SKGK – Session 16 – Topic: Anaesthesia Machine (Answers)

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SKGK – Session 16 – Topic: Anaesthesia Machine – Answers.

1⃣ It is a device that dispenses a mixture of gases and vapour/drug, and vary the proportions to control a patient’s level of consciousness and/or analgesia during surgical procedure.

2⃣ PV/T=k.                                              -When the pressure of a closed gas system is increased- at constant temperature-the volume goes down in the same proportion.                             -when the temperature is increased-with constant volume-the pressure will increase in the same proportion.

3⃣ Gas flow & Flow meter-provide required gas. Flowmeter delivers the desired flow to the patient.                          Breathing circuit-deliver oxygen anaesthetic to the patient. Also removes carbon dioxide produced by the patient.                                               Scavenging system-prevents entry of anaesthetic agents into the operating room. These agents are flammable, and chronic exposure can cause high fever and severe liver damage.

Mixing board & rotameter-the ratio of the fresh gases is continuously measured by flowmeter. Rotameter measuresg gas flowm.                              Anaesthesia monitor-monitors patient’s oxygenation, ventiltion, circulation, expired CO2 levels, temperature.             Bellows-allows anaesthetist to measure patient ventilation.

4⃣ Power supply, user errors, leaks, sticky valves.

5⃣ Continuous flow system requires supply of compressed gases whereas draw over machined do not.

6⃣ Carry out the following inspectionsin order to maintain its mechanical condition.                                                   -visual inspection.                                      -performance testing.                               Environmental inspection.

7⃣ Incorrect gas in the marked cylinder.                                                    -defective/impaired flow metres.

8⃣ General anaesthesia.                               -Local anaesthesia.                                    -saddle block anaesthesia.                                   -spinal anaesthesia.

9⃣ Plenum vaporiser-for continuous flow systems.                                             -draw over vaporiser-for draw over systems.                                                    -dual circuit gas vapour blender-used only for the agent desflurane.

🔟 Saturated vapour pressure-is the maximum vapour pressure at a particular temperature. It occurs when the number of molecules leaving a liquid through vapourisation equal the number of molecules re-entering.

Prepared by:
Jairos Muyaba.
3rd year student.
Northern Technical College.
Ndola, Zambia.


1⃣ An Anaesthesia machine is used to support the administration of Anaesthesia
It mainly consists mixture  of nitrous oxide and oxygen also isoflurane.

2⃣ Boyle’s law states that At constant temperature,pressure is inversely proportional to the volume.

Charles law states that At constant pressure , volume of Anaesthesia gas is directly proportional to the temperature.
V/T = constant.

Gay Lussac’s law states that At constant volume, pressure is directly proportional to temperature.
P/T = constant.

3⃣ Components of Anaesthesia machine~~~~~

Vaporiser is the important vital component of the Anaesthesia machine.
It provide accurate dosage control.

Connections to piped hospital oxygen supply.

Reserve gas cylinders of oxygen, fresh air,nitrous oxide with specific Bodok seal.

A high flow oxygen flush which provides pure oxygen at 30 -75 L / min.

Pressure gauge, regulator and pop off valves to protect the machine components and patient from high pressure gases.

Flow meters for control and measure the flow for oxygen,air and nitrous oxide.

An integrated ventilator to properly ventilate the patient during administration of Anaesthesia.

A patient monitoring system for monitoring the different parameters such as heart rate , BP , temperature etc.
Tubes and breathing bags also..

4⃣ Errors~~~~~

1) Fails to function properly.

2) Inadequacy or lack of component.

3) leaks and disconnects.

4) Misassembly.

5⃣ Difference~~~~

Draw over machine…..

1 User friendly assembly.

2 Requires specially designed low resistance draw over vaporiser.

3 Vaporiser are less accurate at different temperature and flow.

4 No need of inhalation induction.

5 No need of compressed flow of gas.

Continuous flow……

1 Complex assembly , needs trained technician.

2 High resistance plenum vaporiser are used.

3 vaporiser are more accurate at different temperature and flow.

4 Needs heavy pressurised flow of gas.

5 Easier use of inhalation induction.

6⃣ Maintenance~~

1 A leak test..

2 Daily cleaning….

Breathing bags and tubes need to be cleaned to prevent illness.

