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At least 19 recordsLinked to original sources
PubMed2025

Defining alarm thresholds for the load of pathogenic viruses in wastewater for decision making: An application to three French cities.

Wastewater monitoring has the potential to complement infectious disease surveillance systems. However, the absence of predefined viral signal thresholds in wastewater is often presented as a limiting factor in triggering public health action. To overcome this issue, the feasibility of defining alarm threshold for viral loads in wastewater samples was assessed by quantifying genome fragments of SARS-CoV-2, influenza A virus (IAV), respiratory syncytial virus (RSV), norovirus (NoV), and rotavirus (RoV) by RT-digital PCR (dPCR) in untreated wastewater samples from three treatment plants. Cut-point values were calculated for periods with a high rate of visits to emergency rooms or at-home visits by SOS Médecins for the related diseases. ROC curves were constructed, and the values of alarm threshold in wastewater were defined using the Youden index. For each targeted virus, alarm thresholds were close to each other across the three WWTPs. As indicated by likelihood ratios, evidence to rule in the diagnosis of high rate of visits when the alarm threshold was exceeded ranged from weak to strong and was highest for RSV and SARS-CoV-2. Evidence to rule out the diagnosis when the alarm threshold was not exceeded was strong or moderate for IAV, SARS-CoV-2 and RSV. Diagnostic performance of the test was not as high for NoV and RoV. Positive predictive value was highest for SARS-CoV-2 and RSV. For SARS-CoV-2 and RSV, the definition of an alarm threshold in wastewater could substantially inform the diagnosis of a period with a high rate of medical visits for COVID-19 and bronchiolitis, respectively.

Wastewater↗
PubMed1988

Detection of interruptions in the breathing gas of ventilated anaesthetized patients.

Interruption of the breathing gas to a ventilated anaesthetized patient due to accidental disconnection or anaesthesia system malfunction may have serious consequences if not detected quickly. A series of tests which covers the range of foreseeable mechanical problems was developed and used to test the performance of three breathing gas interruption monitors, two commercially available and one developed at Vancouver General Hospital. The tests were designed to evaluate the performance of monitors as installed on anaesthesia systems under a variety of failure conditions, including endotracheal tube disconnection with and without occlusion of the opening, kinks in the inspiratory and fresh gas hoses, disconnection of the fresh gas hose, leaks in the breathing circuit, excessive high or low pressure in the scavenging circuit, continuing high breathing circuit pressure, and kinks in the circuit pressure sensing hose. Ability to detect both significant changes in ventilation variables and faults existing at initiation of ventilation were also tested over a representative range of ventilator and patient variables using circle, coaxial and paediatric circuits. Only complete endotracheal tube disconnections with no obstruction of the opening were reliably detected by all three monitors. A commercial monitor with a single fixed-threshold alarm level also detected fresh gas interruptions in circle and adult coaxial circuits, but failed to alarm in response to any other fault condition. A monitor with selectable pressure thresholds and high, low, and continuing pressure limits detected just under half of the fault conditions. A microprocessor-based monitor developed at Vancouver General Hospital detected and correctly identified roughly 80 per cent of the faults. The series of tests forms the basis for a Canadian Standards Association Preliminary Standard (Z168.10) and will allow hospitals to test the performance of breathing gas interruption monitors in use in their institutions. Comments on the test series are solicited.

Anesthesia↗
PubMed1992

[Incidence of nosocomial infections in a military hospital].

Over a 2-year period, 479 cases of nosocomial infections were identified in our hospital by a surveillance method based on the bacteriological laboratory results. The monthly incidence rate ranged from 1.8 to 4 percent of all in-patients. With this method, a 2 percent background noise and a 4 percent alarm threshold could be defined. The most frequent nosocomial infections were urinary tract infections (77 percent), purulent skin infections (12 percent) and septicaemias (10 percent). Compared during 15 days with the most sensitive surveillance method of the National Nosocomial Infections Surveillance System, our method proved insufficient to detect nosocomial lung infections and superficial surgical wound infections. On the other hand, it was highly satisfactory to watch for urinary tract infections and septicaemias. Improvements that would not put a heavy burden on the work of clinical departments are suggested.

Adolescent↗
PubMed1992

[Time-series analysis applied to nosocomial infection].

