The use and effectiveness of exercise for managing postural orthostatic tachycardia syndrome in young adults with joint hypermobility and related conditions: A scoping review.

Purpose: Postural Orthostatic Tachycardia Syndrome (POTS) is a form of dysautonomia. It may occur in isolation, but frequently co-exists in individuals with hypermobile variants of Ehlers-Danlos Syndrome (EDS) and related conditions (chronic fatigue syndrome [CFS] and fibromyalgia). Exercise is recommended for non-pharmacological POTS management but needs to be individualised.

Interaction of large artery stiffness and baroreceptor function explored through multiple measurement techniques - a pilot study.

Baroreceptors, sensors that play a role in controlling arterial blood pressure (BP), are mechanical stretch receptors located in the aortic arch and carotid sinuses. Factors affecting the degree of stretch in the vessel wall with BP, such as increased arterial stiffness, may compromise baroreceptor sensitivity (BRS) to BP changes. Yet, evidence of this is scattered, as both baroreceptor sensitivity (BRS) and arterial stiffness are calculated variables with multiple methodological approaches.

Inspiratory muscle reflex control after incomplete cervical spinal cord injury.

In healthy individuals, loading inspiratory muscles by brief inspiratory occlusion produces a short-latency inhibitory reflex (IR) in the electromyographic (EMG) activity of scalene and diaphragm muscles. This IR may play a protective role to prevent aspiration and airway collapse during sleep. In people with motor and sensory complete cervical spinal cord injury (cSCI), who were able to breathe independently, this IR was predominantly absent.

The prevalence and impact of orthostatic intolerance in young women across the hypermobility spectrum.

Orthostatic intolerance (OI) is frequently reported in young women with generalized hypermobility spectrum disorder (G-HSD) and hypermobile EDS (hEDS). However, it remains currently unclear whether OI is a comorbidity or fundamental part of the pathophysiology of G-HSD or hEDS. This study investigated the prevalence and impact of OI in young women across the hypermobility spectrum.

Assessing breast lymphoedema following breast cancer treatment using indocyanine green lymphography.

Purpose: Breast lymphoedema is a largely unrecognised survivorship issue for women following breast cancer treatment. While a few objective methods have previously been applied to assess breast lymphoedema, none are capable of imaging breast lymphatics or identifying lymphatic morphological changes indicative of breast lymphoedema. The purpose of this study was to determine if indocyanine green (ICG) lymphography, a validated assessment technique in breast cancer-related lymphoedema), can visualise breast lymphatics and identify breast lymphoedema.

Distress during airway sampling in children with cystic fibrosis.

Background: Oropharyngeal suction and oropharyngeal swab are two methods of obtaining airway samples with similar diagnostic accuracy in children with cystic fibrosis (CF). The primary aim was comparing distress between suctioning and swabbing. A secondary aim was establishing the reliability of the Groningen Distress Rating Scale (GDRS).

Resting heart rate variability and exercise capacity in Type 1 diabetes.

People with type 1 diabetes (T1D) have lower exercise capacity (O) than their age-matched nondiabetic counterparts (CON), which might be related to cardiac autonomic dysfunction. We examined whether Heart Rate Variability (HRV; indicator of cardiac autonomic modulation) was associated with exercise capacity in those with and without T1D. Twenty-three participants with uncomplicated T1D and 17 matched CON were recruited.

A simplified method for quantifying the subject-specific relationship between blood pressure and carotid-femoral pulse wave velocity.

Devices that estimate blood pressure from arterial pulse wave velocity (PWV) potentially provide continuous, ambulatory blood pressure monitoring. Accurate blood pressure estimation requires reliable quantification of the relationship between blood pressure and PWV. Regression to population normal values or, when using limb artery PWV, changing hydrostatic blood pressure within the limb provides a calibration index.

Influence of cerebral blood flow on central sleep apnea at high altitude.

Study Objectives: To further our understanding of central sleep apnea (CSA) at high altitude during acclimatization, we tested the hypothesis that pharmacologically altering cerebral blood flow (CBF) would alter the severity of CSA at high altitude.

Design: The study was a randomized, placebo-controlled single-blind study.

Setting: A field study at 5,050 m in Nepal.

