Anesthesia machine step by step presentation.pptx

Anaesthesia machine step by step

1. Anesthesia Machine step by step Prepared by The anesthesia team Al shifa medical complex Palestine zoom

2. The anesthesia warkestation (machine) divided into 3 main components : 1- electrical component 2- Pneumatic component 3- scavenging system In this lecture we will focus on the pneumatic component step by step.. introduction

3. Safety features were incorporated sequentially over this huge time span of nearly 100 years of evolution of the anaesthesia machine (since 1917), With more and more safety systems being added as realisation of the problems and mishaps surfaced. Various national associations of anaesthesiologists have recommended the minimum safety features for machines used in their countries or by their members. Many international standards exist for the anaesthesia machines specifying the safety features that are absolutely required and those that are relative/desirable. Anaesthesia machines are covered by the american society for testing and materials ( astm ) standard. introduction

4. The most popular ones are those from the American Society of Anesthesiologists (ASA), (CAS),(ANZCA). Most professional associations e.g., Association of Anaesthetists of Great Britain and Ireland (AAGBI) and ASA also recommend pre- anaesthesia checkout procedures that check the proper functioning of all the safety features incorporated in the machine. In a review conducted over the years 1962-1991 by ASA, 72 of 3791 (ASA closed claims Project): malpractice claims were related to gas delivery equipment. Death and permanent brain damage accounted for a majority of the claims (76%). Misuse of equipment was 3 times more common than equipment failure, highlighting the necessity of proper equipment check and training before use The ultimate responsibility for the safe use of the machine rests with the end user – the anaesthesia provider . introduction

5. Pneumatic component Generally the pneumatic component of anesthesia machine divided into 3 areas : A-high pressure area Consists of: Cylinders Yoke assemblies, Bodok seal. 1 st Pressure regulators. pressure relief valve Cylinder pressure indicators ( bourdon gauge) C-Low pressure area. Consists of: This part contains: The flow meters, Hypoxia prevention devices Vaporizers, Unidirectional valves Pressure relief devices. B- intermediate pressure area Consists of: The pipeline inlet. Master switch (present in newer machines), Pipeline pressure indicators, 2 nd stage pressure regulators, Auxiliary gas outlets for ventilators, Oxygen failure devices, Oxygen flush The flow control valves.

6. 1-Cylinder supply source Anesthesia machines have reserve E cylinders if a pipeline supply source is not available or if the pipeline fails . O 2  tanks are fitted at the factory to a pressure of approximately 2000 psig = 137 bar = 13,700 kPa at room temperature. A full E cylinder of O 2   (2000 psig ) will produce approximately 660 L of gaseous O 2  at atmospheric pressure . The cylinder attaches to the machine through the hanger-yoke assembly. The cylinders should be turned off except during the preoperative machine checking period or when pipeline source is unavailable, to avoid depletion of the cylinder A-high pressure area

7. 2 -the hanger yoke assembly Orients and supports the cylinder. Provides a gas-like seal . ( Bodok seal). Ensures a unidirectional flow of gases into the machine. Each hanger yoke is equipped with a pin index safety system (PISS). The PISS is a safeguard introduced to eliminate cylinder interchanging. Each gas or combination of gases has a specific pin arrangement . A-high pressure area

8. 3- Bodok seal The yoke contains a Bodok seal . Bodok seals ( bonded disk ). These are non-combustible neoprene washers with aluminium edges placed between the cylinder head and yoke to provide a gas-tight seal. Under no circumstances may oil or grease be used as a seal ; the pressurized gases give off heat as they are released from the cylinder and may cause an explosion if oil is used. A-high pressure area

9. 4- check valve(one way valve) Check valves or one-way valves are normally placed on/after the yoke . Has several functions: 1- It minimizes gas transfer from a cylinder at a high pressure to one with lower pressure. 2- It allows exchanging a cylinder while gas flow continues from the other cylinder into the machine with minimal loss of gas. 3- It minimizes leakage from an open cylinder to the atmospheres if one cylinder is absent. The check valves may leak; therefore if a yoke does not have a tank hanging on it, a yoke plug should be inserted . A-high pressure area

10. 5 - Primary pressure regulator ( for the cylinders) Not only reduce the pressure of gases from the cylinders. But provide them at constant pressure of 4 bar or 400 kpa to the flow meters. Note: some manufacturers adjust the cylinder regulators to just under 400 kpa , which allows the machine to preferentially use the higher pressure pipeline gas. Regulators may weep the cylinder contents, hence the importance of turning a cylinder off after a machine A-high pressure area

11. 6- A pressure relief valve Cylinders have exploded because of over-pressure in them either due to over filling or mis -filling. To prevent explosion, astm standards require all cylinders to have pressure relief devices, It vent over-pressurized contents of the cylinder to the atmosphere. They are of two types : Rupture disc , where, when a predetermined pressure is reached a disc guarding an orifice ruptures releasing the contents. Fusible plug , which is a thermally operated plug providing protection against high temperatures, but not pressure. A combination of these two is sometimes used as well. A-high pressure area