BACKGROUND: In this study we introduce a new view of hospital infection, to apply time series techniques to it. Our objective is to complement hospital infection's epidemiological surveillance by means of obtaining alert and alarm thresholds that make easy to the epidemiologist the decision of intervention, in case they are exceeded. METHODS: We have used the classic time series analysis described by Rumeau-Rouquette, and ARIMA (Autoregresive Integrated Moving Average) models developed by Box and Jenkins. The study focus on three hospital units: one intensive care, one long term care and one surgical unit. The nosocomial infection intervals have been calculated with a 68% (1SD) and 95% (2SD) confidence levels. RESULTS: We detect an ascending general trend in the last two units, without the detection of seasonal variations. Two ARIMA (1, 0, 0) models we obtained for surgery and long term care, discarding other better adjusted models, more complex and difficult to obtain, but with no real advantage in prediction power. Confidence intervals were calculated with both methods. We did not find general trend and seasonal variations for intensive care unit. No model was considered valid, because of its high random component. The nosocomial infection intervals have been calculated with mean +/- 1SD and mean +/- 2SD. CONCLUSIONS: We think that more precise knowledge of hospital infection, with a high random component in our study, can be in addition useful to assign priority to human and material resources.

Analysis of Variance↗
PubMed1987

A new conventional and high-frequency ventilator for small animals.

A pressure limited, time controlled ventilator has been designed especially for studies on experimental animals with severe respiratory distress syndrome (SRDS). Inspiration: Expiration (I:E) ratio (1:99-99:1) and frequency can be changed independently. Frequency ranged from 1 to 199/min in conventional ventilation (CV), while in high-frequency jet ventilation (HFJV) from 1 to 30 Hz. The gas delivery system consists of 3 magnetic valves (inspiration, expiration and HFJV, respectively) to ensure superposition of CV with HFJ or to use them separately. A monitoring unit switches off inspiration gas sources during HFJV if intratracheal pressure exceeds the alarm threshold. The device has been used in the following animal models: premature newborn rabbits with surfactant deficient lungs, emphysematous rats and guinea pigs as well as dogs and rabbits with SRDS due to lung lavage. Ventilation was most effective with an I:E ratio of 4:1 during pressure controlled CV, whereas during HFJV optimum gas exchange could be maintained with an I:E ratio of 1:4 and a frequency of 15 Hz in beagle dogs and 10 Hz in rabbits, respectively.

Animals↗
PubMed1976

Effects of stimulus presentation and instructions on pure-tone thresholds and false-alarm responses.

The effects of three instructional sets (conventional Carhart-Jerger, strict, and lax) and of two stimulus presentation methods (continuous tones, pulsed tones) on pure-tone thresholds and false-alarm responses were determined for 20 male subjects. False alarms were tallied during hearing measurement periods and during 30-second time-out periods totaling nine minutes of time-out per subject. Results showed that 50% of the subjects made false-alarm responses to some extent at 250, 1000, and 4000 Hz. Instructions and stimulus mode, along with frequency, affected the number of false alarms, but thresholds under the experimental conditions were unchanged. It is suggested that a method for assessing and controlling false alarms is an important clinical consideration.

Acoustic Stimulation↗
PubMed1991

Methods for estimating infant thresholds.

Detection thresholds for 1000-Hz, 16-ms tone bursts were estimated for 3- and 6-month-old infants and for young adults. The test procedure used was the observer-based psychoacoustic procedure. Thresholds were estimated using two different adaptive procedures and the method of constant stimuli. There was little difference among the average thresholds determined by any of these techniques. The least variable thresholds were obtained in the method of constant stimuli. In addition, 10 infants at each age completed two 30-trial blocks of trials in the method of constant stimuli; 22 adults completed 8 blocks of 30 trials. For 3- and 6-month-olds and for adults, there was no significant change in average threshold between blocks. Individual 6-month-olds' thresholds rarely changed by more than 5 dB between blocks, and the correlation between the thresholds obtained in the two blocks was significant. Individual 3-month-olds' thresholds, however, sometimes changed by as much as 10 dB between blocks, and the correlation between first and second block threshold was not significant. The effects of response bias on threshold were assessed by examining receiver operating characteristic plots of hit and false alarm rates at threshold and the correlation between false alarm rate and threshold. Although there was some variability in response bias, infant/observer teams tended to respond in an unbiased fashion. In one of the adaptive procedures only, false alarm rate was significantly correlated with threshold. In all procedures, the exclusion of infants with high false alarm rates changed the average thresholds obtained by less than 5 dB.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiometry, Pure-Tone↗
PubMed1988

Computer-assisted Doppler monitoring to enhance detection of air emboli.

