1,721,096 research outputs found
Postural lung volume reduction, expiratory flow limitation, and orthopnoea in diaphragmatic weakness: Preliminary observations
Full text linkEffects of venous compression of the legs on overnight rostral fluid shift and obstructive sleep apnea
No full textThe amount of fluid displaced overnight from the legs into the neck as a consequence of lying recumbent
correlates with the number of apneas and hypopneas per hour of sleep (AHI). Sedentary living promotes
dependent fluid accumulation in the legs that can be counteracted by venous compression of the legs
(compression stockings). We hypothesized that, in non-obese sedentary men with obstructive sleep
apnea (OSA), wearing compression stockings during daytime will reduce the AHI by reducing the amount
of fluid available for the displacement into the neck overnight. Polysomnography and measurement of
overnight changes in leg fluid volume and neck circumference were performed at baseline and after one
day of legs venous compression. The median AHI decreased from 30.9 (interquartile range 19.6–60.4) to
23.4 (12.9–31.8) (P = 0.016) in association with a median 40% reduction in the change in leg fluid volume
(P = 0.016) and a median 42% reduction in the increase in neck circumference (P = 0.016). These results
provide proof-of-principle that overnight fluid displacement into the neck plays a causative role in OSA
Dynamic hyperinflation and flow limitation during methacholine-induced bronchoconstriction in asthma
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Postural preinspiratory cortical activity, genioglossus activity and fluid shift in awake obstructive sleep apnoea patients
No full textThe anatomy and mechanical properties of the upper airway (UA) depend on posture. Lying in a supine position causes cephalad fluid shift to the neck, thus narrowing the UA and pre- disposing the individual to obstructive sleep apnoea (OSA). Increased UA dilator muscle activity during wakefulness prevents the UA collapse but the underlying mechanism has not yet been elucidated. In the sitting position during wakefulness, some OSA patients exhibit preinspiratory cortical activity (preinspiratory potential, PIP) probably related to UA abnormalities. The aim of this study was to investigate changes in the preinspiratory cortical activity and UA dilator muscle in OSA patients during postural challenge. An electroencephalogram was used to detect PIP, and the genioglossus electromyographic activity and ventilation were analysed in 17 awake, male OSA patients while they were sitting, just after lying down, and then in response to leg positive pressure to enhance cephalad fluid shift. The prevalence of PIP decreased from 53% (sitting) to 12% (supine) (P = 0.002) in association with increased genioglossus activity (tonic from median (25th, 75th centiles) 2.3 (1.8, 2.8)% to 3.6 (1.7, 5.0)% of voluntary deglutition, P = 0.019; phasic from 2.3 (1.9, 2.8)% to 3.7 (2.0, 6.1)%, P = 0.024), and with increased transcutaneous carbon dioxide pressure (from 43.0 (42.4, 44.2) to 44.6 (43.5, 45.2) mmHg). No change was observed during leg-positive-pressure application. Moving from the sitting position to the supine position reduces respiratory-related premotor cortical activity in awake OSA patients. The concomitant increase in genioglossus activity, therefore, is not driven by cortical respiratory activity
Electroencephalographic evidence for pre-motor cortex activation during inspiratory loading in humans
No full textFaced with mechanical inspiratory loading, awake animals and anaesthetized humans develop
alveolar hypoventilation, whereas awake humans do defend ventilation. This points to a
suprapontine compensatory mechanism instead of or in addition to the ‘traditional’ brain-
stem respiratory regulation. This study assesses the role of the cortical pre-motor representation
of inspiratory muscles in this behaviour. Ten healthy subjects (age 19–34 years, three men)
were studied during quiet breathing, CO2-stimulated breathing, inspiratory resistive loading,
inspiratory threshold loading, and during self-paced voluntary sniffs. Pre-triggered ensemble
averaging of Cz EEG epochs starting 2.5 s before the onset of inspiration was used to
look for pre-motor activity. Pre-motor potentials were present during voluntary sniffs in all
subjects (average latency (±S.D.): 1325 ± 521 ms), but also during inspiratory threshold loading
(1427 ± 537 ms) and during inspiratory resistive loading (1109 ± 465 ms). Pre-motor potentials
were systematically followed by motor potentials during inspiratory loading. Pre-motor
potentials were lacking during quiet breathing (except in one case) and during CO2-stimulated
breathing (except in two cases). The same pattern was observed during repeated experiments
at an interval of several weeks in a subset of three subjects. The behavioural component of
inspiratory loading compensation in awake humans could thus depend on higher cortical motor
areas. Demonstrating a similar role of the cerebral cortex in the compensation of disease-related
inspiratory loads (e.g. asthma attacks) would have important pathophysiological implications:
it could for example contribute to explain why sleep is both altered and deleterious in such
situations
Effect of salbutamol on dynamic hyperinflation in chronic obstructive pulmonary disease patients.
