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Effects of various countermeasures against the adverse effects of weightlessness on central circulation in the healthy man.

The effect of lower body negative pressure, local negative pressure below the knee joint, and both pneumatic and mechanical occlusion cuffs at the upper third of the femur on central circulation, oxidative metabolism, and acid-base equilibrium of blood was studied on eight healthy male volunteers with doublelumen Swan-Ganz flow-directed thermodilution catheters implanted for 7 d into the pulmonary artery. The counter-measures against the adverse effects of weightlessness were used in two regimens: regimen I at -30, -50, +40 torr and regimen II at -60, -100, and +60 torr. The parameters were re…

Abnormal baroreflex responses in patients with idiopathic orthostatic intolerance.

BACKGROUND: Patients diagnosed with idiopathic orthostatic intolerance report symptoms of lightheadedness, fatigue, and nausea accompanied by an exaggerated tachycardia when assuming the upright posture. Often, these symptoms are present in the absence of any decrease in arterial pressure. We hypothesized that patients with idiopathic orthostatic intolerance would have impaired cardiac vagal and integrated baroreflex function, lower blood volume, and increased venous compliance. METHODS AND RESULTS: Sixteen patients and 14 healthy control subjects underwent the modified Oxford technique to as

Cerebral versus systemic hemodynamics during graded orthostatic stress in humans.

BACKGROUND: Orthostatic syncope is usually attributed to cerebral hypoperfusion secondary to systemic hemodynamic collapse. Recent research … ESULTS: To test this hypothesis, we studied 13 healthy men (age, 27 +/- 7 years) during progressive lower body negative pressure (LBNP). We measured systemic flow (Qc is cardiac output; C2H2 rebreathing), regional forearm flow (FBF; venous occlusion plethysmography), and blood pressure (BP; Finapres) and calculated systemic (SVR) and forearm (FVR) vascular resistances. Change …

Evaluation of the routine use of the nasogastric tube in digestive operation by a prospective controlled study.

This prospective, randomized controlled trial was undertaken to evaluate the effect of tube decompression of the stomach after surgical procedure on the digestive tract. One hundred and nine patients were randomly allocated to postoperative treatment with (57 patients) or without (52 patients) nasogastric tubes. No significant differences were found between the two groups in the duration of hospitalization, time to begin peroral fluid intake, occurrence of hiccups, vomiting, nausea, parotiditis, nasal septum necrosis, anastomotic leak and wound dehiscence. Moreover, abdominal distension, pyros

Impact of acute mild and severe poikilocapnic hypoxia on dynamic cerebral autoregulation and its directional sensitivity in young healthy volunteers.

Dynamic cerebral autoregulation (dCA) stabilizes cerebral blood flow (CBF) during rapid mean arterial pressure (MAP) changes and exhibits di … xt]= 0.21), on dCA and its directional sensitivity. Twenty participants completed 6-min oscillatory lower body negative pressure (OLBNP) trials at 0.05 and 0.10 Hz in three distinct sessions, where MAP and middle cerebral artery mean blood velocity (MCAv) were continuously recorded. dCA and its hysteresis-like pattern were quantified using transfer function analysis (TFA) and …

Cardiovascular responses to cold pressor and LBNP tests before and after 20-day-bedrest.

The orthostatic hypotension after weightlessness has been suggested mainly because of the blood volume reduction, and decrease in stroke vol … hanges in the response to the cold pressor test, they may be related to the changes of responses to lower body negative pressure (LBNP) test.

Effects of lower body positive pressure on muscle sympathetic nerve activity response [correction of respopnse] to head-up tilt.

The benefits of lower body positive pressure (LBPP) are generally accepted for clinical treatment in medical emergencies caused by massive bleeding to maintain the systemic blood pressure. They are also used by NASA post spaceflight for preventing orthostatic hypotension in the astronauts. However, controversy still exists concerning the mechanisms underlying LBPP benefits. The purpose of this study was to test the hypothesis that the baroreflex-mediated enhancement in sympathetic activity would be attenuated by LBPP during an orthostatic challenge in humans. Specifically, we studied 1) the sy

Variability in orthostatic tolerance during heat stress: cerebrovascular reactivity to arterial carbon dioxide.