Currently, two of the most sensitive clinical approaches commonly used to monitor for venous air embolism, i.e., precordial Doppler audio and capnography, require the attention of the anesthesiologist's eye or ear, which is a distraction from other aspects of care. To assess the feasibility of allowing the computer to relieve the necessity for continuous human monitoring, we developed a computer algorithm for monitoring the precordial Doppler audio. This algorithm extracted (1) the amplitude of certain higher-frequency components of the Doppler audio, (2) a measure of the average value of the envelope of Doppler audio, and (3) the ratio between the average value of the Doppler envelope and the amount of envelope signal variation at heart rate frequency and its multiples. These three features were monitored by an adaptive pattern recognition algorithm that compared each new value for each feature with the previously developed mean and standard deviation for that feature. If the changes in the three features exceeded a detection threshold, an alarm (indicating suspected air embolism) was activated. Implemented as a prototype system, the algorithm was given preliminary testing in 2 dogs and activated alarms at levels of air well below those reported to cause clinically significant hemodynamic changes in dogs. While decreasing the distraction for the anesthesiologist, this early prototype alarm system alerts its user to the need for analysis of the Doppler signals when it senses an air embolus.

Algorithms↗
PubMed1991

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↗
PubMed1986

[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↗
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↗
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↗
PubMed1989

Alarms and their limits in monitoring.

The need to incorporate alarms in monitoring systems is related to the growing complexity of monitoring and the large number of variables. For sophisticated alarms, information about the inputs to the patient is of importance; for example, clinical interventions such as drug administration and ventilation readjustment need to be known to the monitoring system. Alarms are triggered by signals or signal features that exceed thresholds. Each threshold must be seen as a level that needs to be set, either manually or automatically. The large number of levels to be set creates an extra workload for the clinician. Approaches to determine such levels automatically are discussed in this article. Most promising seems the multiple signal approach using an expert system. It seems reasonable to expect that information concerning alarm limits, needed for the operation of knowledge-based alarm systems, may come from integrated departmental data bases.

Anesthesia, General↗
PubMed1986

The detection of phantom targets in noise by serotine bats; negative evidence for the coherent receiver.

Using a target simulator three serotine bats, Eptesicus serotinus, were trained to judge whether a phantom target was present or absent. The echolocation sounds emitted by the bats during the detection were intercepted by a microphone, amplified and returned by a loudspeaker as an artificial echo, with a delay of 3.2 ms and a sound level determined by the overall gain and cry amplitude. The cry level of each pulse was measured and the echo level received by the bat was calculated. The target was presented in 50% of the trials and the gain adjusted using conventional up/down procedures. Under these conditions between 40 and 48 dB peSPL were required for 50% detection (Figs. 2, 3). In a subsequent experiment the phantom target was masked with white noise (No) with a spectrum level of -113 dB re. 1 Pa X Hz-1/2. The thresholds were increased by 7-14 dB. Energy density (S) of a single pulse was measured and used to estimate S/No, which ranged from 36-49 dB at threshold. Theoretically the coherent receiver model predicts the ratio between hits and false alarms observed for the bats at a S/No of ca. 1-2 dB. Since the bats require 40-50 dB higher S/No (Fig. 3), this is taken as negative evidence for coherent reception (cross correlation). Furthermore, a strong sensitivity to clutter was found since there seemed to exist a fixed relationship between thresholds and clutter level.

Animals↗
PubMed1986

Naturalistic psychophysics: thresholds of ducklings (Anas platyrynchos) and chicks (Gallus gallus) to tones that resemble mallard calls.

