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PubMed2006

Age threshold for endoscopy and risk of missing upper gastrointestinal malignancy--data from the Scottish audit of gastric and oesophageal cancer.

BACKGROUND: Urgent endoscopy is indicated for suspected upper gastrointestinal malignancy. However, there is limited evidence on the age threshold for performing urgent endoscopy in uncomplicated dyspepsia (that is, without alarm features). AIM: To quantify the risk of missing upper gastrointestinal malignancy within Scotland, if the age threshold for urgent endoscopy in uncomplicated dyspepsia was increased from 45 to 55 years. METHODS: Analysis of data collected prospectively by the Scottish Audit of Gastric and Oesophageal Cancer. 'Alarm' features at presentation were defined as dysphagia, weight loss, gastrointestinal bleeding, anaemia, vomiting, history of gastric surgery and history of peptic ulcer disease. RESULTS: Of the 3293 patients diagnosed with upper gastrointestinal malignancy, 290 (8.8%) patients were <55 years of age. Twenty-one of the patients aged <55 years had no alarm features (0.64% of all patients); 12 were aged 45-55 years and nine were aged <45 years. Only two patients (one aged <45 years) underwent potentially curative surgery. CONCLUSION: Upper gastrointestinal malignancy is uncommon under 55 years of age and most of the patients present with alarm features. Raising the age threshold for endoscopy for new-onset uncomplicated dyspepsia from 45 to 55 years would not impact adversely on the diagnosis or outcome of upper gastrointestinal malignancy.

Adult↗
PubMed2002

Central and peripheral chemoreflexes in panic disorder.

Klein (Arch Gen Psychiatry, 50, 1993, 306-317) has suggested that panic disorder patients have a false suffocation alarm that may be associated with a lowered threshold for carbon dioxide detection. We compared the thresholds and sensitivities of the central and peripheral chemoreflexes between panic disorder patients and age- and sex-matched healthy volunteers to test this aspect of the hypothesis. We used a modified version of Read's rebreathing technique in 11 panic disorder patients and 10 healthy volunteers to examine the peripheral and central chemoreflex characteristics in these two populations. Subjects were examined during three rebreathing tests: training, hyperoxic (central chemoreflex alone) and hypoxic (combined central and peripheral chemoreflex). Panic symptoms were retrospectively assessed between groups using a DSM-IV derived Panic Symptom Scale. Comparisons of panic disorder patients with agoraphobia and healthy volunteers showed no significant differences in sensitivities or thresholds. Klein's hypothesis is not supported by these data. If a false suffocation alarm exists, its triggering may not be implemented within the respiratory chemoreflexes.

Adult↗
PubMed1992

Acute opioid administration effects on sensory and motor function in baboons: buprenorphine, morphine, and naloxone.

The effects of acute administration of the opioid compounds buprenorphine, morphine, and naloxone were studied on auditory and visual threshold functions and reaction time performances in baboons. Baboons were trained in a reaction time procedure to hold a lever depressed, and release the lever when a signal was presented. Auditory and visual signals were employed in separate sessions. Drug was administered 30min prior to testing. Dose-related increases in visual and auditory thresholds were observed following buprenorphine, with visual thresholds being somewhat more drug-sensitive. Buprenorphine also increased reaction times to both high-intensity and low-intensity stimuli. High doses of morphine increased reaction times to high-intensity auditory and low-intensity visual stimuli; thresholds for both modalities were unaffected by any dose of morphine. Naloxone produced no consistent effects on thresholds or reaction times. False alarm rates were not significantly changed by buprenorphine, morphine, or naloxone.

Journal Article↗
PubMed1984

Effect of subliminal visual material on an auditory signal detection task.

An experiment assessed the effect of subliminally embedded, visual material on an auditory detection task. 22 women and 19 men were presented tachistoscopically with words designated as "emotional" or "neutral" on the basis of prior GSRs and a Word Rating List under four conditions: (a) Unembedded Neutral, (b) Embedded Neutral, (c) Unembedded Emotional, and (d) Embedded Emotional. On each trial subjects made forced choices concerning the presence or absence of an auditory tone (1000 Hz) at threshold level; hits and false alarm rates were used to compute non-parametric indices for sensitivity (A') and response bias (B"). While over-all analyses of variance yielded no significant differences, further examination of the data suggests the presence of subliminally "receptive" and "non-receptive" subpopulations.