INTRODUCTION: A high degree of interindividual variability exists in the magnitude of heat stress (HS)-induced reductions in orthostatic tolerance relative to normothermia (NT). This variability may be associated with HS-mediated reductions in cerebral perfusion (indexed as middle cerebral artery blood velocity; MCAV(mean)) and altered cerebrovascular regulation. METHODS: We tested the hypothesis that cerebrovascular reactivity to hypocapnia would be positively correlated with differences in tolerance to lower body negative pressure (LBNP) [assessed with a cumulative stress index (CSI)] betwe…

The roles of orthostatic hypotension, orthostatic tachycardia, and subnormal erythrocyte volume in the pathogenesis of the chronic fatigue syndrome.

BACKGROUND: Orthostatic hypotension during upright tilt is an important physical disorder in patients with chronic fatigue syndrome. We have tested its occurrence during prolonged standing, whether it is correctable, and whether reduced circulating erythrocyte volume is present. METHODS: Fifteen patients were randomly selected from a large population of patients with chronic fatigue syndrome, studied, and observed for several years (by DSB). Blood pressure (BP) and heart rate (HR) measured with Dinamap every minute for 30 minutes supine and 60 minutes standing were compared with these finding

Abdominal decompression in normal pregnancy.

BACKGROUND: Abdominal decompression was developed as a means of pain relief during labour. It has also been used for complications of pregnancy, and in healthy pregnant women in an attempt to improve fetal wellbeing and intellectual development. OBJECTIVES: The objective of this review was to assess the effects of prophylactic abdominal decompression on pregnancy outcomes such as admission for pre-eclampsia, fetal growth, perinatal morbidity and mortality and childhood development. SEARCH METHODS: We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (2 February 2012). S

Cardiovascular adaptations, fluid shifts, and countermeasures related to space flight.

Significant progress has been made related to understanding cardiovascular adaptations to microgravity and development of countermeasures to … ons of the body. Over the past 10 years, our studies have documented that treadmill exercise within lower body negative pressure counteracts most physiologic decrements with bed rest in both women and men. Future studies should improve hardware and protocols to protect crew members during prolonged missions. Finally, it is proposed that transcapillary fluid shifts in microgra …

Altered baroreflex control of forearm vascular resistance during simulated microgravity.

Reflex peripheral vasoconstriction induced by activation of cardiopulmonary baroreceptors in response to reduced central venous pressure (CV … grees head-down bedrest for 7 days and measured specific hemodynamic responses to low levels of the lower body negative pressure to determine if there are alterations in cardiopulmonary baroreceptor stimulus-FVR reflex response relationship during prolonged exposure to an analog of microgravity.

Reflex control of circulation and angiotensin converting enzyme inhibition in man.

Removal of the facilitating effect of angiotensin II on sympathetic cardiovascular influences may enhance the antihypertensive effect of angiotensin converting enzyme (ACE) inhibitors but may also disturb reflexes involved in blood pressure homeostasis. To test this hypothesis in essential hypertensive subjects, the forearm vasomotor response to cardiopulmonary receptor deactivation (lower body negative pressure) was studied before and after acute or prolonged administration of captopril at doses capable of lowering blood pressure and blocking the formation of angiotensin II. After either acut…

Cardiopulmonary baroreflexes fail to modulate sympathetic responses during isometric exercise in humans: direct evidence from microneurographic studies.

To further evaluate the reported interaction in animals and humans between cardiopulmonary baroreflexes and the somatic pressor reflex, studies were performed in 16 normal men using direct measurements of efferent sympathetic nerve activity to muscle (microneurography) during sustained isometric handgrip (30% maximal voluntary contraction). Forearm vasoconstrictor (plethysmography) and muscle sympathetic nerve activity responses to sustained handgrip were measured during cardiopulmonary baroreceptor deactivation (lower body negative pressure, n = 8) and activation (volume expansion, n = 8). In…

Biological sex modulates dynamic cerebral autoregulation and its directional sensitivity.

