Measuring Cardiac Output Using Point-of-Care Ultrasound

Calculating cardiac output via bedside ultrasound requires the integration of two primary variables: stroke volume and heart rate. Determining stroke volume involves measuring the left ventricular outflow tract (LVOT) diameter and the velocity time integral (VTI). The LVOT diameter is measured in the parasternal long axis view during mid-systole, while the VTI is obtained through an apical five-chamber view using pulse wave Doppler. This VTI represents the length of the blood column moving across the aortic valve, with a normal range typically falling between 18 and 25 centimeters. Heart rate is simultaneously calculated by measuring the distance between E-wave peaks on the Doppler waveform. Combining these measurements allows clinicians to visualize blood flow as a cylinder and calculate the total volume of blood ejected per minute. This process provides a non-invasive method for hemodynamic monitoring in clinical settings, utilizing phased array transducers to assess patient status accurately.