Joseph D. Vondrasek1, Brett L. Cross1,,2, Gregory J. Grosicki1, Andrew A. Flatt1. 1Georgia Southern University, Savannah, GA. 2Florida State University, Tallahassee, FL.

BACKGROUND: Blood pressure (BP), baroreflex sensitivity (BRS), and central arterial stiffness (carotid-femoral pulse wave velocity, cf-PWV) are health markers associated with cardiovascular disease risk, and cost-effective methods for optimizing these metrics are desirable. Previously, device-guided paced breathing improved BP, BRS, and cf-PWV, but there may be a cost barrier for some consumers. Free smartphone applications (app) with breathing guidance are widely available and may be a cost-effective means to improve BP, BRS, and cf-PWV. Therefore, we evaluated the acute cardiovascular effects of paced breathing using a cost-free app. METHODS: Twenty-one apparently healthy young adults (13M:9F; Age: 23.1 ± 3.7 yrs; body mass index: 23.5 ± 2.0 kg/m2) performed 10 min of spontaneous breathing (CTRL) and 10 min of app-guided paced (PACE) breathing (supine, 6 breaths∙min-1; 5-s inhale, 5-s exhale) in a counterbalanced order. Ten min of stabilization preceded both conditions, and 3 min of standing served as a washout period between conditions. BP and cf-PWV were measured immediately before and after each condition using a SphygmoCor XCEL. During each condition, R-R intervals were recorded via electrocardiography and beat-to-beat BP via a continuous non-invasive arterial pressure monitor. Cardiovagal BRS was determined using the sequence method (≥ 3 cycles, ± 4 ms, ± 1 mmHg, R2 ≥ 0.85). Two-way repeated measures analysis of variance was used to assess pre- and post-condition measures (BP, cf-PWV), and a paired t-test was used to compare BRS between conditions. RESULTS: There were no time×condition interactions for systolic or diastolic BP (P > 0.05). There was a time×condition interaction for cf-PWV (P = 0.02). Cf-PWV increased (P = 0.018, d = 0.25) from pre-PACE (5.8 ± 0.8 m/s) to post-PACE (6.0 ± 0.7 m/s), whereas no change (P > 0.05, d = 0.00) occurred from pre-CTRL (5.7 ± 0.7 m/s) to post-CTRL (5.7 ± 0.7 m/s). A total of 14/22 participants met criteria for BRS, which was higher (P = 0.02, d = 0.94) during PACE (26.4 ± 10.8 ms/mmHg) vs. CTRL (19.3 ± 7.5 ms/mmHg). CONCLUSIONS: In young adults, paced breathing guided by a free app promoted acute increases in BRS while minimally affecting BP. Arterial stiffness statistically increased during PACE, but the magnitude of change was well below previously reported clinical meaningfulness (± 0.5 m/s) or minimal detectable change thresholds (± 0.411 m/s).

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