Slow breathing as a means to improve orthostatic tolerance: a randomized sham-controlled trial

Endogenous oscillations in blood pressure and cerebral blood flow have been associated with improved orthostatic tolerance. Although slow breathing induces such responses, it has not been tested as a therapeutic strategy to improve orthostatic tolerance. Utilising a randomized crossover, sham-controlled design, we tested the hypothesis that breathing at 6 breaths⋅min(-1) (vs. spontaneous breathing) would improve orthostatic tolerance via inducing oscillations in mean arterial blood pressure (MAP) and cerebral blood flow. Sixteen healthy participants (aged 25±4 y; mean±SD) had continuous beat-to-beat measurements of middle cerebral artery blood velocity (MCAv), blood pressure (finometer), heart rate (ECG) and end-tidal PCO2 during an incremental orthostatic stress test to pre-syncope by combining head-up tilt with incremental lower-body negative pressure. Tolerance time to pre-syncope was improved (+15%) with slow breathing compared with spontaneous breathing (29.2±5.4 vs. 33.7±6.0 min; P