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Effects of two procedural modifications of the frequency of false-alarm responses during pure-tone threshold determination.

In normal-hearing young adults without tinnitus, HTLs were collected using 5-db steps, and false alarms (FA's) noted, at octaves from .25-8 kc/s either in quiet or in a white noise background set at 15 db sensation level for each S. In Exper. I (N:10), the ascending and descending modes did not yield significantly different numbers of FA's in quiet; in noise, FA's increased significantly vs the quiet condition in the ascending but not in the descending modes, while in noise, furthermore, FA's increased significantly for the ascending vs the descending mode. In a similar Exper. II (N:10), the 4 combinations (single- and pulsed-tone presentations, ascending and descending modes) showed that FA's were significantly fewest with a descending, pulsed-tone technique. It was recommended that when FA's pose a problem when using the ascending mode, single-tone technique (ASHA guidelines), the clinician change to the descending, pulse-tone technique to reduce FA's by increasing the stimulus certainty under difficult listening circumstances.

Audiometry↗

Dissociation of sensitivity and response bias in children with attention deficit/hyperactivity disorder during central auditory masking.

Forty-three children (ages 7.0-14.5 years old) with and without attention deficit/hyperactivity disorder (ADHD), combined type had thresholds for detection of a 500-Hz pure tone estimated with and without a noise masker in the contralateral ear. The ear receiving the signal in the masked condition was varied randomly. A single-interval maximum-likelihood method estimated thresholds and false-alarm rate. Whereas the increase in threshold in children with ADHD in the presence of contralateral masking was comparable with controls, the increase in false-alarm rate was significantly greater. This dissociation between changes in sensitivity and response bias in the presence of masking noise supports suggestions that children with ADHD have difficulty inhibiting maladaptive responses and indicates that this deficit is quantifiable using psychoacoustic methods.

Adolescent↗

Hypersensitivity to carbon dioxide as a disease-specific trait marker.

There is now substantial evidence that an abnormal threshold for suffocation alarm underlies panic disorder. Because this disorder is highly familial, evidence of an abnormal suffocation threshold may be apparent in high-risk individuals before they develop clinical illness. To explore this possibility, we used a single inhalation of 35% CO2 vs. air to evaluate 11 subjects who had at least one first-degree relative with DSM-III-R panic disorder, 13 who had at least two relatives treated for mania or for depression (HR-AD), and 15 low-risk controls who had no family history of panic disorder, affective disorder, or alcoholism (LR-C). All were aged 18-34 and had no history of panics or of any Research Diagnostic Criteria disorder. Five (45.5%) of the subjects at high risk for panic disorder, but none of the LR-C subjects (p = .007), nor any of the HR-AD subjects (p = .011), developed a panic attack following inhalation of the CO2 mixture.

Adolescent↗

Timely detection of meningococcal meningitis epidemics in Africa.

BACKGROUND: Epidemics of meningococcal disease in Africa are commonly detected too late to prevent many cases. We assessed weekly meningitis incidence as a tool to detect epidemics in time to implement mass vaccination. METHODS: Meningitis incidence for 41 subdistricts in Mali was determined from cases recorded in health centres (1989-98) and from surveillance data (1996-98). For incidence thresholds of 5 to 20 cases per 100000 inhabitants per week, we calculated sensitivity and specificity for detecting epidemics, and determined the time lapse between threshold and epidemic peak. FINDINGS: We recorded 9084 meningitis cases. Clinic-based weekly incidence of 5 and 10 cases per 100000 inhabitants detected all meningitis epidemics (sensitivity 100%, 95% CI 93-100), with median threshold-to-peak time of 5 and 3 weeks. Under-reporting reduced sensitivity: only surveillance thresholds of 5 or 7 cases per 100000 inhabitants per week detected all epidemics. Crossing the lower threshold before the 10th calendar week doubled epidemic risk relative to crossing it later (relative risk 2.1, 95% CI 1.4-3.2). At 10 cases per 100000 inhabitants per week, specificity for outbreak prediction was 88%, 95% CI 83-91). For populations under 30000, 3 to 5 cases in one or two weeks predicted epidemics with 85% to 97% specificity. INTERPRETATION: Low meningitis thresholds improve timely detection of epidemics. Ten cases per 100000 inhabitants per week in one area confirm epidemic activity in a region, with few false alarms. An alert threshold of 5 cases per 100000 inhabitants per week allows time to investigate, prepare for an epidemic, and initiate mass vaccination where appropriate. For populations under 30000, the alert threshold is two cases in a week. High quality surveillance is essential.

