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GAS LAWS Physics & Anaesthetic implication

GAS LAWS Physics & Anaesthetic implication . Dr.J.Edward Johnson.M.D ., D.C.H., Asst. Professor Kanyakumari Govt Medical College & Hospital, Asaripallam , Nagercoil , Tamilnadu , INDIA. "We live submerged at the bottom of an ocean of air - Torricelli, 1644". Molecular Theory.

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GAS LAWS Physics & Anaesthetic implication

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  1. GAS LAWSPhysics & Anaesthetic implication

    Dr.J.EdwardJohnson.M.D., D.C.H., Asst. Professor KanyakumariGovt Medical College & Hospital, Asaripallam, Nagercoil, Tamilnadu, INDIA. "We live submerged at the bottom of an ocean of air - Torricelli, 1644"
  2. Molecular Theory Van der Waals forces Lattice (oscillates) All matter is made of tiny particles called atoms. These atoms are in constant motion Brownian motion (random motion). Each particle has kinetic energy. Collisions between particles are perfectly elastic.
  3. Interface Pressure Saturated Vapour Pressure
  4. The Gas Laws Introduction 1. Definitions: Pressure = force/area P = F/A 2. Units: Pascal (Pa):  1 Pa = 1 Newton/m2 or 1N/m2 The Pascal is the Standard International Unit of pressure The Newton is the Standard International Unit of force Atmosphere (atm): one atm  =101325 Pa   Pounds per sq inch (psi): one atm = 14.7 psi or lbs/in2 Torricelli (torr): one atm = 760 torr mmHg: 1 mmHg = 1 torr Millimeters Hg: one atm = 760 mmHg 1 atm = 14.7 psi = 760 mmHg = 101 kPa
  5. In the Torricellian tube, the atmospheric pressure supports, mercury 760 mm tall
  6. Pressure P= f/a Pressure is inversely proportional to area 20ml 1 atm 10ml 2 atm
  7. Pressure P= f/a Anesthesia Machine Examples Pressure Relief Valve Expiratory Valve Pressure-reducing valve AKA pressure regulator Oxygen Failure warning device
  8. Boyle’s Law (Pressure – Volume Law) The volume of a given amount of gas at a constant temperature varies inversely with the pressure P1V1 = P2V2
  9. Graph of pressure vs. volume for a gas enclosed in a cylinder at constant temperature (Boyle's law)
  10. Example - Cylinders For example, if we have a cylinder of gas under pressure equivalent to 13,800 kPa (the internal volume or capacity of the cylinder is about 10 liters), how much gas would be available at atmospheric pressure which we will say is about 100 kPa. Cylinder Atmosphere P2 100 kPa P1 13,800 kPa V2 ? V1 10 liters P1V1 = P2V2 13,800 x 10 = 100 x V2 V2 = 13,800 x 10 100 V2 = 1380 lts
  11. Charles’ Law (Temperature-Volume Law)Gas volume varies directly with temperature at a constant pressure Remember, always use degrees Kelvin for temperature representation V1/T1=V2/T2
  12. Amontons' Law of Pressure-Temperature Gas pressure varies directly with temperature at a constant volume P1/T1=P2/T2
  13. Gay-Lussac LawLaw of combining volumesThe ratio between the volumes of the reactant gases and the products can be expressed in simple whole numbers. STP- 273.15˚ k(0˚C) - 101kPas(760mmHg)
  14. Pressure-Volume-TemperatureRelationships “Pay TV Can Be Good” Pay- T - V - Can Be Good Pressure constant-Charles Temperature constant-Boyles Volume constant- GayLussac
  15. Avogadro's LawFor a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.
  16. Avogadro's Law “Equal volumes of any two gases at the same temperature and pressure contain the same number of molecules.” V∝ n (at constant T and P) One mole of any gas contains the same number of molecules (Avogadro's number =6.02×1023) Gram molecule (mass of gas) Same number of molecules in one gram molecule H2 O2 H2O 2H2+O2=2H20
  17. Ideal Gas Law (Universal Gas Law) Under the same condition of temperature and pressure, equal volumes of all gases contain the same number of molecules. He N2 O2
  18. Calibration of Vaporizers One mole of Gas 22.4 L At STP Mol.wt of Iso – 184.5 184.5 gm of Iso = 1 mol 224 L Isoflurane O2 + Isoflurane O2 18.45gm 2.24 = 1% 224 2.24 L 0.1 mol
  19. 3.4kg Calculation of volume of Nitrous Oxide gas Mol. Wt of N2O - 44 44 gm(1mol) occupies = 22.4 L 3400 gm occupies = 22.4 x 3400 = 1730 L 44 1 mol = 44 gm
  20. Combined gas law The combined gas law is a gas law which combines Charles's law, Boyle's law, and Gay-Lussac's law
  21. Combined gas law
  22. Dalton’s Law of Partial Pressures The total pressure exerted by a mixture of gases is the sum of their individual partial pressures PARTIAL PRESSURE of AIR Ptotal = Pa + Pb + Pc + etc
  23. Dalton’s Law of Partial Pressures Entanox Cylinders
  24. Dalton’s Law of Partial Pressures What is the partial pressures of O2 and N2O if you are administering a ratio of 70/30? N20 70% X 760 mmHg = 532 mmHgO2 30% X 760 mmHg = 228 mmHg 760 mmHg Would this differ if you were administering anesthesia at Denver General Hospital? N20 70% X 630 mmHg = 441 mmHgO2 30% X 630 mmHg = 189 mmHg 630 mmHg Miami = 14.7 psi Denver = 12.2 psi Miami = 760mmHg Denver = 630mmHg
  25. Adiabatic heating and coolingAdiabatic changes in temperature occur due to changes in pressure of a gas while not adding or subtracting any heat Cryoprobe – N2O or CO2
  26. Critical Temperature As the substance approaches critical temperature, the properties of its gas and liquid phases converge, resulting in only one phase at the critical point Critical Temp of N2O = 36.5˚C Critical Temp of O2 = -119 ˚C
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