No Laughing Matter...
Posted by Jeremy Windsor on Apr 8, 2022
Much of my mountain medicine teaching is focused around pressure - in particular, the fall in atmospheric pressure that occurs during an ascent to high altitude. As an example, I often tell my students that the atmospheric pressure on the summit of Everest (8850m) is just one third of that found at sea level. In practise, this means that the human body has to undergo a battery of physiological changes if it's going to get anywhere close to the summit. But what happens if the atmospheric pressure increases? What if the atmospheric pressure jumps by a factor of 2, 4 or 6? This recent case will give you a good idea...
I could hear something that sounded like a ticking clock. The patient was 18 and had recently arrived in the Resuscitation Room of our Emergency Department. It was Christmas and Tim* had been to a party. After drinking beer and spirits, he'd started inhaling nitrous oxide with friends. Just to show us what he'd been using, he'd brought a collection of empty shiny metal cartridges with him. Measuring less than 10cm long and 2cm wide these had contained 8g of compressed gas. At room temperature this would amount to between 3 and 4l of nitrous oxide, or "laughing gas" as it's perhaps more commonly known. Rather than release the contents into a balloon and take small "sips" as his friends had done, he'd decided to try something different. Using a short length of rigid plastic tubing Tim had fashioned a mouthpiece and a port to insert the canister. On opening it, he had inhaled its entire contents. Given that this was about 10 times the size of a normal breath, a considerable amount of damage was done.
Nitrous oxide is a colourless gas that is widely used an an anaesthetic agent. It is also a food additive - E942 - where it is commonly used as a propellant for whipped cream. As a result, canisters (sometimes known as "whippets") are freely available to buy. Commonly known as "Laughing Gas" inhalation causes a brief sensation of elation that's often accompanied by bursts of spontaneous laughter
As the gas flew into his body it had stretched and split the tissues along its path. Not only had it damaged the lungs and caused both to collapse, it had also torn the oesophagus and caused gas to track into the mediastinum. The noise of a ticking clock was "Hamman's Sign" - the sound of Tim's heart beating inside his chest against a stiff cushion of air and nitrous oxide. If this wasn't enough, the tissues in his face, neck and chest had also split apart and were swollen with trapped gas. This proved incredibly painful and needed a combination of intravenous morphine and ketamine to keep the discomfort under control.
The 2018/19 Crime Survey for England and Wales reported that 8.7% of those aged between 16 and 24 had used nitrous oxide - street name "Hippy Crack" - in the preceding year. In this age group it was the second most popular substance of abuse after cannabis. According to the Office of National Statistics, 29 deaths between 2010 and 2017 were attribute to nitrous oxide misuse
After chest drains were inserted, the patient was transferred to the ITU for observation. Over the course of the next week, the swelling started to fade and the chest drains were removed. Unfortunately, the tear in the oesophagus took much longer to heal. Although surgery was not required, Tim needed feeding through a naso-gastric tube for almost 3 months. It would take a year before he could eat a normal diet again.
It might be said that in this case, using nitrous oxide was no laughing matter...
There's a lot more to read about pressure on this blog! See how changes in the seasons have a dramatic effect on summiting Everest. Read about what's needed to climb 8000m peaks in winter.
The work of the BMRES focuses upon the effects of altitude on the body. Read about how this research group started and the many wonderful adventures they've had along the way!
Here's how a simple change in body position can reduce the effects of altitude!
Here's an interview (and a webinar!) with Victor Saunders. Is there anyone better able to cope with the fall in atmospheric pressure than Victor?
*Please note that the details of this patient have been changed.
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10/04/2022 @ 19:36:09
wow. terrifying but fascinating case.
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