Hypocapnia and Cerebral Hypoperfusion in Orthostatic Intolerance

Novak, Vera; Spies, Judith M.; Novák, Péter; McPhee, Benjamin R.; Rummans, Teresa A.; Low, Phillip A.

doi:10.1161/01.str.29.9.1876

Cited by 163 publications

(192 citation statements)

References 23 publications

Supporting

Mentioning

175

Contrasting

Order By: Relevance

“…Nevertheless, intermittent hyperventilation, presenting as postural hypocapnic hyperpnea, has been reported 14, 15, 16, 17. We observed hypocapnic hyperpnea in POTS in response to a rapid initial orthostatic decrease in CO and CBV 15.…”

mentioning

confidence: 56%

“…The relationship of hyperventilation to orthostasis has been revived by recent reports from our laboratory14, 15 and a report from the Mayo autonomic group,17 contemporary with the definition of POTS 3. More recently, “hyperventilation syndrome” (but not “postural hyperventilation”) has been subsumed under the aegis of “dysfunctional breathing” treated with variable success by breathing retraining 42…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Postural Hyperventilation as a Cause of Postural Tachycardia Syndrome: Increased Systemic Vascular Resistance and Decreased Cardiac Output When Upright in All Postural Tachycardia Syndrome Variants

Stewart

Pianosi

Shaban

et al. 2018

JAHA

View full text Add to dashboard Cite

BackgroundPostural tachycardia syndrome (POTS) is a heterogeneous condition. We stratified patients previously evaluated for POTS on the basis of supine resting cardiac output (CO) or with the complaint of platypnea or “shortness of breath” during orthostasis. We hypothesize that postural hyperventilation is one cause of POTS and that hyperventilation‐associated POTS occurs when initial reduction in CO is sufficiently large. We also propose that circulatory abnormalities normalize with restoration of CO 2.Methods and ResultsFifty‐eight enrollees with POTS were compared with 16 healthy volunteer controls. Low CO in POTS was defined by a resting supine CO <4 L/min. Patients with shortness of breath had hyperventilation with end tidal CO 2 <30 Torr during head‐up tilt table testing. There were no differences in height or weight between control patients and patients with POTS or differences between the POTS groups. Beat‐to‐beat blood pressure was measured by photoplethysmography, and CO was measured by ModelFlow. Systemic vascular resistance was defined as mean arterial blood pressure/CO. End tidal CO 2 and cerebral blood flow velocity of the middle cerebral artery were only reduced during head‐up tilt in the hyperventilation group, whereas blood pressure was increased compared with control. We corrected the reduced end tidal CO 2 in hyperventilation by addition of exogenous CO 2 into a rebreathing apparatus. With added CO 2, heart rate, blood pressure, CO, and systemic vascular resistance in hyperventilation became similar to control.ConclusionsWe conclude that all POTS is related to decreased CO, decreased central blood volume, and increased systemic vascular resistance and that a variant of POTS is consequent to postural hyperventilation.

show abstract

mentioning

confidence: 56%

Section: Discussionmentioning

confidence: 99%

Postural Hyperventilation as a Cause of Postural Tachycardia Syndrome: Increased Systemic Vascular Resistance and Decreased Cardiac Output When Upright in All Postural Tachycardia Syndrome Variants

Stewart

Pianosi

Shaban

et al. 2018

JAHA

View full text Add to dashboard Cite

show abstract

“…Cerebral autoregulation dynamics are usually evaluated by the changes in BFV and BP during the interventions that induce rapid BP reductions or increases such as the Valsalva maneuver, thigh cuff deflation and the head-up tilt [2,9,50,[60][61][62][63]. The conventional approach is valuable, because it allows assessments of the autoregulation responses during rapid variations in systemic pressure under the stressed conditions.…”

Section: Ivc Assessment Of Cerebral Autoregulation From Spontaneousmentioning

confidence: 99%

Altered phase interactions between spontaneous blood pressure and flow fluctuations in type 2 diabetes mellitus: Nonlinear assessment of cerebral autoregulation

