The Variable-Pressure Neck-Chamber Method for Studying the Carotid Baroreflex in Man

1977 ◽  
Vol 53 (2) ◽  
pp. 165-171 ◽  
Author(s):  
J. Ludbrook ◽  
G. Mancia ◽  
A. Ferrari ◽  
A. Zanchetti
Keyword(s):  
Negative Pressure ◽  
Carotid Sinus ◽  
Venous Blood ◽  
Baroreceptor Reflex ◽  
Variable Pressure ◽  
Positive Pressure ◽  
Chamber Method ◽  
Carotid Baroreceptor ◽  
Pressure Changes ◽  
Neck Chamber

1. The variable-pressure neck-chamber method was analysed in ten healthy volunteer subjects to determine its suitability for the study of the carotid baroreceptor reflex in man. 2. Positive and negative pressures applied to the neck (range ± 60 mmHg) were always transmitted linearly to a tissue catheter outside the carotid sinus, but only 86% of positive pressure, and 64% of negative pressure. Tissue pressures were confirmed by simultaneous measurement in the internal jugular vein adjacent to the carotid sinus. 3. Positive and negative pressure changes within the above range did not alter Po2 of internal jugular venous blood, suggesting that cerebral blood flow was unaltered. 4. Positive pressure changes induced reflex pressor responses of similar magnitude at arterial Po2 12·8 and 70·1 kPa (96 and 527 mmHg), suggesting that the carotid chemoreceptors were not involved. 5. It is concluded that the variable-pressure neck chamber is a valid method for selectively studying the carotid baroreceptor reflex in man. However, transmission of external pneumatic pressure to the carotid sinus is imperfect and greater for positive than for negative pressure. This must be recognized to avoid underestimation of gain and distortion of shape of the reflex.

Factors Influencing the Carotid Baroreceptor Response to Pressure Changes in a Neck Chamber

1976 ◽  
Vol 51 (s3) ◽  
pp. 347s-349s ◽  
Author(s):  
J. Ludbrook ◽  
G. Mancia ◽  
A. Ferrari ◽  
A. Zanchetti
Keyword(s):  
Carotid Sinus ◽  
Pressor Response ◽  
Baroreceptor Reflex ◽  
Chamber Pressure ◽  
Positive Pressure ◽  
Carotid Baroreceptor ◽  
Factors Influencing ◽  
Correct Analysis ◽  
Pressure Changes ◽  
Neck Chamber

1. Transmission of pneumatic pressure from a neck chamber to the region of the carotid sinus is imperfect and asymmetric (86% of positive pressure, 64% of negative pressure). This has to be taken into account in the correct analysis of the carotid baroreceptor reflex. 2. There is no evidence for a reduction in cerebral blood flow nor of carotid chemoreceptor stimulation in response to an increase in neck chamber pressure of about 45 mmHg. Thus it is likely that the pressor response to this manoeuvre is in fact due to reduction in carotid baroreceptor activity.

Effect of Isometric Hand-Grip Exercise on the Carotid Sinus Baroreceptor Reflex in Man

1978 ◽  
Vol 54 (1) ◽  
pp. 33-37 ◽  
Author(s):  
G. Mancia ◽  
J. Iannos ◽  
G. G. Jamieson ◽  
R. H. Lawrence ◽  
P. R. Sharman ◽  
...  
Keyword(s):  
Maximal Voluntary Contraction ◽  
Carotid Sinus ◽  
Voluntary Contraction ◽  
Baroreceptor Reflex ◽  
Transmural Pressure ◽  
Variable Pressure ◽  
Hand Grip ◽  
The Moment ◽  
Normal Men ◽  
Neck Chamber

1. The changes in R—R heart interval that result from step-increase and step-decrease in carotid sinus transmural pressure induced by a variable-pressure neck chamber were measured in seven normal men. Observations were made at rest, and during isometric hand-grip exercise at 24%, 44% and 64% of maximal voluntary contraction. 2. The response of heart interval to increase in carotid sinus transmural pressure was progressively and markedly diminished according to the strength of hand-grip. This effect was fully developed from the moment of onset of the exertion. 3. The response of heart interval to decrease in carotid sinus transmural pressure was much less consistently affected by hand-grip exercise.

Study of Toynbee Phenomenon by Combined Intranasopharyngeal and Tympanometric Measurements

1988 ◽  
Vol 97 (2) ◽  
pp. 199-206 ◽  
Author(s):  
Yehuda Finkelstein ◽  
Yuval Zohar ◽  
Yoav P. Talmi ◽  
Nelu Laurian
Keyword(s):  
Middle Ear ◽  
Negative Pressure ◽  
Pressure Change ◽  
Positive Pressure ◽  
New Information ◽  
Pressure Changes ◽  
Rapid Pressure

The Toynbee maneuver, swallowing when the nose is obstructed, leads in most cases to pressure changes in one or both middle ears, resulting in a sensation of fullness. Since first described, many varying and contradictory comments have been reported in the literature concerning the type and amount of pressure changes both in the nasopharynx and in the middle ear. In our study, the pressure changes were determined by catheters placed into the nasopharynx and repeated tympanometric measurements. New information concerning the rapid pressure variations in the nasopharynx and middle ear during deglutition with an obstructed nose was obtained. Typical individual nasopharyngeal pressure change patterns were recorded, ranging from a maximal positive pressure of + 450 to a negative pressure as low as −320 mm H2O.