12. 6- Pressure gauges ( Bourdon gauge) Colour -coded Bourdon gauges indicate the pressures of the piped and cylinder supplies. The Bourdon gauge consists of a tube bent into a coil or an arc. As the pressure in the tube increases, the coil unwinds. A pointer connected to the end of the tube can be attached to a lever and a pointer calibrated to indicate pressure. A-high pressure area

13. 1-The pipeline inlet connections Connectors that can be fitted to the wrong gas terminals have caused patient dangers and led to the development of safety features such as non-interchangeable screw thread (NIST), diameter index safety system (DISS), etc. Schrader probe: The probe for each gas supply has a protruding indexing collar with a unique diameter , which fits the Schrader socket assembly for the same gas only . Hose pipes: These are flexible, colour -coded and have built in reinforcements in the wall to make them kink proof. B- intermediate pressure area

14. Pipeline attachments: Each terminal unit that connects to the main pipeline system is equipped with the DISS . non-interchangeability of connections is achieved by differing diameters of the shoulders that surround the nipple. Properly engaged parts allow the thread to connect to each other so that gas starts to flow. Quick connectors are other safety devices, which allow correct attachments by using varying combinations of shapes and spacing of the different portions of the components that couple with each other. Each gas inlet also contains a unidirectional check valve that prevents leakage into the pipeline system when cylinders are being used as the main source. B- intermediate pressure area

15. Machine end of gas pipelines: NIST connection to the anaesthetic machine each flexible hose ends in a unique fitting of nut and probe. This ensures a hose connection specific to each gas service. It comprises of a nut and probe. The probe has a unique profile for each gas , which fits only the union on the machine for that gas. The nut has the same diameter and thread for all gas services, but can only be attached to the machine when the probe is engaged. The term NIST is in fact misleading; the screw thread does not determine the unique fit. A one-way valve ensures unidirectional flow. B- intermediate pressure area

16. 2- Pipeline pressure indicators Indicators are required for each gas . they usually have a colour -coded dial in some indicators satisfactory working pressures zones have a special colour for easier identification. B- intermediate pressure area

17. 3- Second stage pressure regulator Most modern machines have a second stage regulator . It is located just upstream of the flow meters . so that flow is constant at the flow meters even if there are fluctuations in the pipeline pressure. It reduces pipeline pressure (4 bar) down to the machine working pressure (around 1 bar) . B- intermediate pressure area

18. 4- Oxygen failure devices: The 2000 ASTM F 1850-00 standard states : “ The anesthesia gas supply device shall be designed so that whenever O 2  supply pressure is reduced to below the manufacturer specific minimum, the delivered O 2  concentration shall not decrease below 19% at the common gas outlet .” If the oxygen pressure in the high-pressure system decreases (usually to <30 psig), an oxygen supply alarm is activated within 5 s . A- O2 failure alarm The O2 failure alarm was originally introduced to prevent the unobserved emptying of oxygen cylinders before piped gases were in common use. An alarm must sound for 7 s duration when the pressure in the oxygen supply falls below 200 kPa. Originally, this alarm was a mechanical device called a Ritchie whistle but modern anaesthetic machines employ electronic alarms. B- intermediate pressure area

19. B-Fail-safe valves 1- in datex-ohmeda machines : When the oxygen pressure in the machine’s high pressure system falls below 20 psig , The flow of N 2 O and all other gases to their flow-control valves is interrupted . This valve is an all-or-nothing valve ; It opens at oxygen pressures of 20 psig or more And it is closed at pressures less than 20 psig B- intermediate pressure area

20. 2- Dräger Narkomed machines ( Dräger , Lübeck , Germany) Is called the oxygen failure protection device (OFPD). There is 1 OFPD for each of the gases supplied to the machine. As the oxygen supply pressure decreases, the OFPD proportionately reduces the supply pressure of each of the other gases to their flow-control valves. The supply of N 2 O and other gases is completely interrupted when o 2  supply pressure falls below 12 ± 4 psig B- intermediate pressure area

21. The oxygen failure safety device and the oxygen supply failure alarm both depend and detect failure based on pressure and not on flow . These mechanisms work on supply connections upstream of the machine. Hence they do not protect against hypoxic gas delivery, which may occur because of: empty cylinders or misconnected pipelines or the wrong proportion of gases being dialled on the flow meters. B- intermediate pressure area

22. 5- Oxygen flush Named as flush or emergency oxygen or by other numerous names. this switch directs a high pressure flow of oxygen direct to the CGO from the source, either pipeline or cylinder. It is bypassing all intermediate meters and vaporizers. Barotrauma and awareness may result from inappropriate activation of this switch . To prevent accidental activation these are usually: 1- placed in a recessed setting. 2- will deactivate as soon as the finger activating the switch is removed. B- intermediate pressure area

