P1476

         Physiol Res 1991;40(3):257-60

        Fixed breathing frequency decreases end-tidal PCO2 in humans.

        Vízek M, Šmejkal V, Paleček F.

        Institute of Pathophysiology, 2nd Medical Faculty, Charles University,

        Prague.

        We tested the effect of a fixed breathing frequency on the partial

        pressure of CO2 in the end-tidal air (PETCO2) in resting healthy

        subjects. In the first experiment, three different rates of breathing

        were dictated: the same frequency of breathing as the subject's control

        one (1f), a double frequency (2f), and half of the control frequency

        (0.5f). 10 min dictate of 1f and 2f induced a decrease of PETCO2. The

        dictate of 0.5f had no significant effect on PETCO2. In the second

        experiment, 1f was dictated for 30 min, inducing a decrease of PETCO2

        throughout the duration of the dictate. These results demonstrate that

        fixing the breathing frequency by the dictate affects the chemostatic

        control of ventilation.