Cardiac Output Case Study

Cardiac Output Case Study

Introduction

A sufficient cardiac output (CO), the volume of blood pumped by the heart each minute, is required to ensure adequate oxygenation to vital organs. Consequently, CO is often measured in critically-ill patients and during surgery. Many methods for assessing CO are highly invasive, such as placing a measurement device into the ascending aorta. It is possible to estimate CO from the arterial blood pressure (ABP) signal, which is often already measured in order to monitor BP in these patients. Therefore, methods for estimating CO from the ABP signal are commonly used. However, studies have shown that these methods can be imprecise, particularly during changes in cardiovascular state. Therefore, the aim of this case study is to assess the performance of two exemplary algorithms for estimating CO from the ABP signal, and to investigate how their performance is affected by changes in cardiovascular state.

The case study is described in this article.

Reproducing this case study

Requirements

You will need the following to reproduce the case study:

• The pwdb_data.mat file, which contains all of the data required for this case study. This file is available for download, and was produced when exporting the database.
• The Matlab ® script for this case study: co_case_study.m
• The Matlab ® script for setting the paths for post-processing: setup_paths_for_post_processing.m
• An installation of Matlab ®

Steps

To reproduce the case study:

1. Make a directory in which to store the data and analysis, which will be known as the storage folder. For instance, you might choose: C:/Desktop/PW_studies/
2. Obtain the pwdb_data.mat file by either: (i) downloading it (see links here); or (ii) generating it yourself by reproducing the database (NB: this will take a long time).
3. Store pwdb_data.mat in a subdirectory of the storage folder named pwdb_#/exported_data/, where # is the number of the database. For instance, this directory might be: C:/Desktop/PW_studies/pwdb_1/exported_data/
4. (This can be skipped if already done previously) Open the setup_paths_for_post_processing.m, and adjust PATHS.storage_folder to the path of the storage folder (such as C:/Desktop/PW_studies/).
5. Open the co_case_study.m script in Matlab ®.
6. Run the script, specifying the number of the PWDB to be analysed (e.g. number 1). The script can be run using a command such as:

co_case_study(1);

7. The plots showing the results of the case study should be saved in C:/Desktop/PW_studies/pwdb_1/case_studies/ . The following plots are relevant to this case study: (i) CO_analysis_corr_liljestrand, and (ii) CO_analysis_corr_rms.