Anesthesia Machine

CHAPTER 1

INTRODUCTION

1.1 Biomedical Instrumentation

Biomedical instrumentation is an extremely broad category—essentially covering all health care

products that do not achieve their intended results through predominantly chemical (e.g.,

pharmaceuticals) or biological (e.g., vaccines) means, and do not involve metabolism.

A medical device is intended for use in:

the diagnosis of disease or other conditions, or

in the cure, mitigation, treatment, or prevention of disease,

Some examples include pacemakers, infusion pumps, the heart-lung machine, dialysis machines,

anesthesia machines, artificial organs, implants, artificial limbs, corrective lenses, cochlear

implants, ocular prosthetics, facial prosthetics, somato prosthetics, and dental implants.

Stereolithography is a practical example of medical modeling being used to create physical

objects. Beyond modeling organs and the human body, emerging engineering techniques are also

currently used in the research and development of new devices for

innovative therapies, treatments, patient monitoring, and early diagnosis of complex diseases.

Medical devices are regulated and classified (in the US) as follows:

Class I devices present minimal potential for harm to the user and are often simpler in design

than Class II or Class III devices. Devices in this category include tongue depressors, bedpans,

elastic bandages, examination gloves, and hand-held surgical instruments and other similar

types of common equipment.

Class II devices are subject to special controls in addition to the general controls of Class I

devices. Special controls may include special labeling requirements, mandatory performance

standards, and postmarket surveillance. Devices in this class are typically non-invasive and

include x-ray machines, PACS, powered wheelchairs, infusion pumps, and surgical drapes.

Class III devices generally require premarket approval (PMA) or premarket notification

(510k), a scientific review to ensure the device's safety and effectiveness, in addition to the

general controls of Class I. Examples include replacement heart valves, hip and knee joint

implants, silicone gel-filled breast implants, implanted cerebellar stimulators, implantable

pacemaker pulse generators and endosseous (intra-bone) implants.[1]

[1]. http://en.wikipedia.org/wiki/Biomedical_engineering#Medical_devicesMahant Bachittar Singh College of Engineering and Technology 1

Anesthesia Machine

1.1.1 Anesthesia

Anesthesia or anaesthesia (from Greek αν-, an-, "without"; and αἴσθησις, aisthēsis,

"sensation"),traditionally meaning the condition of having sensation (including the feeling of pain)

blocked or temporarily taken away, is a pharmacologically induced and reversible state of amnesia,

analgesia, loss of responsiveness, loss of skeletal muscle reflexes, decreased stress response, or all of

these simultaneously. These effects can be obtained from a single drug which alone provides the correct

combination of effects, or occasionally a combination of drugs (such as hypnotics, sedatives, paralytics

and analgesics) to achieve very specific combinations of results. This allows patients to undergo surgery

and other procedures without the distress and pain they would otherwise experience. An alternative

definition is a "reversible lack of awareness", including a total lack of awareness (e.g. a general

anesthetic) or a lack of awareness of a part of the body such as a spinal anesthetic. The pre-existing word

anesthesia was suggested by Oliver Wendell Holmes, Sr. in 1846 as a word to use to describe this state.

[2]

[2]. http://en.wikipedia.org/wiki/Anesthesia

The purpose of anesthesiology was reduction of surgery-induced pain. However, the present goal

of anesthesiology is control of excessive biological responses induced by a variety of stresses

and protection of patients from stress-induced complications. Clinical activity is divided into

anesthesia in the operation theater, pain control for a variety of diseases and critical care

medicine. The aim is to protect a living body from stresses including surgical stresses, pain,

injuries and inflammation for the benefit of patients. Anesthesia has many purposes including:

Pain relief (analgesia).

Blocking memory of the procedure (amnesia).

Producing unconsciousness.

Inhibiting normal body reflexes to make surgery safe and easier to perform.

