The Anaesthesia Machine 4th year MB ChB tutorial

Anaesthesia Delivery Systems Draw-over Machines Uses the atmospheric supply of Oxygen (21%) Oxygen source to augment atmospheric O2 if required Rural areas Boyles Machine Requires a supply of oxygen and other piped medical gases (Air, Nitrous oxide) under pressure Modern machines Available in most hospitals

The Boyle’s Machine Purpose of the machine Delivery of gases to the patient Anaesthetic gases (volatiles, inhalationals etc) Medical gases: air, O2 and N20 Ability to ventilate patient Provide IPPV (Intermittent Positive Pressure Ventilation)

5 Basic parts to the machine Supply of gases under pressure Piped medical gas supply from central depot Cylinders on machine Means of controlling / measuring gas flow Flowmeters / rotameters Vaporisers Breathing System Circle systems Open systems: Magill, Bain and Ayre’s T-piece Means to ventilate patient Reservoir bag for manual ventilation Ventilator for IPPV

THE MACHINE Many different types ranging from ...

Simple

Most modern Dräger Zeus

The Blease Machine @ GSH

SUPPLY OF GASES

O2 Oxygen Reticulated supply

Piped Medical Gases

Liquid Oxygen Tank

Gas outlets in theatre

Oxygen on machine Reticulated supply Cylinder O2 concentrator

N2O Nitrous oxide Nitrous Oxide Cylinders

FLOWMETERS

Rotameters SA standard has O2 on the Right. (UK and other commonwealth countries have it on the Left)

VAPORISERS

Vaporisers

BREATHING SYSTEMS

Circle system

Soda-lime canister

Soda-lime The main components of soda-lime Calcium hydroxide (75%) Water (20%) Sodium hydroxide Potassium hydroxide The patient's expired gases which contain carbon dioxide, are passed through a circle absorber filled with soda-lime granules Medical grade soda-lime has indicators which change colour when the soda-lime loses its carbon dioxide absorbing capacity

Magill Open System

Ayre’s T-piece (Jackson-Rees modification)

Ayre’s T-piece

Reservoir bag Converts a continuous flow to an intermittent flow Manual ventilation PEEP Watch patient’s own ventilation Check the circuit for leaks

Self-inflating resuscitator In case the machine fails!!

VENTILATION

Ventilator

Other devices on anaesthetic machine Oxygen Flush Oxygen analyser Oxygen supply failure alarm “Pop - off” valve Non - return valve

SUCTION

Suction apparatus Check function - 50 kPa negative pressure if occluded Check presence of suction nozzle (Yankauer) and catheters

ANCILLARY EQUIPMENT

Airway Trolley IMALES Introducer Mask, Magills forceps Airways (Guedel) Laryngoscopes, LMA (alternative airway) Endotracheal tubes (ETT) Suction

Defibrillator

MONITORING APPARATUS

Monitors of machine-patient interface Oxygen analyser - FIO2 Ventilatory parameters Tidal volume - VT, RR, I : E ratio, MV Airway pressure - PAW Capnograph / disconnect alarm - PETCO2 Agent monitor for anaesthetic gases FIAA FETAA (≈ MAC)

Monitors of the Patient ECG NIBP Capnograph Pulse Oximeter Temperature probe Nerve stimulator Invasive Arterial line for BP CVP monitoring Urinary catheter Pulmonary artery catheter – rarely used

ECG Monitor

NIBP: Non-invasive blood pressure

Capnograph

Pulse oximeter

Peripheral nerve stimulator

Central venous access and pressure line (CVP)

Pulmonary artery catheter: PAC or Swan-Ganz catheter

PAC

PAC