Adult↗
PubMed1979

[Definition and realization of a microprocessor system for monitoring during artificial ventilation (author's transl)].

A medical application of a microprocessor system is presented. The definition of a system able to control the quality of the respiratory exchanges for a patient submitted to artificial ventilation is given. The measurement system is composed by two rapid analysers of CO2 and O2 (Beckman LB2 and OM 11), a flow meter devices and an airway pressure sensor (Monaghan M 700). The monitoring of the ventilation is based on the determination of FAECO2 simultaneous the determination of FECO2, FIO2, FEO2 and FAEO2 allow, with the sequential entries of the blood gaz values, to calculate: VA/V, D (a--A) CO2, D (A--a) O2, VO2, VCO2 and respiratory quotient. Now, we are working out a system composed by: a microprocessor (Intel 8080) which allows acquisition and treatment of the signals; a peripherical with a key board for the dialogue between the operator and the system; a visual display unit and a printer. Measurements are made on the patient every 13 mn during five respiratory cycles. All the stated above parameters are then computed. When there is a variation of FAECO2, an alarm is triggered, of predeterminated threshold is exceeded. This system simple, not too expensive, not invasive, has been conceived to work on one to four patients.

Carbon Dioxide↗
PubMed1996

The use of cumulative distributions to determine critical values and levels of confidence for clinical distortion product otoacoustic emission measurements.

Distortion product otoacoustic emission (DPOAE) input/output functions were measured at nine f2 frequencies ranging from 500 to 8000 Hz in 210 normal-hearing and hearing-impaired subjects. In a companion paper [Stover et al., J. Acoust. Soc. Am. 100, 956-967 (1996)], L1-L2 was held constant at 10 dB, and L2 was varied from 65 to 10 dB SPL in 5-dB steps. Based upon analyses using clinical decision theory, it was demonstrated that DPOAE amplitudes for 65/55 dB SPL primaries (L1/L2) and DPOAE thresholds resulted in the greatest separation between normal and impaired ears. In this paper, the data for these two conditions were recast as cumulative distributions, which not only describe the extent of overlap between normal and impaired distributions, but also provide the measured value (i.e., the specific DPOAE amplitude or threshold) for any combination of hit and false alarm rates. From these distributions, confidence limits were constructed for both DPOAE amplitude and threshold to determine the degree of certainty with which any measured response could be assigned to either the normal or impaired population. For these analyses, DPOAE measurements were divided into three categories (a) response properties that would be unlikely to come from normal ears, (b) response properties that would be unlikely to come from impaired ears, and (c) response properties for which hearing status was uncertain. Based upon DPOAE amplitude measurements, the region of uncertainty, defined between the 95 percentile for impaired ears and the 5 percentile for normal ears, was relatively narrow for f2 frequencies ranging from 707 to 4000 Hz. For DPOAE thresholds, this region was relatively narrow for F2 frequencies ranging from 1414 to 4000 Hz.

Auditory Perception↗
PubMed1990

A critical review of trend-detection methodologies for biomedical monitoring systems.

Information gained through early detection of patient vital sign changes typically can be used to anticipate future difficulties. Detection of these changes through monitoring, however, can be difficult. Many of the monitored processes are random in nature. For that reason simple threshold algorithms exhibit a high incidence of false alarms, which can decrease the operator's confidence in the monitor. Many problems associated with threshold-based biological monitors can be alleviated by introducing statistical detection techniques. The purpose of this review is to develop and critique the major trend detection algorithms used in biological monitors. This review contains an evolution of trend detection through current state-of-the-art algorithms.

Algorithms↗
PubMed1993

Audibility and identification of auditory alarms in the operating room and intensive care unit.

