THE VALIDITY OF A SIMPLIFIED PAIRED NECK CHAMBER FOR ACTIVATION OF CAROTID BARORECEPTORS IN HUMAN

Background and Objectives: Recently, novel noiseless device for the assessment of baroreceptor function with the neck suction (NS) has been presented. In this study, we present another in-house approach to the variable-pressure neck chamber method. Our device offers further critical improvements. First, it enables delivery of negative (NS) as well as positive pressure (neck pressurizing, NP) in a noiseless manner. Second, we used small, 3D-printed cups positioned over the carotid sinuses instead of cumbersome neck collar to improve subject comfort and to test feasibility of tracking the pressure-induced changes in carotid artery with ultrasonography.Methods: Five healthy, non-smoking, normal-weight subjects aged 29 ± 3 years (mean ± SD) volunteered for the study. Heart rate (HR, bpm) and mean arterial pressure (MAP, mmHg) responses to short, 7-s long episodes of NS and NP were recorded. Each trial consisted of 12 episodes of variable-pressure: six episodes of NS (suction ranging between -10 and -80 mmHg) and six episodes of NP (pressure ranging between + 10 and + 80 mmHg). Carotid artery sonography was performed during the NS and NP in four subjects, on another occasion.Results: The variable-pressure episodes resulted consistently in the expected pattern of hemodynamic alterations: HR and MAP increases or decreases following the NP and NS, respectively, as evidenced by the coefficient of determination (R2) of ≥0.78 for the carotid-HR response curve (for all five participants) and the carotid-MAP response curve (for four out of five participants; the curve cannot be calculated for one subject). We found a linear, dose-dependent relation between the applied pressure and the systolic-diastolic difference in carotid artery diameter.Conclusion: The novel device enables noiseless stimulation and unloading of the carotid baroreceptors with the negative and positive pressure, respectively, applied on the subject’s neck via small, asymmetric and one-side flattened, 3D-printed cups. The unique design of the cups enables concomitant visualizing of the carotid artery during the NS or NP administration, and thereby direct monitoring of the intensity of mechanical stimulus targeting the carotid baroreceptors.

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Impairment of carotid-cardiac vagal baroreflex in wheelchair-dependent quadriplegics

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1991.260.3.r576 ◽

1991 ◽

Vol 260 (3) ◽

pp. R576-R580 ◽

Cited By ~ 10

Author(s):

V. A. Convertino ◽

W. C. Adams ◽

J. D. Shea ◽

C. A. Thompson ◽

G. W. Hoffler

Keyword(s):

Buffer Capacity ◽

Prolonged Exposure ◽

Bed Rest ◽

Maximum Slope ◽

Stimulus Response ◽

Carotid Baroreceptors ◽

Blood Pressures ◽

Pressure Changes ◽

Neck Chamber ◽

Interval Response

The incidence of orthostatic hypotension can increase after prolonged exposure to chair rest and bedrest and is associated with post-bed rest impairment of the carotid-cardiac baroreflex response. We therefore hypothesized that the hypotension observed in humans confined to wheelchairs may be manifested by a reduced baroreflex sensitivity. We compared baroreflex responses of 16 wheelchair-dependent (WCD) quadriplegics with those of 15 able-bodied subjects (ABS) matched for age, height, and weight. Beat-to-beat R-R intervals were measured during application of graded pressures from 40 to -65 mmHg using a neck chamber for noninvasive stimulation of the carotid baroreceptors. Changes of R-R intervals were plotted against carotid distending pressures. The maximum slope of the stimulus-response relationship was greater (P less than 0.0001) in ABS (6.1 +/- 0.6 ms/mmHg) than in WCD (2.6 +/- 0.4 ms/mmHg). The range of the R-R interval response, i.e., the capacity to buffer blood pressure changes, was only 138 +/- 19 ms in WCD compared with 253 +/- 19 ms in ABS (P less than 0.001). Mean sitting systolic-to-diastolic blood pressures in WCD (92/60 mmHg) were less (P less than 0.0001) than in ABS (120/77 mmHg), although there were no significant differences between groups in supine resting blood pressures. Chronic loss of stimulation to carotid baroreceptors by routine standing posture is associated with attenuated sensitivity and reduced buffer capacity of the arterial baroreflex and hypotension during sitting in WCD patients.

