RATIO OF THE SURFACE AREA OF THE TWO DIAPHRAGMS DECIDE THE RATIO OF PRESSURE REDUCTION HERE IT IS 10 : 100 – SO, PRESSURE REDUCTION IS 1/10 CBE-SZ
- 33. CYLINDER PRESSURE = P SMALLDIAPHRAGM AREA = a LARGE DIAPHRAGM AREA = A REDUCED PRESSURE = p FLOW METER SCHEME OF A MODIFIED PRESSURE REGULATOR S1 S2 P X a X S1 = p X A X S2 CBE-SZ
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- 35. PRESSURE OF THESPEEDING FLUID CBE-SZ 6.WHAT DO YOU MEAN BY VENTURI PRINCIPLE…?
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- 37. BASIC PRICIPLE OFVENTURI INJECTOR
- 38. BASIC PRINCIPLE OFA NEBULISER
- 39. VENTI MASKS FOROXYGEN THERAPY
- 40. CBE-SZ Some more applications OfVenturi principle…. Bunsen burner Insect sprayer
- 41. THE BRILLIANCE OFANCIENT CHOLA KING, RAJA RAJA CHOLAN CBE-SZ
- 42. IRRIGATION SYSTEM OFTHE CAUVERY BASIN WATER LET-OUT SYSTEM FROM THE LAKES
- 44. DANIEL BERNOULLI -1738 GIOVANNI BATTISTA VENTURI - 1746 - 1822 RAJA RAJA CHOLAN - 985 - 1014 CBE-SZ
- 45. THANK YOU dr.r.selvakumar. m.d.d.a.dnb professorof anaesthesiology, k.a.p.viswanatham govt. medical college, trichy