23. C- Low-pressure system 1- Flowmeter : Gases pass through an adjustable needle valve into flowmeters to accurately measure gas flow . The conventional form of a flowmeter on an anaesthetic machine is called a Rotameter . Increasingly many modern anaesthetic machines do not have rotameters . They deliver fresh gas of a desired flow rate and oxygen concentration by the use of electronic solenoid valves. Flowmeters measure consist of: 1. A flow control valve or needle valve 2. A tapered transparent tube 3. A lightweight rotating bobbin or ball

24. 1. Flow control valves It allow manual adjustment of the flow through rotameters . There is one brass valve situated at the base of each pair of rotameter tubes adjusted by means of a labelled , colour -coded knob. If knob is turned anticlockwise, it will opens up the valve allowing increased flow through the rotameter . The knob of oxygen is larger than for other gases, with grooves cut into the side . This is a safety feature that allows quick identification of the O2 even in the dark . Another means of quick identification is the UK convention that always places the O2 knob and rotameter to the left of other gases (Boyle’s left-handed influence) A minimal basal flow of 100-300mls/min is always flowing if the anaesthetic machine is on to prevent hypoxia if a patient is connected with no flow. C- Low-pressure system

25. 2. A tapered tube clear tubes with varying internal diameters . The higher the gas flow the further the bobbin or ball will move up the tube. the graduations get closer together higher up the tube due to it widening towards the top. The O2 rotameter and control knob are always on the left O2 is actually the last gas to join the back bar at the top right- hand side of the rotameter unit. This is to preserve the O2 supply in the event a leak or damage to any of the other rotameter tubes . They have an anti-static coating on the inside to prevent the bobbin sticking and are accurate to within 2.5%. C- Low-pressure system

26. 3. A bobbin or ball The bobbin (most common) or ball floats within the tube as the gas flow passes around giving a measure of the flow rate . The higher the flow, the higher the bobbin rises. It is important to check that the bobbin is freely rotating and for this purpose each bobbin is marked with a clearly visible dot. Always read the gas flow rate from: The TOP of the bobbin (not the dot) The MIDDLE of the ball. C- Low-pressure system

27. Proportioning Systems (Hypoxic link) Nitrous oxide and oxygen are interfaced mechanically or pneumatically or electronic so that the minimum oxygen concentration at the common gas outlet is between 23% and 25%, depending on the manufacturer . C- Low-pressure system

28. 2- Back bar: The back bar is a structure that supports and connects the flow meters and the gas pathways . It is where all the gases finally meet . Most machines use a system that allows the user to add or remove specific vaporizers quickly and easily while maintaining a gas-tight system. Some machines have space for a single vaporizer; others allow the attachment of two or more vaporizers . However, only one vaporizer can be turned on at any given time system due to an interlock. This is to prevent the transfer of upstream agents to the downstream vaporiser and simultaneous delivery of two agents. Once a vaporizer is attached and turned on, gas flow is diverted from the back bar into the vaporizer to provide the required concentration of anaesthetic vapour . C- Low-pressure system

29. 3-Vaporizers Vaporizers convert volatile anaesthetic liquid into measured allow inhalational anaesthesia. The vapour is added after the flowmeters . All modern vaporizers are precise and agent specific. Colour -coded Individual keyed filling systems are used to ensure the vaporizers cannot be filled with the wrong agent. Low-pressure system

30. Modern vaporizers (e.g. Tec 5, 6 and 7) have several safety advantages over their predecessors: an interlock to isolate vaporizers not in use; a clear indication of liquid level ; a non-spill reservoir with up to 180° of allowable tilt; a keyed-filler or pour-fill systems prevent filling with an incorrect volatile agent and minimize leaks; an increased wick capacity. accurate to within 2.5% Low-pressure system

31. Aladin cassettes veporiser The cassettes are lighter (2–3 kg), virtually service-free have no restrictions for tilting. Integrated real-time electronic fresh gas flow measurement of gas mixtures enables the unit to dispense more accurately dialled concentrations , compared with traditional vaporizers.

32. DIVA Draeger has the DIVA ( direct injection of volatile anaesthetics ) In some of its newer machines that use injectors. They inject the volatile directly into the fresh gas flow allowing rapid increases in concentration even with minimal flows, which normal vaporisers and Aladdin units cannot do. Low-pressure system

33. 4 - Pressure relief devices Modern machines have a pressure relief device between the vaporizer and the CGO it vents to the atmosphere in case dangerous pressures develop downstream due to occlusions, thus protecting the machine 5 - Alternate oxygen flow meter Many newer machines have the facility of a separate, stand-alone mechanical flow meter. which has to be consciously activated in the rare instance of electronics in the machine failing to provide a gas flow to the CGO . This flow usually may or may not pass through the vaporizers. 6 - Common Gas output This has a standard 15 mm female slip joint fitting with 22 mm coaxial connector . C- Low-pressure system