Neonatal ducklings and chickens were tested for responsiveness to a pulsing pure tone that was as similar as possible to the mallard maternal alarm call. It is known that ducklings momentarily cease vocalizing when they hear the alarm call and that chicks do the same when they hear pure tones. The duration of peep suppression can thus be used as a measure of whether subjects of either species heard the stimulus. Chicks might not be as sensitive as ducklings to a mallard alarm call because the signal is less significant to them. An adaptive or staircase procedure was used to estimate absolute thresholds, and group psychometric functions were reconstructed for each species from the trial-by-trial data. Ducklings had lower thresholds than chickens as well as steeper psychometric functions to this stimulus. The results suggest that more sensitive and consistent behavioral responses can be elicited by naturalistic sounds than by more arbitrary acoustic stimuli.

Animals↗
PubMed1990

Automatic seizure detection: improvements and evaluation.

Improvements to an existing automatic seizure detection program are described. They are aimed at taking into account a larger temporal context and thus improving the specificity of the detections. Results were evaluated on 293 recordings from 49 patients, totaling 5303 h of 16-channel recording. They showed that 24% of the 244 seizures recorded were missed by the automatic detection; in 41% of the seizures, the patient alarm was not pressed but the computer made detections. The false detection rate was of the order of 1 false detection per hour of recording. Conclusions are: (1) automatic seizure detection must be used in conjunction with a patient alarm button since some seizures, having poorly defined EEG activity, are not detected; (2) the automatic detection allowed capture of many seizures, clinical and subclinical, for which the alarm was not pressed; (3) the low false detection rate indicates that lower detection threshold could be used, yielding better seizure detection.

Adolescent↗
PubMed1986

A unified biosocial theory of personality and its role in the development of anxiety states.

A general theory of heritable personality traits and their neurobiological basis is described. Three independent dimensions of personality are defined and related to heritable variation in patterns of response to specific types of environmental stimuli: 'novelty seeking' is due to a heritable tendency toward frequent exploratory activity and intense excitement in response to novel stimuli; 'harm avoidance' is due to a heritable tendency to respond intensely to aversive stimuli and to learn to avoid punishment, novelty, and non-reward passively; and 'reward dependence' is due to a heritable tendency to respond intensely to reward and succorance and to learn to maintain rewarded behavior. Evidence suggests that variation in each dimension is strongly correlated with activity in a specific central monoaminergic pathway: novelty seeking with low basal dopaminergic activity, harm avoidance with high serotonergic activity, and reward dependence with low basal noradrenergic activity. These neurobiological dimensions interact to give rise to integrated patterns of differential responses to punishment, reward, and novelty. The combination of high novelty seeking, high reward dependence, and low harm avoidance (histrionic personality) or the combination of high harm avoidance, low reward dependence, and low novelty seeking (obsessional personality) are each associated with information-processing patterns that lead to unreliable discrimination of safe and dangerous situations and hence to chronic anxiety. In individuals with high novelty seeking, chronic anxiety is characterized by global uneasiness or alarm without specific premonitory cues, frequent bodily pains due to low pain and sensation thresholds, low sedation threshold, and slow fatigability. In contrast, in individuals with high harm avoidance, chronic anxiety is characterized by frequent anticipatory worries based on specific cues, high pain and sedation thresholds, and easy fatigability. In response to frustrative non-reward, individuals with high reward dependence are susceptible to compensatory noradrenergic hyperactivity and hence acute or recurrent states of agitated dysphoria associated with reward-seeking behaviors such as overeating and increased sexual activity. Specific predictions are made about normal personality development as well as the development and familial aggregation of anxiety, somatoform, depressive and personality disorders. These predictions are compared with available information, and recommendations are made for future research.

Animals↗
PubMed1992

Determination of growth value thresholds for BACTEC PLUS aerobic blood culture vials.

Growth value thresholds used to identify positive blood culture vials can be defined by users for each BACTEC NR-660 bacteremia detection instrument. Growth values were compared with the recovery of organisms from vials flagged as positive during the testing of 3.056 high-volume vials containing aerobic (BACTEC PLUS 26) medium over a 2-month period. Results showed that optimal threshold values for our use of these vials varied from those recommended by the manufacturer; if the thresholds defined from these data had been used during the study period, total vials flagged as positive from which no organisms were recovered (false alarms) would have been reduced from 181 (5.9/100 vials tested) to 71 (2.3/100 vials tested), with a minimal decrease in the identification of vials containing usual or occasional pathogens (hits). Adjustments of growth value thresholds by the individual user can make the use of BACTEC instruments more efficient by decreasing further processing of vials from which no organisms are recovered.

Bacteremia↗