Disease Outbreaks↗

Management of fluid balance in CRRT: a technical approach.

BACKGROUND: The possibility of making fluid balance errors during continuous renal replacement therapy has been identified since the beginning of this modality of treatment. The advent of automated machines has partially overcome this problem. Nevertheless, there are conditions and operation modes in which the potential for fluid balance errors is still present. OBJECTIVE: To analyse fluid balance management in CRRT therapies across a range of currently marketed machine. METHODS: The tests were conducted in vitro, utilizing saline solution for the blood circuit and regular dialysate/reinfusate for the dialysate/reinfusion circuit. The methodology used was based on the voluntary creation of a fluid balance error by altering the correct flow in the circuit of the different machines. Subsequently, the time for alarm occurrence and the threshold value for fluid balance error was evaluated. The alarm was overridden and the overall fluid error allowed by the machine was evaluated. Each machine was tested in conditions of different dialysate/filtrate flow rates and in different simulated treatment modalities. RESULTS: Fluid balance errors can be easily avoided not only by a correct and careful adherence to the protocols of use of the current CRRT machines, but also by the compliance to prescriptions and programmed controls during therapy. Most importantly, if an alarm appears on the machine, one can try to override it without major problems; major problems may occur when multiple override commands are operated without identifying the problem and solving it adequately. CONCLUSION: Machines seem to be designed with adequate safety features and accurate alarm systems. However, features and alarms can be manipulated by operators creating the opportunity for serious error. Physicians and nurses involved in prescription and delivery of CRRT should have precise protocols and defined procedures in relation to machine alarms to prevent major clinical problems.

Acute Kidney Injury↗

Online pattern recognition in intensive care medicine.

In intensive care physiological variables of the critical-ly ill are measured and recorded in short time intervals. The existing alarm systems based on fixed thresholds produce a large number of false alarms. Usually the change of a variable over time is more informative than one pathological value at a particular time point. Intelligent alarm systems which detect important changes within a physiological time series are needed for suitable bedside decision support. There are various approaches to modeling time-dependent data and also several methodologies for pattern detection in time series. We compare several methodologies de-signed for online detection of measurement artifacts, level changes, and trends for a proper classification of the patient s state by means of a comparative case-study.

Aged↗

Radiation protection system at the RIKEN RI beam factory.

The RIKEN RI (radioactive isotope) Beam Factory is scheduled to commence operations in 2006, and its maximum energy will be 400 MeV u(-1) for ions lighter than Ar and 350 MeV u(-1) for uranium. The beam intensity will be 1 pmicroA (6 x 10(12) particles s(-1)) for any element at the goal. For the hands-on-maintenance and the rational shield thickness of the building, the beam loss must be controlled with several kinds of monitors. Three types of radiation monitors will be installed. The first one consists of a neutron dose equivalent monitor and an ionisation chamber, which are commercially available area monitors. The second one is a conventional hand-held dose equivalent monitor wherein the logarithmic signal is read by a programmable logic controller based on the radiation safety interlock system (HIS). The third one is a simple plastic scintillator called a beam loss monitor. All the monitors have threshold levels for alarm and beam stop, and HIS reads all these signals.

Equipment Design↗

Assessment of a new infusion pump for epidural PCA.

The use of epidural fentanyl by patient-controlled analgesia (PCA) may be a useful method of providing high-quality postoperative analgesia on the general surgical ward. The successful use of this technique requires an infusion pump with specific characteristics. Three Provider 5500, newly-developed, battery-powered PCA pumps, were tested to determine their accuracy, threshold of occlusion alarm limits and stored volume characteristics. These measurements were repeated following the in-line addition of an 18 gauge epidural catheter and two 0.2 micron filters. Pumps delivered on average within 3% of stated infusion rates and within 3% of bolus dose size. Occlusion pressures generated were between 1200 and 1360 mmHg, while the mean stored volume was 0.12 ml. Accuracy of delivery was maintained at lower voltage inputs. Addition of the catheter failed to alter the accuracy of the pumps tested. Siphoning of fluid was possible on disconnection of cartridge from pump. This problem did not occur with the addition of an epidural catheter and filter. This device has features which make it suitable for the safe delivery of epidural PCA. Care, however, needs to be taken on changing cartridges to prevent accidental administration of a drug bolus to the patient.

Analgesia, Patient-Controlled↗

Further studies of a maximum-likelihood yes-no procedure.

