I’m pleased to be joined by Kristy McCaffrey today as part of the blog blitz for her novel Deep Blue. Kristy is sharing a fascinating guest post about diving and its remarkable effects on the human body.
The Master Switch Of Life
In 1963, Per Scholander, a Swedish-born researcher working in the United States, discovered a Master Switch of Life in vertebrate animals—a defence against asphyxia. For humans, it’s a nod to our dormant amphibious reflexes. In simple terms, it’s the body’s response to being underwater. As soon as we place our faces in water, an onslaught of physiological reflexes affects our brain, lungs and heart. When your mother told you to “splash water on your face” during times of upset, she was on to something.
What happens to the human body as it enters an arena usually reserved for marine life? As a diver descends, blood begins flooding away from limbs and toward vital organs. This shunting—called peripheral vasoconstriction—from less important areas helps keep the brain and heart oxygenated longer, thereby extending the amount of time a diver can remain submerged. When a diver descends to 300 feet—a depth frequently reached by modern freedivers—vessels in the lungs engorge with blood, preventing them from collapse. The deeper a human descends, the stronger the peripheral vasoconstriction becomes. What’s curious is that Scholander found that a person need submerge only his face in water to activate these lifesaving reflexes. But these responses can only be triggered by water and it must be cooler than the surrounding air.
Today, freedivers exploit the Master Switch to their advantage, but it isn’t without risk. Here is what occurs in the body as a swimmer freedives:
First 30 feet: With the lungs full of air, the swimmer must paddle to descend.
Once past 30 feet: The pressure on the body doubles and the lungs shrink. The swimmer is now in neutral buoyancy and feels weightless. It’s here that something extraordinary happens—the ocean pulls the diver down. Swimming is no longer required.
At 100 feet: The pressure triples and the ocean’s surface is barely visible.
At 150 feet: The diver experiences high levels of carbon dioxide and nitrogen in the bloodstream, causing a dream-like state.
At 250 feet: The pressure is now so extreme that the lungs shrink to the size of a small apple and the heart beats at half its normal rate to conserve oxygen. Some freedivers report heartrates as low as 14 beats per minute
At 300 feet: This is where the Master Switch really kicks in. There is a free flow of blood and water into the thoracic cavity as the chest collapses to half its original size. The effects of nitrogen narcosis are so strong that divers forget where they are, what they’re doing, and why they’re in such a dark place. Hallucinations are common, as is the loss of motor control.
As a diver reverses and begins to ascend, the Master Switch also reverses. The heart rate increases and blood floods back into the veins and arteries and organs. However, the lungs ache to breathe and the vision fades. The chest convulses from the buildup of carbon dioxide. A diver must hurry or risk blacking out. If a black out occurs, a diver can stay submerged for up to two minutes. At the end of two minutes, the body will wake itself up and breathe one last time before death. If a diver has been rescued and carried to the surface by this time, he or she will inhale much-needed air and probably survive. If the person is still underwater, their lungs will fill with water and they’ll drown.
Humans connection to the ocean runs deep. In the womb, we grow within an amniotic fluid that is similar in makeup to ocean water. At one month, an embryo will grow fins first, then feet. At five weeks, that same embryo will have a 2-chambered heart, akin to a fish. Human blood has a chemical composition similar to seawater.
Ancient cultures knew all about the Master Switch and employed it for centuries to harvest sponges, pearls, coral, and food hundreds of feet below the surface of the ocean. We carry within us latent abilities that connect us to the whales and dolphins, a key from our distant past.
Thanks to Kelly at Love Books for inviting me to be part of the blog blitz. Deep Blue is available in paperback and ebook formats. You can order a copy online here: Deep Blue
From the back of the book
In the deep blue ocean lives an ancient predator…
Dr. Grace Mann knows great white sharks. As the daughter of an obsessed shark researcher based at the Farallon Islands, Grace spent her childhood in the company of these elegant and massive creatures. When a photo of her freediving with a great white goes viral, the institute where she works seeks to capitalize on her new-found fame by producing a documentary about her work.
Underwater filmmaker Alec Galloway admires Dr. Mann and jumps at the opportunity to create a film showcasing the pretty biologist. As he heads to Guadalupe Island in Baja California Sur for a three-week expedition, it’s clear that his fan-boy crush on Grace is turning into something more serious. But even more pressing—Grace’s passionate focus on the sharks just might get her killed.
About the Author
Kristy McCaffrey has been writing since she was very young, but it wasn’t until she was a stay-at-home mom that she considered becoming published. A fascination with science led her to earn two mechanical engineering degrees—she did her undergraduate work at Arizona State University and her graduate studies at the University of Pittsburgh—but storytelling has always been her passion. She writes both contemporary tales and award-winning historical western romances.
With the release of Deep Blue, Kristy is launching The Pathway Series, a project she’s been developing for years. Each book will combine her love of animal conservation and environmental awareness, while also shining a light on unique and diverse locations around the world. Come along for high adventure with honorable heroes, determined heroines, and Kristy’s trademark mysticism.
An Arizona native, Kristy and her husband reside in the desert where they frequently remove (rescue) rattlesnakes from their property, go for runs among the cactus, and plan trips to far-off places like the Orkney Islands or Machu Picchu. But mostly, she works 12-hour days and enjoys at-home date nights with her sweetheart, which usually include Will Ferrell movies and sci-fi flicks. Her four children have nearly all flown the nest, and the family recently lost their cherished chocolate Labrador, Ranger, so these days a great deal of attention is lavished on Ranger’s sister, Lily, and the newest addition to the household—Marley, an older yellow Labrador they rescued in early 2018. Both dogs are frequently featured on Kristy’s Instagram account, so pop over to meet her canine family.
“When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” – John Muir