catheter may be monitored by dynamic pressure readings from the catheter tip or with the aid of fluoroscopy. The standard pulmonary artery catheter has two lumens (Swan-Ganz) and is equipped with an inflatable balloon at the tip, which facilitates its placement into the pulmonary artery through the flow of blood. The balloon, when inflated, causes the catheter to "wedge" in a small pulmonary blood vessel. So wedged, the catheter can provide an indirect measurement of the pressure in the left atrium of the heart, showing a mean pressure, in addition to a, x, v, and y waves which have implications for status of the left atria and the mitral valve. Left ventricular end diastolic pressure (LVedp) is measured using a different procedure, with a catheter that has directly crossed the aortic valve and is well positioned in the left ventricle. LV edp reflects fluid status of the individual in addition to heart health. See also pulmonary wedge pressure and ventricular pressure. Technical developments Thermal dilution The idea for a sail or balloon tip modification of Ronald Bradley's simple portex tubing method came about from Swan's observation from the Laguna Beach CA shore of sail boats on the water on a relatively calm day. Boats with conventional slot sails were still; one with a spinnaker was able to make reasonable headway. The concept of using thermodilution to measure cardiac output was originally the idea of Arnost Fronek. As a former colleague of Fronek, Ganz added the thermistor modification after Swan showed him the initial balloon design, which was fabricated by Edwards Laboratories, which had previously contracted with Swan as a consultant. After Swan developed the initial balloon tip, Ganz used Fronek's idea and added a small thermistor (temperature probe) about 3 cm behind the tip. 10 ml of saline (0.9% NaCl) under 10° Celsius or room temperature (not as accurate) is injected into an opening in the right atrium. As this cooler fluid passes the tip thermistor, a very brief drop in the blood temperature is recorded. A recent variation in design is the incorporation of a heating coil on the catheter (30 cm from the tip, residing in the atrium area) which eliminates the cold fluid bolus, a major factor in human technique variation. By attaching both the injector site and the ventricular thermistor to a small computer, the thermodilution curve can be plotted. If details about the patient's body