Measuring left ventricular ejection time using under-the-mattress sensor

Internal bleeding may be hard to recognize before hypovolemic shock onset. Early detection of a shortening in LVETmay expedite medical care and increase survival rate. The current experiment aimed to demonstrate the ability to measure LVET using analysis of the cardio-ballistic effect measured with a piezoelectric sensor (PE) placed under the mattress. 10 participants were asked to lie supine on a bed with their Lower Body enclosed in a Negative-Pressure (LBNP) chamber. Study's protocol included a baseline phase followed by a gradient reduction of the pressure inside the chamber from −20 to −60 mmHg with 10mmHg steps and returning to normal at the end. Blood pressure was measured and a trained echo-cardiographer performed echo measurements (EC-LVET) to create reference datasets. The PE system was used to measure heart rate, respiration and later extract ES-LVET throughout the test. Comparing the PE's measurements with the reference showed a correlation of 0.76 (p<0.001). Simple criteria for hypovolemia detection performed better based on LVET than on other vital signs. The current study's results support the ability to use the PE system under-the-mattress for early detection of hemorrhage.