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

1982 ◽  
Vol 242 (2) ◽  
pp. H185-H190 ◽  
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.

Plasma Catecholamines and Blood Pressure Responses to the Carotid Baroreceptor Reflex in Essential Hypertension

1979 ◽  
Vol 57 (s5) ◽  
pp. 165s-167s ◽  
Author(s):  
G. Mancia ◽  
G. Leonetti ◽  
G. B. Picotti ◽  
A. Ferrari ◽  
M. D. Galva ◽  
...  
Keyword(s):  
Essential Hypertension ◽  
Arterial Pressure ◽  
Sympathetic Activity ◽  
Plasma Catecholamines ◽  
Variable Pressure ◽  
Carotid Baroreceptor ◽  
Pressure Variable ◽  
Blood Pressure Responses ◽  
Neck Chamber ◽  
Noradrenaline And Adrenaline

1. Slight decreases and increases in carotid baroreceptor activity were induced in subjects with essential hypertension by slight alterations in carotid transmural pressure (variable pressure neck-chamber technique) in order to obtain limited increases and reductions in sympathetic adrenergic activity. 2. When sympathetic activity was reflexly increased there was a rise in arterial pressure but no significant increase in plasma catecholamines. Likewise when sympathetic activity was reflexly reduced there was a fall in arterial pressure but no significant reduction in plasma catecholamines. 3. Plasma noradrenaline and adrenaline significantly and markedly increased in the same subjects when sympathetic activity was increased by activation of both arterial and low pressure baroreceptor reflexes with tilting. 4. It is suggested that measurements of catecholamines in systemic plasma may reveal marked degrees of sympathetic activation but may not be a sensitive index of more moderate changes in sympathetic tone.

scholarly journals Neck Chamber Technique Revisited: Low-Noise Device Delivering Negative and Positive Pressure and Enabling Concomitant Carotid Artery Imaging With Ultrasonography

2021 ◽  
Vol 12 ◽  
Author(s):  
Rafał Seredyński ◽  
Tymoteusz Okupnik ◽  
Przemysław Musz ◽  
Stanisław Tubek ◽  
Beata Ponikowska ◽  
...  
Keyword(s):  
Carotid Artery ◽  
Response Curve ◽  
Applied Pressure ◽  
Low Noise ◽  
Variable Pressure ◽  
Positive Pressure ◽  
Carotid Baroreceptors ◽  
Dependent Relation ◽  
3D Printed ◽  
Neck Chamber

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.

scholarly journals The Mechanism of Gill Ventilation in Three Freshwater Teleosts

1958 ◽  
Vol 35 (4) ◽  
pp. 807-823 ◽  
Author(s):  
G. M. HUGHES
Keyword(s):  
Negative Pressure ◽  
Time Course ◽  
Phase 1 ◽  
Quantitative Relationship ◽  
Differential Pressure ◽  
Positive Pressure ◽  
Pressure Curve ◽  
Suction Pump ◽  
Opening And Closing ◽  
Pressure Changes

1. A study has been made of the respiratory movements of three species of freshwater fish. The time course of pressure changes in the buccal and opercular cavities was recorded and movements of the mouth and operculum plotted from ciné films taken simultaneously. 2. Opening and closing of the mouth precede respectively abduction and adduction of the operculum by about one-fifth of a cycle. 3. The most prominent part of the buccal pressure curve is a positive pressure associated with mouth closing. The size of a negative pressure as the mouth opens is small in the trout but may be relatively large in the tench. 4. Abduction of the operculum produces a marked negative pressure in the opercular cavity of all three species and there is a slight positive pressure during its adduction. 5. The respiratory system is divided into a buccal and two opercular cavities and the concept of gill resistances separating them is introduced. 6. The respiratory cycle is made up of four phases which succeed one another. These are: phase (1) opercular suction pump predominant; phase (2) transition with a reduction in differential pressure between the buccal and opercular cavities; phase (3) buccal pressure pump predominant; and phase (4) transition with reversal of differential pressure. 7. With the exception of phase (4), which occupies only about one-tenth of a cycle, the pressure in the buccal cavity exceeds that in the opercular cavity throughout the cycle. It is therefore concluded that water will flow across the gills for almost the entire cycle but may reverse for this brief period. The quantitative relationship between the pressures and the volume of water flowing across the gills during different parts of the cycle will depend upon the properties of the gill resistances.

