We tested whether seal location at iliac crest (IC) or upper abdomen (UA), before and during lower body negative pressure (LBNP), would affect thoracic electrical impedance, hepatic blood flow, and central cardiovascular responses to LBNP. After 30 min of supine rest, LBNP at -40 mmHg was applied for 15 min, either at IC or UA, in 14 healthy males. Plasma density and indocyanine green concentrations assessed plasma volume changes and hepatic perfusion. With both sealing types, LBNP-induced effects remained unchanged for mean arterial pressure (-3.0±1.1 mm Hg), cardiac output (-1.0 l min-1), and plasma volume (-11 %). Heart rate was greater during UA (80.6±3.3 bpm) than IC (76.0±2.5 bpm) (p<0.01) and thoracic impedance increased more using UA (3.2±0.2 Ω) than IC (1.8±0.2 Ω) (p<0.0001). Furthermore, during supine rest, UA was accompanied by lower thoracic impedance (26.9±1.1 vs 29.0±0.8 Ω , p<0.001) and hepatic perfusion (1.6 vs 1.8 l.min-1, p<0.05) compared to IC. The data suggest that the reduction in central blood volume in response to LBNP depends on location of the applied seal. The sealing in itself altered blood volume distribution and hepatic perfusion in supine resting humans. Finally, application of LBNP with the seal at the upper abdomen induced a markedly larger reduction in central blood volume and greater increases in heart rate than when the seal was located at the iliac crest., N. Goswami ... [et al.]., and Obsahuje seznam literatury
Diabetes mellitus 2 (DM2) is the seventh cause of death worldwide. One of the reasons is late diagnosis of vascular damage. Pulse wave velocity (PWV) has become an independent marker of arterial stiffness and cardiovascular risk. Moreover, the previous studies have shown the importance of beat-to-beat PWV measurement due to its variability among the heart cycle. However, variability of PWV (PWVv) of the whole body hasn't been examined yet. We have studied a group of DM II and heathy volunteers, to investigate the beat-to-beat mean PWV (PWVm) and PWVv in the different body positions. PWV of left lower and upper extremities were measured in DM2 (7 m/8 f, age 68±10 years, BP 158/90±19/9 mm Hg) and healthy controls (5 m/6 f, age 23±2 years, BP 117/76±9/5 mm Hg). Volunteers were lying in the resting position and of head-up-tilt in 45° (HUT) for 6 min. PWVv was evaluated as a mean power spectrum in the frequency bands LF and HF (0.04-0.15 Hz, 0.15-0.5 Hz). Resting PWVm of upper extremity was higher in DM2. HUT increased lower extremity PWVm only in DM2. Extremities PWVm ratio was significantly lower in DM2 during HUT compared to controls. LF and HF PWVv had the same response to HUT. Resting PWVv was higher in DM2. Lower extremity PWVv increased during HUT in both groups. PWVm and PWVv in DM2 differed between extremities and were significantly influenced by postural changes due to hydrostatic pressure. Increased resting PWVm and PWVv in DM2 is a marker of increased arterial stiffness.
Sustained orthostasis elicits the elevation of arterial blood pressure (BP) via sympathetic activation in conscious Wistar rats for at least 2 hours. We tested the hypothesis whether vestibular apparatus plays a role in BP and heart rate (HR) control in response to prolonged gravitational stress. BP and HR responses to 45º head-up for either 2 or 24 hours were monitored by telemetry. Vestibular lesions (VL) were performed by a modified microsurgical-chemical technique. Horizontal BP and HR were not influenced by VL preceding 2-hour tilt. VL abolished the sustained 2-hour BP response to head-up tilt (8.3±0.9 mm Hg relative to horizontal values) while suppressed HR transiently only. VL eliminated diurnal BP fluctuations and decreased HR in horizontal position for 24 hours. Head-up tilt for 24 hours increased BP and HR progressively in intact animals, raising their daily average value by 5.6±0.7 mm Hg and 22.2±6 BPM, respectively. VL resulted in an initial BP rise followed by progressive BP reduction in response to long-term head-up tilt (4±2.2 mm Hg) without eliminating the tachycardia (34.4±5.4 BPM). Thus, blockade of labyrinthine inputs attenuates the BP responses elicited by both intermediate and long-term gravitational stress of orthostatic type. However, other sensory inputs derived from non-vestibular cues (e.g. proprioceptive, visual, visceral, cutaneous etc.) seem to be effective enough to maintain BP normal., G. Raffai ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy