• Welcome to the MBW Glossary :

    To use this interactive glossary simply click on the word from the list that you want the meaning of it's specialized or specific term explained in more detail and it will be revealed.


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  • Acinus

    The ending of a tiny airway in the lung, where the alveoli (air sacs) are located.

  • Area Under the Curve (AUC)

    That is the ability of measures to determine the true positive rate and the true negative rate. Area under the receiver operating curves (AUCROC) were assessed (1.0 = perfect discrimination considering sensitivity and specificity).

  • Bias flow block

    A block delivering a supply of washin and/or washout gas in one direction.

  • Body temperature and pressure saturations (BTPS)

    A gas volume has been expressed as if it were saturated with water vapour at body temperature (37°C) and at the ambient barometric pressure; used for measurements of lung volumes.

  • Bronchiectasis

    Permanently dilated airways caused by chronic bronchial inflammation secondary to inappropriate clearance of various micro-organisms and recurrent infections in the airways.

  • Calibration

    The activity of checking, by comparison with a standard, the accuracy of a measuring instrument of any type.

  • CO2 airway adapter / capnostat / CO2 cuvette and senor

    Equipment parts making up the C02 sensor in the Exhalyzer D device.

  • Coefficient of variation

    A measure of the spread of a set of data as a proportion of its mean. It is often expressed as a percentage.

  • Conducting airways

    The zone of the respiratory system that conducts the air into the lungs (nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles).

  • Convective gas mixing

    The transfer of heat by the circulation or movement of the heated parts of a liquid or gas.

  • Correlation

    The process of establishing a relationship or connection between two or more things.

  • Deadspace reducer

    An equipment part that will reduce the equipment space the patient has to breath through to reach the fresh gas supply.

  • Diffusive gas mixing

    The net movement of a gas from a region of high concentration to a region of low concentration.

  • Expirogram

    A diagram of an expired gas over volume.

  • Feasibility

    The degree of being easily or conveniently done.

  • FEF25-75

    Forced expiratory flow at 25-75% of the pulmonary volume.

  • FEV1

    Forced Expiratory Volume in the first second. The volume of air that can be forced out in one second after taking a deep breath.

  • Flow gas delay

    Delay-times between flow and gas signals.

    The degree of flow gas delay can depend on a number of factors: the gas transport-times from the flow sensor near the patients mouth to the gas analyzer(s) as well as on the response-times of the gas analyzer(s).

  • Flow past circuit

    The parts of washout system delivering the supply of washin and/or washout gas.

  • Flow volume loop

    A graphical depiction of the rate of airflow on the Y-axis and the total volume inspired or expired on the X-axis.

  • Flowhead/ Flowmeter

    Instrument measuring flows and volumes.

  • Flowmeter linearization

    The accuracy of the flow measurements over the full range of the flowmeter.

  • Functional Residual Capacity (FRC)

    The volume of gas contained in the lung after a normal expiration.


    The FRC as measured by the MBW device

    FRC is calculated as follows

    FRC =  net volume of inert gas exhaled / Cetstart – Cetend


    where Cet is the concentration at end-tidal volume of the

    inert gas, at the start (Cet start ) and end (Cet end) of the

    MBW recording.

  • Inert gas

    A gas that does not react with many substances- neither absorbed nor excreted by the body to any significant degree.

  • Minimal clinically important difference

    The smallest change in a treatment outcome that a patient would identify as important.

  • Nafion tube

    Tubing for gas sampling sensors.

  • Patient interface

    The equipment making up the parts of the washout system through which the patient breathes.

  • Peripheral airways

    Airways that are less than 2 mm in diameter and consist of small membranous, terminal and respiratory bronchioles, as well as alveolar ducts.

  • Photo-acoustic gas analyser

    The measurement of the effect of absorbed electromagnetic energy on matter by means of acoustic detection.

  • Post sampling gas point equipment deadspace volume

    The equipment deadspace volume  between the gas sampling point and the bias flow supply.

  • Pre-sampling gas point equipment deadspace volume

    The equipment deadspace volume between the patient and the gas sampling point.

  • Reliability

    Degree to which a measurement is consistent and free from error.

  • Reservoir bag

    A bag in the washout system circuit containing a reservoir of washin and/or washout gas.

  • Respiratory quotient

    The ratio of carbon dioxide to oxygen.

  • Responsiveness

    Degree to which a test changes in response to an intervention .

  • Sacin

    The contribution of inhomogeneity arising in the acinar airway zone- derived from the  analysis of the progression phase III slope (alveolar inert gas in a breath).

  • Scond

    The contribution of inhomogeneity arising in the conductive airway zone- derived from the  analysis of the progression phase III slope (alveolar inert gas in a breath).

  • Simple Washout software

    A software programme to analyse data files generated by the Innocor™ gas analyser during multiple breath washouts, to generate indices of ventilation inhomogeneity including lung clearance index.

  • Spirette

    Single use disposable breathing tubes.

  • Tidal volume

    The lung volume moved into and out of the lungs during quiet breathing.

  • Treatment effect

    The causal effect of a intervention on an outcome variable.

  • Validity

    Degree to which a test correlates with a “gold standard” criterion test which has been established as a valid test of the attribute of interest.

  • Ventilation Inhomogeneity (VI)

    Differences in ventilation arising between lung regions.

  • Washin

    MBW systems using exogenous gases (e.g. SF6) require a washin phase, to allow the inspired gas to reach equilibrium within the lungs.

  • Washout

    Clearance of a gas from the lungs is measured during the washout phase.

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The MBW test central over reading facility in Belfast (lcioverreading@qub.ac.uk) linked to this eLearning resource has received support from the Innovative Medicines Initiative Joint Undertaking under grant agreement n° 115721, resources of which are composed of financial contribution from the European Union's Seventh Framework Programme (FP7/2007-2013) and EFPIA companies’ in kind contribution.

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