Relaxing the muscles of the body.[3]

[3]. http://medical-dictionary.thefreedictionary.com/general+anesthesia

1.2 Branch of Science

Anesthesiology is a medical specialty dealing with anesthesia and related matters, including

resuscitation and pain. Originally concerned only with general anesthesia in the operating room,

anesthesiology now includes epidural anesthesia (injection of local anesthetics into the spinal

fluid, cutting off feeling below the point of injection); artificial respiratory support during

operations requiring paralyzing drugs that render patients unable to breathe; clinical

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management of all unconscious patients; management of pain relief and cardiac and respiratory

resuscitation problems; respiratory therapy; and treatment of fluid, electrolyte, and metabolic

disturbances. Progress in anesthesiology has made possible more complex operations and

surgery for more critically ill patients. The anesthesiologist's role has become increasingly

important and complex.[4]

[4].http://www.merriam-webster.com/dictionary/anesthesiology

1.3 Types of Anesthesia

Types of anesthesia include local anesthesia, regional anesthesia, general anesthesia, and

dissociative anesthesia.

Local anesthesia is any technique to induce the absence of sensation in part of the

body, generally for the aim of inducing local analgesia, that is, local insensitivity to pain,

although other local senses may be affected as well. It allows patients to undergo surgical

and dental procedures with reduced pain and distress. It inhibits sensory perception within a

specific location on the body, such as a tooth or the urinary bladder. It numbs only a small,

specific area of the body. With local anesthesia, a person is awake or sedated, depending on what

is needed. Local anesthesia lasts for a short period of time and is often used for minor outpatient

procedures (when patients come in for surgery and can go home that same day). For someone

having outpatient surgery in a clinic or doctor's office (such as the dentist or dermatologist), this

is probably the type of anesthetic used. The medicine used can numb the area during the

procedure and for a short time afterwards to help control post-surgery discomfort.

In many situations, such as cesarean section, it is safer and therefore superior to general

anesthesia. It is also used for relief of non-surgical pain and to enable diagnosis of the cause of

some chronic pain conditions. Anesthetists sometimes combine both general and local anesthesia

techniques. [5] [6]

[5]. http://en.wikipedia.org/wiki/Local_anesthesia

[6]. http://kidshealth.org/teen/your_body/medical_care/anesthesia_types.html

Regional anaesthesia is anaesthesia affecting a large part of the body, such as a limb or the

lower half of the body by blocking transmission of nerve impulses between a part of the body

and the spinal cord. Regional anaesthesia is generally used to make a person more comfortable

during and after the surgical procedure. Regional anaesthetic techniques can be divided into

central and peripheral techniques. The central techniques include so called neuraxial

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blockade (epidural anaesthesia, spinal anaesthesia). The peripheral techniques can be further

divided into plexus blocks such as brachial plexus blocks, and single nerve blocks. Regional

anaesthesia may be performed as a single shot or with a continuous catheter through which

medication is given over a prolonged period, e.g. continuous peripheral nerve block (CPNB).

Regional anaesthesia can be provided by injecting local anaesthetics directly into the veins of an

arm (provided the venous flow is impeded by a tourniquet.) This is called intravenous regional

techniques (Bier block).

This differs from Local anaesthesia, which, in a strict sense, is anaesthesia of a small part of the

body such as a tooth or an area of skin, and Conduction anaesthesia is a comprehensive term

which encompasses a great variety of local and regional anaesthetic techniques.[7]

[7]. http://en.wikipedia.org/wiki/Regional_anaesthesia

General anaesthesia is a medically induced coma and loss of protective reflexes resulting from

the administration of one or more general anaesthetic agents. It refers to inhibition of sensory,

motor and sympathetic nerve transmission at the level of the brain, resulting in unconsciousness

and lack of sensation. It can be given through an intra-venous (which requires sticking a needle

into a vein, usually in the arm) or by inhaling gases or vapors by breathing into a mask or tube. A

variety of medications may be administered, with the overall aim of

ensuring sleep, amnesia, analgesia, relaxation of skeletal muscles, and loss of control

of reflexes of the autonomic nervous system. The optimal combination of these agents for any

given patient and procedure is typically selected by an anaesthesiologist or another provider such

as an anaesthesiologist assistant or nurse anaesthetist, in consultation with the patient and the

medical or dental practitioner performing the operative procedure.[6] [8]

