Detecting Blood Loss

Patients who lose too much blood during surgery can suffer heart attacks.

But measuring blood volume requires either inserting a catheter into the pulmonary artery, ordering an expensive echocardiogram, or resorting to guesswork.

Kirk ­Shelley, an anesthesiologist at Yale University, has devised a way to noninvasively measure blood loss using a pulse oximeter, a finger-clip device commonly used to measure pulse rate and blood oxygen levels in hospital patients. The pulse oxime­ter measures how much light of different wavelengths the blood absorbs.

After gathering pulse oximeter data from operating rooms for more than seven years, ­Shelley developed an algorithm that translates subtle absorption changes into accurate estimates of blood volume.

Shelley says the algorithm can detect when blood loss exceeds one pint, information that can be used to guide transfusions. ­

Shelley is negotiating with manufacturers that might license or buy the technology. If all goes well, the technology could reach operating rooms in 2006.