JP-2021523764-A5 -

Dates

Publication Date

20230522

Application Date

20190429

Description

The present invention relates to a method for determining cardiac stroke volume. Furthermore, the present invention relates to an apparatus for determining cardiac stroke volume and a computer-readable medium for performing the method. In particular, the present invention relates to a method, apparatus and computer-readable medium for determining cardiac stroke volume, also known as pulse contour stroke volume (PCSV), based on invasive or non-invasive arterial pulse contour analysis. Cardiac output (CO), defined as the amount of blood the heart pumps over time, is a crucial parameter for both the diagnosis and management of patients, particularly during surgery, in intensive care units and emergency departments. Cardiac output is typically measured in liters per minute. Cardiac output (CO) depends on the stroke volume, the amount of blood the heart pumps with each pulse or heartbeat, and the heart rate (HR), corresponding to the pulse rate (PR), which is the number of heartbeats within a given time. Traditionally, cardiac output, or stroke volume, has been measured using pulmonary artery thermodilution. In pulmonary artery thermodilution, a clearly defined small amount of cold fluid at a known temperature is injected into the right atrium, and the time-dependent progression of blood temperature is measured in the pulmonary artery after passing through the right ventricle. Given the known volume, specific gravity, and specific heat capacity of the injected fluid, as well as the specific gravity and specific heat capacity of the blood, the time-dependent progression of blood temperature allows for the calculation of cardiac output using the Stewart-Hamilton equation. (Mean) stroke volume is calculated by dividing cardiac output by heart rate. However, determining stroke volume using the highly invasive pulmonary artery thermodilution method is risky due to the potential for fatal complications, time-consuming, and rather expensive and impractical in operating rooms or emergency departments. To make cardiac output (CO) comparable between individuals, CO is typically normalized to body surface area, resulting in a cardiac index (Cl) in l/min/m² units. Several methods have traditionally existed for quantifying cardiac output (CO). The CO method, which is generally less invasive and less invasive, is the so-called pulse contour analysis. Here, specific characteristics of the arterial pressure waveform are used to estimate the pulse contour stroke volume (PCSV) for each pulse. A further method involves identifying the portion of the arterial pressure waveform corresponding to the left ventricle's blood ejection and estimating the PCSV from there. Here, the algorithm for determining or estimating the PCSV can take into account several parameters, including the pressure pulse wave region (i.e., systolic pressure region) during the ejection phase, arterial compliance, impedance, and total peripheral vascular resistance. The obtained PCSV estimates are based solely on blood pressure and time data and are therefore not yet related to or calibrated as stroke volume in ml of blood for individual patients, e.g., size and condition. As shown above regarding the determination of pulse contour stroke volume (PCSV), no invasive procedures are required. Therefore, any non-invasively measured arterial pulse contour- related data can be used. Even under emergency surgery, non-invasive pulse contours can be successfully determined, pressure values and pressure curves can be obtained to determine blood pressure, and in particular, time-dependent arterial pressure data or non-invasive tissue pressure pulse waveforms can be used to determine cardiac stroke volume. However, the present invention is also applicable to pulse contours measured in a less invasive manner. Even in such cases, improvements in risk, time, and cost are achieved compared to pulmonary artery thermodilution for determining stroke volume. WO2009/014420A1 describes a method for determining the stroke volume between pulses using arterial pressure data waveforms. However, it has been found that (mean) stroke volume (hereafter, pulse contour stroke volume (PCSV)) determined solely using time-dependent arterial pressure data only moderately agrees and correlates with (mean) stroke volume (hereafter, SVref) determined by reference methods, such as pulmonary artery and transpulmonary thermodilution or transesophageal echocardiography. PCSV can be calibrated initially or repeatedly using the SVref method, but this is an invasive procedure using thermodilution, which is always expensive and very time-consuming. For this reason, the application of such calibrated PCSV is impractical during surgery in the intensive care unit or emergency department. More importantly, changes in PCSV from existing methods show poor or moderate correlation, agreement, and fit with large percentage errors when compared to changes in SVref, providing strong evidence that such PCSV methods canno