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CardioQ-ODM is designed to allow clinicians to guide fluid and drug administration during surgery and critical care

Guided fluid and drug administration during surgery and critical care

Now succeeded by ODM+, ODM (also known as CardioQ-ODM) enables hospital clinicians to deliver accurate, real-time, guided Intraoperative Fluid Management (IOFM). It is an important aid in avoiding the dangers of reduced oxygen delivery.

The ODM monitor is highly responsive in tracking changes in Stroke Volume and Cardiac Output during surgical intervention and in the critical care setting. Only oesophageal Doppler has been shown to have the precision to drive the 10% Stroke Volume Optimisation algorithm, widely acknowledged as the basis for IOFM.

Uniquely, oesophageal Doppler monitoring (ODM) directly measures blood flow in the central circulation. It is highly sensitive to changes in flow and measures them immediately and accurately. The system offers a high degree of precision (low repeatability error), which allows it to recognise the small changes in Stroke Volume, which is the basis of published Stroke Volume Optimisation protocols.

Extensive clinical trials have demonstrated that with direct measurement of blood flow, clinicians can correct individual patient circulating blood volume. It has been reported that 70% of patients have hypovolaemia (low blood volume) when they are prepared for surgery. This hypovolaemia can result from the combined effects of poor diet, dehydration, preoperative fasting, and the the vasodilatory effects of anaesthetic agents. It can be compounded by blood loss during the surgical procedure.

ODM guided fluid management is a cornerstone of Enhanced Recovery, delivering better quality and more cost-effective care as it means patients recover from their surgery faster and leave hospital sooner and in better health than they otherwise would.

Additional information

ODM Product Brochure

View the full range of mounting arms available from GCX which attach the monitor to anaesthesia stations, here.

For further information relating to this product or for any sales enquires please contact Customer Services quoting part code 9051-7103.

 

How the ODM works

The CardioQ-ODM is unique in its ability to directly measure central blood flow by way of a minimally invasive disposable probe. The probe is placed in the patient’s oesophagus and uses Doppler ultrasound to measure the velocity of blood flow in the adjacent aorta, hence the name of the technology which is abbreviated to ODM. The oesophagus 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.

Access the Training Workbook for a deeper understanding of how to use this technology.

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 farther 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 ODM 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 centre 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).

Technical Review

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

  • A short history of the development of oesophageal Doppler monitoring
  • How oesophageal 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 Intraoperative Fluid Management (IOFM)
  • Results of clinical application
  • Limitations of use

 

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 pulmonary artery catheter (PAC) is regarded as the ‘gold standard’ in this respect but is known to be no better than ±20%.

For clinical use this is regarded as acceptable and within the clinical norm of ±30%. The basic measurement of Stroke Distance (SD) by ODM has an accuracy on a single waveform of ±3%. The conversion to SV through the nomogram results in a greater error, similar to that of a PAC.

However when using a device to guide IOFM in a 10% SVO protocol it is its precision that matters most of all, that is the ability to detect change in sequential measurements, in this case the effect of a fluid challenge on SD or SV. Precision is the ability to measure the same result repeatedly with minimal error.

Prof. Singer established that the error of repeatability of measuring SD for the ODM 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 haemodynamic 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).

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

For further information on Accuracy and Precision, please contact clinical@deltexmedical.com

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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 CardioQ-ODM monitor uses Doppler ultrasound technology to directly measure a patient’s central vascular blood flow velocity to deliver the following flow parameters:

Flow Based Parameters

Stroke Distance (SD)

Stroke Distance is a Doppler flow based parameter only. SD is simply the distance the blood ejected by the left ventricle travels down the aorta every beat. It is measured in centimeters per second. If the aorta approximates to a cylindrical pipe then the SD can be represented a series of cylinders of blood moving down the aorta as each pulse of the left ventricle propels them into the bodies arterial system.

Stroke Distance (SD)

Stroke Distance (SD)

The CardioQ-ODM is distinct from other ODM devices in possessing the ability to calculate Stroke Volume and so Cardiac Output from its own patient nomogram. The patient nomogram was created as a result of research by Prof. Mervyn Singer. The patient nomogram is a calibration of Stroke Distance against the total Cardiac Output as measured by a Pulmonary Artery Catheter (PAC) for patients of both genders and various races, ages, weights and heights.

SD is the basic parameter for IOFM and Stroke Volume (SV) is automatically calculated by the monitor. The patient’s age, weight and height are input during the monitor set up. This information accesses the nomogram which effectively provides the dynamic aortic root diameter.

SV = SD x Aortic Root Diameter

As a result ODM has been found to be equivalent in terms of accuracy to a PAC. However it is the precision of ODM in tracking change that is key to recognising how and why ODM guides Stroke Volume Optimisation (SVO) so effectively which has resulted in an unparalleled evidence base.

