anaesthesia machine and equipments.pptx

Airway equipments

1. ANAESTHESIA MACHINE AND EQUIPMENTS

2. ANAESTHESIA MACHINE First Boyles machine was made by Edmund Gaskin Boyle in 1917. The Boyles machine is continuous flow type of machine used for administration of Anaesthesia .

3. MECHANICS OF GAS FLOW IN ANAESTHESIA MACHINE Gases in cylinders are at high Pressure (2000psi for oxygen and 760 psi for nitrous oxide ) which are reduced to 45 to 60psi by pressure regulator (1 st pressure reducing valve)) . The newer machines have second pressure reducing valve which further decrease the pressure to 15 to 20 psi

4. Gases from pressure reducing valve reach flow meters where flow is regulated by flow control knobs. These gases mix in a common manifold at the top of flow meter from where they pass through a vaporizer containing inhalational agent ,the vapor's of which get incorporated in gaseous mixture which finally reaches the machine outlet at a pressure of 5 to 8 psi .

5. Anesthesia machine is divided into 3 parts: High pressure system Intermediate pressure system Low pressure system

6. High pressure system which includes cylinders ,pressure regulators (also called as 1 st pressure reducing valve),yoke assembly and oxygen flush. Intermediate pressure system which starts from 2 nd pressure reducing valve to flow control valve. It includes 2 nd pressure reducing valve ,oxygen failure alarms and fail safe valve.

7. Low pressure system includes downstream to flow control valve up to machine outlet. It includes rotameter, vaporizers, check valve.

8. HIGH PRESSURE SYSTEM 1.CYLINDERS Cylinders are made up of molybdenum steel because molybdenum steel can withstand high pressures. Some of the newer cylinders contains chromium alloy to decrease their weight . Since steel is not compatible with MRI therefore aluminum cylinders are used in MRI suites.

9. CYLINDER VALVES It is fitted at the top of cylinder. Different type of cylinder valves are available like flush type ( most commonly used) ,bull nosed etc., To start and close gas these valves are rotated anticlockwise and clockwise respectively.

10. PRESSURE GAUGE It is used to measure the cylinder pressure . Most commonly used type is Bourdon type.

11. 2.YOKE ASSEMBLY It is the portion of machine at which cylinder get fitted. It consists of index pins ,a gas seal ( Bodok seal ) to prevent leak between cylinder and yoke and a filter .

12. PIN INDEX SYSTEM This is the safety mechanism so that one cylinder can not be fitted at the others position. It consists of 2 pins ,4mm and 6mm long on yoke of the anaesthesia machine. The pins are so positioned that the cylinder with corresponding hole can only be fitted.

13. MAKING OF PIN INDEX SYSTEM A 9/16 inch circumference semicircle is made and 6 equidistant points are made on arc ( additional 7 th point if entonox is to be used). The pins for oxygen are at 2 and 5 position and oxygen cylinders have holes at the same position.

14. Similarly , for nitrous oxide pin are at 3,5 position and nitrous oxide cylinder has holes at same position. It is not possible to fit any other cylinder at this position.

15. CENTRAL SUPPLY OF GASES: In large hospitals where consumption of gases is more oxygen ,Nitrous oxide and air are supplied through central supply pipelines. In central supply rooms oxygen and nitrous oxide are stored in a set of 4 to 8 large H type cylinders connected to a common manifold.

16. (Many hospitals use liquid oxygen tanks instead of cylinders). In India ,oxygen and nitrous oxide are supplied at a pressure of 60psi through central supply.

17. There is color coding for central supply pipelines . White for oxygen, blue for nitrous oxide and black for air.( fourth ,yellow color pipe is for central suction) Like pin index system which prevent wrong fitting of cylinders to machine Diameter index safety system DISS , to prevent wrong fitting of central supply pipes to machine.

18. 3.OXYGEN FLUSH ( EMERGENCY OXYGEN FLUSH) It is a bypass system which bypasses the intermediate and low pressure System and oxygen directly reaches at machine outlet. It delivers 35 liter's of oxygen per minute at a pressure of 60psi.

