Arterial wave reflections increase during voluntary apnea and the cold pressor test, increasing aortic systolic blood pressure.

Acute sympatho-excitation increases peripheral blood pressure (BP) through sympathetically mediated vasoconstriction. Aortic BP and pulsatile hemodynamics are stronger predictors of cardiovascular risk and outcomes compared with brachial BP. How pulsatile hemodynamics respond to sympatho-excitation and the impact on aortic BP are incompletely understood. The purpose of this study was to assess the effects of maximal voluntary apnea and the cold pressor test (CPT) as sympatho-excitatory perturbations on aortic BP and measures of pulsatile hemodynamics. Radial artery pressure waves were acquired at rest and during maximal voluntary end-expiratory apnea, end-inspiratory apnea, and the CPT in 28 healthy young adults. Radial artery pressure waves were transformed into aortic pressure waves and underwent wave morphology, wave separation, and pressure time integral analyses. Aortic systolic BP and augmentation index (a surrogate measure of wave reflection) increased during end-inspiratory (100 ± 7 vs. 110 ± 14 mmHg; 15 ± 12 vs. 24 ± 11%, both P < 0.001) and end-expiratory apnea (100 ± 10 vs. 111 ± 12 mmHg; 12 ± 13 vs. 21 ± 12%, both P < 0.001). Reflection magnitude (42 ± 7 vs. 48 ± 6%, P < 0.001) and wasted pressure effort relative to the product of flow and aortic characteristic impedance pressure-time integral ratio (WPE:QZc, 45 ± 18 and 62 ± 19%, P < 0.001) increased during the CPT. Change in backward pressure wave amplitude was the only significant predictor of the change in aortic systolic BP across apneas and the CPT models. The apnea-chemoreflex (via voluntary breath holds) and nociceptive pain response (via the CPT) increased measures of arterial wave reflection, which played a significant role in increasing aortic systolic BP in healthy young adults.NEW & NOTEWORTHY Acute maximal voluntary apnea and the CPT increased aortic blood pressure, arterial wave reflection, and indices of pulsatile arterial load associated with cardiovascular disease risk. There were no differences between end-expiratory/inspiratory apnea or between sexes, but CPT elicited more robust hemodynamic responses than apneas. For all conditions, change in backward pressure wave amplitude was the only predictor of change in aortic systolic blood pressure, highlighting wave reflection as a key mechanism underlying central pressor responses.