[8]. http://en.wikipedia.org/wiki/General_anaesthesia

Dissociative anesthesia uses agents that inhibit transmission of nerve impulses between higher

centers of the brain (such as the cerebral cortex) and the lower centers, such as those found

within the limbic system. It reduces anxiety and produces a trancelike state. The person is not

asleep, but rather feels separated from his or her body.[6]

1.4 History

After anaesthesia was invented and introduced with the public demonstration of ether anaesthesia

by WTG Morton in 1846, for many years an anaesthesia machine was not required for providing

anaesthesia to the patients until oxygen (O2) and nitrous oxide (N2O) were introduced as

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Anesthesia Machine

compressed gases in cylinders by the late 19th century.[7] A metal skeleton was required for

mounting these cylinders. Boyle’s machine was invented by Henry Edmund Gaskin Boyle in

1917. His machine was a modification of the American Gwathmey apparatus of 1912 and

became the best known early continuous flow anaesthetic machine. The Boyles apparatus was

first made by Coxeter and Sons, under the direction of Lord George Wellesly, which was later

acquired by the British Oxygen Company (BOC). “Boyle” was the trade name of BOC. It was

named so to respect the inventor, Boyle. However, Boyle was not the pioneer in manufacturing

anaesthesia machines. Two other great men had done excellent work before him. One was James

Taylor Gwathmey who was practicing in New York who invented the Gwathmey machine in

1912. Later, Geoffrey Marshal developed a machine during the First World War (1914-1918)

based on the Gwathmey machine. Boyle, who developed his machine from Gwathmey’s basic

model in 1917, presented his invention at the Royal Society of Medicine in London in 1918.

Even though Marshal had developed his machine much before Boyle, he presented his machine

before the medical community in 1919, much later than Boyle. All the credit had gone to Boyle,

although Gwathmey and Marshal had developed their machines before him.[10,11]

• 1921 – Waters to and fro absorption apparatus was introduced.[9]

• 1927 – Flow meter for carbon dioxide was included, the volatile controls were of the lever type

and the familiar back bar made its first appearance.[9]

• 1930 – The plunger of the vaporiser appeared in the 1930 model.[9]

• 1930 – Circle absorption system was introduced by Brian Sword.[9]

• 1933 – Dry bobbin flow meters were introduced.[12]

• 1952 – Pin index safety system (PISS) by Woodbridge.[12]

• 1958 – Introduction of Bodok seal.[12]

[9]. Thompson PW, Wilkinson DJ. Development of anaesthetic machines. Br J Anaesth

1985;57:640-8.

[10]. Abraham A. Trade names that have become generic names in anaesthesia. Indian J Anaesth

2012;56:411-3.

[11]. Ball C, Westhorpe R, Kaye G. Museum of anaesthetic history. Anaesth Intensive Care

1999;27:129.

[12]. Watt M. The evolution of the Boyle apparatus 1917-67. Anaesthesia 1968;23:103-18.

1.5 Anesthesia Machines

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Anesthesia Machine

The most important piece of equipment that the anaesthesiologist uses is the anesthesia machine.

Safe use of anesthesia machine depends upon an interaction between the basic design of the

machine with its safety features and the knowledge and skills of the anaesthesiologist. The basic

function of an anaesthesia machine is to prepare a gas mixture of precisely known, but variable

composition. The gas mixture can then be delivered to a breathing system. Anaesthesia machine

itself has evolved from a simple pneumatic device to a complex array of mechanical, electrical

and computer – controlled components. Much of the driving force for these changes have been to

improve patient safety and user convenience.[13] Though many modifications have been brought

out still the basic design has not much changed. Hence, knowledge of the basic design of the

anaesthesia machine is must for all the practicing anaesthesiologists to understand the modern

anaesthesia workstation.

[13]. Brockwell RC, Andrews GG. Understanding Your Anaesthesia Machine. ASA Refresher

Courses. Vol. 4. Philadelphia, Pennsylvania: Lippincott Williams and Wilkins; 2002. p. 41-59.