3. Vaporiser should be at stable temperature. The best temperature is 20-22℃. Don’t place Anaesthesia machine close to Windows where temperature can fluctuate widely.

Routine maintenance should be done to save time and money and to protect against any hazard.

7⃣ Safety features..~~~~

1 An oxygen failure alarm to indicate that there is no supply of oxygen.

2. Hypoxic mixture alarms.

3. Ventilator Alarms to warn the high or low pressure of  airways..

4. Pin index safety system prevents cylinders being accidentally connected to wrong yoke..

8⃣ Different types of Anaesthesia machine……

1 Portable –

As named it is a flexible and can be transferred from one place to another. It is light in weight .

Universal type~~~~ The structure and operational aspects are simple .
It contains a ventilator, security system and vaporiser.

High flow type~~~

The Anaesthesia machine which mainly administers the flow upto 0.5L/min of Anaesthetic gas..

Low flow type~~~~~

The Anaesthesia machine which mainly administers the flow upto 0.02 to 0.03L/min.

9⃣ Types of vaporiser~~~

The purpose of vaporiser is adding anaesthetic vapor into the fresh gas flow.

1. Plenum vaporiser…..

It uses the positive pressure developed by the patient resistance.

It is usually mounted on the device.

It is a device which works without external power for many hundred of hours of continuous use and Requires very little maintainence .

Draw over vaporiser~~~

It is simpler vaporiser.

It is mounted nearby the reservoir of the breathing attachments.

It is mainly used for the mix of diethyl ether and chloroform.

It uses or works on negative pressure of patient resistance..

Dual gas blender~~~~~

The third category of vaporiser…

It is mainly used for Desflurane.

🔟 The pressure of vapor which is in equilibrium with its liquid ( as steam with water) is called as saturated vapor pressure.

11 Anaesthesia cart contains extra push medication for Anaesthesia , sedation and reversal, extra equipment that the person giving Anaesthesia might need and the hardware for respiratory support and resuscitation.

12 Anaesthesia machine was invented by William T.G Morton on 16th October 1946 using the agent like diethyl ether.

The agent was soon surpassed by chloroform..


Yash Gajanan Tiknayat

Final year Biomedical

D.B.N.C.O.E.T, Yavatmal.

E-mail ID

Have a good day 😊😊

Thank you!!..

1. Anaesthesia machine is designed to provide an accurate and continuous supply of medical gases , mixed with an accurate concetration of anaesthetic vapour.

2. The gas law applied to know the volume of oxygen in cylinder:
boyle’s law – at constant temperature, the volume of a given mass of gas is inversely proportional to the absolute pressure.
Charle’s law – at constant pressure, volume of a gas is directly proportional to the temperature.
Gay lussac’s law – at constant volume, the absolute pressure of the given mass of gas is directly proportional to the temperature.

3. Pressure manometer- indicates the pressure that is within the breathing circuit.
Vaporiser- contains the anesthetic gas in liquid form, which is converted to vapour as the oxygen flows through it.
Flutter valves- inspiratory and expiratory valves that ensures undirectional flow of gases.
Scavenger canister- gets rid of the exhaled anesthetic and throws outside.
Pop off valve- maintains the normal operating pressure of the anesthetic system.

4. Most common unsafe acts is commited by a person who are in direct contact with patient , slip and lapse.

7. Safety considerations are : gas supplies, flow meters , scavenging and monitoring.

8. Different types of anaesthesia: 1. General 2. Local 3.regional 4.spinal

9. Types of vaporisers :
A. Plenum vaporisers – driven by positive pressure from anaesthetic machine.
B. Drawover vaporisers – driven by negative pressure developed by the patient.
C. Dual circuit gas vapour blender – created specifically for the agent desflurane which boils at 23.5 degree celcius.

10. The pressure of water vapour above a surface of water is saturated vapour pressure.

11. Anaesthetic tools are contained in anaesthesia cart.

Nishita ghariwala , student.
Gujarat , India.


Anesthesia is a way to control pain during a surgery or procedure by using medicine called anesthetics. It can help control your breathing, blood pressure, blood flow, and heart rate and rhythm.

Anesthesia may be used to:

Relax you.Block pain.Make you sleepy or forgetful.Make you unconscious for your surgery.

Other medicines may be used along with anesthesia, such as ones to help you relax or to reverse the effects of anesthesia.

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