Evaluation of CPB devices relative to their capabilities of reducing the transmission of gaseous microemboli (GME) to a patient during cardiopulmonary bypass

ISO/TR 19024:2016 recommends acceptable methodology for conducting gaseous microemboli (GME) testing and discusses limitations of current test methods. Tests described in ISO/TR 19024:2016 are limited to those conducted using an in vitro circulatory system. It is applicable to all devices intended for extracorporeal circulatory support during cardiopulmonary bypass (CPB). It outlines approaches currently used to assess the ability of CPB devices to handle GME.

Évaluation des dispositifs PCP relative à leurs capacités de réduire la transmission des micro-embolies gazeuses (MEG) à un patient durant un pontage cardiopulmonaire

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Status
Published
Publication Date
11-Aug-2016
Current Stage
6060 - International Standard published
Completion Date
12-Aug-2016
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ISO/TR 19024:2016 - Evaluation of CPB devices relative to their capabilities of reducing the transmission of gaseous microemboli (GME) to a patient during cardiopulmonary bypass
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TECHNICAL ISO/TR
REPORT 19024
First edition
2016-09-01
Evaluation of CPB devices relative
to their capabilities of reducing the
transmission of gaseous microemboli
(GME) to a patient during
cardiopulmonary bypass
Évaluation des dispositifs PCP relative à leurs capacités de réduire la
transmission des micro-embolies gazeuses (MEG) à un patient durant
un pontage cardiopulmonaire
Reference number
ISO/TR 19024:2016(E)
ISO 2016
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ISO/TR 19024:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

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ii © ISO 2016 – All rights reserved
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ISO/TR 19024:2016(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Abbreviated terms .............................................................................................................................................................................................. 2

5 Recommendations .............................................................................................................................................................................................. 2

5.1 General ........................................................................................................................................................................................................... 2

5.2 Materials and methods .................................................................................................................................................................... 2

5.3 Results and verification of test .................................................................................................................................................. 3

5.4 Components ............................................................................................................................................................................................... 3

Annex A (informative) Rationale for the recommendations of this document ........................................................5

Bibliography ................................................................................................................................................................................................................................ 6

© ISO 2016 – All rights reserved iii
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ISO/TR 19024:2016(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,

as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the

Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.

The committee responsible for this document is ISO/TC 150, Implants for surgery, Subcommittee SC 2,

Cardiovascular implants and extracorporeal systems.
iv © ISO 2016 – All rights reserved
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ISO/TR 19024:2016(E)
Introduction

Present-generation extracorporeal circuit devices are not designed to generate gas bubbles, as was

the case with bubble oxygenators, as a function of their mechanism to achieve gas transfer. Gaseous

microemboli (GME), while significantly reduced in current extracorporeal circuits, are still detectable.

The presence of GME in blood is not a normal condition and can trigger potentially adverse conditions

as both a foreign surface and as a particle or embolus. Adverse systemic sequelae from GME may include

activation of blood cells, immune responses, and blockage of blood vessels.

While attributing a causal relationship between GME and significant adverse clinical sequelae is not

clear, laboratory equipment and methodology for testing extracorporeal devices on the bench top and

are clinically available for use.

This document will review the current scientific literature on GME detection methodologies and their

clinical relevance.

GME testing is currently being performed by companies and research groups. Both users and

manufacturers will benefit from the creation of standardized terminology for use in this work.

Development of a consensus position on the clinical implications of GME and the capabilities and

limitations of currently utilized monitoring equipment will also serve both users and manufacturers.

The currently available monitoring equipment will have a cost impact on all manufacturers and may

burden small enterprises more so than existing larger companies. The equipment cost, however, is less

expensive than equipment currently required to evaluate many of the extracorporeal devices such as

blood gas analysers, cell counters or spectrometers. Independent investigators with such equipment

and expertise are also an option.
© ISO 2016 – All rights reserved v
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TECHNICAL REPORT ISO/TR 19024:2016(E)
Evaluation of CPB devices relative to their capabilities of
reducing the transmission of gaseous microemboli (GME)
to a patient during cardiopulmonary bypass
1 Scope

This document recommends acceptable methodology for conducting gaseous microemboli (GME)

testing and discusses limitations of current test methods. Tests described in this document are limited

to those conducted using an in vitro circulatory system.

This document is applicable to all devices intended for extracorporeal circulatory support during

cardiopulmonary bypass (CPB). It outlines approaches currently used to assess the ability of CPB

devices to handle GME.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• ISO Online browsing platform: available at http://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
3.1
cardiopulmonary bypass

extracorporeal circuit used to support a subject’s circulatory and gas exchange requirements when the

heart and lungs are temporarily functionally excluded from normal circulation during cardiac surgery

3.2
gaseous microemboli

air bubbles present in circulating blood that are in the range 10 µm to 500 µm diameter

3.3
ultrasonic detector

device based on Doppler phenomenon (pulsed or continuous wave) that emits sound signals from a

piezoelectric crystal that are reflected from moving blood

EXAMPLE 1 Transcranial Doppler, transesophageal echocardiography, or clamp-on sensors for extracorporeal

tubing with the latter used for bench top in vitro testing.