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Sympathetic transients caused by abrupt alterations of carotid baroreceptor activity in humans

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1982.242.2.h185 ◽

1982 ◽

Vol 242 (2) ◽

pp. H185-H190 ◽

Cited By ~ 27

Author(s):

B. G. Wallin ◽

D. L. Eckberg

Keyword(s):

Sympathetic Activity ◽

Chamber Pressure ◽

Reduced Pressure ◽

Cardiac Responses ◽

Carotid Baroreceptor ◽

Sympathetic Responses ◽

Nerve Muscle ◽

Neck Pressure ◽

Pressure Changes ◽

Neck Chamber

We examined the role of carotid baroreceptors in the short-term modulation of sympathetic outflow to the muscle vascular bed and parasympathetic outflow to the heart in 10 healthy adults. Afferent carotid baroreceptor activity was modified with 30-mmHg neck suction or pressure applied during held expiration, and efferent sympathetic activity was measured with microelectrodes inserted percutaneously into peroneal nerve muscle fascicles. Sympathetic responses were conditioned importantly by directional changes of carotid transmural pressure: increased pressure (onset of neck suction or offset of neck pressure) inhibited (totally) sympathetic activity, and reduced pressure (offset of neck suction or onset of neck pressure) augmented sympathetic activity. Responses occurred after a latency of about 2 s and did not persist as long as changes of neck-chamber pressure. Cardiac intervals were prolonged by increased carotid transmural pressures and shortened by decreased carotid transmural pressures, but, in contrast to sympathetic responses, cardiac responses adapted only slightly during neck-chamber pressure changes. Our results suggest that in the human a common baroreceptor input is processed differently in central vagal and sympathetic networks. Muscle sympathetic responses to changing levels of afferent baroreceptor traffic are profound but transitory. They appear to be conditioned more by changes of arterial pressure than by its absolute levels.

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Carotid baroreflex control of heart rate during acute exposure to simulated altitudes of 3,800 m and 4,300 m

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.273.4.r1219 ◽

1997 ◽

Vol 273 (4) ◽

pp. R1219-R1223 ◽

Cited By ~ 12

Author(s):

S. Sagawa ◽

R. Torii ◽

K. Nagaya ◽

F. Wada ◽

Y. Endo ◽

...

Keyword(s):

High Altitude ◽

Sea Level ◽

Logistic Function ◽

Cardiac Response ◽

Baroreflex Control ◽

Carotid Baroreflex ◽

Maximal Gain ◽

Neck Chamber ◽

Male Subjects ◽

Made In

To examine the baroreflex response in humans during acute high-altitude exposure, the carotid baroreflex cardiac responsiveness was studied using a neck chamber in seven unacclimatized male subjects. Measurements were made in a high-altitude chamber on separate days at sea level and during 1-h exposure at two different altitudes of 3,800 m [partial pressure of oxygen in inspired air (Pi O2 ) = 90 mmHg] and 4,300 m (Pi O2 = 82 mmHg). R-R intervals were plotted against neck chamber pressures, and the baroreceptor response was analyzed by applying a four-parameter sigmoidal logistic function. The baroreceptor response curve shifted downward in either altitude, reflecting a tachycardic response at high altitude, and the magnitude of the shift was greater at 4,300 m than at 3,800 m. There was no change in the sigmoidal parameters at 3,800 m compared with sea level except for a reduction ( P < 0.05) of the minimum R-R interval. At 4,300 m the maximal R-R range, slope coefficient, minimum R-R interval, and maximal gain of the curve decreased significantly ( P < 0.05) compared with sea level values, whereas the centering point of the curve remained unchanged. These results suggest that hypoxia (Pi O2 = 82 mmHg) reduces the sensitivity of carotid baroreflex cardiac response.

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Preliminary design and testing of neck chamber device for baroreflex sensitivity assessment

BMJ Innovations ◽

10.1136/bmjinnov-2019-000390 ◽

2020 ◽

Vol 6 (4) ◽

pp. 132-142

Author(s):

Pratik V Paliwal ◽

Prathamesh H Kamble ◽

K A Desai ◽

Rajesh Sharma ◽

Anish Singhal

Keyword(s):

Standard Test ◽

Design Development ◽

Test Protocol ◽

Non Invasive ◽

Carotid Baroreceptor ◽

Sensitivity Assessment ◽

Neck Chamber ◽

Design And Testing ◽

Opening Up ◽

Stimulation Of

This paper presents the design, development and testing of a novel neck chamber device for non-invasive stimulation of an individual carotid baroreceptor in a graded manner. The proposed neck chamber device is a strap-free design that avoids discomfort during testing due to tight seal generated by the neck collar design, and facilitates unilateral testing and targeted assessment without stimulating other neck baroreceptors. The device consists of two independent components to achieve these requirements: an outer suction mechanism and an inner chamber. The outer mechanism consists of multiple suction cups to grip the device over the human neck, while the inner chamber creates controlled positive and negative pressure for stimulation of baroreceptors using a pump. The indigenously developed device was employed for the testing by providing neck chamber stimulation in discrete steps of –20 mm Hg, –40 mm Hg, −60 mm Hg, 0 mm Hg, 20 mm Hg, 40 mm Hg and 60 mm Hg with the gap of 60 s between each stimulation as per the standard test protocol of autonomic function test. The changes in heart rate and RR interval were recorded to determine the baroreceptor gain using the logistic equation derivative and gain curve plot. The results of the present study show that the estimated baroreceptor gain is –0.109±0.04, which is consistent with the previous studies conducted using neck collar devices. The testing results showed that the desired objectives are achieved successfully by the prototype device, opening up the possibility of its use for the treatment of resistant hypertension.

