Acute nasal breathing lowers diastolic blood pressure and increases parasympathetic contributions to heart rate variability in young adults

Figures

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  Figure 1.. Experimental design. Participants visited the laboratory on one occasion for consent, screening, and testing. The experimental protocol included three 5-min periods at rest with free breathing (to measure participants’ self-selected breathing rate) before nasal-only and oral-only breathing in random order. Next, participants completed the same paradigm (free breathing then randomized nasal and oral breathing) during three 7-min periods while cycling at 75 W on a lower-body ergometer.

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  Figure 2.. Brachial blood pressure during rest. A: systolic blood pressure (BP) was not different between conditions. Mean (B) and diastolic (C) BP were lower during nasal breathing. We used two-tailed, paired t tests for all tests except diastolic BP (Wilcoxon test). n = 20 for all graphs.

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  Figure 3.. Heart rate variability metrics during rest. Heart rate (A), the standard deviation of NN intervals (SDNN, B), the percentage of detected NN intervals greater than 50 ms different from the immediately preceding NN interval (pNN50, C), and the low-frequency (LF) contribution were not different between conditions (D). The high-frequency (HF) contribution was lower (E) and the low-frequency (LF)/HF ratio (F) was higher during nasal breathing. We used two-tailed, paired t tests for all tests except SDNN (Wilcoxon test). n = 20 for all graphs.