During last triathlon season, there were a string of deaths in the water. Fourteen deaths in races were largely from swimming (one death occurred on the bike) These unfortunate events led a Washington Post writer to postulate that the deaths during the swim were the result of panic attacks. I have also heard medical personell postulate that these events were the results of heart attacks and heat stroke. Of the deaths, the mean age was 44 and 11 were men. 6 deaths were in sprint triathlon (1/4-1/2 mile swim, 12 mile bike, 3.1 mile run), 4 in Olympic distance (1.5k swim, 40k bike, 10k run) and 3 in the longer distances (half Iron distance or Iron distance 2.4mile swim, 112mile bike, 26.2mile run) The cause of these deaths has been ruled drowning, but no matter what the cause of death, if it occurs in the water, chances are it will lead to drowning. Feelings of panic are commonplace in open water, mass start events, but they do not mean that they are panic attacks. You can feel panicky from too much coffee, a rapid heart rate, feelings that you can’t breathe, etc. It is the things that cause the rapid heart rate and rapid breathing that can lead to metabolic problems which can lead to fatal problems. Let’s examine what happens when you jump into a cold lake. Most swims are in bodies of water that are at least 10 degrees colder than body temperature. Cold water immersion leads to a phenomenon known as the Mammalian Diving Reflex. This reflex decreases breathing and slows the need for oxygen and is life saving for non-swimmers and children who fall into water . The more dangerous response is the Cold Shock Reflex. This reflex will cause you to take a deep breath, followed by uncontrolled hyperventilation. A triathlete who jumps into cold water, or at least puts their face in cold water, will have a temporary breath-holding reflex. If this same triathlete starts swimming quickly, they would be out of breath before even starting. Imagine running down the block while holding your breath; you would feel out of breath very quickly. Hyperventilation will happen immediately following and is one of the components of feeling panicky. A rapid rise in heart rate will also accompany the Cold Shock Reflex and can also lead to a feeling of panic. A tight wetsuit can make breathing difficult as well. It is these heart and lung changes, not panic, that are responsible for many open water deaths. In a 2010 review of triathlon swim deaths, 7 of 9 patients were found to have cardiac abnormalities. However, 6 of the 7 were found to have left ventricular hypertrophy, which is a common finding in endurance athletes and is expected in trained endurance athletes. One of the patients had abnormal coronary arteries, which may have contributed to the death. This is not compelling evidence that there is a cardiac cause of sudden death in the water. Hyperventilation can have a negative impact on the lungs. It is not uncommon for hyperventilation to have an effect on the airways and lead to coughing or even spasm of the vocal cords. This makes it harder to breathe and leads to increased hyperventilation. Which can in turn lead to increased anxiety. Anxiety worsens the cold shock response. With repeated cold water immersions (4 days apart), the amount of hyperventilation is shorter and not as much. Less frequent immersions diminish the length but not the magnitude of the response. One way to reproduce this habituation to the cold shock reflex is taking repeated cold showers at 50 degrees fahrenheit for 3 minutes. 3 minute showers at 50 degrees may save your life Finally, how can we screen for the ill-effects of the cold shock reflex? One way is to perform maximum hyperventilation while monitoring lung changes. This is a regular component of the cardiopulmonary exercise testing. If changes in measured lung volumes or coughing is present, perhaps these changes should be treated. Standard cardiac stress tests will probably not be useful for screening for the cold shock reflex. If we are to prevent triathlon swim death, other tests and decreasing the response to cold water are essential. -Michael Ross
