Researchers have developed a laser device that can tell in real time whether tissues in the body are receiving enough oxygen. The laser system relies on resonance Raman spectroscopy, and could help doctors to predict cardiac arrest, as low oxygen levels in heart muscle is a warning sign that the heart could stop pumping.

“With current technologies, we cannot predict when a patient’s heart will stop,” says John Kheir, of the Boston Children’s Heart Center, who was involved in the research. “We can examine heart function on the echocardiogram and measure blood pressure, but until the last second, the heart can compensate quite well for low oxygen conditions. Once cardiac arrest occurs, its consequences can be life-long, even when patients recover.”

Under low oxygen conditions within cells, electrons accumulate in proteins inside an organelle called the mitochondrion. Mitochondria are the power-houses of cells that rely on oxygen to produce energy, which is particularly important for heart muscle that is constantly moving.

Resonance Raman spectroscopy can measure the fraction of mitochondrial proteins that have electrons on them, based on how the laser light scatters when it hits the tissue. “We wanted to create an organ-specific, continuous, reliable readout of how adequately mitochondria are being fed oxygen,” says Kheir. “This is the first demonstration of a device that can monitor mitochondria in living tissues to predict impending organ failure.”

The team have tested their device, which is currently the size of a pen, during heart surgeries in rats and pigs. However, they hope to miniaturize the probe in the future, so that it can be implanted in the chest on a longer-term basis, to monitor the hearts of at-risk patients.