Critical closing pressure explains cerebral hemodynamics during the Valsalva maneuver

1999 ◽  
Vol 86 (2) ◽  
pp. 675-680 ◽  
Author(s):  
Suzanne L. Dawson ◽  
Ronney B. Panerai ◽  
John F. Potter
Keyword(s):  
Blood Pressure ◽  
Valsalva Maneuver ◽  
Intrathoracic Pressure ◽  
Pulse Interval ◽  
Cerebrovascular Resistance ◽  
Arterial Blood ◽  
Critical Closing Pressure ◽  
Pressure Changes ◽  
Closing Pressure ◽  
Phase Iv

The Valsalva maneuver (VM), a voluntary increase in intrathoracic pressure of ∼40 mmHg, has been used to examine cerebral autoregulation (CA). During phase IV of the VM there are pronounced changes in mean arterial blood pressure (MABP), pulse interval, and cerebral blood flow (CBF), but the changes in CBF are of a much greater magnitude than those seen in MABP, a finding to date attributed to either a delay in activation of the CA mechanism or the inability of this mechanism to cope with the size and speed of the blood pressure changes involved. These changes in CBF also precede those in MABP, a pattern of events not explained by the physiological process of CA. Measurements of CBF velocity (transcranial Doppler) and MABP (Finapres) were performed in 53 healthy volunteers (aged 31–80 yr). By calculating beat-to-beat values of critical closing pressure (CCP) during the VM, we have found that this parameter suddenly drops at the start of phase IV, providing a coherent explanation for the large increase in CBF. If CCP is included in the estimation of cerebrovascular resistance, a temporal pattern more consistent with an autoregulatory response to the MABP overshoot is also found. CCP is intricately involved in the control of CBF during the VM and should be considered in the assessment of CA.

scholarly journals Frequency Dependence of Cerebrovascular Impedance in Preterm Neonates: A Different View on Critical Closing Pressure

1997 ◽  
Vol 17 (10) ◽  
pp. 1127-1131 ◽  
Author(s):  
Erik Michel ◽  
Stefanie Hillebrand ◽  
Johanna vonTwickel ◽  
Boris Zernikow ◽  
Gerd Jorch
Keyword(s):  
Blood Pressure ◽  
Frequency Response ◽  
Cerebral Blood Flow Velocity ◽  
Preterm Neonates ◽  
Pass Filter ◽  
Arterial Blood ◽  
Critical Closing Pressure ◽  
Cerebrovascular System ◽  
Closing Pressure ◽  
Zero Frequency

The nonproportional relationship between instantaneous arterial blood pressure (BP) and cerebral blood flow velocity (CBFv) is well explained by the concept of critical closing pressure (CCP). We aimed to determine the frequency response of the neonatal cerebrovascular system, and to establish the exact mathematical relationship between cerebrovascular impedance and CCP under physiologic conditions. In 10 preterm neonates (gestational age, 25–32 weeks; birth weight, 685–1,730 g; age 1–7 days) we Doppler-traced CBFv of the internal carotid artery. Blood pressure was traced simultaneously. Critical closing pressure was graphically determined. Cerebrovascular impedance was calculated as the square root of the ratio of the corresponding peaks in the power spectra of BP and CBFv at zero frequency, and at heart rate (H) and harmonics (xH). Uniformly, the impedance between H and 3H (2 to 6 Hz) was reduced about fivefold, compared with the impedance at zero frequency. The cerebrovascular system behaves like a high-pass filter, leading to a reduction of the DC (direct current) component of CBFv (analogous to current) relative to that of the driving force BP (analogous to voltage). The frequency response of cerebrovascular impedance reflects the ratio of CCP and DC BP. A mathematical derivation of this relationship is given matching the observed results. Thus, both the CCP and the impedance approach are valid.

Pharmacological dissection of components of the Valsalva maneuver in adrenergic failure

1991 ◽  
Vol 71 (4) ◽  
pp. 1563-1567 ◽  
Author(s):  
P. Sandroni ◽  
E. E. Benarroch ◽  
P. A. Low
Keyword(s):  
Blood Pressure ◽  
Phase Ii ◽  
Early Phase ◽  
Valsalva Maneuver ◽  
Late Phase ◽  
Adrenergic Regulation ◽  
Arterial Blood ◽  
Patient Groups ◽  
Age And Sex ◽  
Phase Iv

The arterial blood pressure (BP) components of the Valsalva maneuver (VM) were analyzed to ascertain whether they could be used as an index of adrenergic regulation of the circulation. We studied a control and three age- and sex-matched patient groups. Sympathetic adrenergic failure was graded on the basis of the degree of systolic BP (SBP) reduction during tilt: orthostatic hypotension (OH; SBP greater than 30 mmHg), borderline OH (BOH; 30 less than SBP greater than 10 mmHg), and sympathetic sudomotor failure (SSF). Controls exhibited a biphasic phase II, consisting of a modest decrement (early phase II) followed by a rise in BP (late phase II; II1) above resting values. All the patient groups including SSF exhibited a significant reduction in II1. An excessive BP fall in phase II and an absent phase IV overshoot were observed in the OH group. BOH and, to a lesser extent, SSF groups showed a significant reduction in phase IV overshoot. We conclude that BP changes during VM will detect adrenergic vasoconstrictor failure with greater sensitivity than orthostatic BP recordings.

