ISO 4135, Fourth Edition: Two Decades of Progress in ISO/TC 121

Abstract

The publication of ISO 4135, Anaesthetic and respiratory equipment—Vocabulary, fourth edition, highlights expansion of the scope of the International Organization for Standardization (ISO) Technical Committee (TC) 121 and its Subcommittees and Working Groups during two decades of work. This document stands alongside ISO 19223:2019, Lung ventilators and related equipment—Vocabulary and semantics, to promote consistency and specificity of terminology across ISO/TC 121 standards.

Twenty-one years after the publication of the third edition,1 ISO 4135:2022, Anaesthetic and respiratory equipment—Vocabulary, fourth edition, presents updated definitions with a revised and expanded scope.2 This document was developed by the International Organization for Standardization (ISO) Technical Committee (TC) 121 (Anaesthetic and respiratory equipment) Subcommittee (SC) 4, (Vocabulary and semantics) Working Group (WG) 1 (Respiratory equipment vocabulary), with Dr. Steven Dain as convenor and Dr. Paul Dixon as WG secretary. All SCs of ISO/TC 121, Anaesthetic and respiratory equipment, actively participated in this multiyear project,3 with the overall objective of consistency in terminology in ISO TC 121 standards. The fourth edition was developed in accordance with the Agreement on Technical Cooperation between ISO and the European Committee for Standardization (CEN), known as the Vienna Agreement,4 as well as published ISO standards on development and use of terminology.5,6

Changes in Scope

The publication of ISO 19223:2019, Lung ventilators and related equipment—Vocabulary and semantics,7–9 enabled WG 1 to focus on those terms in ISO TC 121 standards that were not specifically related to lung ventilators. The WG reviewed all terms defined in ISO 4135:2001 and removed those that were defined in more widely applicable ISO standards, such as ISO 14971:2019, Medical devices—Application of risk management to medical devices, as well as those that were no longer relevant to ISO TC 121 standards. Some terms defined in ISO 19223:2019 also appear in ISO 4135:2022 if they are used in contexts outside mechanical ventilation.

During the two decades since publication of the third edition of ISO 4135, the Work Programme of ISO/TC 121 and its joint WGs with International Electrotechnical Commission (IEC) Technical SC 62A (Common aspects of electrical equipment used in medical practice) and SC 62D (Electromedical equipment) has expanded to include devices such as noninvasive sphygmomanometers, clinical thermometers, thermographs for fever screening, electrocardiography, near-infrared spectroscopy, and cerebral tissue oximetry equipment. Biocompatibility evaluation of breathing gas pathways also is included in the ISO/TC 121 Work Programme. The fourth edition of ISO 4135 addresses this expansion.10

Historical Note

The third edition of ISO 4135 and its 1995 predecessor were developed under the chairmanship of the late Dr. Jerry Dorsch, who alongside his wife Dr. Susan Dorsch,11 coauthored a preeminent textbook on anesthesia equipment.12 Several ISO systematic reviews reaffirmed this standard's continued relevance. The need for revision was increasingly recognized. During the chairmanship of Dr. Dain (2008–17), who now chairs the parent TC 121, ISO/TC 121/SC 4 investigated the evolving modalities of controlled vocabularies and terminology databases13,14 to determine the most effective way to update ISO 4135 within the context of published ISO standards and the availability of the ISO Online Browsing Platform (OBP)15 and IEC Electropedia.16 WG 1, with Dain as convenor and Dixon as secretary, was formally established in 2017 to focus on this project. During this period, ISO/TC 121/SC 4, under the project leadership of Dr. Norman S. Jones, completed the work on ISO 19223,7–9 with Dr. Kenneth LeDez as chair from 2018.

Before ISO/TC 121/SC 4, Anaesthetic and respiratory equipment, Vocabulary and semantics, was formally established in 1981, the ISO/TC 121 WG on terminology had published the first edition of ISO 4135 in 1979.17 In a lecture delivered at the Royal College of Surgeons on March 17, 1982, the late Prof. Peter W. Thompson, FFARCS, ISO/TC 121's first chairman, described ISO 4135 as “the first true anaesthetic International Standard,” because standardization of equipment was founded on agreement of terminology and definitions.18 After the 1966 meeting of the World Federation of Anaesthetic Societies in Copenhagen, Denmark, the Council for International Organisations of Medical Sciences supported compilation of a glossary of anesthestic terms by the late Dr. George Edwards of St. George's Hospital, London, U.K., and Dr. J.B. Valetta of Paris, France. In 1967, an ISO/TC 121 WG was established to standardize vocabulary under the chairmanship of Prof. Guy Vourc'h,18 physician to Charles de Gaulle, former President of France.19 Vourc'h later was succeeded as chair by Prof. James Freeman.

Noteworthy Changes in Fourth Edition

In addition to its revised scope, the fourth edition of ISO 4135 features innovations and changes in format from its predecessor (Table 1).

Table 1.

ISO 4135:2022: highlights of changes since the 2001 edition. Abbreviations used: ISO, International Organization for Standardization; TC, Technical Committee.

