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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Despite recent therapeutic advances, chronic cardiac failure is still associated with a significant morbidity and mortality. Sleep apnoea syndrome is common in this population, affecting almost half of these patients. However, it is rarely diagnosed and treated. There are two types of sleep apnoea syndrome, which can sometimes co-exist: the obstructive apnoea syndrome with collapse of the upper airways, and the central apnoea syndrome with cyclical Cheyne-Stokes respiration, linked with anomalies of central control. Apnoea leads to sympathetic stimulation and an increase in the left ventricular post-charge which can alter cardiac function and the prognosis. Diagnosis of sleep apnoea syndromes is now made with small ambulatory oxymeters which do not disturb sleep and which allow precise detection of episodes of desaturation. Treatment with positive pressure ventilation brings an improvement in daytime symptoms (fatigue, drowsiness) as well as an improvement in cardiac function. Screening for sleep apnoea is thus essential in patients with chronic heart failure, especially in those resistant to optimal drug treatment, in order to improve their management.
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PMID:[Sleep apnoea syndrome and cardiac failure]. 1581 21

Obstructive sleep apnoea (OSA) is a major clinical disorder characterised by recurring episodes of pharyngeal collapse during sleep. At present, there remains no satisfactory treatment for OSA. Pharmacological therapies as a potential treatment for the disorder are an attractive option and include agents that increase the contractility of the pharyngeal muscles. The aim of the present study was to examine the effects of nicotine on upper airway muscle contractile properties. In vitro isometric contractile properties were determined using strips of rat sternohyoid muscle in physiological salt solution containing nicotine (0-100 microg/ml) at 25 degrees C. Isometric twitch and tetanic tension, contraction time, half-relaxation time and tension-frequency relationship were determined by electrical field stimulation with platinum electrodes. Fatigue was induced by stimulation at 40 Hz with 300 ms trains at a frequency of 0.5 Hz for 5 min. Nicotine at a concentration of 1 microg/ml was associated with a significant increase in sternohyoid muscle specific tension compared to control data. Dose-dependent increases in contractile tension were not observed. Nicotine had effects on tension-frequency relationship and endurance properties of the sternohyoid muscle at some but not all doses. A leftward shift in the tension-frequency relationship was observed at low stimulus frequencies (20-30 Hz) for nicotine at a concentration of 1 and 5 microg/ml and a significant increase in fatigue resistance was observed with nicotine at a concentration of 10 microg/ml. As fatigue of the upper airway muscles has been implicated in obstructive airway conditions, a pharmacological agent that improves muscle endurance may prove useful as a potential treatment for such disorders. Therefore, further studies of the effects of nicotinic agonists on upper airway function are warranted.
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PMID:Effects of nicotine on rat sternohyoid muscle contractile properties. 1599 35

Estimation of the hip joint contact area and pressure distribution during activities of daily living is important in predicting joint degeneration mechanism, prosthetic implant wear, providing biomechanical rationales for preoperative planning and postoperative rehabilitation. These biomechanical data were estimated utilizing a generic hip model, the Discrete Element Analysis technique, and the in vivo hip joint contact force data. The three-dimensional joint potential contact area was obtained from the anteroposterior radiograph of a subject and the actual joint contact area and pressure distribution in eight activities of daily living were calculated. During fast, normal, and slow walking, the peak pressure of moderate magnitude was located at the lateral roof of the acetabulum during mid-stance. In standing up and sitting down, and during knee bending, the peak pressures were located at the edge of the posterior horn and the magnitude of the peak pressure during sitting down was 2.8 times that of normal walking. The peak pressure was found at the lateral roof in climbing up stairs which was higher than that in going down stairs. These results can be used to rationalize rehabilitation protocols, functional restrictions after complex acetabular reconstructions, and prosthetic component wear and fatigue test set up. The same model and analysis can provide further insight to soft tissue loading and pathology such as labral injury. When the pressure distribution on the acetabulum is inverted onto the femoral head, prediction of subchondral bone collapse associated with avascular necrosis can be achieved with improved accuracy.
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PMID:Three-dimensional dynamic hip contact area and pressure distribution during activities of daily living. 1612 Apr 42

