Summertime means swimming. But all of those water fights and games of "Marco Polo" come with a serious risk: drowning.

Drowning kills about 10 people per day in the United States, and children younger than 5 are at the highest risk. But while most people are alert to the obvious signs of drowning, those signs don't happen in all cases, and not everyone realizes someone can drown even after he or she is pulled out of the water.

Events that nonexperts sometimes call "dry drowning" or "secondary drowning," (these are not actual medical terms) can occur up to a day after the person had trouble in the water. This type of drowning is quite rare, making up just 1 to 2 percent of all drowning incidents, said Dr. Mark Zonfrillo, a pediatric emergency and injury researcher at The Children's Hospital of Philadelphia.

People may think of drowning as occurring at the same time as death, but drowning is actually a medical condition, and not everyone dies from it immediately. People should know that anyone who's been submerged under the water involuntarily and had trouble getting oxygen has drowned — and even if the person is conscious, he or she is having a medical emergency, several experts said. [7 Common Summer Health Concerns]

"If someone does swallow water, there can be a delayed response, where they may not be safe and may be at risk for sudden death," said Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City.

What is drowning?

Drowning occurs when a person is submerged under water for any length of time, goes into respiratory distress and can't get enough oxygen in his or her body, said Dr. Justin Sempsrott, CEO of Lifeguards Without Borders, a nonprofit organization that aims to reduce drowning deaths worldwide. After being submerged, most people become unconscious within 30 to 60 seconds of being forced to hold their breath, and people can drown either with water in their lungs or no water in their lungs. As long as they're having trouble getting oxygen, they have drowned, he said.

"There is no such thing as 'dry drowning' or 'secondary drowning' or 'wet drowning' — it's all just drowning," Sempsrott told Live Science.

Drowning is a condition that occurs on a spectrum, ranging from no long-lasting harms, to severe brain damage, to death.

Moreover, drowning is not the dramatic affair shown in the movies, Zonfrillo said. Typical victims do not splash or cry for help. Rather, they are very, very quiet and still, he said.

"Drowning is often very fast, and very silent," Zonfrillo told Live Science.

Drowning on dry land

Sometimes, a person who is drowning may be coughing and spluttering but is still conscious when he or she is pulled from the water. A small percentage of such drowning victims will go on to have a life-threatening emergency.

Some of these cases are what's historically been called dry drowning, when a small amount of water irritates the larynx, or vocal chords, causing them to close up and restrict the airways. This event, called a laryngospasm, can also occur during surgery, when people are on anesthetics such as ketamine, Glatter said.

Laryngospasm can trigger a shock reflex in the body called neurogenic pulmonary edema. When this happens, pressure rises in the lungs and heart, and reduces the body's ability to get oxygen. Without treatment, a laryngospasm sets off a deadly downward spiral, he said.

"It can be very dangerous," Glatter told Live Science.

The symptoms of a laryngospasm are not subtle: Children may make a high-pitched breathing noise called stridor, gasp or cough, bolt upright in an attempt to get more oxygen, turn blue or become unusually sleepy, Glatter said. Some children may become incontinent. These symptoms can occur soon after a child is removed from the water; however, very rarely, the response can occur up to 24 hours after an incident, Glatter said.

If a child shows any of these symptoms, people should call 911 immediately, he said.

To stop the events that follow laryngospasm, emergency room doctors may put a mask on the child and pump oxygen into the lungs, administer a drug to stop the throat muscles from closing up, or perform a procedure called Larson's maneuver, which manipulates the jaw to open up the vocal cords, Zonfrillo said. (Only trained medical professionals should try this maneuver, Zonfrillo said.) [16 Oddest Medical Cases]

Secondary drowning

Delayed drowning (historically called secondary drowning) occurs when a small amount of water enters someone's lungs.

That water can wash away some of the substance that normally coats the inside of the lungs, called surfactant, which allows the lungs to absorb oxygen. This prevents people from getting enough oxygen, and can lead to death, Sempsrott said.

People who are coughing and spluttering for more than a minute or two after being pulled up from the water and who have foam around the mouth need to be taken to an emergency room immediately. Most of these people will be observed for 4 to 6 hours before being released, Glatter said.

Some may need to be put on oxygen for a day or two, until their surfactant regenerates, Sempsrott said.

But in some rare cases, patients can go downhill quickly and must be put on a respirator to prevent death or brain damage, Glatter said.

The symptoms of "secondary drowning" are similar to those caused by laryngospasm, because oxygen depletion is the underlying cause, Sempsrott said.

And contrary to some media reports, children who have died of a delayed drowning reaction typically show some symptoms of drowning immediately after they are pulled from the water, even if they are still breathing and conscious, Sempsrott added.

Prevention is the best response

While parents should be aware of the signs of a delayed response to drowning, prevention is the best way to keep little swimmers safe.

That includes putting fences around pools, actively supervising children at all times when they're in the pool, keeping a keen eye on younger children and being aware of everyone's swimming level. Parents can also institute a buddy system, where older, more proficient swimmers are responsible for looking out for younger kids, Glatter said.

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