Original anesthesia machine was made by the firm COXTERS. There are several differences

between newer and older anesthesia machines. Advanced ventilators are the biggest difference

between newer and older gas machines. The differences between older gas machines -such as the

Ohmeda modulus, Excel, or Aestiva and the DrägerNarkomed GS, Mobile, MRI, 2B, 2C, 3 or 4-

are less than their similarities. While the differences between new models from GE Healthcare

(ADU, Aisys, Aespire, Avance) and Dräger (Fabius GS, Narkomed 6000/6400, Apollo) are more

than their similarities.[14]

[14]. http://www.slideshare.net/imran80/anaesthesia-machine

Some specifications of various older and newer anesthesia machines are discussed here.

1.5.1 Ohmeda Modulus IITM Anesthesia Machine

The Ohmeda Modulus II™ Anesthesia Machine provides oxygen and volume monitoring and

has optional pulse oximetry and endtidal CO2 modules. This high-end anesthesia machine is

great for university and research facilities. DRE Veterinary also has available the Ohmeda

Modulus II Plus.[15]. Fig1.1 shows the Ohmeda Modulus II™ Anesthesia Machine.[16]

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Anesthesia Machine

Fig1.1 Ohmeda Modulus II™ Anesthesia Machine

[16]. http://www.wemed1.com/catalog/an-mod.htm

Features:

Double Flowmeter Tubes (O2 & N2O)

Flowmeter Protection Shield

Link-25 Hypoxic Guard

Touch-Coded Oxygen Knob

Oxygen Supply Pressure Sensor / Alarm

Oxygen Supply Pressure Failure Device

A.C. Line Power Sensor / Alarm

D.C. Power Sensor / Indicator

Selectatec 3 Vaporizer SM Manifold

Minimum Oxygen Flow

Anti-Disconnect Fresh Gas Outlet

3 Drawer Lockable Cabinet

Integral Footrest

Integrated D.I.S.S. Pipeline Inlets

Modular Oxygen & Nitrous Oxide Yokes

High Pressure Regulator and Gauges

Pneumatic / Electric Interface Main SwitchMahant Bachittar Singh College of Engineering and Technology 7

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O2 and N2O (Standard)

Air (Optional)

Hypoxic Guard (Standard)

Oxygen and Volume Monitoring (Standard)

Optional integrated Pulse Oximetry, Endtidal CO2

GMS CO2 Absorber (Standard)

E-Cylinder and Central Gas Connections (Standard)

Guarded Oxygen Flush

Middle Shelf

“Tilt” Adjustable Top Shelf

Monitor “Swivel” Pod

5400 Volume Monitor

5100 Oxygen Monitor

Electrical Outlet Panel

Oxygen Power Outlet

High-Pressure Hose Hanger

Centralized Patient Interface Panel

Shelf-Mounted Utility Hooks

Anesthetic Bottle Holder

“Telescoping” Absorber Arm

“Lockable” Front Casters

Monitor Securing Straps

Battery Back-Up of the Ventilator

Specifications:

Dimensions: 61"H x 34.5"W x 25.2"D | 155 H x 88 W x 64 D (cm)

Weight:

Without Monitors or Shelves - 360 lbs| 163 kg

With Monitors on Shelves - 477 lbs | 217 kg

Absorber Swivel Arm Length: 14" | 35.5 cm

Push Button Vertical Adjustment (from floor): 10" to 26" | 25.4 to 66 cm

Range of Horizontal Adjustment:

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5.5" Minimum

11" Maximum[13]

[15]. http://www.dreveterinary.com/veterinary-equipment/veterinary-anesthesia/anesthesia-

machines/ohmeda-modulus-ii-anesthesia-machine

1.5.2 Drager Narkomed GS Anesthesia Machine

One of the more popular machines on the market, the durable Narkomed GS machine features

the familiar-style flow head, visible bellows, and reliable performance. It is intuitive, and easy-

to-use. Its built-in monitor displays volume, pressure and oxygen monitoring, and is available in

2 or 3 vaporizer configurations.  With its simplistic approach, versatility, and reliability, the

Narkomed GS provides next-level technology in a user-friendly machine, and offers a large 3-

drawer cabinet, writing tray and auxiliary flow meter.

