CHAPEL HILL, N.C. - Scientists at the University of North Carolina at Chapel Hill have invented a solid-state metal sensor -- roughly the thickness of three human hairs -- that can measure the acidity (pH) of chemical solutions, including body fluids.
A report describing the invention, including successful laboratory tests in animals, is published in the December issue of Analytical Chemistry.
"This particular electrode can be applied to any solution ? from a chemical process in the laboratory to the measurement of tissue pH in physiologic studies," says co-inventor Dr. Wayne E. Cascio, associate professor of medicine at the UNC-CH School of Medicine.
But according to new findings by Cascio and his UNC-CH colleagues, the pH electrode may even prove useful for monitoring the hearts of hospitalized patients, especially those in intensive coronary care. Attached to the tip of a catheter and then threaded via vein to the heart, the pH electrode may offer advance warning when cardiac muscle is becoming more acidic, a condition that occurs during ischemia. Ischemia takes place when the supply of oxygen is cut to portions of the heart and can arise from fat-clogged coronary arteries. This condition could lead to a heart attack.
"If the pH is falling, indicating more acidity, then you know that the tissue is ischemic," Cascio, a cardiologist, explains. "The process of ischemia generates acid, and the degree of acidification offers an index of the severity of ischemia. But a falling pH also seems linked to other electrical and metabolic changes that occur and can predispose to heart rhythm disturbances such as ventricular fibrillation and sudden death," he adds.
In terms of pH in the human body, metabolic actions occur properly when fluids
are close to chemical neutrality ? neither too acid nor too alkaline. On a scale
of zero to 14, a pH of below 7 signals acidity. In cardiac tissue, ischemia
results in the loss of protons from cells, which leads to
Contact: Lynn Wooten
University of North Carolina School of Medicine