from the product can vary widely but is generally wellbelow the level that could cause harmful effects. TheCPSC used human adult volunteers to help determinehow much of the chemical is released when the plas­tic is chewed or sucked. The CPSC established a levelused internationally as an acceptable daily intakelevel for DINP, and for a measure of safety, this level is100 times less than the amount found not to causeany adverse health effects in laboratory animals.

The study identified several areas of uncertaintyrequiring additional scientific research. As a precau­tion, the CPSC requested, and about 90% of manufac­turers have agreed, to remove phthalates from softrattles and teethers by early 1999. In addition, majorretailers have removed teethers and rattles contain­ing phthalates from store shelves.

The CPSC will also take the following steps:

Flaherty and Snyder/JOURNAL OF EMERGENCY NURSING

• Recommend that a Chronic Hazard Advisory Panelmade up of independent scientists be formed tocarry out an additional scientific assessment of po­tential risk, including whether phthalates pose acancer risk to humans

• Undertake further study to determine the amountof time that children mouth products that couldcontain phthalates

• Continue testing to determine the amount ofphthalates released from children's products

As a precaution, parents of young children whomouth plastic products for long periods may wish todispose of the products. For a full listing of manufac­turers and retailers who have agreed to comply withCPSC recommendations, visit the CPSC Web site athttp://www.cpsc.gov, or call the CPSC hotline at (800)638-2772.

ALook Back: The electrocardiogram

Willem Einthoven

References

In the 19th century, medical therapies for heart disease were sparse. Peopleusually died of an infectious disease before they ever reached an age atwhich heart disease could claim their life. The cardiac cycle was a mystery,and clues relating to its function were difficult to interpret. In 1842, an Italianphysicist, Carlo Matteucci, discovered that an electric current accompaniedeach heart beat. In 1878, British physiologists John Burden Sanderson andFrederick Page used a capillary electrometer to record the 2 phases of theheart's electrical current, later referred to as the QRS and T. Three yearslater, Augustus Waller, a British physiologist with a reputation for scrupulousaccuracy, published the first electrocardiogram showing how the varyingcardiac potentials could be measured on the body surface. However, hismethod involved complicated calculations.

In 1901, Dutch physiologist Willem Einthoven (1860-1927) modified astring galvanometer to measure cardiac electrical current and project animage on a photographic plate. His early instrument, which weighed 600pounds, was also cumbersome and complicated, and involved having pa­tients place their hands and feet in 4 buckets of water. Einthoven continuedto refine his instrument and research and, in 1905, began transmitting EKGsfrom a hospital to his laboratory 1.5 km away via telephone. He was awardeda Nobel Prize for his work in 1924.-Linda Manley, RN, BSN, CEN, CCRN

Jenkins D. ECG library: a brief history of electrocardiography. Available from: URL: http.//homepages.enterprise.netldjenkins/ecghist h tm]

Porter R. The Cambridge illustrated history of medicine. New York: Cambridge University Press; 1996.

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