Introduction

The characteristics of ventilation-modes of current automatic lung ventilators are often not well understood. The current terminology used for their description is based on that introduced in the early days of mechanical ventilation, but with the advances in ventilators, and ventilation-modes that have evolved over recent years, the language used has been continuously adapted. In the absence of any effective international coordinating action, this has inevitably led to increasing inconsistencies in the way in which well-established terms and their derivatives are used.

To further compound the difficulties in understanding these complexities, some ventilator manufacturers have created new proprietary terms to describe these alternative ways of ventilating patients, and others have used existing terms with different meanings in different situations. This has led to patient safety hazards, an example being that lung ventilator clinical orders (settings) for one model of ventilator can be quite different from those required to get the same result from a different ventilator.

Recognizing these difficulties, the terminology and semantics for patient ventilation have been reviewed to compile a standardized vocabulary that is applicable to current and, as far as possible, future practice. The primary objective was to use as terms language already in use in the field of lung ventilation where possible, while clarifying the meaning of each term and limiting its potential for misuse by defining it more precisely. New terms were only introduced where there was no alternative, either in order to name new concepts or where the misuse of existing vocabulary has become so widespread that the term has become meaningless or unacceptably ambiguous. Importance was placed on a vocabulary that would communicate a clear mental model of how the selected settings would determine the interaction between the patient and the ventilator.

In order to achieve a vocabulary that is coherent, consistent and applicable to a range of fields such as patient care, research, data collection and incident reporting, this document has been developed with the participation, cooperation and assistance of members of other standards development organizations, and of major international ventilatormanufacturers. The applications include lung ventilators, medical data systems facilitating clinical care and research, interoperability, incident reporting and equipment maintenance.

It was recognized that much of the current terminology has its origins in the early use of automatic ventilation, when the emphasis was inevitably on how best to save the lives of patients who are not able to breathe for themselves and, consequently, only made basic provisions for the patient's own respiratory activity. Since that time, ventilators have become increasingly interactive with the patient, such that it is now necessary to consider their use from a ventilator-patient system perspective because it is no longer possible, with any certainty, to predict ahead of time how that interaction will take place.

The terminology in this document is defined and used in a way that makes it capable of facilitating, unambiguously, both the setting of a ventilator and how to describe and record the resultant ventilator-patient interactions, continuously and at defined points within the course of ventilation.

The ISO 19223 series does not specify terms specific to physiologic closed-loop ventilation or negative-pressure ventilation; nor to respiratory support using liquid ventilation or extra-corporeal gas exchange, or oxygen, except where it has been considered necessary to establish boundaries between bordering concepts.

In general, the ISO 19223 series is intended to provide a consensus view and the basis for a coherent language for describing ventilator function. Now that the fundamental concepts of artificial ventilation practice within the scope of this document have matured, it has been possible to review the boundaries between the various concepts of established ventilation-modes and the methods of artificially inflating a patient's lungs and to formulate definitions that clarify the common elements and the distinctions. In particular, the scopes of several concepts that were appropriate to earlier technology and practice have become inadequate to encompass new developments and it was found necessary to subdivide them. Some of their designating terms have, therefore, had to be deprecated, replaced, or constrained using more restrictive definitions, resulting in an inevitable reintroduction of some little-used legacy terms and the need to create a few new terms.

The overall objective is to encourage a more disciplined use of ventilator vocabulary so that users trained in the application of this document will be able to move easily from one ventilator to another and operate each one, with confidence, after a minimum amount of training. Although it is recognized that change will not be immediate, it is expected that this discipline will feed through into scientific publications, textbooks and training so that, over time, a standardized basic language of artificial ventilation will become internationally established.