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NEWS
17th May 2013

How many Trekkers and Investigators suffered with the KHUMBU COUGH !?â

Professor David Howard

Now that the very successful Xtreme Everest 2 scientific expedition is nearing its end, many of our wonderful trekkers and investigators will have already returned home and others will be in the final stages back in Kathmandu. The logistics and investigator teams at Namche and Base Camp will also be heading down and many of theâtoughâ team at Base Camp will have been at an altitude of 5300 metres for a period of two months.

Whilst everyone who went to Base Camp had the potential to develop a high altitude cough, which in this region is known as the Khumbu Cough, it can, in some individuals, begin at altitudes as low as Lukla,the starting point of the trek to Base Camp. Some lucky folks will have even developed a good cough before they reached Namche! Generally, however, the longer and higher you are at altitude the greater the likelihood of developing this persistent, dry, hacking cough which can be extremely debilitating and disable even the toughest and most experienced high altitude mountaineer, let alone the rest of us mere mortals. Pick up almost any book written by a famous high altitude mountaineer and somewhere in the book there will be a description of this severe cough and its painful consequences which include cracked ribs, pneumonia and even death as a consequence. There are some detailed accounts from the Everest expeditions in 1921, 1922 and 1924, let alone in the ever increasing mountaineering literature of the last 60 years, since Everest was first climbed. Whilst high altitude cough can occur in any mountain region it is most famous as the Khumbu cough, and I am sure that many of you will have heard, or experienced, the staccato sounds of this coughing during the nights at Everest Base Camp.

Despite being known about for so many years this altitude cough was not studied scientifically until Peter Barry and colleagues looked into it on the British Mount Everest Expedition in 1994. They accurately recorded the increasing cough frequency with increasing altitude and length of stay. It had long been assumed that the cold, dry air at altitude was probably responsible for the cough,(many people still think that this is the cause) BUT, Peter Barry and his colleague Nick Mason continued with their research in the 90âs and in a long-term hypobaric chamber study (Operation Everest II) very interestingly showed that when subjects in the chamber were subjected to low atmospheric pressures equivalent to 7000 metres in height they developed the exact same cough EVEN though the HUMIDITY and TEMPERATURE in the chamber were kept at normal levels. So, this would suggest that the hypobaria is the main stimulus, but it does not tell us exactly what factors are involved in the generation of this potentially severe cough. Cough itself has a complex physiological mechanism depending on many factors. The noise of your cough is produced in the main by the air travelling at up to 600mph through your windpipe (trachea) and your voice box (larynx).

My interest in the Khumbu Cough was accelerated by my involvement with the team during the Caudwell Xtreme Everest expedition in 2007 when my remit as the ENT surgeon was to assist with the muscle biopsy programme but specifically to look at the nose, sinuses, ears, throat and larynx (the upper airway) and to relate these findings to the lungs (lower airway). These so called âseparateâ parts of our airway are very closely related and not separate at all, we have one airway! In addition those of you who were ârepeatâ trekkers this time will remember the âScratch and Sniff Smell Testsâ, the Taste Tests and the SNOT-20 questionnaire in 2007. Whilst the SNOT-20 (Sino-Nasal Outcome Test) is primarily designed to assess the nose and sinuses it also includes cough severity and dramatically demonstrated the frequency and severity of cough in those people reaching Base Camp. This year's investigator team and all the trekkers, including our amazing Sherpas, have filled in an updated SNOT-22 form at sea-level and as they ascend the mountain. As the ascent profile of everyone is identical to last time we will be able to pool the results to produce by far the largest study of its type on the airway and the Khumbu Cough. As with so many aspects of the science it will be interesting to compare the results of the evaluation in the Sherpas with all the other trekkers from around the world.

Once again we have to thank all of our trekkers who gave up their valuable time, let alone their hard-earned finance, to assist us with the research and I look forward to seeing you all at future trekker gatherings and letting you know the results of the airway studies. One final tantalizing aspect of the Khumbu Cough is the possibility that it might be generated by tiny pulses of acid refluxing up from the stomach and irritating the larynx and trachea. So my final blog will be to tell you about a wonderful device, the Restech pH probe, the first of its kind which, when positioned into the back of the mouth via the nose, can measure the pH (acidity or alkalinity) in the throat every 5 seconds and transmit this information wirelessly to a small recording box fixed on your trouser belt or in a pocket. It measures alterations with coughing, eating, drinking, sleeping etc. for 24 hours. In keeping with many of the tests I do it was only done on some very hardy âspecialâ trekkers and Sherpas but also inflicted on all the Base Camp investigators. Tough or what! All in the cause of science.

Such is the interest in our science that when the two senior ladies who run the Restech company in America (who just happen to be mother and daughter) came to London in January to discuss using the device, they asked to visit the sea-level testing lab. Bree Fisk, the daughter, who is responsible for the distribution/demonstration of the device over the whole East of the USA, promptly signed up to be a trekker and did her sea-level testing there and then!

David Howard (XE2 Investigator)

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