03 Anaesthesia machine.pdf

Department of Anaesthesia University of Cape Cape Town

The Anaest Anaesthesia hesia Ma Machine ch ine and Monitori Monit oring ng  Anaesthesia delivery delivery systems can be split into 2 broad categories: Those that require a supply of Oxygen (O 2) and other gases under pressure, such as the anaesthetic machines / workstations found in most hospitals, and Those which rely on on atmospheric Oxygen, such as the draw-over  anaesthesia  anaesthesia apparatus, that may be used in the field, where Oxygen Oxygen cylinders may not be available. available. In these situations, Oxygen cylinders or Oxygen concentrators may be used to augment the augment  the atmospheric Oxygen.

THE ANAESTHESIA MACHINE (BOYLE'S (BOYLE' S MACHINE) The basic machine consists of: 1. A supply supply of gases under under pressure pressure Pipeline from a central depot Cylinders on the machine (colour coded and pin indexed) 2. A means of controlling and measuring measuring gas flow flow Pressure reducing valves or regulators Rotameters, which consist of flow control valves and tapered tubes for flow measurement. measurement. 3. A means means of administering administering anaesthetic vapours Vaporisers (each designed for a single agent) 4. A conduit to deliver deliver gases and and vapour to the patient patient - anaesthesia anaesthesia breathing system system 5. Means for providing providing intermittent intermittent positive pressure ventilation ventilation (IPPV) - i.e. “artificial “artificial ventilation” Reservoir bag for manual ventilation Mechanical ventilator 6. Additional safety devices devices - e.g. e.g. an O2 flush valve, an O 2-supply failure alarm, a “hypoxic guard” to prevent administering hypoxic hypoxic mixtures, a "pop off" valve and optionally, a non-return valve.

DIAGRAM OF AN A NAESTHESIA NAESTHESIA MACHINE MA CHINE The various components of the anaesthetic machine should be identified either in theatre or during the tutorial. In addition, the machine machine checking procedure procedure should be carried out with the anaesthetist. anaesthetist.

High Pressure Zone

Low Pressure Pressure Zone

(< 14 000 kPa Cylinder pressures) pressures)

(< 9 kPa - Airway pressures) pressures)

Intermediate Pressure Zone (± 280 - 420 kPa - Central supply pressures) pressures )

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The anaesthesia machine and monitoring

BREATHING SYSTEMS Mapleson’s classification of anaesthesia breathing sys tems W Mapleson (1954) classified the breathing systems, according to the position of the components of a Magill system, and this nomenclature is still widely used. Five different arrangements were proposed, labelled A to E. A sixth, labelled F, was added (1975) to accommodate the Jackson-Rees modified Ayre's T-piece. Fresh gas flow

 A

Magill System (1928) Humphrey system in A mode (1981)

B

Obsolete

C

Water's system - Obsolete for anaesthesia, but still used for resuscitation and transport

D

"Classic" Mapleson D system Bain's System (1972) Humphrey system in D mode

E

 Ayre's T-piece (1937)

F

Jackson-Rees modified Ayre's T-piece (1950)

Mapleson systems are highly dependent on the fresh gas flow in limiting the rebreathing of Carbon dioxide (CO2) to acceptable levels. Magill breathing system (Mapleson A) The original breathing system still found on many older rural machines, but not at major hospitals. Excellent for spontaneous breathing, but unsuitable for IPPV as it requires a very high fresh gas flow. Required fresh gas flow -1 -1 -1 Spontaneous ventilation 50 ml kg  min ≈ 3,5 l min for adults -1 IPPV 200 ml kg (with hyperventilation) Bain system (Mapleson D)  A co-axial version of the Mapleson D system, with the fresh gas delivery pipe inside the system. Not often seen in SA, but common in the UK. Good for IPPV, but inefficient for spontaneous breathing Required fresh gas flow -1 -1 -1 Spontaneous ventilation 150 – 200 ml kg  min ≈ 9 – 12 l min for adults -1 -1 IPPV 70 ml kg  min  (with hyperventilation) for normocarbia -1 -1 100 ml kg  min  (with hyperventilation) for hypocarbia Jackson-Rees modified Ayre's T-piece (Mapleson F) The Ayre’s T piece (Mapleson E) with an open-ended reservoir bag. This system has no valves and thus a low resistance, making it suitable for paediatrics; where it remains the preferred system Required fresh gas flow -1 -1 -1 Spontaneous ventilation 200 ml kg  min with a minimum of 3 l min -1 -1 IPPV 70 ml kg min  (with hyperventilation) for normocarbia -1 -1 100 ml kg  min  (with hyperventilation) for hypoocarbia

