Diamedica Glostavent Helix User manual

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GLOSTAVENT

®

HELIX ANAESTHESIA SYSTEM

User Manual

For anaesthesia in difficult circumstances

Diamedica (UK) Ltd

Grange Hill Industrial Estate * Bratton Fleming * Barnstaple * Devon EX31 4UH * U K

Tel:+44(0)1598 710066 * Fax:+44(0)1598 710055 * Email:info@diamedica.co.uk * www.diamedica.co.uk

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Introduction

FOREWORD

This manual is intended to provide guidance on the function, performance and user

maintenance of the Glostavent

®

Helix Anaesthesia System. The information given in

this manual is correct at the date of publication, January 2013.

The policy of Diamedica (UK) Ltd is to continuously improve its products. Changes

may be made to this manual without notice being given.

Users of the Glostavent

®

Helix Anaesthesia System must read, understand and

follow the guidance given in this manual before using the system.

THE NEED FOR PATIENT MONITORING

WARNING

The Glostavent

®

Helix Anaesthesia System delivers mixtures of gases and vapours

which could cause injury or death to the patient. The effect of anaesthesia drugs on

individual patients can vary so that “typical” machine settings for concentrations

delivered to the patient do not necessarily ensure patient safety.

It is essential that the patient’s respiration and cardiovascular status are frequently

checked by the anaesthetist.

The anaesthetist is ultimately responsible for patient safety and should always have a

secondary means of maintaining patient safety.

Observations of the patient must take precedence over machine settings in judging the

condition of the patient.

The system is only intended to be used by Qualified Anaesthetists

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THE GLOSTAVENT

®

HELIX MANUAL

1. INTRODUCTION

2. THE THEORY OF THE GLOSTAVENT

®

HELIX

3. THE COMPONENT PARTS OF THE GLOSTAVENT

®

HELIX

4. THE GLOSTAVENT

®

HELIX – CONTROL AND OPERATION

5. TEST PROCEDURE BEFORE USE

6. USE OF THE GLOSTAVENT

®

HELIX IN ADULTS

7. USE IN PAEDIATRIC PATIENTS

8. TROUBLE SHOOTING

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1. INTRODUCTION

In many parts of the world anaesthetics are administered in situations far removed

from those found in modern, well equipped hospitals in wealthy countries. There may,

for example, be no oxygen, electricity or technical support. In these circumstances the

latest sophisticated anaesthetic machines with their delicate monitoring devices are

unable to function and are rapidly consigned to the graveyard of anaesthetic

equipment which litters the developing world.

Anaesthetists working in such environments need equipment which goes beyond the

standards of those required for hospitals in rich countries. Equipment is needed that

has been specifically designed to meet the additional requirements of harsh

environmental conditions and limited infrastructure and that will continue to function

in those prevailing conditions. When advice has been sought from anaesthetists

working in these areas the following properties have been most frequently requested:

The anaesthetic machine should be:

1. easy to understand and operate

2. robust and not easily damaged

3. inexpensive to purchase and economical to run

4. maintained using locally available skills

5. safe to use in the absence of expensive electronic monitoring equipment

6. versatile, so that the same machine can be used on any size of patient, with

a variety of volatile agents, in either draw over or continuous mode, both as an

anaesthetic machine in the operating room and a ventilator in a recovery or

intensive care unit

7. able to continue operating without interruption in the absence of oxygen or

electricity.

The Glostavent

®

Helix anaesthetic machine has been developed to meet these

requirements and the needs of anaesthetists working in difficult environments.

This manual has been prepared to provide practical guidance for those using the

Glostavent

®

Helix anaesthetic machine. It should only be operated by experienced

anaesthetists who have received specific training in its use and are fully conversant

with its operation.

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2. THE GLOSTAVENT

®

HELIX ANAESTHETIC MACHINE

The Glostavent

®

Helix (Figure 1) is a free standing anaesthetic machine which has

been specifically designed to facilitate the administration of inhalational anaesthesia

in difficult environments. It is easy to understand and operate, economical to run and

can be maintained and serviced using locally available skills. Above all, it can

continue to function, without interruption, if either the oxygen or electricity supply

fails.

The Glostavent

®

Helix principal components which make this possible are:

1. A low resistance breathing system and vaporiser which can function in the absence

of pressurised oxygen.

2. A ventilator which is gas driven and can function in the absence of electricity.

3. An oxygen concentrator which produces oxygen and air for the patient to breathe

and oxygen to drive the ventilator.

4. An integrated method of manual assisted ventilation that can be taken to the

patient’s side.

Figure 1

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3.1. THE BREATHING SYSTEM.

Before a volatile anaesthetic agent can be administered to a patient it must first be

vaporised. A carrier gas containing oxygen passes through the chamber of a vaporiser

where vaporisation occurs and the resulting mixture is delivered to the patient.