Absolute thresholds were estimated for pure tones of 500, 1000, and 2000 Hz using both a maximum-likelihood yes-no procedure and a traditional three-down one-up forced-choice adaptive procedure. Threshold estimates obtained with the two procedures were highly correlated. In the maximum-likelihood yes-no procedure, the false-alarm probability was poorly estimated. A simple change in that procedure produced less-biased estimates of the false-alarm rate. In a second experiment, the influence of the false-alarm rate on the threshold estimates was investigated. The listeners' absolute thresholds were estimated when they adopted either a liberal or conservative criterion for detecting the signals. Data were collected using both a constant-stimulus yes-no procedure and a maximum-likelihood yes-no procedure. Threshold estimates are 5 to 6 dB higher for the low than for the high false-alarm rates. Psychometric functions based on a stimulus-power model provided the best fit to the data obtained with the constant-stimulus method. This stimulus-power model was used to produce the assumed psychometric function in the maximum-likelihood yes-no procedure. Computer simulations were conducted to determine how threshold estimates were affected by the listener's inattention or by mismatches between the slope parameter of the listener's psychometric function and that assumed in the maximum-likelihood procedure.

Attention↗

Automated detection of infectious disease outbreaks: hierarchical time series models.

The purpose of infectious disease surveillance is to inform the public health policy makers on the incidence and trends of infectious diseases and to trigger appropriate actions to control infectious disease outbreaks. The enormous amount of data collected with automated laboratory-based surveillance systems require automated algorithms for detecting unexpected aberrations that may signal infectious disease outbreaks. In this paper, we explore the potential of hierarchical time series models to detect deviations from expected incidence. As these count data are extremely noisy it can be expected that these models are suitable to detect signal from noise and accommodate for possible autocorrelation. The proposed procedure consists of three steps; (1) the model parameters are estimated by empirical Bayes on a training period of, e.g. a year; (2) the expected values are updated for small time steps (e.g. daily) as new data arrive; (3) threshold levels are updated conditionally on the past expected values and an alarm is triggered when the threshold level is exceeded. To test the potential of the models we estimated sensitivity, specificity and timeliness on simulated time series and compared the results with an alternative approach of a linear regression model adjusted for trends and season. We also used two observed series for Rubella notifications and Salmonella infections and compared our findings with the expert opinions on these series. The hierarchical time series models approach shows high sensitivity and specificity and correctly identifies outbreaks at an early stage. This, in our opinion, makes the proposed model a reliable tool for adequate automated detection of infectious disease outbreaks.

Algorithms↗

[A video-sensor system for predicting the time of parturition in the chimpanzee].

A system of predicting the time of parturition in the chimpanzee was developed to assure care of the newborn as soon as possible after delivery. To quantify activity, the number of times that a parturient chimpanzee crossed a sensor marker of a TV monitor was recorded by a videosensor on the market for crime prevention. The amount of activity increased remarkably just prior to parturition. A system using a personal pocket alarm ("beeper"), which rang automatically when the number of crossings by the chimpanzee exceeded a selected level within a certain period of time, was tested. In the present study, the threshold for sounding the alarm was set at 50 crossings within 10 minutes. As a result, the pocket alarm began to ring at about 40 minutes before parturition. This enabled us to be present at parturition and to tend to a newborn abandoned by its mother in one case. The present system could be useful to predict the time of parturition in the chimpanzee.

Animals↗

Testing the suffocation false alarm theory of panic disorder.

The need for hypotheses concerning the nature of those functions that have been impaired in stereotyped psychiatric syndromes is emphasized. With regard to panic disorder, the key role of the spontaneous panic attack became apparent from several viewpoints. However, panics seem to be a type of misreleased fear, which guided the thinking concerning the nature of possible psychological or physiological malfunctions. We indicate that spontaneous panic cannot be fear, but must represent some other malfunction and suggest that the spontaneous panic is a suffocation false alarm. The development of this idea is outlined, and attempts to develop tests of this hypothesis are indicated. In particular, studies of children with congenital central hypoventilation syndrome, patients with Chronic Obstructive Pulmonary Disease, dyspnea, field measures of panic, pregnancy, childbirth and the postpartum period, as well as the premenstrual syndrome afford pointed opportunities, new information and potential tests of the theory. A recent challenge to the theory from acetazolamide infusion is discussed. Developing a possible antecedent for the pathologically depressed threshold for the suffocation alarm, in the form of a phasic endorphinergic deficiency, is presented.

Adult↗

Missing gastric cancer in dyspepsia.