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Humphrey ADE (Mapleson A & D)  A simple 2 tube system with a lever that converts the system from an A mode to a D mode. The A mode is used for induction and spontaneous ventilation and the D mode for IPPV. Popular in Natal (originally designed by D Humphrey in Durban) and often used by vets. Required fresh gas flow -1 -1 -1 Spontaneous ventilation 50 – 70 ml kg  min ≈ 3,5 – 5 l min for adults -1 -1 IPPV 70 ml kg  min (with hyperventilation) The Circle system The most frequently used system worldwide. It has become the universal system because of its ability to use low flows (economical) and less pollution (cleaner). It has a Soda-lime canister to absorb exhaled CO2 and thus enable rebreathing of gas. Two one-way valves ensure a unidirectional gas flow through the Soda lime. The reaction of CO 2 and Soda lime is exothermic and produces water. Thus the gas is also humidified and warmed. Minimum fresh gas flow -1 -1 -1 3 ml kg  min ≈ 200 ml min for adults – this equates to the basal utilisation of O 2 -1

In practice we rarely achieve this fresh gas flow due to leaks etc., but flows of 500 – 1 000 ml min  are the norm. The Soda lime is eventually exhausted and will result in increasing hypercarbia. Signs of exhausted Soda lime Colour change (Indicator) White to purple (some pink to white)

Soda lime

Temperature Exhausted Soda lime is cold Capnograph Rising baseline ( ↑ PICO2) Clinical Signs of hypercarbia (too late!)

VENTILATORS Most anaesthesia workstations / Boyle’s machines incorporate a ventilator to enable automatic artificial ventilation of the patient. They are not essential, as artificial ventilation may easily be provided by squeezing the reservoir bag, but do free-up the anaesthetist from a repetitive task that allows him to concentrate on other matters. Positive pressure ventilation is the normal mode of controlled ventilation applied during anaesthesia. INHALATION is achieved by applying a positive airway pressure to enable gas flow to occur down the pressure gradient. EXHALATION is passive (once the positive pressure is released) as a result of the elastic recoil of the lung and thoracic cage increasing intra-thoracic pressure, allowing gas flow out of the lungs. In contrast, spontaneous ventilation (i.e. patient breathes normally) is a form of negative pressure ventilation. INHALATION is achieved by contracting muscles, increasing intra-thoracic volume and decreasing intra-thoracic pressure, allowing gas flow to occur down the pressure gradient. EXHALATION is again a passive process and is identical to that occurring with IPPV. Modes of intermittent posit ive pressure ventilation  (IPPV) found on anaesthesia ventilators: Continuous mandatory ventilation (CMV) - This is volume controlled where a preset tidal volume is delivered and airway pressure varies -  monitor the airway pressure. Pressure cont rolled ventilation (PCV) - This is pressure controlled where a preset pressure is applied and tidal volume varies -  monitor the minute volume. The former is usually used in adults with cuffed ETTs, whilst the latter is commonly used in paediatrics with uncuffed ETTs as this mode compensates for leaks. Positive end-expiratory pressure (PEEP) may be applied to any mode and aids oxygenation and preventing atelectasis. Synchronised intermittent mandatory ventilation  (SIMV) and Pressure support ventilation (PSV) are sophisticated ICU modes found on some ventilators.

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MONITORING IN ANAESTHESIA Introduction The purpose of anaesthesia is to provide varying degrees of hypnosis, analgesia and muscle relaxation to patients undergoing an operation or distressing procedure. This is relatively easy to achieve with the use of modern anaesthetic agents. However the drugs and methods used have profound effects on physiological homeostasis (e.g. vasodilatation and hypotension). Similarly the procedure may also have life threatening implications (e.g. excessive haemorrhage). It is the responsibility of the anaesthetist to safeguard the patient throughout and restore him to a condition at least as good as pre-operatively. You are the patient’s guardian. To achieve this it is necessary to constantly provide all the body cells with Oxygen and nutrients by ensuring adequate: Inspired Oxygen %  Ai rw ay patency Breathing Circulation Diligent monitoring of the above enables the anaesthetist to constantly appraise the patient’s condition and, by following trends, anticipate and treat the adverse effects of anaesthesia and surgery. Depth of anaesthesia and degree of muscle relaxation can also be monitored to ensure adequate anaesthesia and optimal surgical conditions. Temperature monitoring is important, particularly in infants, as cold theatres and wet exposed patients lead to hypothermia. Hyperthermia can also occur and Malignant Hyperthermia (MH) is a potentially fatal complication of anaesthesia.

