It was the middle of the night. The lights were off, the house was still, the six members of the Nuttall family were sound asleep. The machinery that monitors the blood sugar levels of 7-year-old Luke Nuttall, who suffers from dangerous type 1 diabetes, was utterly quiet.
But Jedi, Luke's diabetes-sniffing dog, was not.
The black lab jumped on and off of the bed Luke shared with his parents, thumping onto the mattress in an attempt wake the slumbering adults. When that didn't work, he lay on top of Dorrie Nuttall, startling her out of sleep.
She clambered out of bed and examined her son's continuous glucose monitor, but its reading was normal. Still, the dog was unrelenting. He bowed again and again, repeating the signal he'd been trained to send if he sense that Luke's blood sugar had gotten too low.
"Then I knew he meant business," Nuttall wrote in a Facebook post describing the incident. "The sleepy fog started to wear off and I began to think clearer. I suddenly was fully awake and I knew there was an issue."
She pricked her son's finger and got a blood sugar level that was almost half as high as the one on the monitor — much too low, and falling fast.
Nuttall quickly gave her sleeping son a glucose tablet and warily monitored the tense tableau: attentive dog, sleeping boy, a frightening number on a screen.
"Luke was laying right next to me, just inches from me, and without Jedi I would have had no idea that he was dropping out of a safe range," she wrote in her post that has since gone viral. ". . . This is a picture of a Jedi saving his boy."
Nuttall said that she posted the photo to expose other people to the daily (and nightly) reality of Type 1 diabetes. Her Facebook page and website chronicle countless middle-of-the-night moments like this one; they're so frequent they might become routine, if it weren't for the fact that in any one of them, Luke could die.
But it's also a testament to a scientific fact that is something of a medical marvel: Dogs can literally smell how well a diabetes patient is doing. In some circumstances — like Luke's — a dog is a better judge of a little boy's health than his parents, his myriad high tech monitoring machinery, even the patient himself.
A dog's nose is an incredibly powerful sensory tool: Their sense of smell overpowers our own by a factor of 10,000 to 100,000, James Walker, former director of the Sensory Research Institute at Florida State University, told PBS.
Their advantage is so staggering it's hardly fair. When dogs breathe in through their noses, a fraction of the air they inhale is sent to a special olfactory area, where specialized structures called turbinates sieve through odor molecules based on their chemical properties. By comparison, humans have no designated smell center — just a swath of cells that incoming air whiffs past on its way to our lungs.
Dogs smell in stereo (they can tell which nostril a smell came in through) and they can wiggle their nostrils independently — a feat not even matched by Samantha Stephens from Bewitched.
And when dogs exhale, the air goes out through special slits in the sides of their noses, rather than back out via the nostrils through which it came. This means that dogs can be sniffing basically continuously as they breathe, and air they've already smelled doesn't get mixed up with new scents flowing in.
Then there's the vomeronasal organ, a separate olfactory system designed specifically for detecting hormones — from potential mates, incoming predators, vulnerable prey and — luckily for us — emotional or ailing humans. Dogs are thought to be able to sniff out cancer, deadly bacteria and seizures.
What exactly dogs are smelling when they sense that a patient's blood sugar has fallen too low is still a mystery to scientists. Is it the scent of sweat, or a smell carried on the breath? Is it a hormone? Are they even "smelling" the diabetic emergency at all? (A 2013 paper in the journal Diabetes Care suggested that they might not be, though the study only tested dogs' ability to detected hypoglycemic patient's skin.)
But anecdotal evidence — along with a small but growing body of research — indicates that whatever sense dogs are relying on to detect low blood sugar, they're incredibly good at it.
Diabetes alert dogs are difficult to train and, for some people, prohibitively expensive. According to the website for the non-profit Dogs Assisting Diabetics Foundation, patients must pay a $15,000 adoption fee and another $1,000 a year for food and other expenses.
But for patients like Luke, whose brains are so accustomed to swings in blood sugar they don't show any of the emotional or physical signs of hypoglycemia (a condition known as hypoglycemic unaware), a dog that can detect an emergency when the body can't may mean the difference between life and death. As many as 1 in 20 young type 1 diabetes patients die in their sleep from unknown causes thought to be related to hypoglycemia - a phenomenon known as "dead in bed syndrome."
"It's in those moments when our guards are down, when we are just living life, when we let our minds drift from diabetes, that (the disease) has the upper hand-and things can get scary very fast," Dorrie Nuttal wrote in her Facebook post. "But thankfully we have Jedi."