Figure 2

In order for the carrier gas to pass through the vaporiser there must be a pressure

gradient between entry and exit ports of the vaporiser. The carrier gas must therefore

either be PUSHED through by positive pressure from upstream or DRAWN through

by negative pressure from downstream (Fig 2).

In the standard continuous flow type of anaesthesia machine the carrier gas is

PUSHED through the vaporiser by gases under pressure (Fig 3). Under normal

conditions, i.e. when oxygen is available, this system works well but there is one

serious disadvantage. It is entirely DEPENDENT ON AN UNINTERRUPTED

SUPPLY OF PRESSURISED OXYGEN. If the oxygen supply fails, as it frequently

does in many parts of the world, a continuous flow type of anaesthetic machine

cannot function.

Figure 3

Flow

Pressure Gradient

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By contrast in DRAWOVER anaesthesia the carrier gas is DRAWN over the

vaporiser by negative pressure generated by the patient’s inspiration (Fig 4). The great

advantage of draw over anaesthesia is that it can still be administered EVEN IF THE

OXYGEN SUPPLY FAILS. In this situation room air, containing 21% oxygen, can

be used as the carrier gas for the volatile agent which is supplemented with oxygen if

available.

The Glostavent

®

Helix can function as a continuous flow machine when gases are

provided by the concentrator or an auxiliary source. However if the electricity fails

and there is no auxiliary ‘cylinder’ oxygen available it will default to a drawover

machine in order for anaesthesia to continue safely.

Figure 4

Because of the frequency of failure of the oxygen supply in some parts of the world

the Glostavent

®

Helix can use either a continuous flow or a drawover breathing

system.

This conversion happens automatically in the event of gas failure or drawover can be

used in order to conserve both oxygen and anaesthetic agent. This is described further

in later sections of the manual.

The Diamedica vaporisers output is consistent in both modes, the output from other

drawover vaporisers may not suitable for both these modes.

PATIENT VALVE SYSTEM

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Features of the drawover system

In its simplest form, a drawover system has the following features (Fig 5):

Figure 5

(1) A reservoir tube with an open end through which air is entrained during

inspiration.

(2) A side port for supplementary oxygen, if available.

(3) A vaporiser with a low resistance to breathing, such as the Diamedica vaporiser

above. (The standard plenum type vaporiser, such as the Selecta-tec, is unsuitable for

drawover anaesthesia because the resistance is too high).

(4) A self-inflating bag for I.P.P.V. with a valve to ensure the anaesthetic mixture

moves towards the patient and cannot re-enter the vaporiser.

(5) Inspiratory tubing leading to the patient.

(6) A non-rebreathing valve system that ensures that, during inspiration, the

anaesthetic mixture is not diluted by atmospheric air and that, during expiration, the

expired gas cannot re-enter the system and lead to re-breathing. The valve can

function with either spontaneous or controlled ventilation.

(7) Expiratory port leading to a scavenging system if available.

The function of the reservoir tube is to store the supplementary oxygen during the

phase of expiration so that it is not wasted and is included in the patient’s next breath.

This enables satisfactory inspired oxygen concentrations to be achieved with minimal

flows of supplementary oxygen (Fig 6).

Figure 6

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In a simple drawover system the reservoir consists of a one metre length of corrugated

anaesthetic tubing. While this is satisfactory during normal breathing it is less

satisfactory during hyperventilation, for example as occurs during pre-oxygenation.

This is because, when respiration is increased, more air is drawn into the reservoir and

the oxygen is diluted. To increase the efficiency of the drawover system the reservoir

has been modified for the Glostavent

®

by three additions (Fig 7).

Figure 7

(a) A valve at the open end to prevent spillage of oxygen

(b) A reservoir bag to increase the volume of the reservoir. Movement of the reservoir

bag also provides an indication of the rate and depth of respiration.

(c) A blow-off valve set at 5 cm H

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O to prevent over-distension of the reservoir bag.

The modified reservoir conveys one other important advantage. It enables the

Glostavent® Helix to be used for both continuous flow and drawover anaesthesia

simply by adjusting the rate of gas flow in relation to the patient’s minute volume.

DRAWOVER MODE. If the patient’s minute volume leaving the reservoir exceeds

the supplementary oxygen flow entering the reservoir, the pressure in the reservoir

falls below atmospheric, air is drawn in through the open end of the reservoir tube and

the system is in drawover mode.

CONTINUOUS FLOW MODE. If the supplementary oxygen flow rate is increased

until it exceeds the patient’s minute volume, the pressure in the reservoir rises and the

system automatically transfers to continuous flow mode. In this mode any of the

standard anaesthetic breathing systems (e.g. Mapleson A, D, etc.) can be used by

substituting them for the drawover system at the common gas outlet and using the

fresh gas flow recommended for the particular system selected. A one way valve after

the vaporiser on the Glostavent

®

Helix prevents backflow through the system when

these circuits are in use.