AQA · A-Level · Physical Education

    Course version: 7582 · Version from Sept 2016

    Respiratory system: Tidal volume.

    Tidal volume is the volume of air moved into or out of the lungs during one normal breath at rest, so it measures the depth of quiet breathing rather than a maximum effort.

    Checked against the AQA 7582 specification (opens in a new tab) on .

    • Point 5 of 17
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Tidal volume is the volume of air moved into or out of the lungs during one normal breath at rest, so it measures the depth of quiet breathing rather than a maximum effort. A typical resting value is about 0.5 dm³, which is 500 cm³, and it is measured with a spirometer trace by taking the vertical height of one resting breath and converting that volume using the spirometer's calibration. Because it is a per-breath volume, it is not the same as minute ventilation, which multiplies tidal volume by breathing frequency. During exercise tidal volume rises as breathing becomes deeper, but it plateaus once the lungs are close to full use.

    What earns the marks

    • Tidal volume is the volume of air inspired or expired in one normal breath at rest.
    • Tidal volume increases during exercise as breathing deepens, then plateaus near maximal lung use.

    Common mistakes and how to put them right

    • Confusing tidal volume with vital capacity.

      Put it right: Tidal volume is one resting breath, whereas vital capacity is the largest volume that can be forcibly expired after a maximal inspiration.

    • Confusing tidal volume with minute ventilation.

      Put it right: Minute ventilation is the volume breathed per minute, calculated as tidal volume multiplied by breaths per minute.

    • Treating tidal volume as a fixed maximum.

      Put it right: It is a resting measure that rises with exercise, so it is not the greatest volume a person can move.

    • Reading a spirometer trace without applying its calibration.

      Put it right: The trace height must be converted to a volume using the scale, not reported as a raw distance.

    Exam tips

    • Learn the definition and a typical resting value so you can distinguish tidal volume from other lung volumes in a multiple-choice question.
    • Practise reading a spirometer trace: identify one resting breath, measure its height, then convert using the stated calibration.
    • Check the units offered in the options; 0.5 dm³ equals 500 cm³, so a correct value may appear in either unit.
    • Link tidal volume to exercise by noting that it increases with deeper breathing but does not rise indefinitely.

    Try the lesson

    The start of the Respiratory system: Tidal volume. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which term describes the volume of air breathed in or out during one normal resting breath?

    Listen

    Tidal volume is the volume of air moved into or out of the lungs during one normal breath at rest, so it measures the depth of quiet breathing rather than a maximum effort. A typical resting value is about 0.5 dm³, which is 500 cm³, and it is measured with a spirometer trace by taking the vertical height of one resting breath and converting that volume using the spirometer's calibration. Because it is a per-breath volume, it is not the same as minute ventilation, which multiplies tidal volume by breathing frequency. During exercise tidal volume rises as breathing becomes deeper, but it plateaus once the lungs are close to full use. A strong answer earns marks for these points. Tidal volume is the volume of air inspired or expired in one normal breath at rest. Tidal volume increases during exercise as breathing deepens, then plateaus near maximal lung use. Exam tip: Learn the definition and a typical resting value so you can distinguish tidal volume from other lung volumes in a multiple-choice question.

    See it

    A top-down flowchart. The top node reads 'Tidal volume: air moved in one normal breath at rest'. From it, one branch leads to 'Measured with a spirometer trace', which leads to 'Take the vertical height of one resting breath', which leads to 'Convert the height using the spirometer's calibration'. A second branch from the top node leads to 'Typical resting value about 0.5 dm³ (500 cm³)'. A third branch leads to 'Distinct from minute ventilation', which leads to 'Minute ventilation = tidal volume × breathing frequency'. A fourth branch leads to 'During exercise tidal volume rises as breathing deepens', which leads to 'Then plateaus near maximal lung use'.
    It shows what tidal volume is, how it is read from a calibrated spirometer trace, how it differs from minute ventilation, and how it changes during exercise.

    Key words

    Say what each word means before you turn the card.

    Tidal volume

    Try answering aloud or in your head before turning the card.

    Spirometer trace

    Try answering aloud or in your head before turning the card.

    Minute ventilation

    Try answering aloud or in your head before turning the card.

    Vital capacity

    Try answering aloud or in your head before turning the card.

    See every definition
    Tidal volume
    The volume of air moved into or out of the lungs during one normal breath at rest, measuring the depth of quiet breathing rather than a maximum effort.
    Spirometer trace
    A trace from which tidal volume is measured by taking the vertical height of one resting breath and converting that volume using the spirometer's calibration.
    Minute ventilation
    The volume breathed per minute, which multiplies tidal volume by breathing frequency and is not the same as a per-breath volume.
    Vital capacity
    The largest volume that can be forcibly expired after a maximal inspiration, distinct from one resting breath.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. The top node reads 'Tidal volume: air moved in one normal breath at rest'. From it, one branch leads to 'Measured with a spirometer trace', which leads to 'Take the vertical height of one resting breath', which leads to 'Convert the height using the spirometer's calibration'. A second branch from the top node leads to 'Typical resting value about 0.5 dm³ (500 cm³)'. A third branch leads to 'Distinct from minute ventilation', which leads to 'Minute ventilation = tidal volume × breathing frequency'. A fourth branch leads to 'During exercise tidal volume rises as breathing deepens', which leads to 'Then plateaus near maximal lung use'.

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    • 2Box 2

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