Stroke Volume (SV)

Stroke Volume is the amount of blood in millilitres pumped from the human heart every heart beat. It is the volume ejected from the left ventricle due to the contraction of the heart muscle which compresses the left ventricle. Stroke Volume can be calculated as a Doppler Flow Based Parameter by CardioQ-ODM and CardioQ-ODM+.

The CardioQ-ODM calculates Stroke Volume by multiplying the Stroke Distance by a constant accessed from the built in patient nomogram. The patient nomogram was created as a result of research by Prof. Mervyn Singer. The patient nomogram is a calibration of Stroke Distance against the total Cardiac Output as measured by a Pulmonary Artery Catheter (PAC) for patients of various ages, weights and heights. The calibration factor is functionally the dynamic aortic root diameter for typical patient of the input age, weight and height.

Stroke Volume

Stroke Volume

Heart Rate (HR)

Heart Rate is displayed on the CardioQ-ODM and CardioQ-ODM+ from Doppler based measurement. From the Doppler the heart beats per minute is calculated from the analysed waveform.

The monitor updates the heart rate display after each calculation period depending on the number of cycles set.

Cardiac Output (CO)

The CardioQ-ODM and CardioQ-ODM+ can calculate Cardiac Output in Doppler flow mode.

Cardiac Output is the volume of blood being pumped by the left ventricle in the time interval of one minute. The units of Cardiac Output are litres per minute (l/min). The CardioQ-ODM calculates the Cardiac Output based on the setting of ‘cycles for calculation’. If set at ‘every beat’ the individual Stroke Volume in millilitres of each beat is multiplied by the Heart Rate at that time and is displayed in litres per minute.

Cardiac Output = Stroke Volume x Heart Rate

Peak Velocity (PV)

Peak Velocity is a Doppler only parameter and is available on both the CardioQ-ODM and CardioQ-ODM+ as the maximal velocity of the blood.

PV is an indicator of contractility and typical values change with age. The peak velocity of 20 year old may be 90 – 120 cm/s whereas at age 90 it may only be 30 – 60 cm/s. Thus a PV markedly below the typical expected value may be an indicator of increased afterload or decreased cardiac function. A higher than normal PV may be indicative of decreased afterload.

Minute Distance (MD)

Minute Distance is a Doppler only parameter and is available on both the CardioQ-ODM and CardioQ-ODM+. MD is simply the distance blood moves in one minute down the aorta.

Minute Distance = Stroke Distance x Heart Rate

Peak Velocity

Peak Velocity

Flow Time corrected (FTc)

Flow Time corrected is a Doppler only parameter and is available on both the CardioQ-ODM and CardioQ-ODM+. Flow Time (FT) is the duration of time of the flow from the left ventricle during systole.  Flow Time corrected (FTc) is Flow Time duration of blood flow in the aorta normalised to 60 beats/min using Bazett’s equation.

Corrected Flow Time

Corrected Flow Time

Typically FTc is one third of the cardiac cycle. When standardised to 60 beats/min one cycle is one second. FTc is then 0.33 seconds or 333 milliseconds.

Thus typical values for normally hydrated resting healthy individuals is 330 – 360 milliseconds. This can be used as an indicator of hypovolaemia.

FTc is inversely related to afterload/resistance and the most common cause of an increased afterload/resistance is hypovolaemia.  Other causes of increased afterload/resistance should be considered.  High FTc is usually seen in low afterload/resistance states such as the vasoactive effects of drugs and sepsis.

Flow Time to peak (FTp)

Flow Time to peak is a Doppler only parameter and is available on both the CardioQ-ODM and CardioQ-ODM+. Flow Time to peak is the time in milliseconds from the start of systole to the point of peak velocity. Flow Time to peak is when combined with Peak Velocity and Mean Acceleration, a parameter for evaluating cardiac contractility and the effects of preload and afterload.

Flow Time to Peak (FTp)

Flow Time to Peak (FTp)

Cardiac Index (CI)

The CardioQ-ODM and CardioQ-ODM+ can calculate Cardiac Index in Doppler flow mode.

Cardiac Index relates the Cardiac Output to body surface area (BSA), thus relating heart performance to the size of the individual. The unit of measurement is litres per minute per square metre (l/min/m2).

Cardiac Index = Cardiac Output/Body Surface Area

Stroke Volume Index (SVI)

Stroke Volume Index is the amount of blood in millilitres pumped from the human heart every heart beat indexed for body surface area. Stroke Volume Index can be calculated as a Doppler Flow Based Parameter by CardioQ-ODM and CardioQ-ODM+.

Stroke Volume Index relates the Stroke Volume to body surface area (BSA), thus relating heart performance to the size of the individual. The unit of measurement is millilitres per square metre (ml/m2).

