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

doi:10.1007/s10286-004-0180-4

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

Medicine - Cardiology Division

Research output: Contribution to journal › Article › peer-review

33 Scopus citations

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 language	English (US)
Pages (from-to)	240-248
Number of pages	9
Journal	Clinical Autonomic Research
Volume	14
Issue number	4
DOIs	https://doi.org/10.1007/s10286-004-0180-4
State	Published - Aug 2004

Bibliographical note

Funding Information:
This research was supported by a Cooperative Research and Development Agreement between the US Army Institute of Surgical Research and the National Aeronautics and Space Administration (CRDA No. DAMD17–01–0112). The views expressed herein are the views of the authors and are not to be construed as representing those of the National Aeronautics and Space Administration, Department of Defense or Department of the Army.

Keywords

Baroreceptor resetting
Baroreflex function
Blood
Heart rate
Pressure
Respiratory resistance

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10.1007/s10286-004-0180-4

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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

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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.",

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

note = "Funding Information: This research was supported by a Cooperative Research and Development Agreement between the US Army Institute of Surgical Research and the National Aeronautics and Space Administration (CRDA No. DAMD17–01–0112). The views expressed herein are the views of the authors and are not to be construed as representing those of the National Aeronautics and Space Administration, Department of Defense or Department of the Army.",

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AU - Convertino, Victor A.

AU - Ratliff, Duane A.

AU - Ryan, Kathy L.

AU - Cooke, William H.

AU - Doerr, Donald F.

AU - Ludwig, David A.

AU - Muniz, Gary W.

AU - Britton, Deanna L.

AU - Clah, Savran D.

AU - Fernald, Kathleen B.

AU - Ruiz, Alicia F.

AU - Idris, Ahamed

AU - Lurie, Keith G.

N1 - Funding Information: This research was supported by a Cooperative Research and Development Agreement between the US Army Institute of Surgical Research and the National Aeronautics and Space Administration (CRDA No. DAMD17–01–0112). The views expressed herein are the views of the authors and are not to be construed as representing those of the National Aeronautics and Space Administration, Department of Defense or Department of the Army.

PY - 2004/8

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N2 - 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.

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

Abstract

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