ISO 4135 Edition	Scope	Arrangement	Languages/Format	Term Repetition/Contextual Definitions	Deprecated or Obsolete Terms
Third edition, 2001	Includes terms from all ISO/TC 121 standards	Categorical with alphabetical index	English, French, German/parallel columns	Terms repeated with cross-references when defined in different contexts	Not included
Fourth edition, 2022	Excludes terms specific to lung ventilators included in ISO 19223:2019; includes terms from TC 121 Standards for devices added to the ISO TC 121 Work Programme since 2001	Categorical, with alphabetical sequence within subcategories; alphabetical index	English, French, German/sequential format	Use of domain-specific identifiers (< >) where appropriate; pre-coordination of terms	Included with mapping to current preferred terms

Domain Specifiers

Instances occur in which the same term is used to express different concepts applicable to specific subject areas or domains. In the third edition of ISO 4135, such terms were repeated in each category with cross-references where the definitions differed. In the fourth edition, domain specifiers, such as <thermometry>, have been added to designate the specific contexts of the definitions. For example, the term cuff has definitions specific to the domains <airway devices> (clause 3.1.4.7) and <blood pressure measurement> (clause 3.1.4.8).

Controlled Vocabularies and Pre-coordination of Terms

ISO 4135 is a controlled vocabulary defined by ISO 25964-1:2011, Information and documentation—Thesauri and interoperability with other vocabularies—Part 1: Thesauri for information retrieval, as a “prescribed list of terms, heading or codes, each representing a concept” (clause 2.12).13 Pre-coordination of terms (clause 2.44) is the combination of distinct terms or concepts from a controlled vocabulary at the time of its compilation, or when used for indexing or creating a subject classification system.13 Minute volume (clause 3.1.5.8)2 is an example of a pre-coordinated term. In contrast, post-coordination of terms refers to a case where after compilation of a controlled vocabulary, two or more separate terms are combined as a search expression or for a similar purpose (clause 2.4313; e.g., ventilator [clause 3.4.1.1] and accuracy [clause 3.1.3.12]).

Deprecated Terms

Due to obsolescence or lack of continuing usage, terms used in previous editions of ISO 4135 that are neither preferred terms (3.8.3.05)14 nor secondary synonyms, or admitted terms (3.4.1.3.2),6 are known as deprecated terms (3.8.3.13).14 In the fourth edition, 22 terms are designated as deprecated and included in the Alphabetical Index, which has been designed to direct the user from the deprecated to the current preferred term.

Trilingual Format

The parallel columns of terms and definitions in English, French, and German were a familiar feature of the earlier editions of ISO 4135.1 Because of changes in ISO publishing software and linkage to the ISO OBP,15 the English, French, and German sections of the fourth edition are now sequential. The three official languages of ISO are English, French, and Russian. The ISO National Member Body of the Russian Federation, GOST R, published its own version of ISO 4135:2001, numbered GOST R 52423-2005.20 In the English, French, and German texts of ISO 4135 published by ISO, only the English and French entries are considered ISO terms and definitions. Germany's ISO Member Body, Deutsches Institut für Normung e.V. (DIN), is responsible for the published German language equivalents.

International Collaboration and Communication During Global Pandemic

ISO/TC 121/SC 4 WG 1 invited and collected comments on the Draft International Standard from the other ISO/TC 121 SCs and the National Member Bodies of SC 4. The ballot, which closed on Feb. 18, 2020, produced only affirmative votes but generated nearly 500 comments (general, editorial, and technical) that required discussion and resolution. The COVID-19 pandemic resulted in cancellation of the WG's meeting planned for May 2020, as well as extra demands on the schedules of the clinicians and regulatory and manufacturer experts who comprise the WG. The WG's secretary and convenor successfully resolved many questions by correspondence with TC 121 SC officers and experts, and two series of virtual meetings were held in fall 2020 to address the comments and prepare the text for the Final Draft International Standard.

As Prof. Thompson had suggested nearly 40 years earlier,18 agreement on terminology and definitions is fundamental to the standards development process. The WG was tasked with review of the parameters of device-specific metrics and ranges, such as those recommended for flow rates, frequencies, and pressures. The German Mirror Group recommended adherence to ISO/IEC Guide 99 (International Vocabulary of Metrology)21 wherever possible and the WG agreed. In some instances, terms in common general or medical usage, such as “paediatric,” were deliberately excluded because of the breadth of jurisdictional variation.

Plans for Future Work

The WG and SC 4 of ISO/TC 121 work closely with the other TC 121 SCs and their WGs. Liaisons are maintained with ISO/TC 215 (Medical informatics) and CEN/TC 215 (Respiratory and anaesthetic equipment). SC 4 experts will follow developments in terminology as they evolve. Future projects may focus on areas requiring increasingly domain-specific vocabulary, such as respiratory therapy, the emergency and home healthcare environments, and medical gases.

Along with colleagues across the standards development community, the WG and SC look forward to resumption of in-person meetings when public health considerations permit. At the same time, the experience acquired in the effective conduct of remote international meetings and optimal use of electronic resources for TCs during this challenging time will prove invaluable for future progress.