Peng

Huang

et al. 2008

Physica A: Statistical Mechanics and its Applications

Self Cite

View full text Add to dashboard Cite

Cerebral autoregulation (CA) is an important mechanism that involves dilation and constriction in arterioles to maintain relatively s cerebral blood flow in response to changes of systemic blood pressure. Traditional assessments of CA focus on the changes of cerebral blood flow velocity in response to large blood pressure fluctuations induced by interventions. This approach is not feasible for patients with impaired autoregulation or cardiovascular regulation. Here we propose a newly developed technique-the multimodal pressure-flow (MMPF) analysis, which assesses CA by quantifying nonlinear phase interactions between spontaneous oscillations in blood pressure and flow velocity during resting conditions. We show that CA in healthy subjects can be characterized by specific phase shifts between spontaneous blood pressure and flow velocity oscillations, and the phase shifts are significantly reduced in diabetic subjects. Smaller phase shifts between oscillations in the two variables indicate more passive dependence of blood flow velocity on blood pressure, thus suggesting impaired cerebral autoregulation. Moreover, the reduction of the phase shifts in diabetes is observed not only in previously-recognized effective region of CA (<0.1Hz), but also over the higher frequency range from ~0.1 to 0.4Hz. These findings indicate that Type 2 diabetes alters cerebral blood flow regulation over a wide frequency range and that this alteration can be reliably assessed from spontaneous oscillations in blood pressure and blood flow velocity during resting conditions. We also show that the MMPF method has better performance than traditional approaches based on Fourier transform, and is more sui for the quantification of nonlinear phase interactions between nonstationary biological signals such as blood pressure and blood flow.

show abstract

“…Traditional approaches assess autoregulatory responses by challenging cerebrovascular systems using interventions such as the Valsalva maneuver, thigh cuff deflation and the head-up tilt (Carey et al 2003;Panerai 1998;Novak et al 1998;Tiecks et al 1999;Dawson et al 1999;Panerai et al 2001;Novak et al 2003). These intervention procedures induce large intracranial pressure fluctuations and require patients' cooperation and, therefore, such procedures are limited for clinical evaluation of autoregulation.…”

mentioning

confidence: 99%

Nonlinear Assessment of Cerebral Autoregulation from Spontaneous Blood Pressure and Cerebral Blood Flow Fluctuations

Peng

Czosnyka

et al. 2007

Cardiovasc Eng

Self Cite

View full text Add to dashboard Cite

Cerebral autoregulation (CA) is an most important mechanism responsible for the relatively constant blood flow supply to brain when cerebral perfusion pressure varies. Its assessment in nonacute cases has been relied on the quantification of the relationship between noninvasive beat-to-beat blood pressure (BP) and blood flow velocity (BFV). To overcome the nonstationary nature of physiological signals such as BP and BFV, a computational method called multimodal pressure-flow (MMPF) analysis was recently developed to study the nonlinear BP-BFV relationship during the Valsalva maneuver (VM). The present study aimed to determine (i) whether this method can estimate autoregulation from spontaneous BP and BFV fluctuations during baseline rest conditions; (ii) whether there is any difference between the MMPF measures of autoregulation based on intra-arterial BP (ABP) and based on cerebral perfusion pressure (CPP); and (iii) whether the MMPF method provides reproducible and reliable measure for noninvasive assessment of autoregulation. To achieve these aims, we analyzed data from existing databases including: (i) ABP and BFV of 12 healthy control, 10 hypertensive, and 10 stroke subjects during baseline resting conditions and during the Valsalva maneuver, and (ii) ABP, CPP, and BFV of 30 patients with traumatic brain injury (TBI) who were being paralyzed, sedated, and ventilated. We showed that autoregulation in healthy control subjects can be characterized by specific phase shifts between BP and BFV oscillations during the Valsalva maneuver, and the BP-BFV phase shifts were reduced in hypertensive and stroke subjects (P < 0.01), indicating impaired autoregulation. Similar results were found during baseline condition from spontaneous BP and BFV oscillations. The BP-BFV phase shifts obtained during baseline and during VM were highly correlated (R > 0.8, P < 0.0001), showing no statistical difference (pairedt test P > 0.47). In TBI patients there were strong correlations between phases of ABP and CPP oscillations (R = 0.99, P < 0.0001) and, thus, between ABP-BFV and CPP-BFV phase shifts (P < 0.0001, R = 0.76). By repeating the MMPF 4 times on data of TBI subjects, each time on a selected cycle of spontaneous BP and BFV oscillations, we showed that MMPF had better reproducibility than traditional autoregulation index. These results indicate that the MMPF method, based on instantaneous phase relationships between cerebral blood flow velocity and peripheral blood pressure, has better performance than the traditional standard method, and can reliably assess cerebral autoregulation dynamics from ambulatory blood pressure and cerebral blood flow during supine rest conditions.

show abstract

Hypocapnia and Cerebral Hypoperfusion in Orthostatic Intolerance

Cited by 163 publications

References 23 publications

Postural Hyperventilation as a Cause of Postural Tachycardia Syndrome: Increased Systemic Vascular Resistance and Decreased Cardiac Output When Upright in All Postural Tachycardia Syndrome Variants

Postural Hyperventilation as a Cause of Postural Tachycardia Syndrome: Increased Systemic Vascular Resistance and Decreased Cardiac Output When Upright in All Postural Tachycardia Syndrome Variants

Altered phase interactions between spontaneous blood pressure and flow fluctuations in type 2 diabetes mellitus: Nonlinear assessment of cerebral autoregulation

Nonlinear Assessment of Cerebral Autoregulation from Spontaneous Blood Pressure and Cerebral Blood Flow Fluctuations

Contact Info

Product

Resources

About