Photobiomodulation by light emitting diode applied sequentially does not alter performance in cycling athletes

Lasers in Medical Science - Analyze the effects of sequential application of photobiomodulation therapy (PBMT) at different wavelengths on the performance of cycling athletes. Cyclists (48 male,...     

Management of severe acute renal failure in critically ill patients: an international survey in 345 centres.

The epidemiology of acute renal failure (ARF) has recently displayedan increasing shift of cases from the renal ward to the intensivecare unit (ICU). Accordingly, two groups of physicians are nowhighly involved in the care of ARF patients: nephrologists andintensivists. Renal replacement therapy has also evolved a greatdeal over the last 20 years with the development and increasingapplication of continuous renal replacement therapy (CRRT).Several controversies have developed over which approach topatient care is most desirable and which form of renal replacementtherapy should be applied in preference within the ICU. Thereare also controversies on the best clinical practice for CRRTincluding indications, vascular access, anti-coagulation, membranesand filters, machines and finally, which specialist should bein overall charge of patient care. Taking advantage of two international meetings on renal replacementtherapy and critical care nephrology, we collected the answersto a wide-ranging questionnaire distributed among attendingpractitioners. We now report the responses of 345 physiciansfrom different centres in a wide variety of countries. The questionnaires were accurately prepared and distributedto the delegates of two international meetings carried out inthe US and Europe. The questionnaire was divided into severalsections concerning demographic and medical information, epidemiologyof ARF, practice of CRRT and current opinions about clinicaladvantages and problems related to CRRT. Out of the 375 collected questionnaires, only 345 were completeand could be utilized for the analysis. The respondents werefrom different continents with most in Europe and North America.Physicians were mostly nephrologists or intensivists and onlyfew of them had a combined background. The same was true forthe field of operation and medical specialty. Epidemiology ofARF highlights the shift towards more complicated cases occurringin a critically ill population. High variability was found in the practice of CRRT, althoughit seems that the multidisciplinary approach received a widerconsensus. Anti-coagulation and arterial vascular access stillrepresent a major concern for the treatment, while new machinesand membranes are considered major advances in the field. CRRTare frequently used even in the absence of acute renal failure(52% of the respondents) the prevalent use being for fluid control,congestive heart failure, acute respiratory distress syndrome(ARDS) and sepsis. Our survey describes in detail the problems encountered in theday-to-day practice of CRRT. The analysis outlines the fieldsin which further knowledge and education are definitely needed.A deeper understanding of the mechanisms and procedures involvedin continuous therapies is probably required both from the viewof the nurse and the physician. Several issues are still openand will be matter of controversy in the coming years. For thisreason, we hope that our survey will provide a stimulus fornew studies to seek evidence for different clinical decisions.A wider application of CRRT in the fields of sepsis and multipleorgan failure requires further experience and evidence for clinicalbenefit. In the mean time, several studies will focus on specificaspects such as cytokine removal and physiological responseto continuous versus intermittent therapies. We hope that littleby little these studies will contribute towards piecing togetherthe overall picture. Notes Correspondence and offprint requests to: Dr Claudio Ronco, Departmentof Nephrology, St Bortolo Hospital, I-36100 Vicenza, Italy.     

Probabilistic structure of events controlling the after-storm recovery of coastal dunes

Coastal dunes protect beach communities and ecosystems from rising seas and storm flooding and influence the stability of barrier islands by preventing overwashes and limiting barrier migration. Therefore, the degree of dune recovery after a large storm provides a simple measure of the short-term resiliency (and potential long-term vulnerability) of barrier islands to external stresses. Dune recovery is modulated by low-intensity/high-frequency high-water events (HWEs), which remain poorly understood compared to the low-frequency extreme events eroding mature dunes and dominating the short-term socio-economic impacts on coastal communities. Here, we define HWEs and analyze their probabilistic structure using time series of still-water level and deep-water wave data from multiple locations around the world. We find that HWEs overtopping the beach can be modeled as a marked Poisson process with exponentially distributed sizes or marks and have a mean size that varies surprisingly little with location. This homogeneity of global HWEs is related to the distribution of the extreme values of a wave-runup parameter, HR=HsL0, defined in terms of deep-water significant wave height Hs and peak wavelength L0. Furthermore, the characteristic beach elevation at any given location seems to be tied to a constant HWE frequency of about one event per month, which suggests a stochastic dynamics behind beach stabilization. Our results open the door to the development of stochastic models of beach, dune, and barrier dynamics, as well as a better understanding of wave-driven nuisance flooding.