MONITORS  A MONITORS OF MACHINE - PATIENT INTERFACE  Oxygen analyser for measurement of O 2 concentration at common gas outlet of the machine.  Ventilation: tidal volume, rate, inspiratory time, flow rate, I : E ratio, minute volume, etc.   Airway pressure  Capnograph / disconnect alarm   Agent monitor for measurement of inspired and expired vapour concentration B MONITORS OF PATIENT WELLBEING These complement clinical monitoring of the patient's vital signs by means of observation, palpation and auscultation, with attention paid to the following: airway, breathing, circulation, oxygenation, temperature, depth of anaesthesia, fluid balance and blood loss. Non-Invasive  ECG  Capnograph  Temperature probe  Blood pressure  Pulse oximeter  Nerve stimulator Invasive  Urinary catheter  Central venous pressure   Arterial blood pressure  Pulmonary artery (Swan-Ganz) catheter or trans-oesophageal echo (TOE)

Oxygen and gas supp ly 1) Pressure gauges 1. Pipeline ± 400 kPa or 4 Bar  O2, N2O and Air pipeline gauges are all checked. 2. Oxygen cylinder ± 13 500 kPa Litres available = volume of cylinder x pressure in 100 kPa units (Bar ). 2) Oxygen analysers Inspired % Inspired and expired %

At the fresh gas flow outlet (confirms the gas is O2 when set to 100 %) Aspirated at catheter mount (patient end of breathing circuit)

3) Rot ameters or flo wm eters O2, N2O and Air Monitored to ensure correct fresh gas flow (FGF)

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 Ai rw ay 1) Manometer (Pressure gauge) Measured in hPa (SI unit) or cm“H2O” (more common) 1 cm“H2O” = ± 1 hPa  Airway pressures are usually limited to < 35 hPa (cm”H2O”) to prevent barotraumas 2) Clinical  A clear airway may be confirmed by “feel” (lack of vibration in the mask), by listening at the airway or end of the endotracheal tube, or by using a stethoscope over the trachea.  Air entry to both lungs is also checked and monitored by a stethoscope after endotracheal intubation. The tube depth may change with flexion or extension of the neck, so the presence of bilateral air-entry should be rechecked after a position change. Satisfactory respiratory monitoring e.g. a “good” capnograph (CO 2) trace confirms a patent airway.

Breathing monitors 1) Clinical Observation of excursion of chest and reservoir bag. 2) Spirometer -1 Measures tidal volume (V T), Rate (f) and minute volume (MV). Normal VT is 6 – 10 ml kg  and a -1 -1 normal MV is ± 80 – 100 ml kg  min . 3) Pulse oximeter  (O2 saturation) This measures % O2 saturation of haemoglobin in the peripheral skin arterioles, not the P aO2. O2 transport to the tissues depends on F IO2, Airway, Breathing, and Circulation So, like the capnograph, it monitors multiple parameters. As O 2 transport to tissues is integral in maintenance of cell life many people feel this is the most important monitor of all. (In infants where application of the probe may be insecure two pulse oximeters are often attached) It is vital that a sound (“beep”) is associated with each pulse. This sound must decrease in pitch with each drop in the value of the O 2 saturation. This is an excellent early warning of an impending problem. Anaesthetists become ‘tuned to the beep’ of the pulse oximeter, and recognise immediately if the O 2 saturations decreases without the need to look at it! Normal O2 saturation values in room air (RA) are 96 – 99 % and higher with increased fraction of inspired O2 concentration (FIO2). The maximum value is obviously 100 %. The drop in O 2 saturation is buffered by the shape of the Hb-O 2 dissociation curve and is gradual above 90 % with decreasing P aO2 but precipitous below 90 %.

The pulse oximeter i s an essential monitor for anaesthsia, sedation or in any situation wh ere the airway or breathing may be comprom ised! If saturation is unsatisfactory, give O2 as a holding measure, BUT look for the cause and treat. 4) Capnograph This measures and displays end- tidal CO 2 (PETCO2) levels. There is often an attachment for the capnograph tubing on the heat moisture exchange filter (HMEF) or pitot tube. This attaches directly to the endotracheal tube (ETT) on one side and the catheter mount on the other. This is the closest placement that will give you an approximation of what the alveolar CO 2 is. The fraction of inspired CO 2 (FICO2) should be zero. This ensures correct functioning of Soda lime in the absorber and the one-way valves in a circle system; or adequate fresh gas flow in other breathing systems. End-tidal CO2 should be 5,3 kPa or less. If it’s more, this may indicate under-ventilation. Shape of the trace can indicate airway obstruction, patient’s own respiratory efforts, disconnection, cardiac arrest and respiratory arrest.

