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What on earth is an IMP?

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In my time at the Polar Museum, I looked at every single Antarctic object in the collection for the Antarctic Cataloguing Project, and can reveal that my favourite object is the ‘IMP’, mostly because of its sheer bizarreness.

During the project we found five medical boxes from the Commonwealth Trans-Antarctic Expedition 1955-58 (CTAE), two of which were mysteriously labelled ‘IMP’. IMP, as it turns out, stands for Integrating Motor Pneumotachograph. The IMP was developed in the 1950s by Dr Heinz Wolff to determine energy expenditure. At the time, there was a lot of interest in research on cold adaptation and survival, and the IMP was part of an ambitious programme of physiological experiments devised by Dr Allan Rogers, the medical officer on the expedition, to be conducted during the winter and throughout the trans-continental journey on the CTAE.

The IMP consisted of an air pump and flowmeter housed in a plastic box, which connected on one side with a mask fitted over the face and on the other with a sample-collecting unit packed in a bag worn on the back. The IMP measured the total volume of air breathed out by the wearer over a given time, and from this expired air it automatically took representative (or integrated) samples collected in glass ampoules which could then be analysed to determine the oxygen consumption. There’s a great video of the IMP in action (at 1:23).

https://www.youtube.com/watch?v=5mrq9tNNnHU

https://www.youtube.com/watch?v=5mrq9tNNnHU

Wearing the IMP was not a popular activity – the men had to be bribed and press-ganged into doing so – and only one man, Geoff Pratt, managed to wear it day and night for a whole week (only removing it to eat and drink). Pratt described the experience: ‘having continuously to breathe through the mouth leads to unpleasant dryness and outside in the cold the front teeth become “edgy”. You never, for a single moment, escape from a suffocating feeling and a very conscious effort in breathing’.(1) And he got frostbitten on his face during the experiment! But things were not much easier for Rogers, who had to remain constantly near Pratt in order to change the ampoules and keep an eye on the instruments, and even stayed awake at night to make sure the mask remained in place while Pratt slept. There’s a great photo by George Lowe of Pratt wearing the IMP. (2)

imp-stuff

We have lots of associated IMP equipment that we don’t fully understand what it’s for – gas canisters, a lot of tubing, syringe-like things and a strange electrical unit for example, as well as mouth pieces, nose clips, and lots of spare transistors (click here to view the IMP items on the catalogue). But my favourite bits are the face masks, which were adapted from an RAF rubber face mask, with the cheeks lined with chamois leather. Some of them have foil-backed green felt covers safety pinned to them (which may have been to prevent condensed breath freezing on the masks).  The best bit is that quite a few of the masks we have are marked with the names of the wearer: ‘Geoff’ (John Geoffrey Drewe Pratt); ‘Taffy’ (E. Williams); ‘V.E.F.’ (Bunny Fuchs); ‘Ralph’ (Ralph Lenton); and ‘Roy’ (Desmond Homard).

The IMP was a big improvement on other instruments for measuring energy expenditure but in this case it proved to be a failure. The various components, such as the transistors and batteries, were unreliable and on his return to Britain, Rogers found that the breath samples that had been collected had been contaminated and the entire experiment rendered completely useless!

  • (1) Haddesley, S. (2012). Shackleton’s Dream: Fuchs, Hillary and the Crossing of Antarctica. The History Press. p.121.
  • (2) Lowe, G. and Lewis-Jones, H. (2014). The Crossing of Antarctica: Original Photographs from the Epic Journey that Fulfilled Shackleton’s Dream. London: Thames and Hudson, pp.126-127.

Greta

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