The influence of tobacco smoking on the relationship between pressure and flow in the middle cerebral artery in humans.

Background: Cigarette smoking is associated with an increased risk of stroke but the mechanism is unclear. The study examined whether acute and chronic cigarette smoking alters the dynamic relationship between blood pressure and cerebral blood flow. We hypothesised that acute and chronic smoking would result in a cerebral circulation that was less capable of buffering against dynamic fluctuations in blood pressure.

Cardiac baroreflex gain is frequency dependent: insights from repeated sit-to-stand maneuvers and the modified Oxford method.

Cardiac baroreflex gain is usually quantified as the reflex alteration in heart rate during changes in blood pressure without considering the effect of the rate of change in blood pressure on the estimated gain. This study sought to (i) characterize baroreflex gain as a function of blood pressure oscillation frequencies using a repeat sit-to-stand method and (ii) compare baroreflex gain values obtained using the sit-to-stand method against the modified Oxford method. Fifteen healthy individuals underwent the repeated sit-to-stand method in which blood pressure oscillations were driven at 0.

Worsening of central sleep apnea at high altitude--a role for cerebrovascular function.

Although periodic breathing during sleep at high altitude occurs almost universally, the likely mechanisms and independent effects of altitude and acclimatization have not been clearly reported. Data from 2005 demonstrated a significant relationship between decline in cerebral blood flow (CBF) at sleep onset and subsequent severity of central sleep apnea that night. We suspected that CBF would decline during partial acclimatization.

Effects of acetazolamide on cerebrovascular function and breathing stability at 5050 m.

One of the many actions of the carbonic anhydrase inhibitor, acetazolamide (ACZ), is to accelerate acclimatisation and reduce periodic breathing during sleep. The mechanism(s) by which ACZ may improve breathing stability, especially at high altitude, remain unclear. We tested the hypothesis that acute I.

Alterations in cerebral blood flow and cerebrovascular reactivity during 14 days at 5050 m.

Brain blood flow increases during the first week of living at high altitude. We do not understand completely what causes the increase or how the factors that regulate brain blood flow are affected by the high-altitude environment. Our results show that the balance of oxygen (O(2)) and carbon dioxide (CO(2)) pressures in arterial blood explains 40% of the change in brain blood flow upon arrival at high altitude (5050 m).

Influence of indomethacin on the ventilatory and cerebrovascular responsiveness to hypoxia.

Indomethacin (INDO) has the potential to be a useful tool to explore the influence of cerebral blood flow and its responses to CO(2) on ventilatory control. However, the effect of INDO on the cerebrovascular and ventilatory response to hypoxia remains unclear; therefore, we examined the effect of INDO on ventilatory and cerebrovascular sensitivity to hypoxia and hypercapnia. We measured end-tidal gases, ventilation (V(e)), and middle cerebral artery velocity (MCAv) before and 90 min following INDO (100 mg) in 12 healthy participants at rest and during hyperoxic hypercapnia and isocapnic hypoxia.

Initial orthostatic hypotension at high altitude.

There are several reports on syncope occurring following standing at high altitude (HA), yet description of the detailed physiological responses to standing at HA are lacking. We examined the hypothesis that appropriate physiological adjustments to upright posture would be compromised at HA (5050 m). Ten healthy volunteers stood up rapidly from supine rest, for 3 min, at sea level and at 5050 m.

Exacerbation of obstructive sleep apnea by oral indomethacin.

Patients with obstructive sleep apnea (OSA) are predisposed to instability in central ventilatory control during sleep. Increased instability, as reflected in an enhanced expired volume in per unit time loop gain, has been associated with a greater predisposition to upper airway collapse. Here, in an otherwise healthy patient with untreated mild OSA, we describe the further exacerbation of OSA after oral indomethacin administration.

Influence of indomethacin on ventilatory and cerebrovascular responsiveness to CO2 and breathing stability: the influence of PCO2 gradients.

Indomethacin (INDO), a reversible cyclooxygenase inhibitor, is a useful tool for assessing the role of cerebrovascular reactivity on ventilatory control. Despite this, the effect of INDO on breathing stability during wakefulness has yet to be examined. Although the effect of reductions in cerebrovascular CO(2) reactivity on ventilatory CO(2) sensitivity is likely dependent upon the method used, no studies have compared the effect of INDO on steady-state and modified rebreathing estimates of ventilatory CO(2) sensitivity.