Carbon dioxide, critical closing pressure and cerebral haemodynamics prior to vasovagal syncope in humans

2001 ◽  
Vol 101 (4) ◽  
pp. 351-358 ◽  
Author(s):  
Brian J. CAREY ◽  
Penelope J. EAMES ◽  
Ronney B. PANERAI ◽  
John F. POTTER
Keyword(s):  
Carbon Dioxide ◽  
Blood Pressure ◽  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Vasovagal Syncope ◽  
Previous History ◽  
Normal Subjects ◽  
Cerebrovascular Resistance ◽  
Critical Closing Pressure ◽  
Closing Pressure

The cerebrovascular changes that occur prior to vasovagal syncope (VVS) are unclear, with both increases and decreases in cerebrovascular resistance being reported during pre-syncope. This study assessed the cerebrovascular responses, and their potential underlying mechanisms, that occurred before VVS induced by head-up tilt (HUT). Groups of 65 normal subjects with no previous history of syncope and of 16 patients with recurrent VVS were subjected to 70° HUT for up to 30min. Bilateral middle cerebral artery (MCA) cerebral blood flow velocities (CBFVs) were measured using transcranial Doppler ultrasound, along with simultaneous measures of MCA blood pressure, heart rate, and end-tidal and transcutaneous carbon dioxide concentrations. All 16 patients and 14 of the control subjects developed VVS during HUT. During pre-syncope, mean CBFV declined, due predominantly to a decrease in diastolic rather than systolic CBFV (decreases of 44.5±;19.8% and 6.3±;12.9% respectively; P < 0.0001). CO2 levels and indices of cerebrovascular resistance decreased during pre-syncope, while critical closing pressure (CrCP) increased to levels approaching MCA diastolic blood pressure before decreasing precipitously on syncope. Pre-syncopal changes were similar in syncopal patients and syncopal controls. CrCP, therefore, rises during pre-syncope, possibly related to progressive hypocapnia, and may account for the relatively greater fall in diastolic CBFV. Falls in cerebrovascular resistance, therefore, may be offset by rises in CrCP due to hypocapnia, leading to diminished cerebral blood flow during pre-syncope.

scholarly journals Critical Closing Pressure: Comparison of Three Methods

2009 ◽  
Vol 29 (5) ◽  
pp. 987-993 ◽  
Author(s):  
Jorge A López-Magañna ◽  
Hugh K Richards ◽  
Danila K Radolovich ◽  
Dong-Joo Kim ◽  
Peter Smielewski ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Cardiac Arrest ◽  
Arterial Blood Pressure ◽  
Transcranial Doppler ◽  
Cerebrovascular Circulation ◽  
Waveform Analysis ◽  
Arterial Blood ◽  
Pressure Threshold ◽  
Critical Closing Pressure ◽  
Closing Pressure

Critical closing pressure (CCP) is an arterial pressure threshold below which small arterial vessels collapse. Our aim was to compare different methods to estimate CCP in the cerebrovascular circulation using the relationships between transcranial Doppler flow velocity (FV), laser-Doppler flux (LDF), and arterial blood pressure (ABP). A total of 116 experiments in rabbits were analyzed retrospectively. At the end of each recording, cardiac arrest (CA) was induced. Arterial blood pressure in femoral artery, basilar artery FV, cortical blood LDF, intracranial pressure (ICP) was recorded. Critical closing pressure was estimated using linear regression between decreasing mean ABP values, FV, and LDF during CA. In addition, CCP was calculated from FV waveform just before CA. The correlation between CCP evaluated using LDF and FV during CA was 0.98 ( P < 0.0001). The correlation between CCP measured during CA and CCP estimated from the transcranial Doppler ultrasonography (TCD) waveform was weaker ( R=0.39; P <0.001), with CCP calculated from waveform being significantly greater than CCP from CA (median difference 9 mm Hg; P < 0.003). Critical closing pressures obtained from FV waveform and CA correlated with mean ICP before CA ( R = 0.40; P = 0.001). In conclusion strong correlation exists between CCP values obtained by means of FV and LDF during cardiac arrest. However, predictions of CCP using TCD waveform analysis show substantial differences from values of CCP recorded during cardiac arrest.

scholarly journals Arterial blood pressure response to heavy resistance exercise

1985 ◽  
Vol 58 (3) ◽  
pp. 785-790 ◽  
Author(s):  
J. D. MacDougall ◽  
D. Tuxen ◽  
D. G. Sale ◽  
J. R. Moroz ◽  
J. R. Sutton
Keyword(s):  
Blood Pressure ◽  
Blood Pressure Response ◽  
Valsalva Maneuver ◽  
Pressor Response ◽  
Intrathoracic Pressure ◽  
Pressure Response ◽  
Weight Lifting ◽  
Capacitance Transducer ◽  
Arterial Blood ◽  
Peak Pressures