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The anaesthesia machine and monitoring

The normal capnogram (Sourced from Anaesthesia UK)

CO2 presence in expired gas is not only dependent on ventilation, but circulation (i.e. delivery) and metabolism (i.e. production) as well.

Changes in end-tid al carbon dioxi de (PETCO2) Increased

Reduced

Decreased alveolar ventilation  Reduced respiratory rate  Reduced tidal volume  Increased equipment dead-space

Increased alveolar ventilation  Increased respiratory rate  Increased tidal volume

Increased CO2 production  Fever  Hypercatabolic state o Malignant hyperthermia o Thyrotoxicosis

Reduced CO2 production  Hypothermia  Hypocatabolic state o Myxodoema

Increased inspiratory CO 2 (PICO2)  Rebreathing  Exhausted Soda lime  External source of CO2 o CO2 cylinder on ?

Increased alveolar dead-space  Reduced cardiac output  Pulmonary embolus  High PEEP during IPPV Sampling error  Inadequate tidal volume  Line occlusion o Water o Obstuction   Air entrainment  Large sampling dead-space

Capnography i s th us a mul tiple-parameter monit or (FICO2, airway, breathing, circulation and metabolism).

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Cardiovascular monito ring (Oxygen saturation and capnography have already been described) Cardiac outp ut (CO) is the most important cardiovascular parameter but not easily measured during anaesthesia. Heart rate and blood pressure are directly proportional to CO: BP = CO x Resistance (R) When we measure BP we should take into account the warmth of the peripheral tissues, which gives an indication of the peripheral resistance. If the peripheries are warm and the BP is normal we can extrapolate that CO is normal or higher. CO = HR x Stroke volume (SV) When we note the HR, we should also feel the pulse to assess the volume. A good volume pulse with a normal HR indicates a normal CO. A thready pulse indicates a poor SV, often due to hypovolaemia. The accompanying tachycardia is an attempt by the heart to increase theCO. Tachycardia with normal SV may be due to pain-induced adrenaline release or other stress. 1) Blo od pressu re (BP) Non-invasive blood pressure (NIBP)  measurement using a sphygmomanometer or oscillotonometer has been superseded by automated NIBP measuring devices. Frequency of measurement may be set according to how labile the patient is and the readings stored or printed. Usually measured every 2,5 - 5 min. Systolic-, diastolic- and mean- pressures all have significance. Invasive BP or arterial line. A cannula is placed in an artery and connected to a pressure transducer, which is attached to the monitor. This displays a continuous trace of the arterial pressure waveform; and the systolic-, diastolic- and mean- values, beat by beat. Fix the transducer at the same level as the heart. This is different to zeroing. Zero is obtained by opening the transducer to air and confirming the reading is zero. Both must be done.  An arterial line is essential when on cardiopulmonary bypass as the pressure (mean) created by the mechanical pump is not measurable with a BP cuff. The arterial trace can also be used as a monitor of cardiac filling by measuring the swing associated with positive pressure ventilation, (  up and  down). Increased swing is associated with under-filling. The cannula is also used for sampling arterial blood, and serial measurements of arterial blood gas (ABG, Astrup) and chemistry are another way of monitoring respiration and perfusion which can be invaluable in long cases and in the ICU post-op. 2) Heart rate (HR) Continuous heart rate monitoring is a minimum requirement for anaesthesia. It is traditionally monitored with an ECG but an O 2 saturation monitor or arterial line can be used. It is important that a sound (“beep”) is given with each beat. 3) Electro-cardi ograph (ECG) Besides heart rate ECG monitors rhythm and ischaemia (s-t ), dysrhythmias are common under anaesthesia and may indicate:  Ischaemic myocardium  Halothane overdose (relative) – it is dysrthymogenic  Catecholamine levels high  CO2 levels high  Hypoxaemia 4) Central venous pressure (CVP)  A CVP monitor requires a catheter tip in the central veins of the thorax e.g. superior vena cava (SVC). There must be no valves between the tip and the right atrium (RA). Like an arterial line, it is usually connected to a transducer for continuous wave monitoring; and zeroing and levelling are required for meaningful readings. It can also be measured by a water column. The zero is at the level of the RA. CVP measures the right ventricle’s (RV) ability to deal with the venous return. A failing RV will show a rising CVP. Hypovolaemia is usually associated with a low (normal) CVP. The CVP is not a blood volume monitor as such. It will also not be able to tell you what the cardiac output is as it has no ability to measure what is happening on the left side of the heart.

