Abstract
The circulatory effects of three kinds of respiratory maneuvers--maximum breathing, voluntary hyperventilation, and the Valsalva maneuver--on cerebral blood flow, brachial blood flow, heart rate, and systolic blood pressure were investigated by means of the on-line Doppler ultrasonic technique in 20 men. Arterial gas contents (PO2, PCO2, pH) were also examined. Cerebral blood flow was increased or showed the biphasic response (increase in the former and decrease in the latter part of the maneuver) with maximum breathing. Cerebral blood flow was decreased with voluntary hyperventilation. The cerebral blood flow was maintained at a same level during the maneuver or tended to return to the control level. Cerebral blood flow was decreased in the Valsalva maneuver. There was a transient but conspicious increase of the cerebral blood flow immediately after the maneuver.
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