The purpose of this study was to record the blood pressure response to heavy weight-lifting exercise in five experienced body builders. Blood pressure was directly recorded by means of a capacitance transducer connected to a catheter in the brachial artery. Intrathoracic pressure with the Valsalva maneuver was recorded as mouth pressure by having the subject maintain an open glottis while expiring against a column of Hg during the lifts. Exercises included single-arm curls, overhead presses, and both double- and single-leg presses performed to failure at 80, 90, 95, and 100% of maximum. Systolic and diastolic blood pressures rose rapidly to extremely high values during the concentric contraction phase for each lift and declined with the eccentric contraction. The greatest peak pressures occurred during the double-leg press where the mean value for the group was 320/250 mmHg, with pressures in one subject exceeding 480/350 mmHg. Peak pressures with the single-arm curl exercise reached a mean group value of 255/190 mmHg when repetitions were continued to failure. Mouth pressures of 30–50 Torr during a single maximum lift, or as subjects approached failure with a submaximal weight, indicate that a portion of the observed increase in blood pressure was caused by a Valsalva maneuver. It was concluded that when healthy young subjects perform weight-lifting exercises the mechanical compression of blood vessels combines with a potent pressor response and a Valsalva response to produce extreme elevations in blood pressure. Pressures are extreme even when exercise is performed with a relatively small muscle mass.

scholarly journals Heat stress alters hemodynamic responses during the Valsalva maneuver

2010 ◽  
Vol 108 (6) ◽  
pp. 1591-1594 ◽  
Author(s):  
Scott L. Davis ◽  
Craig G. Crandall
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heat Stress ◽  
Phase Ii ◽  
Valsalva Maneuver ◽  
Late Phase ◽  
Thermal Conditions ◽  
Whole Body ◽  
Hemodynamic Responses ◽  
Arterial Blood

The Valsalva maneuver can be used as a noninvasive index of autonomic control of blood pressure and heart rate. The purpose of this investigation was to test the hypothesis that sympathetic mediated vasoconstriction, as referenced by hemodynamic responses during late phase II (phase IIb) of the Valsalva maneuver, is inhibited during whole body heating. Seven individuals (5 men, 2 women) performed three Valsalva maneuvers (each at a 30-mmHg expiratory pressure for 15 s) during normothermia and again during whole body heating (increase sublingual temperature ∼0.8°C via water-perfused suit). Each Valsalva maneuver was separated by a minimum of 5 min. Beat-to-beat mean arterial blood pressure (MAP) and heart rate were measured during each Valsalva maneuver, and responses for each phase were averaged across the three Valsalva maneuvers for both thermal conditions. Baseline MAP was not significantly different between normothermic (88 ± 11 mmHg) and heat stress (84 ± 9 mmHg) conditions. The change in MAP (ΔMAP) relative to pre-Valsalva MAP during phases IIa and IIb was significantly lower during heat stress (IIa = −20 ± 8 mmHg; IIb = −13 ± 7 mmHg) compared with normothermia (IIa = −1 ± 15 mmHg; IIb = 3 ± 13 mmHg). ΔMAP from pre-Valsalva baseline during phase IV was significantly higher during heat stress (25 ± 10 mmHg) compared with normothermia (8 ± 9 mmHg). Counter to the proposed hypothesis, the increase in MAP from the end of phase IIa to the end of phase IIb during heat stress was not attenuated. Conversely, this increase in MAP tended to be greater during heat stress relative to normothermia ( P = 0.06), suggesting that sympathetic activation may be elevated during this phase of the Valsalva while heat stressed. These data show that heat stress does not attenuate this index of vasoconstrictor responsiveness during the Valsalva maneuver.

24-hour homeodynamic states of arterial blood pressure and pulse interval in conscious rats

1992 ◽  
Vol 73 (2) ◽  
pp. 754-761 ◽  
Author(s):  
B. J. Janssen ◽  
C. M. Tyssen ◽  
H. A. Struijker Boudier ◽  
P. M. Hutchins
Keyword(s):  
Blood Pressure ◽  
Cardiovascular System ◽  
Arterial Blood Pressure ◽  
Single Mode ◽  
Pulse Interval ◽  
Mean Values ◽  
Frequency Distributions ◽  
Set Point ◽  
Arterial Blood ◽  
Wistar Kyoto

In models that describe the homeostasis of the circulation, arterial blood pressure is usually expressed as a single value, which is regarded as the set point in such systems. The aim of the study was to identify in rats from 24-h beat-to-beat recordings the value of blood pressure that describes best such a set point of the cardiovascular system. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR), kept on a 12:12-h lights on-off cycle, were instrumented for computerized 24-h beat-to-beat recording of mean arterial pressure (MAP) and pulse interval (PI). Three-dimensional frequency distributions were constructed by plotting for each beat its MAP vs. its PI. During the dark period, the concurrent distribution of MAP and PI showed two distinct modes while during the light period a single mode was found. Comparable patterns were found in SHRs and WKYs. These three different modes were significantly different from the mathematically calculated mean values of MAP and PI over these periods. Thus in rats the 24-h behavior of the cardiovascular system is better described by dynamic shifts between different modes (homeodynamic states) than by a single set point.

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