Does enternal nutrition affect clinical outcome? A systematic review of the randomized trials

Background: Both parenteral nutrition (PN) and enteral nutrition (EN) are widely advocated as adjunctive care in patients with various diseases. A systematic review of 82 randomized controlled trials (RCTs) of PN published in 2001 found little, if any, effect on mortality, morbidity, or duration of hospital stay; in some situations, PN increased infectious complication rates. Objective: To assess the effect of EN or volitional nutrition support (VNS) in individual disease states from available randomized controlled trials (RCTs). Design: We conducted a systematic review. RCTs comparing EN or VNS to untreated controls, or comparing EN to PN, were identified and separated according to the underlying disease state. Meta-analysis was performed when at least 3 RCTs provided data. The evidence from the RCTs was summarized into one of five grades. A or B indicated the presence of strong or weak (low quality RCTs) evidence supporting the use of the intervention. C indicated a lack of adequate evidence to make any decision about efficacy. D indicated that limited data could not support the intervention. E indicated either that strong data found no effect, or that either strong or weak data suggested that the intervention caused harm. Patients and settings: RCTs could include either hospitalized or non-hospitalized patients. The EN or VNS had to be provided as part of a treatment plan for an underlying disease process. Interventions: The RCT had to compare recipients of either EN or VNS to controls not receiving any type of artificial nutrition or had to compare recipients of EN with recipients of PN. Outcome measures: Mortality, morbidity (disease-specific), duration of hospitalization, cost, or interventional complications. Summary of grading: A – No indication was identified. B – EN or VNS in the perioperative patient or in patients with chronic liver disease; EN in critically ill patients or low birth weight infants (trophic feeding); VNS in malnourished geriatric patients. (The low quality trials found a significant difference in survival favoring the VNS recipients in the malnourished geriatric patient trials; two high quality trials found non-significant differences that favored VNS as well.) C – EN or VNS in liver transplantation, cystic fibrosis, renal failure, pediatric conditions other than low birth weight infants, well-nourished geriatric patients, non-stroke neurologic conditions, AIDS; EN in acute pancreatitis, chronic obstructive pulmonary disease, non-malnourished geriatric patients; VNS in inflammatory bowel disease, arthritis, cardiac disease, pregnancy, allergic patients, preoperative bowel preparation D – EN or VNS in patients receiving non-surgical cancer treatment or in patients with hip fractures; EN in patients with inflammatory bowel disease; VNS in patients with chronic obstructive pulmonary disease E – EN in the first week in dysphagic, or VNS at any time in non-dysphagic, stroke patients who are not malnourished; dysphagia persisting for weeks will presumably ultimately require EN. Conclusions: There is strong evidence for not using EN in the first week in dysphagic, and not using VNS at all in non-dysphagic, stroke patients who are not malnourished. There is reasonable evidence for using VNS in malnourished geriatric patients. The recommendations to consider EN/VNS in perioperative/liver/critically ill/low birth weight patients are limited by the low quality of the RCTs. No evidence could be identified to justify the use of EN/VNS in other disease states

Modern optical astronomy: technology and impact of interferometry

The present `state of the art' and the path to future progress in high spatial resolution imaging interferometry is reviewed. The review begins with a treatment of the fundamentals of stellar optical interferometry, the origin, properties, optical effects of turbulence in the Earth's atmosphere, the passive methods that are applied on a single telescope to overcome atmospheric image degradation such as speckle interferometry, and various other techniques. These topics include differential speckle interferometry, speckle spectroscopy and polarimetry, phase diversity, wavefront shearing interferometry, phase-closure methods, dark speckle imaging, as well as the limitations imposed by the detectors on the performance of speckle imaging. A brief account is given of the technological innovation of adaptive-optics (AO) to compensate such atmospheric effects on the image in real time. A major advancement involves the transition from single-aperture to the dilute-aperture interferometry using multiple telescopes. Therefore, the review deals with recent developments involving ground-based, and space-based optical arrays. Emphasis is placed on the problems specific to delay-lines, beam recombination, polarization, dispersion, fringe-tracking, bootstrapping, coherencing and cophasing, and recovery of the visibility functions. The role of AO in enhancing visibilities is also discussed. The applications of interferometry, such as imaging, astrometry, and nulling are described. The mathematical intricacies of the various `post-detection' image-processing techniques are examined critically. The review concludes with a discussion of the astrophysical importance and the perspectives of interferometry.Comment: 65 pages LaTeX file including 23 figures. Reviews of Modern Physics, 2002, to appear in April issu