No full textPostural respiratory-related cortical activation and rostral fluid shift in awake healthy humans
No full textMoving from sitting upright to lying supine causes anatomical modifications and a fluid shift to the neck, which represent inspiratory loads that predispose to upper airway collapse. The pre- inspiratory potential (PIP) corresponds to the cortical activity observed during inspiratory load. In the sitting position during wakefulness, some obstructive sleep apnoea patients exhibit PIP, probably in relationship to upper airway abnormalities. The aim of this study was to investigate whether moving to the supine position induces respiratory-related cortical activation (PIP) in awake healthy subjects. The ECG was analysed to detect PIP, and EMG activity of the genioglossus muscle and ventilation were measured in the sitting position, immediately after moving to the supine position, and during application of leg positive pressure in the supine position to promote fluid shift, which was measured by bioelectrical impedance. Twenty-four subjects were included. From sitting to lying, PIP prevalence increased from 1/24 to 11/24 (P = 0.002), and ventilation decreased with no change in genioglossus activity. The fluid shift from sitting to supine was higher in the subjects exhibiting PIP while supine compared with the subjects without PIP [median (25th; 75th centiles) 440 (430; 520) versus 320 (275; 385) ml, P = 0.018], without any other differences. From before to during leg positive pressure, PIP disappeared (P = 0.006). These results indicate that moving from sitting to lying induces transient respiratory-related cortical activity in awake healthy subjects with greater fluid shift, supporting possible cortical participation in the response to upper airway loading induced by moving from sitting upright to lying supine. This study offers new perspectives in the understanding of obstructive sleep apnoea pathogenesis
Evening sock marks as an adjunct to the clinical prediction of obstructive sleep apnea
No full textStudy objectives Fluid overload shifting from the legs to the upper airway during sleep promotes obstructive sleep apnea (OSA) and interventions targeting fluid attenuate OSA. Fluid shift has been previously measured by bioelectrical impedance, a complex and time-consuming technique not applicable in the daily clinical settings. The aim of this study is to evaluate the presence of clinically detectable fluid overload and shift and its association with OSA.
Methods Patients undergoing sleep study for suspected OSA were asked to report the presence of 11 signs/symptoms associated to excessive accumulation of fluid in different parts of the body at different times of the day.
Results Among 392 patients (male: 53%, median [interquartile range] age: 56 years [1], body mass index, BMI: 29 kg/m2 [2]) included in the study, 135 (34%) had moderate-to-severe OSA (apnea hypopnea index, AHI ≥ 15). Daytime fluid accumulation and nocturnal fluid shift, clinically detectable by patient-reported “evening sock marks,” “heavy legs during the day,” and “morning stuffed nose,” were prevalent in the entire population (46%, 43%, and 33%, respectively). In multivariate analysis, evening sock marks was an independent correlate of having an AHI ≥ 15, together with male sex, older age, and self-reported snoring and apneas.
Conclusions Clinically detectable fluid overload and shift are prevalent in patients addressed for suspected OSA, and evening sock marks, a marker for leg swelling, is an independent correlate of moderate-to-severe OSA. This sign might contribute to OSA diagnosis and identification of patients likely to be treated by interventions targeting fluid overload and shift
- …
