August 2020


Let’s be honest: extremely important. That is the reason we are so excited that we are providing with our IRt/c temperature sensors  and especially our heat balance principle, a precious solution for ECMO systems.

Extracorporeal membrane oxygenation (ECMO) is a technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate amount of gas exchange or perfusion to sustain life. The technology for ECMO is largely derived from cardiopulmonary bypass, which provides shorter-term support with arrested native circulation. ECMO is used to support patients with the acute viral pneumonia associated with COVID-19 in cases where artificial ventilation is not sufficient to sustain blood oxygenation levels.

Blood is oxygenated outside of the body. When oxygenated blood is infused in the patient again, it needs to be warmed to 37°C (98.6°F) within a strict tolerance, usually ± 0,5°C (0.9°F). Otherwise there is a risk of hyper- or hypothermia.

Exergen's proprietary IR sensor technology is ideally suited to measure fluid temperatures accurately and reliably. For this we use our unique, patented Heat Balance technology as it measures fluid temperature inside of devices by measuring both the tubing surface and ambient temperature, then calculating the internal temperature necessary to maintain the heat balance. In highly critical medical applications like ECMO, this ensures patient safety as it provides a method to measure fluid temperatures non-invasively. A convenient clip head provides a reproducible mounting location for the sensor and can be quickly removed from used tubing and attached to new tubing.

We can take you one step further regarding the technology behind this unique approach. The Heat Balance (HB) Series of IRt/c infrared thermocouples have the ability to measure the internal temperature of the target material, non-invasively, by employing a patented heat balance technique. A typical application in medical equipment is monitoring or controlling the temperature of fluid transported through disposable tubing when warming or cooling:

- ECMO systems

- Transfusion systems

- IV warming systems

- Dialysis systems

- Cardio-pulmonary bypass systems

- Blood analyzers

Principles of Operation

Fluid at temperature Tf flowing in tubing transfers heat via convection through thermal resistance Rf to the tubing inside surface, which in turn conducts heat to the tubing external surface through thermal resistance Rt, which then transfers to the environment via radiation and convection thermal resistance Ro. The temperatures of the wetted surface of the tubing, outside surface of the tubing, and the local ambient are given by Tw, Ts, and Ta, respectively.

Employing the method of thermal analysis with electrical analogs: current = heat flow, and voltage = temperature, the heat transfer equation may be written as follows:

The IRt/c-HB Series measures both Ts and Ta, and solves this equation automatically for fluid temperature Tf, providing a highly accurate method of monitoring or controlling the temperature of interest.

View the technote here

If you would like to know more about Exergen's heat balance technology, please feel free to contact me.

Bram Stelt

CEO Exergen Global