19. 4.1 ST PRESSURE REDUCING VALVE It is also known as pressure regulator or pressure preset valve . It converts high variable pressure in cylinder to Constant working pressure suitable for anesthesia machine. This reduces the pressure to 45 to 60 psi. (In most of the machines in India it is set at a pressure of 60psi)

20. INTERMEDIATE PRESSURE SYSTEM It includes : 1.2 nd PRESSURE REDUCING VALVE It reduces the pressure to 15 to 20 psi. 2.OXYGEN FAILURE ALARMS Machine starts alarming if the pressure of oxygen falls below a preset pressure (usually 30psi).

21. 3.FAIL SAFE VALVE: This is very important safety device which in case of decreased oxygen pressure either cut off or proportionately decreases the flow of nitrous oxide and other gases( that’s why also called as oxygen supply failure protection devices) thus preventing the delivery of hypoxic mixture. It usually shuts off if oxygen pressure becomes less than 25psi.

22. LOW PRESSURE SYSTEM ROTAMETER One of the most important component of low pressure system is Rotameter which contains flowmeter tubes specific for each gas and flow control knobs controlling the flow of gas through each tube.

23. Flowmeter tubes are glass tubes which are transparent and tapered(narrow at base and wider at apex) with markings on each tube indicating flow. These tubes are also called as Thorpe's tube.

24. In each tube there Is a float called as Bobbin which keeps on rotating by the gas stream passing all around the bobbin and the upper end of the Bobbin determines the flow rate. The whole unit with different Thorpe's tubes and control knobs is called as Rotameter .

25. Bobbin is made up of aluminum and it is made antistatic to prevent it from sticking to wall of flow meter. The flow to each tube us adjusted by flow control valve. These flow control valve are also color coded i.e., blue for nitrous oxide ,grey for carbon dioxide and white for oxygen and black for air.

26. To prevent the error of opening wrong knob and oxygen knob is made physically different from other knobs like more fluted, more prominent and large in diameter. The flow at low flow rates is laminar and viscosity determines the flow at low flow rates. Density of gas is important at high flow rates where flow is turbulent due to high flows.

27. SAFETY FEATURES OF ROTAMETER 1.POSITION OF FLOW METER TUBES: Most vulnerable point of leakage is the junction of flow meter tube and common manifold at the top of machine. If oxygen tube is upstream it can leak at 6 points (1,2,3,4,5,6) while if it is most downstream then possibility of leakage Is only at 2 points ( 5 and 6). Therefore oxygen tube should be most downstream i.e., oxygen should be the last gas to enter the Rotameter.

28. 2.OXYGEN NITROUS RATIO CONTROLLER / OXYGEN NITROUS PROPORTIONING SYSTEM Oxygen and nitrous oxide knobs are interconnected by a pulley in such a manner that a rotation of nitrous oxide knob will automatically start oxygen flow so it is not possible to deliver singular flow of nitrous oxide. This ensures a minimum FIO2 of 25% which is mandatory to prevent hypoxia.

29. 3. Florescent back panel of rotameter so that it can be visualized in dark. 4.Rotameters are hand calibrated to minimize errors.

30. Other types of flowmeter: HEIDBRINK FLOWMETER: It is used in past ,it consists of metal tapered tube with inverted black float.

31. CONNELL FLOWMETER: Again used in past it contains a round float (bobbin) . Reading is taken from the centre of float.

32. 2 .VAPORIZERS : Vaporizers are the devices used to deliver inhalational agents. Inhalational agents are in liquid form in vaporizer. Since inhalational agents are volatile therefore fresh gases passing over the agent vaporizes it and its vapours get incorporated in fresh gases and are delivered to patient.

33. The vaporizer material should have high specific heat and high thermal conductivity. Copper possess these properties so vaporizers are made up of copper.