The machine comes standard with the dependable AV2+ ventilator, which is pressure-limited,

time-cycled and volume-preset. Features include pneumatic circuitry, electronic timing,

breathing rate controls, inspiratory to expiratory ratio, tidal volume, inspiratory flow and

inspiratory pressure limit for flexible ventilation. Additional features include inverse I:E ratios

with its built-in safety mechanism which allows for an assortment of conditions.[17]. Fig1.2

shows the Drager Narkomed GS Anesthesia Machine.[18]

Fig1.2 Drager Narkomed GS Anesthesia Machine

[17].http://www.metropolitanmed.com/products/drager-narkomed-gs-anesthesia-machine.php

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[18]. http://www.buckeyemedical.com/North-American-Drager-Narkomed-GS-Anesthesia-

System/

Features:

Includes AV2+ Ventilator, featuring pressure-limited, volume-preset, and time-cycled

controls

Ventilator also measures breathing rate, inspiratory to expiratory (i:e) ratios, inverse i:e ratios,

inspiratory flow and pressure limit, and tidal volume

Designed for durability and flexibility

Absorber

O2, volume, pressure monitor

3-gas delivery system

Active scavenge reservoir

Latex-free goods

Electronic spirometry

3-tier alarm system

Next-level technology

Open architecture

Scavenging system

Sphygmomanometer[17]

1.5.3 Aestiva 7900 Anesthesia Machine

The Aestiva 7900 is a balance of advanced ventilation and exceptional capabilities, delivering a

cost-effective approach to anesthesia therapy. The Aestiva with the 7900 SmartVent provides

sophisticated ventilation capabilities that support the needs of a broad patient range.  

Aestiva's open architecture allows you to use your current monitors and data management

systems, or purchase a fully integrated anesthesia system with GE CARESCAPE Monitors and

Centricity Perioperative Anesthesia information management systems.[19]. Fig1.3 shows the

Aestiva 7900 Anesthesia Machine.[20]

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Fig 1.3 Aestiva 7900 Anesthesia Machine

[20]. http://www.medwow.com/i_preview.php?sale_number=454468925Integrated Breathing System

The Aestiva breathing circuit is integrated, which helps protect the components from damage

and disconnection.

Smart sensors and switches link communication between the breathing circuit and the

SmartVent ventilator.  

Confidence. Control. Comfort.

Get close to your patient with monitors that are easily viewed and controls that are

conveniently located, whether you are sitting or standing.  

Open Architecture

Aestiva’s open architecture means it can fit easily with your existing equipment, monitors and

accessories included.  

Enhanced Workflow Aestiva offers a cost-effective approach to anesthesia therapy and

workflow through:

o Low planned maintenance requirements and durable components to improve uptime.

o An effective system for the practice of low-flow anesthesia, helping to minimize agent

consumption to help save on anesthetic agent costs.

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Aestiva includes a selection of product options:

Standard:

SmartVent ventilator patient breathing system with circle module O2 and N2O gas delivery

Lockable drawer

Light strip

Supports up to three in-line vaporizers

Optional:

Additional gases: air and heliox or CO2

Air-flow tube: single or dual Cylinder

Yokes: up to five

Auxiliary common gas outlet

Integrated auxiliary O2 flowmeter[19]

[19].http://www3.gehealthcare.com/en/Products/Categories/Anesthesia_Delivery/Aestiva/

Aestiva_7900#tabs/tab8A426481213F4317AFE3A58160CDF71E

1.6 Idea of Project

We all have a great interest in biomedical field and wanted to make our project related to this

field only. As we all know, deaths are taking place due to excess amount of anesthesia delivered

to patient before any surgery. And this happens due to the mistake of anesthesiologists. To

overcome this excess amount of anesthesia, we all decided to make an anesthesia machine which

will give the proper mixture of gases in accurate amount. In case of excess amount of mixture of

gases the machine automatically shuts down and the alarm gets activated. This machine is not a

fully developed anesthesia machine, it’s just a basic machine to monitor the proper amount of

anesthesia to be deliver to the patient. By using it number of deaths can be reduced.

