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Spirometry: Is ‘normal’ what it seems?

by Sarah McLusky, Project Manager

One case in the exhibition focuses on medical technologies which have been used over centuries to try and make breath observable and quantifiable, to both define ‘normal’ lung function and diagnose lung disease. Alongside a selection of stethoscopes you will find a pneumometer – a precursor of the device now known as a spirometer. Spirometers are used to diagnose COPD and other lung conditions by measuring how much air can be exhaled in one forced breath.

The results obtained from spirometry can seem satisfyingly scientific and objective. However, as Life of Breath researcher Dr Coreen McGuire has been investigating, these devices, like many medical technologies, have a chequered history. In order to define ‘abnormal’, scientists much first define ‘normal’. This typically means collecting a results from a large number of apparently healthy people. Coreen and other researchers (notably Prof Lundy Braun) have uncovered systematic bias and discrimination in the selection of these ‘healthy reference standards’.

For example, many modern spirometers oblige the operator to first input the ethnicity of the person being measured. This harks back to historic assumptions that people of colour had smaller lungs. Digging a little deeper, Lundy discovered that the supposedly ‘normal’ US population used to create the initial reference standards were poor with jobs and living conditions which we now know can have dramatic detrimental effect on lung function.

This is not only poor science, but it can have devestating personal consequences. Spirometry is often used to quantify lung function related to occupational lung disease. The lower norm for black people could mean someone is deemed ineligible for compensation even with the same degree of lung damage as a white co-worker. Read more about this in Lundy’s book ‘Breathing Race into the Machine’

Coreen has be researching the history of spirometry in the UK, particulalry its use in quantifying lung damage in miners seeking compansation for occupational lung disease. She will be talking about her work in a relaxed evening talk at Palace Green Library on Thursday 24 January 2019.

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