The statistics of extreme events has been well studied in hydrology using the generalized extreme value distribution (1). A particularly relevant statistical model consists of a Poisson process for the occurrence of an exceedance of a high threshold and a generalized Pareto (GP) distribution for the size of the event (termed “Poisson–GP model”). This model underpins the peak-over-threshold method (1, 2) and has been used to analyze the statistics of extreme wave heights (2, 3) and to simulate extreme total water levels in the Pacific West Coast to complement the scarce observational data on events with return periods above 10 y (4).In the context of dune erosion, the focus on extreme events (4, 5)—usually referred to as events with return periods in the 10- to 100-y range—is understandable, as they can overtop mature dunes and lead to an overwash, where most of the dunes and the plant ecosystem supported by them are eroded away. However, extreme events don’t control the short and midterm dune dynamics, as dunes have plenty of time to recover before the next one. In contrast, high-water events (HWEs) with much shorter return periods (of the order of few months or less; Fig. 1A) can affect the after-storm recovery process by eroding small embryo-dunes, preventing plant colonization of washover fans (i.e., low-lying regions created during an overwash) (Fig. 1B).Open in a separate windowFig. 1.(A) Example of predicted daily maximum total water levels ηd(t), representative of conditions in the Virginia barrier islands, showing HWEs above a typical beach elevation (B). Interarrival times Δt and size or mark S of HWEs are also shown. (B) Typical cross-shore profiles of coastal dunes and a washover fan in Metompkin island, Virginia, illustrating potential morphological effects of HWEs. (C) Illustration of the dune erosional regimes that emerge after superimposing return periods of HWEs potentially overtopping dunes in the Virginia barrier islands (symbols) to the undisturbed after-storm dune-recovery curve (black solid line): h(t)=H(1−e−t/Td) (10), with maximum dune height H=2 m relative to the beach (as in B), dune-formation time Td=H/G, and dune-growth rate G=0.5 m/y (9).Remote-sensing data of dune recovery in low barrier islands suggest a sigmoid growth curve with a slower initial recovery and a final saturation to a maximum dune size (6, 7). However, is the slow initial growth a result of intrinsic limitations in the dune-building process or evidence of the erosional effects of HWEs? After all, storm intensity and frequency have been reported to hinder embryo-dune development (8), and initial dune growth can be fast in locations with little impacts of HWEs, such as on the high-elevation backshore of the coast of Oregon (9).The potential for disruption of low-intensity HWEs becomes evident when superimposing calculated return periods of potentially dune-overtopping HWEs (obtained from data in the Virginia barrier islands; see Calculation of HWEs) to theoretical predictions of the undisturbed after-storm dune-recovery curve (Fig. 1C). Recent numerical simulations (10) and dune-growth data (9) suggest that the undisturbed dune recovery follows an exponential saturation curve of the form h(t)=H(1−e−t/Td), where h(t) is the dune height at time t, H is the maximum dune height, and Td=H/G is the dune-formation time defined in terms of the undisturbed dune-growth rate G. Using a relatively large dune-growth rate (0.5 m/y), characteristic of coastal dunes in Oregon (9), and a maximum dune height (2 m) typical for Hog and Metompkin islands, Virginia (e.g., Fig. 1B), HWEs flooding the Virginia barrier islands (e.g., Fig. 1A) could overtop embryo-dunes for about 4 y after an overwash, potentially leading to widespread erosion and slowing down dune recovery. Once dunes reach about 1 to 1.5 m; they seem to enter a safer period of a few decades where most HWEs don’t reach the dune crest and the overtopping probability is low (although the dune base and front can be partially eroded). Mature dunes can then survive for about 100 y before an extreme event leads to another overwash (Fig. 1C).The competition between dune formation and water-driven erosion has important implications for the stability of barrier islands, with low-intensity HWEs preventing dune recovery and potentially keeping the barrier in a low-elevation, highly vulnerable state (11). In fact, the resiliency of barrier islands can be partially defined by the degree of after-storm dune recovery and, thus, by the frequency and intensity of HWEs (11).Here, we use the peak-over-threshold method to define HWEs and describe their probabilistic structure. Our analysis suggests that HWEs can be modeled as a marked Poisson process with exponentially distributed sizes. In a companion paper (12), we use this result to derive and analytically solve a stochastic model of barrier-elevation dynamics.     

