The CO-rebreathing technique for measuring total blood volume and hemoglobin mass is safe to perform in stable coronary artery disease patients having completed cardiac rehabilitation. Trine Karlsen and colleagues show this in a resent study ”Safety of the CO-Rebreathing Method in Patients with Coronary Artery Disease”, published in the Medicine and Science in Sports and Exercise Journal.
“The aim of the study was to investigate the use of this methodology in stable coronary artery disease patients to allow for an implementation of the methodology in this patient group”, Karlsen says. Knowledge of total blood volume and absolute hemoglobin mass is vital when evaluating cardiovascular physiology and function, as well as physical activity performance.
The improved CO-rebreathing methodology, developed by Schmidt and Prommer in 2005, is commonly used in athletes and healthy individuals, but has been used to a limited degree ischemic patient populations. This is due to the 6 % reduction in oxygen bound to hemoglobin in the red blood cells. The methodology is highly accurate, and is currently the least invasive methodology available.
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Eighteen stable coronary artery disease patients were studied with the CO-rebreathing test to detect total blood- and plasma volume, erythrocyte volume and total hemoglobin mass. Heart function, blood pressure and heart rhythm were closely followed for two hours after the procedure. Twenty-four hours after the CO-test, high sensitive troponin-T was measured.
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Patients were in sinus rhythm during the 2-h observation period. There were no ST- or T-wave changes. Patients had a low numbers of premature beats and normal rate variability. Systolic and diastolic blood pressure gradually decreased as the patients were resting during the observation period. Troponin-T was below the 99th percentile for all the participants 24 h after the test. The paper gives a detailed description of the patient demographics, as the results of the study are limited to the patient population.
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The authors concluded that the CO-rebreathing test performed according to the protocol was safe to perform in stable coronary artery disease patients when the percentage of CO bound to hemoglobin increased to approximately 6%.
Trine Karlsen, Researcher at CERG
Cardiac Exercise Research Group 