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Only the CardioQ-EDM+ has the precision and responsiveness to guide the clinically proven >10% change Stroke Volume Optimization (SVO).

The clinical benefits of the EDM+ stem directly from the use of a low frequency ultrasound sound signal to measure blood flow directly in the central circulation.

The EDM+ is the world’s first hemodynamic monitoring system to measure both flow and pressure directly.

An exciting new upgrade to the proven Doppler technology, the EDM+ combines Doppler measurement of blood flow with Pulse Pressure Waveform Analysis (PPWA). This provides users with:

  • “Flow Monitoring Mode” : to guide intervention – with proven and highly senstive measurement of flow
  • “Pressure Monitoring Mode” : for extendended continuous monitoring – using proven Doppler for the simplest calibration yet devised

Previous hemodynamic monitors have either been ideal intervention devices, fast precise responsive flow based measurement but non-continuous, or less responsive pressure based continuous monitors requiring complex calibration and frequent recalibration to be effective. In bringing together simple, minimally invasive esophageal Doppler monitoring (EDM) flow based technology with a PPWA system, the EDM+ provides an unparalleled range of functional hemodynamic parameters. Patients can be continuously monitored for extended periods between intervention and calibration episodes. Designed for surgical and intensive care applications, Deltex Medical has chosen the most stable and extensively researched PPWA algorithm currently available.

View the EDM+ Product Brochure

EDM+ Technical Specification

A technical specification for the EDM+ monitor can be accessed here

Monitor Mounting Arms

There are a range of mounting arms available from GCX which attach the monitor to anesthesia stations.  You can view the full range available here GCX Mounting Solutions

Interface Cables

When making a connection to the EDM+ to the High End Monitor (HEM), an interface cable is required.  Deltex Medical provide a Blood Pressure (ABP) Cable Guide which is available here; Cable Guide

For further information relating to probes or for any sales enquires please call (864)- 527-5913 or email the Corporate Office


In surgery the CardioQ-EDM+ offers the following advantages:
  • Only surgical CO monitor offering both EDM & PPWA
  • Ease of PPWA calibration and recalibration
  • Continuous monitor ‘bridge’ during diathermy episodes
  • ‘Bridge’ in surgical cases where esophagus is displaced or removed
  • Only device able to guide 10% SVO (Doppler guided)
  • Offers fluid responsiveness parameters including:
    • Corrected flow time (FTc)
    • Stroke volume variation (SVV –  flow and pressure)
    • Pulse pressure variation (PPV)
  • Provides post operative monitoring for 6 to12 hrs in awake patients in recovery/ICU (dependent on probe type)
In the Intensive Care Unit CardioQ-EDM+ offers the following advantages:
  • Only critical care monitor offering both EDM & PPWA
  • Ease of PPWA calibration and recalibration
  • Continuous monitor capability
  • Only device able to guide 10% SVO (Doppler)
  • Offers fluid responsiveness parameters including:
    • Corrected flow time (FTc)
    • Stroke volume variation (SVV flow and pressure)
    • Pulse pressure variation (PPV)
  • Offers Cardiac power output (CPO) and Cardiac power index (CPI), combined flow and pressure parameters (German regulations indicate a benefit in managing and monitoring patients at risk of Cardiogenic shock)

How it Works

How the EDM works

The EDM is unique in its ability to directly measure central blood flow with a minimally invasive disposable probe. The probe is placed in the patient’s esophagus and uses Doppler ultrasound to measure the velocity of blood flow in the descending aorta. The esophagus is easy to access for placement of the ultrasound probe as it is close to the patient’s aorta at the level of T5/T6.

Ultrasound explained

Ultrasound emitted by the probe is directed into the aortic blood flow at angle of 45o. The ultrasound will be reflected by the blood’s red cells. As the blood is moving away from the probe tip each reflected wave is emitted from a position further from the observer than the previous wave, so the arrival time between successive waves is increased, reducing the frequency. The distance between successive wave fronts is increased, so the waves “spread out”. The EDM receives the reflected frequency shifted wave and compares its frequency to that of the transmitted wave. The result of this calculation is that the velocity of the blood can be measured during each cardiac cycle.

Ultrasound Waveform

The ultrasound waveform is displayed in red and white with a dark center and it is encapsulated by a green line, which follows the maximal velocity at that point in time. The monitor places three arrows on the screen; the first at the start of systole (on the baseline); the second at the peak velocity (at the top of the waveform) and the third at the end of systole (on the baseline).


The EDM+ directly measures central blood flow in the same way as the EDM. In addition, the device also takes the standard Arterial Blood Pressure (ABP) measurement and calculates a range of Pressure Based Parameters. It is unique in that it can take the Cardiac Output as measured by Doppler flow to calibrate a Pulse Pressure Waveform Analysis (PPWA) algorithm. The PPWA algorithm provides secondary pressure based measures of Stroke Volume (SV) and Cardiac Output (CO) as well as new flow and pressure combined parameters.

By combining both flow and pressure based measurements, the EDM+ allows the user to reduce the inherent weaknesses of PPWA with a quick and simple calibration and recalibration from the Doppler flow based measurements of CO.

For further information relating to probes or for any sales inquiries please call 864-527-5913 or email our Corporate Office

Accuracy & Precision


Many publications cite device performance in terms of accuracy. Accuracy in this context is simply the ability to measure the actual Stroke Volume (SV) in millilitres.