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Stimulus-response characteristics of carotid baroreceptors in the rabbit

Pflügers Archiv - European Journal of Physiology ◽

10.1007/bf02580788 ◽

1982 ◽

Vol 394 (S1) ◽

pp. R53-R53 ◽

Cited By ~ 1

Author(s):

U. Müller ◽

W. Wiemer

Keyword(s):

Stimulus Response ◽

Response Characteristics ◽

Carotid Baroreceptors

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Enhanced vagal baroreflex response during 24 h after acute exercise

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1991.260.3.r570 ◽

1991 ◽

Vol 260 (3) ◽

pp. R570-R575 ◽

Cited By ~ 16

Author(s):

V. A. Convertino ◽

W. C. Adams

Keyword(s):

Acute Exercise ◽

Systolic Pressure ◽

Underlying Mechanism ◽

Chamber Pressure ◽

External Application ◽

Maximum Slope ◽

Acute Bout ◽

Graded Exercise ◽

Pressure Stability ◽

Neck Chamber

We evaluated carotid-cardiac baroreflex responses in eight normotensive men (25-41 yr) on two different test days, each separated by at least 1 wk. On one day, baroreflex response was tested before and at 3, 6, 12, 18, and 24 h after graded supine cycle exercise to volitional exhaustion. On another day, this 24-h protocol was repeated with no exercise (control). Beat-to-beat R-R intervals were measured during external application of graded pressures to the carotid sinuses from 40 to -65 mmHg; changes of R-R intervals were plotted against carotid pressure (systolic pressure minus neck chamber pressure). The maximum slope of the response relationship increased (P less than 0.05) from preexercise to 12 h (3.7 +/- 0.4 to 7.1 +/- 0.7 ms/mmHg) and remained significantly elevated through 24 h. The range of the R-R response was also increased from 217 +/- 24 to 274 +/- 32 ms (P less than 0.05). No significant differences were observed during the control 24-h period. An acute bout of graded exercise designed to elicit exhaustion increases the sensitivity and range of the carotid-cardiac baroreflex response for 24 h and enhances its capacity to buffer against hypotension by increasing heart rate. These results may represent an underlying mechanism that contributes to blood pressure stability after intense exercise.

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Identification of carotid vascular receptors that control adrenal catecholamine secretion in dogs

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1992.262.5.r872 ◽

1992 ◽

Vol 262 (5) ◽

pp. R872-R878

Author(s):

W. C. Engeland ◽

C. D. Zippe ◽

D. S. Gann

Keyword(s):

Carotid Sinus ◽

Carotid Occlusion ◽

Catecholamine Secretion ◽

Adrenal Vein ◽

Carotid Baroreceptors ◽

Cervical Vagotomy ◽

Anesthetized Dogs ◽

Reflex Control ◽

Adrenal Secretion

The role of carotid sinus and thyrocarotid mechanoreceptors in the reflex control of adrenal medullary function was assessed in anesthetized dogs with adrenal vein catheters. Dogs underwent carotid sinus, thyrocarotid junction, combined carotid sinus and thyrocarotid junction, or sham denervation. On the day after surgery, catecholamine secretion was measured after carotid occlusion proximal to the thyrocarotid junction, cervical vagotomy, and repeat carotid occlusion, each separated by 90 min. After combined carotid denervation, baseline norepinephrine secretion was increased, resulting in a decreased epinephrine-to-norepinephrine ratio. Carotid occlusion before vagotomy did not change the secretion of catecholamines or the epinephrine-to-norepinephrine ratio. After sham carotid denervation, acute vagotomy did not affect catecholamine secretion. However, after denervation of the carotid sinus or thyrocarotid junction, vagotomy resulted in small increases in catecholamine secretion without changing the epinephrine-to-norepinephrine ratio; the magnitude of the response was augmented after combined denervation. At 90 min after vagotomy in dogs with intact carotid baroreceptors, carotid occlusion increased adrenal secretion of catecholamines and decreased the epinephrine-to-norepinephrine ratio. After denervation of carotid sinus or thyrocarotid junction receptors, carotid occlusion increased secretion of catecholamines without changing the epinephrine-to-norepinephrine ratio; the response was abolished by combined denervation. These results show that both carotid sinus and thyrocarotid receptors contribute to the adrenomedullary response to carotid occlusion and to acute vagotomy. Also, reduction in the activity of carotid sinus and thyrocarotid junction receptors chronically (by denervation) or acutely (by carotid occlusion) results in preferential secretion of norepinephrine over epinephrine.

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