Journal of applied physiology
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Comparative Study
Cerebral hemodynamics during sensorimotor activation in humans.
We studied the time course and magnitude of cerebral blood flow velocity (CBFV) changes in the middle cerebral artery (MCA) and the regional cerebral blood flow (rCBF) in the MCA territory during stimulation of the left sensorimotor cortex. Healthy right-handed male subjects were examined during performance of right-hand finger movement sequences, vibratory stimulation, and somatosensory discrimination. In somatosensory discrimination there were significant increases of the mean CBFV (4.8 +/- 9.9 cm/s; P < 0.01) and the mean rCBF (10.2 +/- 4.2 ml.100 g-1.min-1; P < 0.01), whereas no significant changes of the mean CBFV and rCBF occurred in finger movement sequences or vibratory stimulation. ⋯ In the two tasks involving finger movements there was an increase of the respiratory rates (4.3 +/- 3.8 breaths/min; P < 0.05) and the pulse rates (11.6 +/- 5.5 beats/min; P < 0.05), respectively. Our data demonstrate a correspondence of mean CBFV and rCBF changes evoked by sensorimotor activation in the human brain. Furthermore, cerebral hemodynamic changes related to motor activity are accompanied by cardiorespiratory effects.
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We evaluated the effect of airflow and gas composition on the linearity of measurement of airflow by a new disposable flowmeter. The flowmeter is based on the principle of differential pressure measurement across two symmetrically disposed Pitot tubes. Nonlinearities arising from the pressure-to-airflow relationship and sensitivity to changes in gas density were linearized with appropriate software and monitoring of the gas composition. ⋯ However, because the errors were predictable, they were corrected by software to within 0.6% of the target volume. Measurement of minute ventilation during exercise was within 1-2% of that determined from bag collections. We conclude that this type of flowmeter can accurately measure exercise minute ventilation and has advantages over some other flowmeters because of its ruggedness, reproducibility, and ease of sterilization or replacement compared with other flowmeters.