Chest
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Comparative Study
Skeletal muscle metabolism in the chronic fatigue syndrome. In vivo assessment by 31P nuclear magnetic resonance spectroscopy.
Previous study of patients with chronic fatigue syndrome (CFS) has demonstrated a markedly reduced dynamic exercise capacity, not limited by cardiac performance and in the absence of clinical neuromuscular dysfunction, suggesting the possibility of a subclinical defect of skeletal muscle. ⋯ Patients with CFS and normal control subjects have similar skeletal muscle metabolic patterns during dynamic exercise and reach similar clinical and metabolic end points. However, CFS patients reach exhaustion much more rapidly than normal subjects, at which point they also have relatively reduced intracellular concentrations of ATP. These data suggest a defect of oxidative metabolism with a resultant acceleration of glycolysis in the working skeletal muscles of CFS patients. This metabolic defect may contribute to the reduced physical endurance of CFS patients. Its etiology is unknown. Whether CFS patients' overwhelming tiredness at rest has a similar metabolic pathophysiology or etiology also remains unknown.
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Supranormal mixed venous oxygen saturation (mixed venous hyperoxia), although reported, has never been characterized in humans resuscitated from cardiac arrest (postarrest cardiogenic shock). By contrast, cardiogenic shock without cardiopulmonary arrest (primary cardiogenic shock) is accompanied by mixed venous hypoxia under similar conditions of low oxygen delivery (DO2). The appearance of mixed venous hyperoxia indicates an excessive supply relative to demand in perfused tissue or cellular impairment of oxygen utilization, ie, low systemic oxygen consumption (VO2). Failure to improve VO2 has been associated with a poor outcome in other shock states. ⋯ These findings indicate an impairment of systemic oxygen utilization in postarrest cardiogenic shock patients. In spite of a lower DO2 than survivors, the OER in nonsurvivors remained lower than expected. Venous hyperoxia is a clinical manifestation of this derangement. Epinephrine dose may have a causal relationship. The inability to attain a VO2 of greater than 90 ml/min.m2 after the first 6 h of aggressive therapy was associated with a 100 percent mortality in 24 h.
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Although weaning parameters can accurately predict weaning outcome, variability of the measurements of these parameters has not been closely examined. In the current study, we examined the reproducibility of these parameters using a standardized technique. Before the weaning trial, maximal inspiratory pressure (PImax), minute ventilation (VE), respiratory frequency (f), tidal volume (VT), rapid shallow breathing index (f/VT), and vital capacity (VC) were obtained on three trials over a period of 15 min. ⋯ The VC was the only parameter that showed statistical differences among three trials (p < 0.05). For the group, respiratory frequency had the lowest coefficient of variation (COV = SD/mean x 100 percent) at 6.7 percent while the VC had the highest COV at 19.6 percent. We concluded that most weaning parameters of breathing pattern can be measured reliably with bedside instruments using a standard technique.
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To evaluate the ability of a variety of scoring systems to predict mortality of patients admitted to an intensive care unit (ICU) with acute respiratory failure (ARF) secondary to AIDS-related Pneumocystis carinii pneumonia (PCP). ⋯ The modified MSOF score and the serum LDH level are the best predictors of mortality of patients admitted to ICU with ARF secondary to AIDS-related PCP. The performance of the MSOF score was enhanced when the LDH level was added. The AIDS score, APACHE II, and the acute lung injury score were not found to be useful in this group of critically ill patients.