34. The characteristics of new vaporizers are: Temperature compensated (vaporizer output not effected by changes in temperature). Variable bypass (by rotating the dial knob, it can be decided that how much fresh gas will pass through vaporizer and how much to be bypasses ( therefore called as spliting ratio) this decides the concentration of

35. Anaesthetic agent to be delivered i.e., at 5% concentration most of the gas will pass through the vaporizer and at 0.1% most of gas will be bypasses) Flow over i.e., gas flow passes over the agent. other type is bubble through in which gas passes through the agent. Not affected by pumping effect( back pressure).

36. Agent specific. Although all vaporizers used now a days are agent sepcific . However the agents with similar vapour pressure can be used interchangeably. For example halothane and isoflurane with almost identical vapour pressure can be used interchangeably with accurate delivery.

37. Different vaporizers: Old vaporizers :Boyles vaporizers for ether ( ether bottle) and trielene ( trielene bottle) and Goldman vaporizer. BOYLE ETHER VAPORIZER: It consists of ether bottle ,a lever for on and off, U tube and a plunger with hood over U tube.

38. Ether bottle is calibrated up to 300ml. When the plunger is brought down, the hood comes under the surface of liquid and the gas pass through liquid delivering high concentrations. U tube is made up of copper which acts as anticatalyst to prevent decomposition of ether. Ether bottle can deliver an arbitarary 5 to 15%

39. Goldman vaporizer: It is a simple glass bottle used to deliver halothane. In these old vaporizer ,output is effected by changes in temperature and they do not deliver accurate concentrations.

40. NEWER VAPORIZERS Vapor 19.1,fluotec III,IV,V and VII are used for delivery of halothane, isoflurane and sevoflurane . Tech VI is specifically designed for desflurane .

41. Aladin cassette vaporizer is the latest vaporizer which can be used to deliver all inhalational agents. It just requires insertion of colour coded cassette of each agent, rest everything is automatically adjusted by vaporizer.

42. SEQUENCE OF VAPORIZERS One machine contains more than one vaporizer at a time. The agent with lower boiling point should be placed first i.e. ,near to Rotameter otherwise the condensed particles will be removed from the second vaporizer. That is why isoflurane is placed before halothane and sevoflurane .

43. Agent Boiling point Vapour pressure ( mmHg) Sevoflurane 58°C 160 Halothane 50°C 243 Isoflurane 49°C 240 Desflurane 23.5°C 680

44. SAFETY FEATURES IN VAPORIZERS Newer vaporizers are agent specific. Fluotec 5 and 7 have special key filling system specific for each agent. There are color coded markings Mentioned in vaporizers and the same color is for filling system.

45. Color code is Red for halothane Purple for isoflurane Orange for enflurane Blue for desflurane

46. ONE WAY CHECK VALVE It is placed just before machine outlet to prevent backflow effect of positive pressure ventilation.

47. Anaesthesia workstation Anaestheisia machines used now a days and are called as Anaesthesia work stations because these are not only the machines but are the compact systems having all essential monitors ( capnograph , pulse oximeter , oxygen analyzer , spirometer ,airway pressure monitor) all essential alarms , ventilators, storage drawers

48. for equipment's, suction port, auxiliary oxygen source, provision for closed and semi closed circuits, scavenging systems and electric plugs integrated as a single unit.

49. SAFETY FEATURES OF ANAESTHESIA MACHINE 1.Antistatic rubber tyres ( to prevent current flow). 2.Pin index system to prevent wrong cylinder placement and diameter index safety system to prevent wrong fitting of central supply pipelines. 3.Pressure reducing valves.

50. 4.Fail safe valve 5.Oxygen failure alarms. 6.Colour coding of flow control knobs. 7.Different physical appearance of oxygen knob. 8.Oxygen nitrous proportioning devices. 9.Fluorescent back panel of Rotameter. 10.Oxygen flow meter tube placed most downstream

51. 11.Trielene lock for closed circuits ( in old machines) 12.pressure relief valve( open when there is excessive pressure in machine) 13.Oxygen flush can deliver high flow in emergency. 14.One way valve before machine outlet to prevent backpressure effects of positive pressure ventilation.