BACKGROUND: Dyspepsia is common in gastric cancer, but also in many benign conditions. European Helicobacter pylori Study Group and American Gastroenterological Association guidelines recommend endoscopy in dyspepsia for patients with alarm symptoms or at age >45 years. However, recommendations are controversial. AIM: To investigate whether criteria for endoscopy in patients with dyspepsia are adequate to detect gastric cancer. METHODS: In 215 patients at initial diagnosis of gastric adenocarcinoma, symptoms were classified as alarm and non-alarm. Cases were staged according to the TNM system. Stages T(1)-T(3)N(x)M(0) were defined as potentially curable. RESULTS: Dyspepsia was present in 128 patients. Among patients with dyspepsia, 15 were < or =45 years and 41 denied alarm symptoms. The combination of both criteria excluded only three (2.3%) patients from endoscopy, but increasing the threshold to >50 and >55 years would have raised the rate of excluded patients to seven (5.5%) and 11 (8.6%). Only 53 potentially curable stages and 18 early gastric cancers occurred, but the tumour stage was not associated with dyspepsia duration, age threshold of 45 years, or alarm symptoms. CONCLUSIONS: Our results support current European Helicobacter Study Group and American Gastroenterological Association criteria for endoscopy in patients with dyspepsia to detect gastric cancer. Regardless, most cancers are advanced at detection.

Adult↗

Effect of electronic ANR and conventional hearing protectors on vehicle backup alarm detection in noise.

An experiment was conducted wherein masked thresholds (using ascending method of limits) for a backup alarm were obtained in pink and red noise at 85 and 100 dBA for 12 participants immersed in a probability monitoring task and wearing a conventional passive hearing protection device (HPD, an earmuff or a foam earplug), an active noise reduction (ANR) headset, or no HPD at all (only in 85 dBA noise). Results revealed statistically significant between-HPD differences in red noise (from 2.3 to 3.1 dB) and in the 100-dBA noise level (from 2.6 to 4.3 dB). An additional finding, which corroborates other studies using different protocols, was that masked thresholds in 85-dBA noise were significantly lower (from 3.2 to 4.4 dB) for the occluded conditions (wearing an HPD) than for the open-ear (unoccluded) condition. This result refutes the belief among many normal-hearing workers that the use of HPDs in relatively low levels of noise compromises their ability to hear necessary workplace sounds. Actual or potential applications of this research include (a) the selection of appropriate HPDs for low-frequency-biased noise exposures wherein signal detection is important and (b) gaining insight into the appropriateness of ANR-based HPDs for certain industrial noise environments.

Adolescent↗

Child abuse in urban setting: a one-year analysis of hospital information on abused children at Yekatit 12 hospital, Addis Ababa.

BACKGROUND: In recent years, there has been growing concern over the rapidly mounting situation of child abuse in Ethiopia. This tragic situation is generally thought to be rare in Sub-Saharan Africa. The government of Ethiopian has ratified and endorsed the Convention of Right of Children in spite of which the situation is considerable. It is important to consider the subject as a momentous issue and review the situation in the capital. OBJECTIVE: To know the extent, magnitude, seriousness and the existing trend of child abuse in the capital city of Ethiopia. METHODS: This study is a prospective cross-sectional analysis undertaken in pediatrics department of Yekatit 12 hospital. Two hundred and fifty six allegedly abused children were seen from July 2001 to June 2002 of which 214 were enrolled in this study that fulfilled the criteria of inclusion RESULTS: Among two hundred and fourteen children less than the age of 15 years 93% were female. Most common mode of abuse was sexual with vaginal penetration N=160 (75%). Forty one percent of abused children had laboratory investigations of which 9% were pathological results. The highest percent of victims reside in Woreda 11. The monthly distribution of abused children shows increasing trend. Only 18% had Psychological follow-up visit. Thirty percent of perpetrators were close neighbors followed by teachers. The age between 35 to 45 years were found to be the commonest age of perpetrators (29%). Among the offenders' occupation disclosed N= 17, 6 (35%) were priests. CONCLUSIONS: This study has tried to prove that child abuse is increasing in magnitude and seriousness & the growing trend of threat is to cross the threshold of public health alarm. Female children are at higher risk and need special protection. The low number of follow-up visits and few laboratory results show that there is lack of awareness on the future prospective of the child and/or lack of financial resources. It is necessary to improve and curb this catastrophic situation through comprehensive measures.

Adolescent↗

Effects of practice and instructional set on the measurement of lingual vibrotactile thresholds.