Rapid resetting of the carotid baroreceptor reflex in the cat

1981 ◽  
Vol 241 (6) ◽  
pp. H802-H806 ◽  
Author(s):  
D. L. Kunze
Keyword(s):  
Carotid Sinus ◽  
Blood Pressure Response ◽  
Systemic Blood Pressure ◽  
Baroreceptor Reflex ◽  
Reflex Response ◽  
Carotid Baroreceptor ◽  
Depressor Reflex ◽  
Sinus Pressure ◽  
Anesthetized Cat

The carotid baroreceptor depressor reflex of the chloralose-anesthetized cat was examined to determine the role of the prevailing carotid pressure in determining the threshold, gain, and range of operation of the reflex response. After the pressure of an isolated perfused carotid sinus was held at 80 mmHg for 20 min the threshold pressure necessary to elicit the reflex systemic blood pressure response was 78 +/- 2.9 (SE) mmHg (n = 5). When carotid pressure was maintained for 20 min at 120 and 160 mmHg the threshold rose to 113 +/- 2.9 and 126 +/- 3.0 mmHg, respectively. The resetting of the threshold to a stable value upon elevating or reducing carotid sinus pressure was accomplished within 15—;20 min. The entire range of operation of the reflex response was shifted to higher carotid pressures as the holding pressure was elevated. The midrange gain of the response was unchanged at the three holding pressures tested. These findings indicate that the carotid baroreceptor reflex need not operate over a fixed range but that the range may be rapidly adjustable to the prevailing pressure. When arterial pressure is sustained at a level that is elevated or depressed from normal the carotid baroreceptor reflex acutely resets to operate in the range of the prevailing pressure with a threshold that has moved toward the prevailing pressure.

Continuous resetting of the human carotid baroreceptor-cardiac reflex

1987 ◽  
Vol 252 (4) ◽  
pp. R732-R736 ◽  
Author(s):  
G. A. Kasting ◽  
D. L. Eckberg ◽  
J. M. Fritsch ◽  
C. L. Birkett
Keyword(s):  
Arterial Pressure ◽  
Reflex Response ◽  
Chamber Pressure ◽  
Systematic Change ◽  
Circadian Changes ◽  
Ongoing Process ◽  
Carotid Baroreceptor ◽  
Pressure Changes ◽  
Neck Chamber ◽  
Human Carotid

Although human baroreflex responses have been studied during night as well as day, there has been no attempt to distinguish circadian changes of baroreflex function from those related to sleep. We measured carotid baroreceptor-cardiac reflex responses serially during a 24-h period in 11 normotensive volunteers who were awake and cooperative during testing. We applied sequences of ramped R-wave-triggered neck chamber pressure changes from +40 to -65 mmHg, during held expiration, at 3-h intervals. Subjects maintained their usual sleep-wake cycles but were awakened for three 30-min periods for night testing. There was no systematic change of baroreflex slope during the 24-h period. There were, however, parallel shifts of the entire sigmoid baroreceptor-cardiac reflex response relation along its R-R interval and arterial pressure axes associated with small, but significant, circadian changes of baseline R-R intervals and arterial pressures. Thus, although our data do not point toward major circadian variability of baro-reflex responsiveness, they provide evidence for an ongoing process of human baroreflex resetting.

A simplified paired neck chamber for the demonstration of baroreflex blood pressure regulation.

1999 ◽  
Vol 277 (6) ◽  
pp. S60 ◽  
Author(s):  
N M Raine ◽  
N T Cable
Keyword(s):  
Blood Pressure ◽  
Baroreflex Sensitivity ◽  
Chamber Pressure ◽  
Variable Pressure ◽  
Performance Tests ◽  
Pressure Regulation ◽  
Response Relationship ◽  
Chamber Method ◽  
Stimulus Response ◽  
Neck Chamber

In this investigation a simplified variable-pressure paired neck chamber was developed as a practical alternative to traditional neck collar designs used to study the arterial baroreceptor reflex in humans. The purpose of this new design was to extend the use of the noninvasive neck chamber method of baroreceptor investigation to teachers of physiology. Performance tests indicate that these new chambers are capable of delineating the stimulus-response relationship for both the blood pressure baroreflex [sensitivity = 0.425 +/- 0.13 mmHg mean arterial pressure (MAP)/mmHg neck chamber pressure (NCP); range = 24.9 +/- 4.6 mmHg MAP] and the heart rate baroreflex (sensitivity 0.273 +/- 0.12 beats.min-1.mmHg NCP-1; range = 16.7 +/- 6.8 beats/min). This was achieved by applying localized positive and negative air pressures to the carotid sinuses throughout the range from +60 to -60 mmHg in steps of 20 mmHg. This simplified neck chamber method offers distinct methodological advantages over traditional neck collars, making it a valuable tool for demonstrating baroreflex regulation of the circulation.

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