1.7 Objective of the Project

The objective of our project is to design an automatic anesthesia machine for controlled

administration of global anesthesia in pre-opreative measures. The main objective of our project

is to deliver accurate quantity of anesthesia to the patient before the operation. If overdose takes

place the alarm activates.

1.7.1 Key Features

The key features of our anesthesia machine are as follows:

1. Inlet Gas Pressure Sensing and Monitoring

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Anesthesia Machine

The Inlet Gas Pressure Sensing and Monitoring System consists of three pressure sensors

attached to three different gas sources i.e. gas cylinders so as to check and maintain the delivery

pressure of source gases used namely Oxygen(breathing essential), Nitrous

Oxide(anesthetic agent) and Air(mixture of gases and water vapor for humidification)

2. Outlet Gas Pressure Sensing and Monitoring

The Outlet Gas Pressure Sensing and Monitoring System consists of one pressure sensor

attached to output gas mixture delivery chamber in order to check and maintain the delivery

pressure of final anesthetic gaseous mixture to the patient.

3. Inlet Valve Control System

Inlet Valve Control System consists of three valves which control the delivery of source gases

according to the desired pressure values.

4. Outlet Valve Control System

Outlet Valve Control System consists of one valve which control the delivery of final anesthetic

gaseous mixture to the patient according to the desired pressure values.

5. Microcontroller

Microcontroller is the control unit of the system and controls all the valve actions of inlet

and outlet systems with respect to the real-time inputs from the pressure sensors and preset

delivery values. It also helps us to display the real-time pressure changes with help of a LCD. It

controls all the system parameters and activates different the alarm systems available.

6. Inlet and Outlet Pressure Value Display

The set pressure values and the real-time pressure changes are displayed on an LCD.

7. Cylinder Empty Alarm

This is activated when atleast one of the three cylinders are close to empty point.

8. Overdose Alarm

This is activated when the anesthesia is delivered over a preset time interval.

9. Emergency Shut Down or Auto-Shut Down

This system is activated immediately if no corrected action is performed on the other alarms

generated or the systems faults in any other situation e.g. power failure, valve malfunction etc..

10. Power Supply

A DC regulated Power supply is designed for different active and passive components of the

system along with different actuators controls e.g. valves.

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Anesthesia Machine

CHAPTER 2

BLOCK DIAGRAM AND CIRCUIT DIAGRAM

2.1 Block Diagram of Anesthesia Machine

Block diagram of the Anesthesia Machine is as shown in Fig 2.1.

Fig 2.1 Block Diagram of Anesthesia Machine

2.1.1 Description of Block Diagram

In this project one pressure sensor, two valves, PIC 16F73 microcontroller, LCD Display and a

buzzer is used. Small description of each component is as given below:

Pressures sensor: In this project we have used pressure sensor MPX5700DP manufactured

by Free scale. This sensor interfaced with Inbuilt ADC of PIC16F73. It shows final pressure

maintained in outlet chamber on LCD.

Valve Control: There are two valves shown to control outlet of two cylinders. To control the

valve automatically with pressure monitoring a motorside mechanism is fitted on the both

valve knob. When motor move clock wise it open the valve. When motor moves anti-clock

wise it closes the valve. To control the direction of dc motor Relay based H-bridge circuit is

used with motors.

Whenever there is low pressure or over pressure an alarm is generated using buzzer.

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PIC

16F73

Pressure Sensor

DC motor withH-bridge- Valve 1

LCD Display

DC motor withH-bridge- Valve 2

Buzzer

Anesthesia Machine

2.2 Circuit Diagram of Anesthesia Machine

Fig 2.2 shows the circuit diagram of the Anesthesia Machine.

Fig 2.2 Circuit Diagram of Anesthesia Machine

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