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The catheter may have 1- (single), 2- (double), 3- (triple) or even 4- (quad) lumens, used for:  CVP measurement   Administration of inotropes  Blood sampling   Approximation of mixed venous saturation (not the true mixed venous saturation)   Administration of irritant drugs – Potassium, chemotherapy  Total parenteral nutrition (TPN)  Patients with difficult IV access or the need for long-term IV therapy  ICU – multiple lumens for drug administration 5) Pulmon ary artery catheter (Swan-Ganz catheter) This invasive monitor has a balloon tip enabling flow directed placement in the pulmonary artery (PA). It is placed like a CVP into the SVC, floated into the RA and then the RV, and finally into the PA. It is used to measure cardiac output, right atrial pressure (RAP), pulmonary artery pressure (PAP), and pulmonary capillary wedge pressure (PCWP - an indirect measure of left atrial pressure). Mixed venous O2 saturation and core temperature can be continuously measured with more sophisticated catheters. Blood samples can be drawn to measure mixed P vO2 It is only used in exceptional circumstances as it has many associated risks. This is the goldstandard monitor for measurement of cardiac output, however there are now many modern and less invasive monitors that can measure cardiac output.

Depth of anaesthesia monitors Cardiovascular responses to surgery ( ↑ HR and ↑ BP) have traditionally been used to monitor adequacy of anaesthesia. Several new neurological monitors are available to measure anaesthetic depth (BIS, Entropy, and AEP). There remains a lack of consensus as to whether depth of anaesthesia is a lack of recall, non-response to painful stimuli or hypnosis. 1) Bi-spect ral index moni tor (BIS) This measures the frequency of the most powerful electro-encephalo gram (EEG) waves. Slow waves indicate deeper anaesthesia. Depth of anaesthesia can be expressed as a single number. 0 indicates an isoelectric EEG and 100 = awake. Target 40 – 60. The same value may mean different levels during different phases of anaesthesia. BIS monitoring, therefore, does not ensure lack of awareness if the patient is in the t arget range. 2) Audi tory evoked potent ials (AEP)  Aural stimuli are applied and the EEG is monitored. EEG response to the stimuli is analysed.  Anaesthesia should suppress the mid-latency AEP. This measure may be used to predict movement, response to verbal command, explicit and implicit memory. A 0 to 100 scale is also used but is not the same as BIS at different levels of anaesthesia. Neither monitor measures depth of anaesthesia directly, but rather the brain’s response to stimulation and is affected by analgesics or other drugs. They are useful but not totally reliable.

 Ag ent anal ysers The fraction of inspired (F AA ) and end-tidal (FET AA) anaesthetic volatile agents (AA) can be I measured. End-tidal concentration of AA is an indication of the % of the minimum alveolar concentration (MAC) that is being delivered. This gives an indication of an adequate dose of inhaled anaesthetic agents and is by extension a depth of anaesthesia monitor.

Muscle relaxation monitor s Electrodes are attached over a nerve (often forearm or temporal) to stimulate it and measure the resultant related muscle response. Single twitch, train of four, double burst stimulation and tetanus  patterns can tell the anaesthetist the type and intensity of paralysis, and when it is safe to give the reversal agents. Unfortunately these tests are useful only at relatively low levels of muscle relaxation.

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The anaesthesia machine and monitoring

Temperature monitor ing The patient’s temperature should be measured for any procedure longer than 15 minutes. This is important in general and regional anaesthesia (although more difficult to measure with regional). Temperature probes can be inserted orally, nasally, oesophageally, rectally, on the skin, in the bladder and in the outer ear. Core temperature (oesophageal and bladder) will be warmer. As the patient loses heat, the core gets smaller, buffering the temperature drop. Peripheral temperature is subject to ambient conditions, but the trend is useful. Usually measured via a naso- or oropharyngeal probe. Heat loss is common during anaesthesia due to the cold ambient theatre temperatures, cold air increasing heat loss via convection, exposed area of body, vasodilatation from anaesthetic agents, and the inability to shiver and generate heat. Make every attempt to keep the patient warm with ® warm fluids and gases, and the forced air warmer blanket e.g. Bair hugger  . In open-heart surgery both core and peripheral temperatures are measured as deliberate cooling, to 28 – 32° C, occurs. Warming requires the rise of both temperatures to normal before coming off bypass. Oesophageal T° reflects heart temperature and nasal the brain. Effects of hypothermia  Adverse effects Vasoconstriction, shivering, poor enzyme function (including cardiac contractility and conduction, coagulation), respiratory depression, diminished muscle relaxant effect, slowed emergence from general anaesthesia Beneficial effects Protects brain cells from hypoxia (used to our advantage during certain cardiac surgical procedures and cardio-pulmonary bypass)

