Effects of inspiratory impedance on the carotid-cardiac baroreflex response in humans

Victor A. Convertino, Duane A. Ratliff, Kathy L. Ryan, William H. Cooke, Donald F. Doerr, David A. Ludwig, Gary W. Muniz, Deanna L. Britton, Savran D. Clah, Kathleen B. Fernald, Alicia F. Ruiz, Ahamed Idris, Keith G. Lurie

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Abstract

We were interested in a therapeutic device designed to increase carotid-cardiac baroreflex sensitivity (BRS) since high BRS is associated with a lower risk for development of hypotension in humans with experimentally-induced central hypovolemia. We hypothesized that spontaneous breathing through an impedance threshold device (ITD) designed to increase negative intrathoracic pressure during inspiration and elevate arterial blood pressure would acutely increase BRS in humans. We tested this hypothesis by measuring heart rate (HR), systolic (SBP) and diastolic (DBP) blood pressures, and carotid-cardiac BRS in 10 female and 10 male subjects breathing through a face mask at three separate ITD conditions: (a) 6 cm H2O; (b) 12 cm H2O; and (c) a control (0 cm H2O). HR was increased (P = 0.013) from 64 ± 3 bpm during control to 68 ± 3 bpm at 6 cm H2O ITD and 71 ± 4 bpm at 12 cm H2O ITD breathing conditions. During ITD breathing, BRS was not altered but responses were shifted to higher arterial pressures. However, SBP and DBP were elevated for both the 6 and 12 cm H 2O conditions compared to the O cm H2O condition, but returned to control (sham) levels by 30 minutes after cessation of ITD breathing. There were no gender effects for BRS or any hemodynamic responses to breathing through the ITD. We conclude that breathing with inspiratory impedance at relatively low pressures can increase baseline arterial blood pressure, i. e., reset the operational point for SBP on the baroreflex stimulus-response relationship, in healthy subjects. This resetting of the cardiac baroreflex may represent a mechanism that allows blood pressure to increase without a reflex-mediated reduction in HR.

Original languageEnglish (US)
Pages (from-to)240-248
Number of pages9
JournalClinical Autonomic Research
Volume14
Issue number4
DOIs
StatePublished - Aug 1 2004

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Keywords

  • Baroreceptor resetting
  • Baroreflex function
  • Blood
  • Heart rate
  • Pressure
  • Respiratory resistance

ASJC Scopus subject areas

  • Endocrine and Autonomic Systems
  • Clinical Neurology

Cite this

Convertino, V. A., Ratliff, D. A., Ryan, K. L., Cooke, W. H., Doerr, D. F., Ludwig, D. A., Muniz, G. W., Britton, D. L., Clah, S. D., Fernald, K. B., Ruiz, A. F., Idris, A., & Lurie, K. G. (2004). Effects of inspiratory impedance on the carotid-cardiac baroreflex response in humans. Clinical Autonomic Research, 14(4), 240-248. https://doi.org/10.1007/s10286-004-0180-4