About Pulse {#AboutPulse}
=========================

The Pulse Physiology Engine can be used as a standalone application or integrated with simulators, sensor interfaces, and models of all fidelities.
The platform includes a common data model for standard model and data definitions, a software interface for engine control, robust physics-based circuit and transport solvers, and a verification and validation suite. 
The architecture was specifically designed to reduce model development time and increase the usability of the engine in simulations by creating a modular, extensible definition for human physiology. 
Pulse provides the following benefits to its user community:

  - <b>Sound underlying physics:</b> Clear, accurate, precise first principles conservation equations
  - <b>Standardized data model:</b> Easily understandable, widely usable, ontologies and software interfaces
  - <b>Extensible:</b> Reusable, repeatable implementation to allow the addition of new capabilities and functionality
  - <b>Modular:</b> Interdependent, hierarchical models for varying fidelity and complexity
  - <b>Thorough documentation:</b> In-depth, referenced descriptions of physiology methodology and software design
  - <b>Cross-platform deployment:</b> Easy compilation on all standard operating systems (Windows, Mac, Linux, and ARM) and multiple languages (C++, C#, Java, Unity)
  - <b>Credible:</b> Computational models transparently derived from evidence-based literature and analyzed with extensive verification and validation tools
  - <b>Open:</b> Public repository managed by experienced Kitware team with a permissible Apache 2.0 license for multicenter and multidisciplinary collaborative development

Pulse is comprised of numerical models representing the different body systems, feedback mechanisms and interactions between the systems, PK/PD, and medical equipment. 
The major systems are modeled using zero-dimensional lumped-parameter circuit analogs (e.g., the cardiovascular circuit) with homeostatic feedback. 
The differential equations contained in each system are calculated through transient analysis with a shared dynamic time step. 
The numerical models currently execute with a time step of 20 ms, which can be reduced, as necessary, to ensure all physiology features of interest are captured, while maintaining real-time execution for the simulation.

Pulse has been developed through a combination of funding by many different government and private entities, and is a significantly improved and extended fork from the DoD-funded BioGears program.
The Pulse repository is maintained by the Kitware team that includes the original core BioGears creators (see the <a href="_f_a_q.html">FAQ</a>). 
Pulse has recently been incorporated into a number of commercial, research, and academic tools for medical simulation (see <a href="pulse-in-action.html">Pulse in action</a>)

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#### Validation Methodology

Models are validated using a combination of peer-reviewed publications and subject matter expertise. The validation process includes:

  - Defining key parameters for system validation
  - Performing literature reviews to gather published data in the form of waveforms, and max, min, and mean values
  - Using custom developed tools to compare data, perform analysis, and generate plots and tables of results

We validate each system at a compartment level (pressure, flow, volume, temperature, etc.). We also validate each action for a variety of system level parameters (heart rate, respiratory rate, tidal volume, blood pressure, etc.). 
We provide reports for each system in our <a href="_system_methodology.html">Methodology documentation.</a>

Below is a summary of our system and compartment level validation.

|	Key	|
|	---	|
|<span class="success"> Good agreement: correct trends or <10% deviation from expected </span>|
|<span class="warning"> Some deviation: correct trend and/or <30% deviation from expected </span>|
|<span class="danger"> Poor agreement: incorrect trends or >30% deviation from expected </span>|

@insert ./test_results/tables/SystemSummaryValidationTable.md

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<div class="container">
  <div class="row">
    <h3>What can I do with the physiology engine?</h3>
    <div class="row-content">
      <div class="patient-actions">
        <div class="action col-sm-4">
          <div class="action-content">
            Define patient parameters, such as height, weight, systolic and diastolic pressure.
          </div>
        </div>
        <div class="action col-sm-4">
          <div class="action-content">
            Simulate specific chronic and/or disease states via conditions.
          </div>
        </div>
        <div class="action col-sm-4">
          <div class="action-content">
            Modify external environmental conditions (weather, submerge in water, etc.)
          </div>
        </div>
        <div class="action col-sm-4">
          <div class="action-content">
            Apply various actions (acute insults/injuries, interventions, conscious breathing, exercise, etc.) to the patient.
          </div>
        </div>
        <div class="action col-sm-4">
          <div class="action-content">
            Have patient interact with equipment models, such as an Anesthesia and/or an ECG Machine as well as an Inhaler via actions.
          </div>
        </div>
        <div class="action col-sm-4">
          <div class="action-content">
            Integrate the engine into your applications.
          </div>
        </div>
      </div>
    </div> <!-- END .row-content -->
  </div> <!-- END .row -->
  <div class="row">
    <div class="row-content">
      <h4>Available data is defined within the engine in three major ways:</h4>
      <ol class="data-definitions row">
        <li class="definition col-sm-4">
          <span>
            System data (Cardiovascular, Respiratory, etc.) that is analogous to system vitals
            <span class="examples"><strong>Examples:</strong> heart rate, oxygen consumption, mean arterial pressure, etc.</span>
          </span>
        </li>
        <li class="definition col-sm-4">
          <span>
            Compartment data
            <ul>
              <li>
                Flow, pressure, and volume related to specific region of the body or component of equipment
                <span class="examples"><strong>Examples:</strong> Cerebral Blood Flow, Right Lung Volume, Right Heart Pressure</span>
              </li>
              <li>
                Substance specific data related to a specific part of the body or component of equipment
                <span class="examples"><strong>Examples:</strong> The Extracellular concentration of succinylcholine in the brain tissue, anesthesia machine gas inlet oxygen volume fraction</span>
              </li>
            </ul>
          </span>
        </li>
        <li class="definition col-sm-4">
          <span>
            Assessments formed at the level of a clinician's report, Intended to mimic test results
            <span class="examples"><strong>Examples:</strong> Pulmonary Function Test</span>
          </span>
        </li>
      </ol>
    </div>
  </div>
</div> <!-- END .container -->