Monitoring patient safety While the patient is under anaesthetic, as mentioned, you are their guardian. They are unable to protect themselves from harm or injury. You must check the patient’s position and cushion their pressure points; tape their eyes; check no part of their skin is in contact with metal or water as they may be burned by the diathermy (cautery) unit; and be concerned for their modesty.

Conclusion Monitoring is essential for safe anaesthesia. The emphasis is on maintaining physiological homeostasis while conducting effective anaesthesia. Minimum monitoring st andards  proposed by SASA (The South A frican Society of Anaesthetists ) are HR, BP, O2 Saturation and Capnography. These and other physiological variables should be noted on the anaesthetic chart every 5 minutes in black ink. This is a medico-legal document.

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BA SIC ANAESTHESIA MACHINE-CHECK The following is a suggested method of checking a basic anaesthesia machine / workstation. These guidelines may be modified to accommodate different types of machine and some checks may not be necessary for modern electronic workstations with an automated “self-check”. Switch ON if an electrical machine, turn off all flow s and connect breathing system Check O2 monitor in room air - calibrate to 21 % & place at the common gas outlet (if possible) Verify correct assembly of breathing system (hoses, reservoir bag, Y-piece etc.) Occlude or “park” the patient-end of the system, and fully open the APL valve -1 If present - Open Air rotameter @ 6 l min  – (O2 monitor should read 21 – 25 %) - and close -1 Open O2 rotameter @ 2 l min  – (O2 monitor should rise) -1 Open N2O rotameter @ 8 l min – (O2 monitor drops, but > 25 % - i.e. Hypoxic guard OK) Disconnect wall O2 (or clo se 1° O2 cy linder) and :Check that N2O flow ceases – (i.e. O 2 failure cut-off switch functional) Wait for O2 failure alarm Open O2 cylinder (or 2° O2 cylinder) and check pressure – (P > 5 000 kPa) Check O2 flush – (Manometer < 5 hPa - i.e. valve / s not sticking & O2 monitor should rise) Close O2 cyli nder and reconnect wall O 2 (or open 1° O2 cyl inder) and :Perform "tug test" on O2, suction and other wall probes Check all pipeline (or cylinder) gauge pressures Replace O2 monitor in normal position Occlude the breathing system, clos e APL valve and perform :Positive pressure leak test of CIRCLE and machine - Vaporisers ON sequentially Check vaporiser interlocks Check function of valves of circle system Check Soda-lime Check APL valve pressure release – (Manometer ± 60 hPa or cm”H2O”) Close all gas flow s Ventilator Check function of ventilator Check presence and function of self-inflating manual resuscitator (e.g. AMBU-, Laerdal- bag etc.) Suction Check function – (> 50 kPa negative pressure) Check for presence of suction nozzle (e.g. Yankauer) & catheters Vaporisers Check if properly attached Filled  Anci ll ary equi pment Check laryngoscopes (x 2) Check for presence of Magill forceps Masks Endotracheal tubes Check monitors Sphygmomanometer Pulse oximeter

Introducer  Airways  Alternative- / Supra-glottic- airway (e.g. LMA) ECG / Defibrillator Capnograph

Most important checks 1. Is there a constant flow of O2 available via the O 2 flowmeter and O2 flush button (1° O 2 supply)? 2. Is there enough O2 in the reserve cylinder (2° O 2 supply)? 3. Is the self-inflating resuscitator (e.g. AMBU bag) present and functioning (3° O2 supply - room air)? 4. Is there no leak in the breathing system with pressure testing and the vaporiser open? 5. Is the suction working with tubes and nozzle / catheters present? Disclaimer  - These guidelines are provided for the sole purpose of guiding students and junior doctors in performing the preoperative check of an anaesthesia workstation. It is not a comprehensive checklist, nor a recommendation for the checking of anaesthesia machines or workstations in clinical practice. These guidelines have not been peer reviewed and have not been sanctioned by the South African Society of Anaesthesiologists.

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