Influence of high altitude on cerebrovascular and ventilatory responsiveness to CO2.

An altered acid-base balance following ascent to high altitude has been well established. Such changes in pH buffering could potentially account for the observed increase in ventilatory CO(2) sensitivity at high altitude. Likewise, if [H(+)] is the main determinant of cerebrovascular tone, then an alteration in pH buffering may also enhance the cerebral blood flow (CBF) responsiveness to CO(2) (termed cerebrovascular CO(2) reactivity).

Clinical screening of autonomic dysfunction in multiple sclerosis.

Background And Purpose: Multiple sclerosis (MS) can affect the autonomic nervous system. Although exercise may be beneficial for people with MS, those with autonomic dysfunction may have altered heart rate responses to exercise. We investigated the hypothesis that the pattern of increase in heart rate on commencement of a simple cycle test would be different in those participants with MS who had been shown to have autonomic dysfunction on laboratory testing compared with both control participants and MS participants not exhibiting autonomic involvement.

Dynamic cerebral autoregulation and baroreflex sensitivity during modest and severe step changes in arterial PCO2.

Changes in the partial pressure of arterial CO2 (PaCO2) regulates cerebrovascular tone and dynamic cerebral autoregulation (CA). Elevations in PaCO2 also increases autonomic neural activity and may alter the arterial baroreflex. We hypothesized that hypercapnia would impair, and hypocapnia would improve, dynamic CA and that these changes would occur independently of any change in baroreflex sensitivity (BRS).

Human cerebral arteriovenous vasoactive exchange during alterations in arterial blood gases.

Cerebral blood flow (CBF) is highly regulated by changes in arterial Pco(2) and arterial Po(2). Evidence from animal studies indicates that various vasoactive factors, including release of norepinephrine, endothelin, adrenomedullin, C-natriuretic peptide (CNP), and nitric oxide (NO), may play a role in arterial blood gas-induced alterations in CBF. For the first time, we directly quantified exchange of these vasoactive factors across the human brain.

Differential effects of acute hypoxia and high altitude on cerebral blood flow velocity and dynamic cerebral autoregulation: alterations with hyperoxia.

We hypothesized that 1) acute severe hypoxia, but not hyperoxia, at sea level would impair dynamic cerebral autoregulation (CA); 2) impairment in CA at high altitude (HA) would be partly restored with hyperoxia; and 3) hyperoxia at HA and would have more influence on blood pressure (BP) and less influence on middle cerebral artery blood flow velocity (MCAv). In healthy volunteers, BP and MCAv were measured continuously during normoxia and in acute hypoxia (inspired O2 fraction = 0.12 and 0.

Human cerebrovascular and ventilatory CO2 reactivity to end-tidal, arterial and internal jugular vein PCO2.

This study examined cerebrovascular reactivity and ventilation during step changes in CO(2) in humans. We hypothesized that: (1) end-tidal P(CO(2)) (P(ET,CO(2))) would overestimate arterial P(CO(2)) (P(a,CO(2))) during step variations in P(ET,CO(2)) and thus underestimate cerebrovascular CO(2) reactivity; and (2) since P(CO(2)) from the internal jugular vein (P(jv,CO(2))) better represents brain tissue P(CO(2)), cerebrovascular CO(2) reactivity would be higher when expressed against P(jv,CO(2)) than with P(a,CO(2)), and would be related to the degree of ventilatory change during hypercapnia. Incremental hypercapnia was achieved through 4 min administrations of 4% and 8% CO(2).

Early morning impairment in cerebral autoregulation and cerebrovascular CO2 reactivity in healthy humans: relation to endothelial function.

The reduction in cerebrovascular reactivity to CO(2) and/or endothelial function that occurs in the early hours after waking are potential causes for the increased risk for cardiovascular events at this time point. It is unknown whether cerebral autoregulation is reduced in the morning. We tested the hypothesis that early morning reduction in endothelium-dependent vascular reactivity would be linked to changes in cerebrovascular reactivity to CO(2) and cerebral autoregulation (CA).