Inspiratory Resistance Delays the Reporting of Symptoms with Central Hypovolemia: Association with Cerebral Blood Flow
ARMY INST OF SURGICAL RESEARCH FORT SAM HOUSTON TX
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We tested the hypothesis that breathing through an inspiratory threshold device ITD during progressive central hypovolemia would protect cerebral perfusion and attenuate the reporting of presyncopal symptoms. Eight human subjects were exposed to lower-body negative pressure LBNP until the presence of symptoms while breathing through either an active ITD -7 cmH2O impedance or a sham ITD 0 cmH2O. Cerebral blood flow velocity CBFV was measured continuously via transcranial Doppler and analyzed in both time and frequency domains. Subjects were asked to report any subjective presyncopal symptoms e.g., dizziness, nausea at the conclusion of each LBNP.
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