The central mechanisms of fatal sleep apnea have not yet been established.  One of the solutions to this clinical problem is the timely identification of patients suffering from sleep apnea deregulation of breathing and blood circulation.  For this purpose it is reasonable to apply in clinical practice the test of "return" breathing.

When conducting the test of "return" breathing, the patient with a clip on the nose makes voluntary breathing movements through the mouthpiece in a closed system consisting of corrugated tubes and an elastic tank of about 50 liters filled with oxygen.  Sensors record blood pressure and pulse rate, the patient's breathing movements, and the oxygen and carbon dioxide content of this system. The high oxygen content in the inhaled air ensures blockade of the carotid body chemoreceptors. With each exhalation the patient increases the content of carbon dioxide in the closed system, which is a natural activator of medullary chemoreceptors. When medullary chemoreceptor function is impaired, the increase in pulmonary ventilation is drastically reduced and accompanied by cardiac arrhythmias.  In patients with established absence of pulmonary ventilation gain during hypercapnia formation there is a high probability of fatal sleep apnea development.

Thus, the fundamental evidence of the key function of medullary chemoreceptors in the initiation of respiratory rhythm and circulatory control is a strong argument for the reasonable prevention of fatal respiratory arrest and cardiac arrhythmias during sleep apnea in patients suffering from prolonged sleep apnea.