J Appl Physiol. 2013 May 16. [Epub ahead of print]
Slow breathing as a means to improve orthostatic tolerance: a randomized sham-controlled trial.
Source
1University of Otago.
Abstract
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<0.01). The improved tolerance was reflected in elevations in low frequency (LF; 0.07-0.2 Hz) oscillations of MAP and mean MCAv, improved metrics of dynamic cerebrovascular control (increased LF phase and reduced LF gain), and a reduced rate of decline for MCAv (-0.60±0.27 vs. -0.99±0.51 cm/s⋅min-1; P<0.01) and MAP (-0.50±0.37 vs. -1.03±0.80 mmHg⋅min-1; P=0.01 vs. spontaneous breathing) across time from baseline to pre-syncope. Our findings show that orthostatic tolerance can be improved within healthy individuals with a simple non-pharmacological breathing strategy. The mechanisms underlying this improvement are likely mediated via the generation of negative intrathoracic pressure during slow and deep breathing and the related beneficial impact on cerebrovascular and autonomic function.
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