EXAMPLE 2 Ultrasonic detectors are able to discriminate circulating particles from background blood flow,

and detected reflections (or signals) can be analysed in real time to produce a display of approximate quantities

and sizes during the sampling time frame.
3.4
whole blood

fluid used for bench-top studies involving gaseous microbubbles is anticoagulated whole blood

© ISO 2016 – All rights reserved 1
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ISO/TR 19024:2016(E)
4 Abbreviated terms
CPB cardiopulmonary bypass
GME gaseous microemboli
5 Recommendations
5.1 General

This document addresses current state-of-the-art bench-top testing and is intended to provide guidance

to those performing such tests so that reproducible results may be obtained to compare devices. Use of

anticoagulated whole blood is noted to provide more relevant results when performing bench-top GME

studies. This clause provides testing recommendations.
5.2 Materials and methods

5.2.1 The bench-top circuit should be described in sufficient detail so that an identical circuit can be

assembled for additional testing by other parties.
5.2.2 The description of the circuit should include the following:
— physical components, including:
— tubing dimensions (material, internal diameter, wall thickness, length);
— types and dimensions of tubing connectors used;
— manufacturer and model of detector;

— number, specific location, and method of attachment of detector sensors in the test circuit;

— other circuit components such as the device being evaluated;
— type of pump used to circulate blood;
— presence of a debubbling chamber (if used);

— conditions of the test, including temperature of test fluid, fluid flow rate, establishment of baseline

conditions, site of injection of bubbles;
— hematocrit (should be specified);
— isotonic solution (shall be used for dilution);
— anticoagulant used (should be specified);
— evidence of calibration of the bubble detector;

— method of introduction of bubbles into the test circuit (e.g. continuous injection vs. bolus injection),

total volume over time of bubbles introduced and means of introduction (e.g. calibrated pump vs.

hand injection);
— gas composition (should be room atmosphere only);
— reservoir level when using a hard shell (should be specified);

— volume of blood and the presence (when a soft bag venous reservoir is being tested) and the position

of volume regulation mechanism (should be described).
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ISO/TR 19024:2016(E)

5.2.3 The duration of the test, sampling schedule, and number of tests should be described.

5.3 Results and verification of test

5.3.1 Bubble counts according to the location of the detector sensors should be quantified in terms of

sizes and numbers.

5.3.2 The total volume of gas may be reported based on calculations of sizes and numbers.

5.3.3 Results may be reported in numerical or graphical form.

5.3.4 As noted in 5.2.3 above, the number of tests performed under a given set of conditions must be

reported with the results, and if the results represent mean values of several tests, this should be noted.

5.4 Components

Components that may be tested include, but are not limited to, one or a combination of the following:

5.4.1 Combination cardiotomy/venous reservoir

This component consists of a hard shell reservoir with multiple inlet connectors and internal chambers

used to process either cardiotomy-suctioned blood or venous blood.

These components may contain gross filters and defoamers for removal of large bubbles and blood

debris such as large clots or fat particles.

After processing both types of blood, a settling chamber collects the blood for removal by a pump and

transmission through the gas exchange section of the oxygenator.
5.4.2 Standalone cardiotomy reservoir

This component is used for processing either cardiotomy-suctioned blood or vent blood.

After processing, blood typically drains by gravity into a larger reservoir and becomes part of the

circulating blood.

Processed blood may be sequestered in the reservoir for additional processing by a cell

salvage/wash unit.
5.4.3 Standalone venous reservoir, either hard shell or flexible bag type
These components only collect blood from the CPB venous drainage tubing.
5.4.4 Oxygenator with or without integral arterial filter

This component consists of multiple fine strands of hollow fibres containing flowing gas arranged in a

configuration to promote mixing of venous blood near the fibre surfaces for gas exchange to take place.

A heat exchanger for circulation of temperature-controlled water most often is integral to the

oxygenator.
An integral arterial filter may or may not be part of the oxygenator.
5.4.5 Standalone arterial filter

This component consists of a fine screen mesh fan-folded to provide sufficient surface area for flows

used during CPB with an acceptable pressure drop.
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ISO/TR 19024:2016(E)
5.4.6 Venous bubble trap

This component consists of a chamber intended to trap and remove air bubbles that may be present in

the CPB venous tubing.
5.4.7 Blood pump
Either a roller pump or a centrifugal pump may be used in the test circuit.
When using a roller pump, the specifications (e.g. dimensions of pump, tubing
...

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