We are convinced that the optimized CO-rebreathing method makes a significant contribution to both the clinical and sports medicine fields.

Having exact knowledge about the amount of hemoglobin circulating and the blood volume in a human body improves vital diagnoses thereby enhancing therapy concepts. In the field of sports, competitive and amateur athletes gain useful knowledge that can be used to record completely new dimensions in the assessment of performance and training control.

Therefore, we have made it our task to take the CO-rebreathing method from basic science into the fields of practical medicine and training science. To do so, we have simplified the established method so that it is suitable for routine measurement in clinical and sports medicine.

History of the company

Blood tec was established in 2005 by Prof. Dr. Walter Schmidt and PD Dr. Nicole Prommer. Initially, the team carried out blood volume testing as part of a service offered to elite athletes and top sports clubs. However, demand quickly exceeded the companies’ capacities. It became necessary to design the testing procedure so that it could be carried out by other experienced scientists. Today, the method is established in over 100 scientific institutions worldwide (see map below) and Blood tec leads the world as the most experienced and exclusive provider of this test method. Blood tec has been awarded various innovation prizes. Since Prof. Schmidt and Dr. Prommer, the inventors, place great importance on the CO-rebreathing method being applied precisely to achieve results that are comparable worldwide, practical training and standardized evaluation software are always associated with the acquisition of equipment.

blood tec worldwide

The specialists of CO-rebreathing

Prof. Dr. Walter Schmidt is an exercise physiologist who focuses on cardiovascular physiology and pathophysiology.

During his 15 years of scientific work at Hannover Medical School, he received his doctoral degree and habilitation in Physiology.

In 1995, after two years at the Free University of Berlin, Prof. Walter Schmidt became head of the Sports Medicine and Sports Physiology Department at the University of Bayreuth.

An outstanding scientific achievement was collaborating with Dr. Prommer
and developing the “optimized CO-rebreathing method” for determining
Hbmass and total blood volume. Based on this technique, Prof. Walter Schmidt has carried out extensive studies on endurance performance, talent finding in endurance sports, acute and chronic altitude adaptation, and the detection of blood manipulations in sports.

In recent years, he has focused on clinical questions regarding the diagnosis of dilutional anemia in heart and liver patients as well as the diagnosis and therapy of polycythemia patients.

Within the framework of Blood tec, Prof. Walter Schmidt is responsible for all scientific matters.


PD Dr. Nicole Prommer started her scientific career at the Department of Sports Medicine and Sports Physiology at the University of Bayreuth in 2000. Her first experience with blood volume testing was during an altitude study with the Chilean military and Aymara Indians at 3500m.

During this time, the idea arose to optimize the CO-rebreathing method for routine use. During her doctorate (Ph.D.) and habilitation (postdoc), her focus was on developing the optimized CO-rebreathing method and applying it to a wide variety of questions.

She was soon awarded various prizes as an expert in hemoglobin measurements and quickly shared the method with scientific institutions around the world.

After completing her habilitation, in 2012, Dr. Nicole Prommer switched to the Department of Sports Medicine and Sports Cardiology at the Technical University of Munich.In 2014, she left the technical university to devote herself entirely to Blood tec.

Having a university degree in sports management, Dr. Nicole Prommer was predestined to take care of all Blood tec business issues.

In addition to her work for Blood tec, Dr. Prommer is the owner of the “Praxis für Faszientherapie und Bowen Therapie” (practice for fascia and bowen therapy) near Munich.


Prospects and research

Until now, active participation of the patient or test subject was a prerequisite for determining human blood volume and Hb-mass. However, in clinical medicine, knowledge of both parameters is of utmost importance, even for ventilated patients. We, therefore, modified the existing CO-rebreathing method so that a single inhalation of CO allows both human blood volume and Hbmass to be precisely measured. The new method has already been successfully tested in healthy volunteers (Krehl et al., 2020). The next step is validating the method for ventilated patients.

But also in spontaneous breathing patients the CO-rebreathing method might have to be re-validated depending on the field of application. Wachsmuth et al. (2019) showed that a slight modification of the method is necessary in patients suffering from polycythemia vera.


Krehl LM, Plumb JOM, Wachsmuth NB, Haupt S, Kumar SB, Otto JM, Schierbauer J, Grocott MPW, Montgomery HE, Schmidt WFJ. A carbon monoxide ‘single breath’ method to measure total haemoglobin mass: a feasibility study. Exp Physiol. 2020 Dec 28. doi: 10.1113/EP089076.

Wachsmuth N, Soria R, Jimenez J, Schmidt W. Modification of the CO-rebreathing method to determine haemoglobin mass and blood volume in patients suffering from chronic mountain sickness. Exp Physiol. 2019 Dec;104(12):1819-1828. doi: 10.1113/EP087870.