Dynamic cerebral autoregulation (dCA) exhibits directional sensitivity, characterized by greater buffering capacity of cerebral blood flow when mean arterial pressure (MAP) increases than when MAP decreases. Although dCA is known to differ between sexes, it remains unclear whether its hysteresis-like pattern is sex-dependent. In 35 healthy participants (17 females and 18 males; age: 29 ± 7 yr), we assessed the influence of sex on dCA and its directional sensitivity. Participants underwent 7 min of oscillatory lower body negative pressure (OLBNP) at ∼0.05 Hz (20-s cycles) and ∼0.10 Hz (10-s cyc…

Поврежденный неактивный поток крови у взрослых с множественным склерозом во время симпатоэксцитационного стимулятора.

Лица с множественным склерозом (МС) демонстрируют снижение физической способности, отчасти из-за автономной дисфункции. Автономные дефекты хорошо задокументированы, однако регулирование периферического потока крови во время физических упражнений остается неясным. Мы сравнили периферийные сосудистые реакции с динамическими упражнениями рукоприкладства, с и без легкой симпатоэксциативной стимуляцией, у людей с MS и без них. Двадцать один человек с MS (M/F: 4/17; 43 ± 10 лет) и 27 человек без MS (M/F: 10/17; 28 ± 6 лет) закончили 5-минутное динамическое ручное упражнение при 15% и 30% максимально

Совпадение в аннотации оригинала
Individuals with multiple sclerosis (MS) exhibit reduced physical capacity, partly due to autonomic dysfunction. Autonomic impairments are w … handgrip exercise at 15% and 30% maximal voluntary contraction, which were repeated during -20 mmHg lower body negative pressure (LBNP). BP was assessed using finger photoplethysmography, and brachial artery blood flow via ultrasound. Individuals with MS had increased forearm vascular conductance to the inactive limb at baseline and in response to exercise compared to control …

The effects of isometric exercise training on resting blood pressure and orthostatic tolerance in humans.

Isometric exercise training has been shown to reduce resting blood pressure, but the effect that this might have on orthostatic tolerance is … ivities throughout the 18 weeks of the study. In all subjects orthostatic tolerance, assessed using lower body negative pressure (LBNP), and resting blood pressure were measured before and after each of the 5 week training or control periods. Estimated lean leg volume was determined before and after leg-training. During all LBNP tests, heart rate and blood pressure were recor …

Subtle involvement of the sympathetic nervous system in amyotrophic lateral sclerosis.

The literature on the involvement of the autonomic nervous system (ANS) in amyotrophic lateral sclerosis (ALS) is conflicting. We therefore investigated several aspects of autonomic function, namely muscle sympathetic nerve activity (MSNA), blood pressure, cardiac function (electrocardiogram; ECG), and respiration in 16 patients with sporadic ALS and in 12 age-matched healthy volunteers, both at rest and during sympathoexcitatory stimulation. We measured MSNA by provoking venous pooling during short-lasting lower body negative pressure (LBNP) and during the cold pressor test (CPT). To assess t…

An assessment of hypercapnia-induced elevations in regional cerebral perfusion during combined orthostatic and heat stresses.

We investigated that the effects of hypercapnia-induced elevations in cerebral perfusion during a heat stress on global cerebrovascular responses to an orthostatic challenge. Seven volunteers completed a progressive lower-body negative pressure (LBNP) challenge to presyncope during heat stress, with or without breathing a hypercapnic gas mixture. Administration of the hypercapnic gas mixture increased the partial pressure of end-tidal CO2 greater than pre-heat stress alone, and increased both internal carotid artery (ICA) and vertebral artery (VA) blood flows (P < 0.05). During LBNP, both ICA