Stroke Volume Index = Stroke Volume/Body Surface

Stroke Volume Variation (SVV)

The CardioQ-ODM and CardioQ-ODM+ can calculate Stroke Volume Variation in Doppler flow.

Stroke Volume Variation is widely considered as a useful indicator of fluid responsiveness. The mechanism of generation of this parameter relates to the observation of variations in left ventricular ejection volumes (Stroke Volume).  It has been shown that return blood flow through the thorax is affected by the positive pressure of the ventilator.  As the ventilator cycles it creates varying periods of higher and lower flow. These fluctuations traverse the lung and are manifest as variations in stroke volume of the heart.

These variations can be detected as variations in flow and pressure. The CardioQ-ODM uses these variations in flow to calculate the percentage variation between the maximum stroke volume and the minimum.

The limitations of this parameter is that the patient must meet the following criteria: Fully mechanically ventilated, sinus rhythm, tidal volume ≥ 7-8 mL/kg and higher tidal volumes elicit higher variations. Increasing PEEP will result in higher variations. HR: Respiratory rate ratio ≥4. Changes in lung or chest compliance, or patient position and right ventricular dysfunction or  abdominal insufflation may affect readings.

Caution is advised and clinicians need to be aware of the particular ‘cut off’ or ‘grey zone’ threshold values for the technology being used and the limitations described in the literature.

Stroke Distance Variation (SDV)

Stroke Distance Variation is a linear mode only parameter and is an indicator of fluid responsiveness when patients are outside the nomogram range of the CardioQ-ODM (typically in bariatric surgery).

The mechanism of generation of this parameter is identical to that of Stroke Volume Variation and relates to the observation of variations in left ventricular ejection volumes (Stroke Volume) due to variations in ejection volumes.

The limitations of this parameter is that the patient must meet the following criteria: Fully mechanically ventilated, sinus rhythm, tidal volume ≥ 7-8 mL/kg and higher tidal volumes elicit higher variations. Increasing PEEP will result in higher variations. HR: Respiratory rate ratio ≥4. Changes in lung or chest compliance, or patient position and right ventricular dysfunction or  abdominal insufflation may affect readings.

Systemic Vascular Resistance (SVR)

Systemic Vascular Resistance can be calculated as a Doppler Flow Based Parameter.

Systemic Vascular Resistance is the resistance to blood flow due to the peripheral vascular system. The formula used in the CardioQ-ODM is as follows:

SVR = 80 (MAP-CVP)
CO

Where MAP is the Mean Arterial Pressure, CVP is the Central Venous Pressure and CO the Cardiac Output.

The Cardiac Output is automatically provided from the flow readings calculated from Stroke Volume and Heart Rate. The user is required to input the MAP and CVP from other sources. The monitor then provides the measurement continuously as the CO is derived.

Systemic Vascular Resistance Index can be calculated as a Doppler Flow Based Parameter by CardioQ-ODM and CardioQ-ODM+.

Systemic Vascular Resistance Index (SVRI)

Systemic Vascular Resistance Index is the resistance to blood flow due to the peripheral vascular system indexed for patient body size. The formula uses the Body Surface Area as calculated from the input weight and height is as follows:

SVRI = SVR x BSA

Where BSA is the Body Surface Area.

The SVRI is automatically updated as SVR changes with CO calculated from the flow readings calculated from Stroke Volume and Heart Rate.

Delivered Oxygen (DO2)

Delivered Oxygen can be calculated as a Doppler Flow Based Parameter by CardioQ-ODM and CardioQ-ODM+.

Delivered Oxygen is the amount of oxygen in the blood delivered to the body’s tissues. The CardioQ-ODM and CardioQ-ODM+ can calculate this parameter but require the user to input measurements of haemoglobin concentration and the saturated oxygen concentration. The Cardiac Output as calculated by the monitor is automatically updated as DO2 changes with CO calculated from the flow readings, the formula used is as follows:

DO2 = 1.34 x Hb x SaO2 x CO

Where Hb is the concentration of haemoglobin, SaO2 is the saturation of haemoglobin and the amount of dissolved oxygen all multiplied by the Cardiac Output (CO).

Delivered Oxygen Index (DO2I)

Delivered Oxygen Index can be calculated as a Doppler Flow Based Parameter by CardioQ-ODM and CardioQ-ODM+.

Delivered Oxygen Index is the amount of oxygen in the blood delivered to the bodies tissues indexed for patient body size. The CardioQ-ODM and CardioQ-ODM+ can calculate this parameter but require the user to input measurements of haemoglobin concentration (Hb) and the saturated oxygen concentration (SaO2). The Body Surface Area (BSA) is calculated by the monitor from the input patient weight and height and this used to automatically updated as DO2 changes with CO calculated from the flow readings, the formula used is as follows:

DO2I = DO2
BSA

 

Technical Specification

Below is the technical specification for the ODM monitor:

ODM Specification

Software Upgrades

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