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The heart rate, peripheral arterial blood pressure (BP), and respiration parameters were simultaneously recorded in adult subjects and young schoolchildren in two modes of testing: using a mask with airflow sensors that did not restrict air inflow but increased the pulmonary dead space and without the mask. It was demonstrated that wearing the mask was a functional test for the state of the cardiorespiratory system in both age groups; however, the responses of the children's and adults' bodies differed from each other, probably, because of the functional immaturity of the sympathetic component of the autonomic control. In adults, the parameters of the cardiovascular system did not change, except that the heart rate variability spectrum was redistributed toward an enhancement of the high-frequency component. In children, testing with the mask on decreased the systolic BP; increased the heart rate; and, as evidenced by the spectral characteristics of BP variability, activated the sympathetic nervous system.