By JV Chamary, Forbes
The Ice Bucket Challenge has raised an impressive amount of money and awareness for motor neuron diseases like Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease). In just one month, the ALS Association has received $80m in donations.
Participants tip buckets of ice water over their heads as they take part in the World Record Ice Bucket Challenge at Etihad Stadium on August 22, 2014 in Melbourne, Australia. Over 700 people took part in setting the new world record. The Ice Bucket Challenge is the social media phenomenon which is helping raise awareness and money for sufferers of Motor Neurone Disease. (Photo by Scott Barbour/Getty Images)
But while the fundraising campaign should be praised, the tragic death of a Scottish teenager reveals that the Ice Bucket Challenge can be dangerous – and potentially deadly.
Cold Water Kills
When you imagine the dangers of cold water, you probably think of hypothermia. “There was a bit of a preoccupation with hypothermia dating right back to the Titanic, and then reinforced during the Second World War,” says Professor Mike Tipton, a physiologist at the University of Portsmouth and co-author of several books on survival at sea.
But fatal hypothermia takes a relatively long time: from 37ºC (99ºF), it takes half an hour for your core body temperature to fall below 35ºC (95ºF). Most deaths in open water occur within minutes, as two-thirds of drowning victims are good swimmers and over half die within 10 feet of safe refuge.
The first thing that Ice Bucket challengers and people immersed in cold water experience is a sudden drop in temperature, which triggers a reflex called the cold shock response.
“It’s basically exactly the same as you would imagine if you stepped or jumped into a pool they said was heated and it wasn’t, or stepped under a shower that had just run cold,” Tipton explains. “It’s a gasp response followed by uncontrollable hyperventilation.”
That gasp for air and rapid inhalation destroys your ability to breathe. Even if you can normally hold your breath for a minute in the bathtub, you would only last a few seconds in cold water. The average volume an adult inhales is 2-3 litres, and the lethal dose for drowning is 1.5 litres of seawater or 3 litres of freshwater. If you’re underwater or waves are battering your face, the cold shock response could kill you.
Death By ‘Drowning’
Drowning is the third-most common cause of accidental death worldwide and unintentional drowning kills 10 Americans every day.
There are many reasons why people lose their lives. Some can’t swim while others succumb to flash floods, for example. But Tipton believes many are killed from being immersed in cold water. He estimates that about 20% succumb to hypothermia, 20% of people die before, during or after being rescued (a phenomenon called circum-rescue collapse) and the remaining 60% are killed by the cold shock response.
The Ice Bucket Challenge has been linked with two deaths so far. The Scottish teenager, 18-year-old Cameron Lancaster, supposedly drowned after jumping into a flooded quarry. Another victim, 40-year-old Willis Tepania from New Zealand, had a heart attack after drinking a bottle of bourbon.
(Although not a consequence of the challenge itself, Corey Griffin, a 27-year-old who raised $100,000 for his friend Pete Frakes – the College baseball player with ALS who made the campaign go viral – died after diving into harbour of Nantucket Island.)
But most Ice Bucket Challenge participants don’t submerge themselves, so how can cold water immersion be dangerous to them? The problem occurs when someone’s face gets wet while they’re holding their breath.
Immersing your head and body in cold water triggers two powerful physiological responses. Cold shock becomes a potential problem when it happens at the same time as another reflex: the diving response.
“If you’ve got those two responses co-activated then you’ve got a response trying to accelerate the heart – the cold shock response – at the same time as you’ve got a response trying to slow it down, the diving response,” says Tipton.
He calls this ‘autonomic conflict‘ because both the cold shock and diving responses send signals to the heart via the nerves that control involuntary body functions, the autonomic nervous system.
Cardiac Conflict
The diving response is vital to marine mammals such as seals and dolphins, but humans have it too. It’s the reflex that tells your heart to slow down, redirects blood flow to the most vital organs (such as the brain) and enables you to hold your breath underwater.
Both the diving and cold shock responses are triggered by receptors in the skin, nerve endings of the autonomic system. The diving response is stimulated by receptors on your face (near the eyes, nose and mouth) while cold shock is triggered by thermoreceptors all around the body. Because these receptors are 0.2mm below the surface of the skin, body fat – which insulates against hypothermia – won’t stop you sensing a temperature drop.
Cold water only becomes hazardous when it’s sensed by the face and rest of the body simultaneously. Both the diving and cold shock responses relay sensory information via the brain to the heart, but their messages contradict each other. Submerge the face alone and heart rate should fall from a normal 60-100 to 40-50 beats per minute, whereas cold water will boost the rate above 100.
Autonomic conflict is like pushing the gas pedal to accelerate the heart’s speed while also repeatedly applying the brakes. This causes an abnormal heart rhythm – arrhythmia – and can occasionally lead to the most dangerous outcome of cold water immersion: sudden cardiac death.
Arrhythmias are common. If you swim or snorkel, you probably experience them all the time. After holding your breath, arrhythmia will start within 10 seconds. It can be monitored by heart rate on an electrocardiogram (ECG).
“I would be really interested in having an ECG on all these people who are doing the Ice Bucket Challenge because I pretty well guarantee there will be a fairly significant number of them having an arrhythmia while they do it,” says Tipton.
In Tipton’s previous studies, 2% of fit and healthy subjects experienced an arrhythmia when their body was immersed in cold water, but the proportion goes up to 82% when the face is submerged. The problem gets worse in stressful situations: among people who train to escape from submerged helicopters, including those who work on offshore platforms or for the military 25% have an arrhythmia during a 10-second drill.
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