The audibility and the identification of 23 auditory alarms in the intensive care unit (ICU) and 26 auditory alarms in the operating rooms (ORs) of a 214-bed Canadian teaching hospital were investigated. Digital tape recordings of the alarms were made and analysed using masked-threshold software developed at the Université de Montréal. The digital recordings were also presented to the hospital personnel responsible for monitoring these alarms on an individual basis in order to determine how many of the alarms they would be able to identify when they heard them. Several of the alarms in both areas of the hospital could mask other alarms in the same area, and many of the alarms in the operating rooms could be masked by the sound of a surgical saw or a surgical drill. The staff in the OR (anaesthetists, anaesthesia residents, and OR technologists) were able to identify a mean of between 10 and 15 of the 26 alarms found in their operating theatres. The ICU nurses were able to identify a mean of between 9 and 14 of the 23 alarms found in their ICU. Alarm importance was positively correlated with the frequency of alarm identification in the case of the OR, rho = 0.411, but was not significantly correlated in the case of the ICU, rho = 0.155. This study demonstrates the poor design of auditory warning signals in hospitals and the need for standardization of alarms on medical equipment.

Adult↗
PubMed2002

Upper GI malignancy, uncomplicated dyspepsia, and the age threshold for early endoscopy.

OBJECTIVES: We sought to determine the frequency with which patients with upper GI malignancies present with uncomplicated dyspepsia and to determine the impact of changing the threshold for early endoscopy from 45 to 55 yr, as has recently been recommended in European studies. METHODS: Three hundred forty-one patients with upper GI malignancies at two Milwaukee teaching hospitals were identified from electronic databases. Trained physician-investigators reviewed the charts using a specifically designed questionnaire. Staging of GI cancers was performed using the TNM classification to determine operability. Uncomplicated dyspepsia was defined as dyspepsia without alarm symptoms/signs (dysphagia, vomiting, weight loss, early satiety, GI bleeding, or anemia). RESULTS: There were 341 patients with upper GI malignancies with a mean age of 68 yr (range = 22-94). Twenty-one patients were younger than 45 and 65 were under 55. Uncomplicated dyspepsia was the presenting symptom in five of 65 (7.7%) patients younger than 55 and one of 21 (4.8%) patients under 45 (p = 0.99). Five patients 55 or younger presented with uncomplicated dyspepsia. All had advanced, inoperable disease (stage III or higher). CONCLUSIONS: 1) In a racially diverse United States population, upper GI malignancy presenting without alarm symptoms is uncommon. 2) Raising the threshold for immediate endoscopy in uncomplicated dyspepsia from age 45 to 55 increases the risk of missing an underlying malignancy but may not affect outcome, as incurable disease was present at diagnosis within a few weeks of the onset of symptoms.

Adult↗
PubMed1997

A user-friendly method for calibrating a subcutaneous glucose sensor-based hypoglycaemic alarm.

A crucial step in developing a glucose monitoring system using a subcutaneous implanted glucose sensor is the transformation of the sensor signal (a current) into an estimation of a blood glucose concentration. We have developed an Electronic Control Unit (ECU) able to recognize, before and after a glucose load, that the sensor current presents a plateau, thus triggering an alarm asking for blood glucose determination. The system, fed with these results, subsequently transforms the current into an estimation of glucose concentration by linear extrapolation based on the sensor sensitivity and the background current computed from the two sets of current and glycaemia values (two-point calibration). In addition, the system is able to trigger an alarm when this estimation decreases below a threshold that can be set by the user. This system was evaluated in experiments performed in 12 normal rats. The quality of the calibration was assessed by comparing, by error grid analysis, the data displayed on the liquid-crystal display of the ECU to concomitant plasma glucose concentration determined at frequent intervals, 65 +/- 6 and 26 +/- 5% of the values were in zones A (good) and B (acceptable estimation) of the grid, respectively. The system was set to trigger an alarm when the estimation of glucose concentration decreased below 70 mg/dl. Following an insulin administration, the alarm was triggered when the system displayed a 64 +/- 2 mg/dl glucose concentration. The concomitant plasma glucose concentration was 59 +/- 5 mg/dl (NS). In conclusion, this work validates experimentally the new, user-friendly method for calibrating the glucose sensor integrated into the ECU, based on an automatic detection of plateaus. The quality of the sensor calibration performed with this procedure is compatible with the appropriate functioning of this continuous glucose monitoring system, which was demonstrated by its ability to detect mild hypoglycaemia following insulin injection.

