"Sudden immersion in cold water causes an immediate fall in skin temperature which triggers several body reflexes. These reflexes are collectively known as the “cold-shock” response, and they last for just the first few minutes after falling in. The cold-shock responses are: 1) instantaneous gasping for air; 2) sudden increase in breathing rate; 3) sudden increase in heart rate; 4) sudden increase in blood pressure; and 4) dramatic decrease in breath-holding time. If your head is underwater and the cold-shock reflex causes you to gasp and inhale (and simultaneously decreases your ability to hold your breath), you may <br />
breathe in water and drown."<br />
<br />
"The increase in blood pressure and heart rate from sudden immersion into cold water can also be fatal. These rapid changes in <br />
the cardiovascular system can trigger irregular heart beats or even <br />
cardiac arrest in susceptible individuals. But even aside from the <br />
potential for cardiac arrest, the irregular heart beats and rapid <br />
breathing rate can be incapacitating for someone struggling to keep <br />
his head above the waves"<br />
<br />
"Sudden immersion in cold water also drastically reduces your <br />
ability to hold your breath. For the average person who can hold <br />
his breath for 60 seconds in air, breath-holding time is reduced to <br />
20-25 seconds or less when submerged in water colder than about <br />
50°F."<br />
<br />
"[T]he rapid breathing that occurs during the first few minutes of <br />
cold-water immersion can lead to a drop in blood levels of carbon <br />
dioxide with subsequent mental confusion or even unconsciousness; both can significantly increase your chances of drowning."<br />
<br />
"It is much harder to swim in cold water than it is in warm water. Your muscles get cold, making it harder to use your arms and legs to stay afloat. And cold water is a bit more viscous than is warm water, requiring you to work harder to swim or stay afloat."<br />
<br />
"Both swimming failure and loss of manual dexterity can occur during the first 30 minutes after falling into cold water."<br />
<br />
"In the early study by Keatinge, swimming failure was attributed to <br />
panic, fatigue and respiratory distress. Today, we understand that <br />
those initial responses to cold water immersion are attributed to <br />
cold shock. The uncontrollable breathing, hyperventilation, gasp <br />
reflex, dyspnoea observed early during cold water immersion can <br />
lead to a lack of coordination between the swim stroke and respiration. In turn, these physiological responses would increase the risk <br />
of developing panic due to water inhalation and inability to swim <br />
and to hold the head above water. Thus, cold shock may explain the <br />
swimming failure observed by Keatinge early during immersion in <br />
5°C/41°F water. This limitation can be easily overcome by ensuring that the respiratory responses have adapted and breathing pattern is under control (about 2-3 minutes) before initiating the swimming activity."<br />
<br />

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