The heart beats rhythmically, and so does a metronome.
So it makes sense that a metronome, typically used by musicians to help keep a steady beat, could help medical professionals restart a heart.
"What we know for sure," says pediatric cardiologist Dianne Atkins, a spokeswoman with the American Heart Association, is that "high-quality CPR improves survival." So anything that improves CPR could save lives.
For CPR to be effective, the rescuer kneels at the side of the person in distress, presses one hand on top of the other in the center of the person's chest and pushes down about 2 inches to force blood through the body before releasing and then compressing again.
The optimal rate for compression is 100 to 120 per minute, which is "fairly fast" says Atkins, and hard to maintain without something to guide you. "When chest compression is too slow or too fast, it decreases the effectiveness of CPR," she says.
That's where the metronome comes in. It offers a consistent guide. With every click, you do a chest compression and the metronome helps you keep the beat. Previously researchers have tried using music, including the songs "Disco Science" and "Achy Breaky Heart" to set the beat.
Now we're not talking about everyone carrying around a metronome just in case CPR is needed. Most studies of metronomes have involved medical professionals doing CPR on adults. The most recent study in the journal Pediatrics looked at using metronomes to guide CPR for children.
More than 150 medical providers performed two rounds of chest compression on pediatric manikins, one with the metronome and one without. It turned out the metronome increased CPR effectiveness by 22 percent.