Search results for "Supine position"

Cardiovascular and respiratory variability during orthostatic and mental stress: A comparison of entropy estimators

2017

The aim of this study is to characterize cardiovascular and respiratory signals during orthostatic and mental stress as reflected in indices of entropy and complexity, providing a comparison between the performance of different estimators. To this end, the heart rate variability, systolic blood pressure, diastolic blood pressure and respiration time series were extracted from the recordings of 61 healthy volunteers undergoing a protocol consisting of supine rest, head-up tilt test and mental arithmetic task. The analysis was performed in the information domain using measures of entropy and conditional entropy, estimated through model-based (linear) and model-free (binning, nearest neighbor)…

Disentangling cardiovascular control mechanisms during head-down tilt via joint transfer entropy and self-entropy decompositions

2015

A full decomposition of the predictive entropy (PE) of the spontaneous variations of the heart period (HP) given systolic arterial pressure (SAP) and respiration (R) is proposed. The PE of HP is decomposed into the joint transfer entropy (JTE) from SAP and R to HP and self-entropy (SE) of HP. The SE is the sum of three terms quantifying the synergistic/redundant contributions of HP and SAP, when taken individually and jointly, to SE and one term conditioned on HP and SAP denoted as the conditional SE (CSE) of HP given SAP and R. The JTE from SAP and R to HP is the sum of two terms attributable to SAP or R plus an extra term describing the redundant/synergistic contribution to the JTE. All q…

Clinical Assessment of Nasal Airway Obstruction

2019

For the evaluation of nasal airway obstruction physical examination, anterior rhinoscopy, laboratory workup, imaging studies, and rhinomanometric studies may be required. Laboratory workup may consist of counts of neutrophil investigating infectious diseases, eosinophil for allergy-related disorders, and mast cell in food allergy. Imaging workup contains computed tomography (CT) and magnetic resonance imaging. Physically based studies involve rhinomanometry and acoustic rhinometry techniques. Nasal resistance is responsible for more than 50% of the resistance of the total airway. Nasal resistance is made up of two layers: the deeper layer consists of underlying bone, cartilage, and muscle, …

Information-theoretic assessment of cardiovascular variability during postural and mental stress

2016

This study was aimed at investigating the individual and combined effects of postural and mental stress on short-term cardiovascular regulation. To this end, we applied measures taken from the emerging framework of information dynamics on the beat-to-beat spontaneous variability of RR interval and systolic arterial pressure (SAP) measured from healthy subjects in the resting supine position and during the separate and simultaneous execution of experimental protocols performing head-up tilt (HUT) and mental arithmetics (MA). The information stored in RR interval variability, a measure inversely related to the complexity of the time series, increased significantly during HUT and HUT+MA compar…

A simple method for preoperative assessment of the best fitting electrode length in single lead VDD pacing.

1996

For single lead VDD pacing, electrodes with various distances between the lead tip and the floating atrial dipole (AV distance) are available. Using different AV distances allows positioning of the atrial dipole in the mid- to high right atrium, regardless of the size of the right heart. In this position, reliable atrial sensing and rejection of ventricular far-field potentials can be expected. A simple test for the preoperative assessment of the best fitting AV distance in the individual patient was tested. We studied 24 consecutive patients prior to implantation of a VDD pacemaker. With the patient in supine position, a test electrode with an AV distance of 13 cm was taped onto the thorax…

Threshold-based vestibular adaptation to cross-coupled canal stimulation

2008

Prior experiments have demonstrated that people are able to adapt to cross-coupled accelerations associated with head movements while spinning at high rotation rates (e.g., 23 rpm or 138°/s). However, while adapting, subjects commonly experience serious side effects, such as motion sickness, non-compensatory eye movements, and strong and potentially disorienting illusory body tilt or tumbling sensations. In the present study, we investigated the feasibility of adaptation using a threshold-based method, which ensured that the illusory tilt sensations remained imperceptible or just barely noticeable. This was achieved by incrementally increasing the angular velocity of the horizontal centrifu…

Sonographic evidence of intraperitoneal fluid. An experimental study and its clinical implications.

1984

In order to evaluate the sensitivity of ultrasound to intraperitoneal fluid, such as ascites or blood, an experimental study was performed in the pig. Various amounts of fluid were injected into the peritoneal cavity to investigate distribution and diagnostic criteria in different positions. As little as 10 ml of fluid was visualized around the urinary bladder in an upright position. In the supine position, 20 ml could be detected around the bladder and 30 ml around the liver. The injection of at least 60 ml resulted in a pattern of free-floating bowel loops. The sonographic findings of fluid distribution were correlated to radiological studies. As different amounts of fluid produce charact…

2017

Purpose Intraocular pressure (IOP) fluctuation is considered as a risk factor for glaucoma progression. We investigated IOP values and IOP fluctuation before and after trabeculectomy (TE) with mitomycin C (MMC) measured by 48-hour diurnal-nocturnal-IOP-profiles (DNP). Methods Pre- and postoperative DNPs of 92 eyes undergoing primary TE with MMC were analysed. Each 48-hour IOP-profile involved 10 IOP measurements (8:00 a.m., 2:00 p.m., 6:00 p.m., and 9:00 p.m. in sitting and at 00:00 in supine position). The “preoperative DNP” was performed a few weeks before TE. The “postoperative DNP” was performed at least six months (range: 6 months—2 years) after TE. Mean IOP values and IOP fluctuations…

Biophysics of venous return from the brain from the perspective of the pathophysiology of chronic cerebrospinal venous insufficiency

2011

This article discusses the biophysical aspects of venous outflow from the brain in healthy individuals and in patients with chronic cerebrospinal venous insufficiency. Blood flows out of the brain differently, depending on body position. In the supine position it flows out mainly through internal jugular veins, while in the upright position it uses the vertebral veins. This phenomenon is probably not due to the active regulation of the flow but instead results from the collapse of jugular veins when the head is elevated. Such a collapse is associated with a significant increase in flow resistance, which leads to redirection of the flow towards the vertebral pathway. Theoretical calculations…

Amputación abdominoperineal extraelevadora en posición prono

2014

The Miles operation is every day more in the limelight. The abdominoperineal resection compared to anterior resection results in increased rate of circumferential resection margin (CRM) infiltration, increased iatrogenic tumor perforation rate and poorer quality of the mesorectum. These worse results may be caused by excessive dissection between the distal mesorectum and the plane of the levator ani and the consequent "resection waist" or "cone" effect in the specimen. A wider excision of the pelvic floor muscles, known as extraelevator abdominoperineal resection (ELAPE), would provide a "cylindrical" specimen which would hypothetically reduce the risk of tumor perforation and CRM infiltrat…