Animals↗
PubMed2005

Statistical analysis of network traffic for adaptive faults detection.

This paper addresses the problem of normal operation baselining for automatic detection of network anomalies. A model of network traffic is presented in which studied variables are viewed as sampled from a finite mixture model. Based on the stochastic approximation of the maximum likelihood function, we propose baselining network normal operation, using the asymptotic distribution of the difference between successive estimates of model parameters. The baseline random variable is shown to be stationary, with mean zero under normal operation. Anomalous events are shown to induce an abrupt jump in the mean. Detection is formulated as an online change point problem, where the task is to process the baseline random variable realizations, sequentially, and raise alarms as soon as anomalies occur. An analytical expression of false alarm rate allows us to choose the design threshold, automatically. Extensive experimental results on a real network showed that our monitoring agent is able to detect unusual changes in the characteristics of network traffic, adapt to diurnal traffic patterns, while maintaining a low alarm rate. Despite large fluctuations in network traffic, this work proves that tailoring traffic modeling to specific goals can be efficiently achieved.

Algorithms↗
PubMed1998

A statistical method for the measurement of muscle activation intervals from surface myoelectric signal during gait.

The aim of this work is to present an original double-threshold detector of muscle activation, specifically developed for gait analysis. This detector operates on the raw myoelectric signal and, hence, it does not require any envelope detection. Its performances are fixed by the values of three parameters, namely, false-alarm probability (Pfa), detection probability, and time resolution. Double-threshold detectors are preferable to single-threshold ones because, for a fixed value of the Pfa, they yield higher detection probability; furthermore, they allow the user to select the couple false alarm-detection probability with a higher degree of freedom, thus, adapting the performances of the detector to the characteristics of the myoelectric signal of interest and of the experimental situation. In this paper, first we derive the detection algorithm and describe different strategies for selecting its parameters, then we present the performances of the proposed procedure evaluated by means of computer simulations, and finally we report an example of application to myoelectric signals recorded during gait. The characterization of the proposed double-threshold detector demonstrates that, in most practical situations, the bias of the estimates of the on-off transitions is smaller than 10 ms, the standard deviation may be kept lower than 15 ms, and the percentage of erroneous patterns is below 5%. These results show that this detection approach is satisfactory in research applications as well as in the clinical practice.

Algorithms↗
PubMed1995

Detection thresholds for 60 Hz electric fields by nonhuman primates.

Because responses of animals to detection of the presence of an electric field (EF) are a possible mechanism for production of biological effects, it is important to know what EF intensities are detectable. Operant methods were used to train six baboons (Papio cynocephalus) to perform a psychophysical task involving detection of EF presence. During the response phase of a trial, a subject responded on one push button to report the presence of the EF and on a different push button to report the absence of the EF. Correct reports of EF presence of absence produced delivery of food rewards. The subjects became proficient at performing this psychophysical detection task; during 35 days of testing, false alarm rates averaged 9%. The average EF detection threshold was 12 kV/m; the range of means among subjects was 5-15 kV/m. Two special test procedures confirmed that the subjects were responding directly to EF presence of absence and not to artifacts that might be associated with EF generation. The EF detection threshold of nonhuman primates is similar to thresholds reported for rats and humans.

Animals↗
PubMed1994

Hearing acuity of anesthesiologists and alarm detection.