The effects on lingual vibrotactile thresholds of three different instructional sets and three different practice conditions were determined for 30 normal adult subjects. Results showed no measurable differences between thresholds obtained with the use of the three different instructional sets, but a high false alarm rate occurred for all conditions. When a subject was given practice at obtaining thresholds with a particular instructional set as a prerequisite to threshold data collection, false alarm responses disappeared. Lower (more sensitive) thresholds also were achieved when the practice condition used required the subject to provide three thresholds within 1 mu of each other before commencing with actual testing.

Adolescent↗

Management of uninvestigated and functional dyspepsia: a Working Party report for the World Congresses of Gastroenterology 1998.

BACKGROUND: The management of dyspepsia is controversial. METHODS: An international Working Party was convened in 1998 to review management strategies for dyspepsia and functional dyspepsia, based on a review of the literature and best clinical practice. RESULTS: Dyspepsia, defined as pain or discomfort centred in the upper abdomen, can be managed with reassurance and over-the-counter therapy if its duration is less than 4 weeks on initial presentation. For patients with chronic symptoms, clinical evaluation depends on alarm features including patient age. The age cut off selected should depend on the age specific incidence when gastric cancer begins to increase, but in Western nations 50 years is generally an acceptable age threshold. In younger patients without alarm features, Helicobacter pylori test and treatment is the approach recommended because of its value in eliminating the peptic ulcer disease diathesis. If, after eradication of H. pylori, symptoms either are not relieved or rapidly recur, then an empirical trial of therapy is recommended. Similarly, in H. pylori-negative patients without alarm features, an empirical trial (with antisecretory or prokinetic therapy depending on the predominant symptom) for up to 8 weeks is recommended. If drugs fail, endoscopy should be considered because of its reassurance value although the yield will be low. In older patients or those with alarm features, prompt endoscopy is recommended. If endoscopy is non-diagnostic, gastric biopsies are recommended to document H. pylori status unless already known. While treatment of H. pylori is unlikely to relieve the symptoms of functional dyspepsia, the long-term benefits probably outweigh the risks and treatment can be considered on a case-by-case basis. In H. pylori-negative patients with documented functional dyspepsia, antisecretory or prokinetic therapy, depending on the predominant symptom, is reasonable, assuming reassurance and explanation are insufficient, unless patients have already failed this approach. Other treatment options include antidepressants, antispasmodics, visceral analgesics such as serotonin type 3 receptor antagonists, and behavioural or psychotherapy although these are all of uncertain efficacy. Long-term drug treatment in functional dyspepsia should be avoided; intermittent short courses of treatment as needed is preferred. CONCLUSION: The management of dyspepsia recommended is based on current best evidence but must be tailored to local factors such as practice setting, the background prevalence of H. pylori and structural disease, and costs.

Decision Trees↗

Robust sensor fusion improves heart rate estimation: clinical evaluation.

OBJECTIVE: To determine if Robust Sensor Fusion (RSF), a method designed to fuse data from multiple sensors with redundant heart rate information can be used to improve the quality of heart rate data. To determine if the improved estimate of heart rate can reduce the number of false and missed heart rate alarms. METHODS: A total of 85 monitoring periods were investigated, 12 from the operating room, 60 from adult ICU and 13 from pediatric ICU. The operating room periods began with induction of anesthesia and ended at the completion of the anesthetic. For the ICU data, four hour blocks of time were studied. For each monitoring period, HR values were recorded at 5 second intervals or less from the ECG, SpO2 and IAC using a SpaceLabs Medical Gateway connected to a SpaceLabs Medical PC2. Fused estimates of HR were derived for every time point using RSF and all results accepted regardless of confidence value. Data were annotated manually to identify the "reference" HR (that HR value most likely to be correct) at all time points. All HR values from the sensors and the fused estimate that were different from the reference HR by more than +/- 5 beats/min were considered inaccurate. For each monitoring period, the total time per hour that data were either inaccurate or unavailable was calculated for each sensor as well as the fused estimates. The total time of false and missed HR alarms was found for all sensors and the fused estimate by comparing the data to thresholds for both high and low HR alarms at 150 bpm, 130 bpm, 110 bpm and 50 bpm, 40 bpm, 30 bpm respectively. RESULTS: The fused estimate of HR was consistently as good or better than the estimate available from any individual sensor. The fused estimates also consistently reduced the incidence of false alarms compared with individual sensors without an unacceptable incidence of missed alarms. DISCUSSION: Redundancy in sensor measurements can be used to improve HR estimation in the clinical setting. Methods like RSF which improve the quality of monitored data and reduce nuisance alarms will enhance the value of patient monitors to clinicians.

Adult↗