Bench-to-bedside review: Chloride in critical illness

Chloride is the principal anion in the extracellular fluid and is the second main contributor to plasma tonicity. Its concentration is frequently abnormal in intensive care unit patients, often as a consequence of fluid therapy. Yet chloride has received less attention than any other ion in the critical care literature. New insights into its physiological roles have emerged together with progress in understanding the structures and functions of chloride channels. In clinical practice, interest in a physicochemical approach to acid-base physiology has directed renewed attention to chloride as a major determinant of acid-base status. It has also indirectly helped to generate interest in other possible effects of disorders of chloraemia. The present review summarizes key aspects of chloride physiology, including its channels, as well as the clinical relevance of disorders of chloraemia. The paper also highlights current knowledge on the impact of different types of intravenous fluids on chloride concentration and the potential effects of such changes on organ physiology. Finally, the review examines the potential intensive care unit practice implications of a better understanding of chloride.     

The history of horizontal glottectomy

The history of horizontal glottectomy (HG) for the treatment of bilateral vocal cord lesions is not entirely clear. The present investigation analyzes the history of HG on the basis of cross-referenced database searches in general and professional medical literature databases. Books, original historical articles and medical history reviews were evaluated. The initial work was done by Moser in years from 1959 to 1965, and in 1961 he published the first paper on HG. Follow-up publications were reported in 1977 by Gramowski and in 1984 by Wilke. In 1970, Romanian laryngologists headed by Cǎlǎraşu described a HG via excision of a rhomboid-shaped portion of the thyroid cartilage, but the authors had neither sufficient numbers of patients nor a sufficiently long follow-up for the procedure to gain widespread acceptance. In 1978, Calearo and Teatini described HG similar to Cǎlǎraşu’s method, but slightly more extended by the eventual inclusion of an arytenoid cartilage in the operative specimen. Theses authors have often been credited as the originators of the procedure, but actually were the first to publish in an English language journal. The procedure, while quite effective for treatment of bilateral and anterior commissure lesions, has never gained general acceptance in the United States, and in current practice, has been supplanted by endoscopic and non-surgical treatments.     

A general basis for quarter-power scaling in animals

It has been known for decades that the metabolic rate of animals scales with body mass with an exponent that is almost always <1, >2/3, and often very close to 3/4. The 3/4 exponent emerges naturally from two models of resource distribution networks, radial explosion and hierarchically branched, which incorporate a minimum of specific details. Both models show that the exponent is 2/3 if velocity of flow remains constant, but can attain a maximum value of 3/4 if velocity scales with its maximum exponent, 1/12. Quarter-power scaling can arise even when there is no underlying fractality. The canonical “fourth dimension” in biological scaling relations can result from matching the velocity of flow through the network to the linear dimension of the terminal “service volume” where resources are consumed. These models have broad applicability for the optimal design of biological and engineered systems where energy, materials, or information are distributed from a single source.