The basic measurement of Stroke Distance (SD) by EDM has an accuracy on a single waveform of ±3%. The conversion of this extremely accurate SD uses a nomogram (a constant using age, weight and height) to calculate a more familiar parameter of SV.

Only Doppler has the precision to guide a 10% SV optimization protocol. EDM has the ability to detect change in sequential measurements. In this case the effect of a small fluid challenge on SD or SV. Precision is the ability to measure the same result repeatedly with minimal error.


EDM’s strength is in its precision, using Doppler to measure flow directly at the source, the decending aorta.

The precision of a technology dictates its ability to guide fluid management. The 10% SV change algorithm used to optimize SV is specific to the EDM and is evidence-based. Other technologies that are less precise may not be as effective in guiding fluid management based on this algorithm.

Prof. Singer established that the error of repeatability of measuring SD for the EDM was 3.8% [1]. For an individual patient the diameter of the aorta will be a constant thus the SV precision will be equal to the known error for SD. [SV = SD x Aortic Root Diameter (from patient nomogram)].

This precision/repeatability error can then be used to determine the least significant change in SD/SV required to ensure confidence in measuring a real hemodynamic change and not just measurement error. With its calculated error of 3.8%, the user can be 99% confident that a measured change in SD/SV of >10% is real (this is based on 99% of normally distributed data points falling within 2.5 standard deviations of the mean).


1Singer, M., J. Clarke, and E.D. Bennett, Continuous hemodynamic monitoring by esophageal Doppler. Crit Care Med, 1989. 17(5): p. 447-52

Flow Parameters

The EDM monitor uses Doppler ultrasound technology to directly measure a patient’s central vascular blood flow velocity to deliver the following flow based parameters:

Flow Based Parameters

Pressure Parameters

The EDM+ uses the proven Doppler technology to control both its Flow Monitoring Mode of use and the calibration of the chosen Pulse Pressure Waveform Analysis (PPWA) algorithm for its Pressure Monitoring Mode of cardiac output (CO). Flow based parameters are also available on the EDM+ monitor.

The direct flow Doppler EDM, is preferred for guidance of intervention with fluid and drugs. EDM can do this effectively in the hemodynamically challenging environment of the Operating Theatre, where anesthesia and surgery result in rapid and frequent changes in compliance. Pressure based technologies are useful in stable postoperative patients but are limited in their ability to guide interventional treatment.  A combination of both technologies, EDM+ is the best of both worlds.

Pressure Based Parameters

Arterial Lines

This section highlights the importance of maintaining and calibrating an Arterial Line

Incorrect setup of pressure readings can lead to inappropriate treatment.

Prior to any transduced pressure readings and then subsequent use with an EDM+, it is essential that the transducer has been:

Levelled to the phlebostatic axis to eliminate the effects of hydrostatic pressure on the readings:

  • The phlebostatic axis is on the 4th intercostal space along the mid axilla line.
  • The phleblostatic axis is relevant for supine and up to 60 degrees of head-up tilt.
  • The transducer should not be levelled to the site of arterial catheter access.
  • If the transducer has not been levelled to the phlebostatic axis, pressure readings will be either falsely high or falsely low.
  • It is not suitable for an abnormal shaped thorax.
  • Levelling should be done at every handover, prior to pressure and EDM+ readings and at any time where there is doubt about the readings. The literature suggests that for consistent readings of pressure trends, the patient bed should be at the same angle each time.

Zeroed to eliminate the effects of atmospheric pressure on the readings. It is sometimes known as calibration:

  • The transducer has to read zero when there is no pressure against it.
  • It is described as being similar to zeroing a set of scales before weighing.
  • This should be done at every handover, prior to pressure and EDM+ readings, if the line is disconnected from the patient monitor and at any time where there is doubt about the readings.

Tested for damping:

  • Damping in the pressure line system acts as shock absorber (like a car suspension).
  • In order to test the system dynamics, the user should carry out the Square Test.
    • The Square Test assesses how fast the system vibrates in response to a pressure signal.
    • Allows the transducer to ‘feel’ some of the 300mmHg in the pressure bag.
    • The user should squeeze the flush valve on the transducer for a few seconds and then let go.
      • Waveform should rise sharply, plateau and drop off sharply when released (Figure 1).

Inaccurate damping can lead to inappropriate treatment:

Overdamping (This is defined when the oscillations following the downstroke are sluggish and can underestimate systolic pressure or overestimate diastolic pressure) Causes include:

  • Loose connections
  • Air bubbles
  • Kinks
  • Blood clots
  • Arterial spasm
  • Narrow tubing

Underdamping (This is defined when the oscillations are too pronounced and can lead to a false high systolic or a false low diastolic pressure):

  • Catheter whip or artefact
  • Stiff non-compliant tubing
  • Hypothermia
  • Tachycardia or dysrhythmia

Technical Review

The Technical Review US is ideal for those seeking a deeper understanding of the EDM technology and contains information on:

  • A short history of the development of esophageal Doppler monitoring
  • How esophageal Doppler measures blood flow velocity in the aorta
  • Comparative results compared to pulmonary artery catheter data
  • Accuracy of measurement
  • Probe placement and focussing
  • Waveform and parameter explanation
  • A summary of Fluid Management
  • Results of clinical application
  • Limitations of use