OSA syndrome is characterized by recurring episodes of upper airway (UA) obstruction during sleep. The UA is subjected to collapse when the negative airway pressure generated by inspiratory activity of the diaphragm and intercostal muscles exceeds the force produced by the UA dilating muscles. Factors that reduce UA calibre lead to increased UA resistance with the generation of a more negative pharyngeal pressure during inspiration, and thereby predispose to UA occlusion during sleep. As a consequence, UA dilating muscles must contract more forcefully to maintain a patent UA, which may predispose to fatigue. Nasal CPAP counteracts these collapsing forces and is associated with resting of the UA muscles. The more recent development of auto-adjusting CPAP (APAP) is a reflection of the understanding that the pressure required to prevent UA collapse fluctuates throughout the night and results in a lower mean pressure that may be more comfortable for some patients. The predominant morbidity of the OSA syndrome is cardiovascular and there is growing understanding of the basic mechanisms involved. Intermittent hypoxia appears to play a central role by activating transcription factors that predispose to atherogenesis, particularly NFkappaB. Sympathetic overactivity also appears to play an important role but the mechanisms involved are unclear.
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PMID:Obstructive sleep apnoea syndrome: translating science to clinical practice. 1654 97

Spinal tuberculosis is usually secondary to lung or abdominal involvement and may also be the first manifestation of tuberculosis. Spinal tuberculosis (often called Pott's disease) is by definition, an advanced disease, requiring meticulous assessment and aggressive systemic therapy. Physicians should keep the diagnosis in mind, especially in a patient from a group with a high rate of tuberculosis infection. This review aims on updating the knowledge on spinal tuberculosis and its management. Skeletal involvement has been reported to occur in approximately 10% of all patents with extrapulmonary tuberculosis, and half of these patients develop infection within the spinal column. Symptoms of spinal tuberculosis are back pain, weakness, weight loss, fever, fatigue, and malaise. It is much more prone to develop neurological manifestation, paraplegia of varying degree. The palpation of spinous process in routine clinical examination is the most rewarding clinical method and is an invaluable measure for early recognition. Diagnosis of spinal tuberculosis is made on the basis of typical clinical presentation along with systemic constitutional manifestation and the evidence of past exposure to tuberculosis or concomitant visceral tuberculosis. Magnetic resonance imaging can define the extent of abscess formation and spinal cord compression. The diagnosis is confirmed through percutaneous or open biopsy of the spinal lesion. Surgery is necessary as an adjunct to antibiotic therapy if the vertebral infection produces an abscess, vertebral collapse, or neurologic compression. Some patents need aggressive supportive care owing to tuberculous meningitis or encephalopathy. Moreover, the importance of immediate commencement of appropriate treatment and its continuation for adequate duration along with the proper counseling of the patient and family members should not be underestimated for successful and desired outcome.
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PMID:Pott's spine and paraplegia. 1657 Mar 78

The aim of this paper is to report on the characterization of the influences of foam homogeneity and the cell strut material on the mechanical behaviour and the fracture mode of metallic foams that are promising candidates for new perfectly tailored medical implants. For two open-cell foams with identical cell geometries produced in the same precision-casting process but using different cell strut materials, the stress-strain behaviour and the evolution of damage until fracture is compared. To account for effects arising from a change in the geometry of the cell structure and the resulting homogeneity of the foam, the main characteristics of fracture for the group of closed-cell foams were included in this study. Monotonic tests carried out in compression revealed that foam homogeneity is the major factor with respect to the formation of deformation bands prior to cell collapse in metallic foams. The influence of the cell strut ductility is particularly pronounced in monotonic tension where the fracture mode changes from extremely brittle fracture to strongly plastically deformed cells, with substantial fracture elongation. In tension-tension fatigue as well as under symmetric push-pull loading conditions, damage is governed by a combination of cyclic creep and fatigue crack propagation through the specimen. From a mechanistic point of view no fundamental differences between the three foams tested were detected for these loading conditions. However, in compression-compression fatigue the same dependencies in terms of homogeneity and ductility influence the mechanisms of strain evolution that are active in monotonic compression.
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PMID:Metallic open-cell foams--a promising approach to fabricating good medical implants. 1706 42

