Vaporizer ppt for Anaesthesia PG students

Vaporizer class for Anaesthesia post graduate students

1. Vapourizers Dr. A. V. Sandeep kumar D Assistant Professor Dept. of Anesthesiology PIMS

2. Define Vapourizer , principles involved in process of Vapourizer What is a gas and vapour . Discuss factors affecting vapourisation (Mar’14) Classify Vapourizer , describe functioning of tec 6 Vapourizers (Mar’15) Principle involved, advantages & disadvantages of diff. vapourizers used in anaesthesia practice Discuss physical properties involved in vapourisation of liquid anaesthetics . Describe Ideal Vapourizer Principles of Draw over vapourizers

3. Above Critical Temperature Below Critical Temperature Gas Vapour Gas Liquid Interconvertible Vapour Vapour Gaseous phase of a substance below its critical temperature which is normally a liquid at room temperature and atmospheric pressure.

4. Vapor pressure: is the pressure exerted by the molecules escaping from the surface of a liquid to the gaseous phase in a closed container.

5. Saturated vapor pressure (SVP): vapor pressure at which the liquid and its vapor are in equilibrium . Is dependant on the temperature and nature of liquid

6. Boiling point : temperature at which SVP is equal to the atmospheric pressure

7. Critical temp : temp above which no amount of pressure will convert a gas into liquid . eg O2 -118.5 , N2O 36.5

8. Latent Heat of Vaporization : - the amount of heat required to vaporize one gram of a liquid at its boiling point with no change in temperature Significance Cooling of liquid No supplied heat Heat of vaporization provided by the liquid Drop in vapour pressure SVP depends on the temp of the liquid Vapour output will decrease

9. Specific heat (1 cal /g/ºC): - the quantity of heat required to raise the temperature of 1 gm of the substance through 1ºC

10. Thermal capacity : Thermal conductivity : Product of specific heat and mass ( amount of heat stored in the vaporizer body) is a measure of how fast a substance transmits heat ,under known temperature gradients.

11. Metal properties Metal Specific heat Thermal conductivity Copper 0.1 0.92 Aluminium 0.214 Glass 0.16 0.0025 Air 0.0003 0.000057 Steel 0.107 0.115 Brass 0.0917 0.260 0.504

12. Concentration of gases: We give in volumes but what matters is partial pressure Volumes percent: The number of units of volume of a gas in relationship to a total of 100 units of volume for the total gas mixture. Partial pressure Volumes percent Total pressure 100 =

13. Partial Pressure: The part of the total pressure due to any one gas in the mixture is called the partial pressure of that gas . DALTON’S LAW OF PARTIAL PRESSURES: The total pressure exerted by a mixture of gases is the sum of their individual partial pressures

14. Calculation of Inhalational agent used… Avogadro’s hypothesis: 1 mole of a substance = 22.4 liters of gas 1 mole of a gas weighs 1 gram molecular weight . Mol. wt of Isoflurane is 185 Density of Isoflurane vapour = 185/22.4 = 8.25 g/L Density of Isoflurane liquid = 1.5 g/ml As mass is constant, 1 gm of liquid gives 1 gm vapour 1ml/1.5 = 1000 ml/8.25 1 ml of liquid gives 1000 x 1.5 / 8.25 = 180 ml mL of vapor /ml of liquid= Density x 22.4 x 1000 x (273+21) Molecular weight 273

15. Amount of vapour used per minute = FGF × time × concentration setting For eg , to deliver 1% Isoflurane at FGF of 2 liters per minute for 60 minutes, 1/100 × 2000 mL × 60 min = 1200 mL of Isoflurane vapour This would correspond to 1200/180 = 6.7 mL of liquid isoflurane Most agents, 1 mL of liquid volatile agent yields about 200 mL vapour. Another formula which can be used with most agents is Ehrenwerth and Eisenkraft formula (1993 ) 3 × FGF (L/min) × volume % = mL liquid used per hour

16. Vapourizer An instrument designed to facilitate the change of a liquid anaesthetic into its vapor and add a controlled amount of this vapor to the fresh gas flow , going to the patient .

17. Why we need precision Can any one tolerate this conc. Answer – we add fresh gas flow in titrated amounts through a splitting valve

18. Splitting ratio

19. Splitting ratio – SVP SVP – specific for agent

20. We know As evaporation proceeds , the temperature falls Cold liquid – vaporize with difficulty Hence all vaporizers need to be temperature compensated Different methods

21. 15 – 35 degrees the best

22. Classification of Vaporizers Dorsch and Dorsch classification

23. Draw Over Vapourizer

24. Goldman Vapourizer

25. Boyle’s bottle

26. EMO OMV

27. Copper Kettle

28. Desflurane (TEC 6) Precisely controlled constant temp Gaseous Desflurane at 2 atm. (1500 mmHg) 40 o C DES Injection into FGF FGF Dial Flow control Solenoid valve

29. Desflurane (TEC 6): High FGF 40 o C FGF Dial Flow Control valve Flow control valve (Pr. Diff.) Circuit Resistance

30. Desflurane (TEC 6): Pressure Regulation FGF Circuit Resistance Differential Pr. Transducer Fixed Resistance