BACKGROUND: With rapid technological advances in anesthesiology, we are acquiring an ever increasing number of auditory alarm systems in the operating room the value of which depend on the hearing acuity of the anesthesiologist monitoring the patient. Presbycusis, the effect of aging on the auditory system, characteristically results in a bilaterally symmetric neurosensory high-frequency hearing loss ( > 2,000 Hz). In this study we attempt to assess the impact of this common hearing disorder on alarm detection. METHODS: We measured air conduction hearing acuities of 188 anesthesiologists who volunteered to participate. Subjects were divided into six age groups (25-34, 35-44, 45-54, 55-64, and > 75 yr of age). Abnormal audiograms were compared to the intensity and frequency of alarms in our operating room to determine which alarms were out of hearing range. Subjects with a history of chronic or excessive noise exposure were excluded from the study. The median hearing threshold for each age group of study subjects was compared to the median hearing threshold of similar age groups in the general population. RESULTS: Overall, 66% of the subjects had an abnormal audiogram, and 7% had one or more alarm intensities less than their detectability threshold (14% unilateral, 86% bilateral). Median hearing threshold was worse than the general population for men and women less than 55 yr of age. Hearing acuity worse than the general population occurred at the lower frequencies while acuity at the higher frequencies was equal or slightly better. However, inability to hear alarms occurred only with those alarms that have frequencies of 4,000 Hz or greater. CONCLUSIONS: Although high-frequency hearing acuity of individuals in our study was better than that of the general population, hearing deficits at high frequencies were of the magnitude to interfere with alarm detection. Also background noise levels vary greatly in different operating rooms. These two problems create a hindrance to alarm detection for certain anesthesiologists. From our data we conclude that the aging human ear may not be capable of accurately detecting some auditory alarms in the operating room. Alarm design should consider hearing acuity because high-frequency alarms may go undetected.

Adult↗
PubMed1997

Alarm pheromone induces stress analgesia via an opioid system in the honeybee.

Changes of the stinging response threshold of Apis mellifera scutellata were measured on foragers fixed on a holder and stimulated with an electric shock as a noxious stimulus. The threshold of responsiveness to the noxious stimulus increased when bees were previously stimulated with isopentyl acetate, which is a main component of the alarm pheromone of the sting chamber. This effect is antagonised by previous injection of naloxone-hydrochloride (Endo Laboratories Inc.). Results suggest that in the honeybee an endogenous opioid system activated by isopentyl acetate is responsible for modulation of perception for nociceptive stimuli. The resulting stress-induced analgesia in the defender bee would reduce its probability of withdrawal thus increasing its efficiency against enemies.

Analgesia↗
PubMed1998

Design of a miniaturized ultrasonic bladder volume monitor and subsequent preliminary evaluation on 41 enuretic patients.

Nocturnal incontinence (enuresis) affects 20% of children over four years old, and this figure typically decreases by 15% each year. At the age of 18, 1% of those people remain enuretic. Nocturnal enuresis can be treated by means of a conditioning device that awakens the patient once the urine level has reached a preestablished threshold of the capacity of his or her bladder. We have designed and implemented a portable miniaturized ultrasonic monitor, which permits estimation of the urine volume with an accuracy of 75%. Prototypes have been completed and validated on 41 patients (children) at Ste. Justine Hospital (Montréal). On the first group of 33 patients, we used a hand-held transducer to determine the volume detection range, which is accurate for volumes between 40 and 400 mL. With the second group of 8 patients, the device was mounted on an elastic belt around the abdomen. Measurements were taken in order to validate the accuracy of urine threshold detection and the activation of the corresponding alarm.

Adolescent↗
PubMed2001

Dyspepsia.

Dyspepsia refers to pain or discomfort centered in the upper abdomen. This symptom is remarkably common, with 1-year prevalence rates averaging 25% in the community. Symptoms suggestive of the irritable bowel syndrome and reflux disease frequently overlap but do not form part of the definition of dyspepsia. Electrical and other stimuli can cause similar or different symptoms in various patients, and even the site to which symptoms are referred varies considerably. Dyspeptic symptoms are therefore a relatively poor guide to the origin or nature of any "disturbances" in the gut. Identification of patients who require further investigation to rule out serious structural disease, such as peptic ulcer disease or cancer, is a key issue because unaided clinical diagnosis is unreliable. The use of an age threshold (typically 45 years) and the identification of alarm features, including weight loss, repeated vomiting, and signs of bleeding, seem to be valid on the basis of the limited evidence available. Dyspeptic symptoms fall into distinct subgroups resembling the perceived clinical entities of ulcer-like and dysmotility-like dyspepsia. Unfortunately, because of overlap with reflux symptoms and between the subgroups, the clinical significance of these groups remains highly questionable. A focus on symptom predominance may be more rewarding. Lack of validated outcome measures has hampered clinical studies and has led to the development of complex outcome measures that integrate and weigh different symptoms or other indirect indicators of outcome into a general score. Further testing and validation are in progress.

Dyspepsia↗