The patency of the upper airway is dependent on the sustained activity of upper airway muscles, in particular the genioglossus (GG) muscles which act to protrude the tongue. Obstructive sleep apnea syndrome (OSAS) is a common and serious disorder in which this mechanism fails, resulting in frequent collapse of the airway during sleep. The properties of the upper airway muscles are therefore of interest in both normal and OSAS subjects, so that their role in the pathogenesis of OSAS can be better understood. Electromyography (EMG) is an important tool for assessing muscle activity and has been used in many GG studies. We have designed a new appliance incorporating a surface electrode array for GG EMG recording. The electrode configuration enables estimation of muscle fibre conduction velocity (CV), an important parameter for monitoring muscle fatigue, which has not been studied before in the GG. The appliance is also designed to provide accurate and repeatable placement of electrodes. Preliminary results presented demonstrate the performance of our appliance, which will now be used to measure GG CV in a range of fatiguing conditions.
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PMID:Design of surface electrode array for electromyography in the genioglossus muscle. 1727 77

In this paper we present a statistical analogy between the collapse of solids and living organisms; in particular we deduce a statistical law governing their probability of death. We have derived such a law coupling the widely used Weibull Statistics, developed for describing the distribution of the strength of solids, with a general model for ontogenetic growth recently proposed in literature. The main idea presented in this paper is that cracks can propagate in solids and cause their failure as sick cells in living organisms can cause their death. Making a rough analogy, living organisms are found to behave as "growing" mechanical components under cyclic, i.e., fatigue, loadings and composed by a dynamic evolutionary material that, as an ineluctable fate, deteriorates. The implications on biological scaling laws are discussed. As an example, we apply such a Dynamic Weibull Statistics to large data collections on human deaths due to cancer of various types recorded in Italy: a significant agreement is observed.
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PMID:A statistical analogy between collapse of solids and death of living organisms: proposal for a 'law of life'. 1733 64

Exertional heat illness can affect athletes during high-intensity or long-duration exercise and result in withdrawal from activity or collapse during or soon after activity. These maladies include exercise associated muscle cramping, heat exhaustion, or exertional heatstroke. While certain individuals are more prone to collapse from exhaustion in the heat (i.e., not acclimatized, using certain medications, dehydrated, or recently ill), exertional heatstroke (EHS) can affect seemingly healthy athletes even when the environment is relatively cool. EHS is defined as a rectal temperature greater than 40 degrees C accompanied by symptoms or signs of organ system failure, most frequently central nervous system dysfunction. Early recognition and rapid cooling can reduce both the morbidity and mortality associated with EHS. The clinical changes associated with EHS can be subtle and easy to miss if coaches, medical personnel, and athletes do not maintain a high level of awareness and monitor at-risk athletes closely. Fatigue and exhaustion during exercise occur more rapidly as heat stress increases and are the most common causes of withdrawal from activity in hot conditions. When athletes collapse from exhaustion in hot conditions, the term heat exhaustion is often applied. In some cases, rectal temperature is the only discernable difference between severe heat exhaustion and EHS in on-site evaluations. Heat exhaustion will generally resolve with symptomatic care and oral fluid support. Exercise associated muscle cramping can occur with exhaustive work in any temperature range, but appears to be more prevalent in hot and humid conditions. Muscle cramping usually responds to rest and replacement of fluid and salt (sodium). Prevention strategies are essential to reducing the incidence of EHS, heat exhaustion, and exercise associated muscle cramping.
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PMID:American College of Sports Medicine position stand. Exertional heat illness during training and competition. 1747 83

This article proposes a novel framework classification for the heat illnesses. It argues that heat stroke is the only described condition that is truly a "heat illness" since it is the only condition in which there is clear evidence for a pathological elevation of the core body temperature. If this is correct the non-descript terms such as heat fatigue, heat exhaustion and heat syncopy should be removed from the modern lexicon. Since the evidence is that most cases of post-exercise collapse are due to the development of postural hypotension immediately on the cessation of exercise, it is further proposed that more specific terms such as exercise-associated postural hypotension should be used, when appropriate, to replace the non-descript terms such as heat exhaustion, heat fatigue or heat syncopy. Furthermore this novel classification acknowledges that heat stroke may occur in some as a result of accelerated rates of endogenous heat production (thermogenesis). It also suggests that the elevated body temperature alone may not be the sole cause of fatal outcomes in heat stroke but that toxic chemicals released from damaged muscles by the processes causing this accelerated thermogenesis may also be involved.
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PMID:A modern classification of the exercise-related heat illnesses. 1752 93


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