Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Alarm threshold”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed2000

Patients' perception of sound levels in the surgical suite.

STUDY OBJECTIVES: To measure sound levels that our patients are exposed to in the surgical suite and their perception of these sound levels. DESIGN: Sound levels experienced by 100 patients undergoing general anesthesia for elective surgery during three phases: induction and maintenance of anesthesia in the operating room (OR), and recovery from anesthesia in the recovery room, were measured using a Type 4436 Noise Dose Meter. The equivalent continuous sound levels (Leq), maximum sound levels (Lmax), and the sources of sounds were noted. Patients were interviewed 24 hours after anesthesia about their perception of the sound levels they had experienced in the OR and recovery rooms. MEASUREMENTS AND MAIN RESULTS: The Leq during the induction, maintenance, and recovery phases were 70.3 +/- 16.8 dB(A), 66.2 +/- 4.1 dB(A) and 71.8 +/- 6.1 dB(A), respectively. These sound levels are much higher than international recommendations for hospital acute care areas and exceed the thresholds to produce noise-induced cardiovascular and endocrine effects. Sound levels were significantly higher during the induction and recovery phases compared to the maintenance phase. Thirty-two patients found the induction phase noisy and 33 patients found the recovery phase noisy. The sound levels distressed 16 patients and 52 patients would have preferred a quieter environment. There was no difference in the sound levels experienced by those who expressed dissatisfaction with the sound levels and those who did not. Much of the noise, particularly staff conversations, unnecessary alarms, and preparation of equipment, could have been prevented by simple measures. CONCLUSION: Noise prevention in the OR and recovery room needs more attention and should be a routine part of patient care.

Anesthesia↗
PubMed1986

[Silent myocardial ischemia].

Silent myocardial ischemia seems a relatively frequent manifestation of coronary insufficiency. The practice of more and more sophisticated tests to detect myocardial ischemia shows that it is a relatively frequent pathological occurrence. It occurs in patients with an abnormality or a transient or constant failure of the alarm system, represented by pain during the ischemia. It is an heterogenous picture which may take the appearance of a completely silent ischemia (the metabolic, hemodynamic and electrical consequences of ischemia being the only symptoms of coronary insufficiency, demonstrated by the presence of severe, angiographic or anatomical, stenoses); of a silent transient ischemia (with alternance of symptomatic and silent episodes or with silent episodes after myocardial infarction); of myocardial necroses without pain or ischemic myocardiopathies. It is the consequences of either an ischemia which is too moderate to reach the pain threshold, or a severe ischemia in patients presenting alterations of the transmission system and of the perception of pain. It has metabolic, hemodynamic and anatomical consequences which may lead to necrosis or degeneration and fibrosis of the myocardium. The prognosis of a painless disease is difficult to make but it does not seem to be as poor as the one of the usual forms of ischemic cardiopathies. Medical treatment is mandatory, and surveillance of its efficacy must be systematic using the techniques of detection of the ischemia.

Aged↗
PubMed1987

Auditory localization in a free field using discrimination procedures.

A rotating boom positioned a loudspeaker at ear height at a distance of 4 ft from the center of the head of S, who was seated in a darkened large anechoic chamber (684 ft); 750-msec bursts of pink noise, separated by 3.25 sec, at 54 db SPL, were presented. During the interstimulus interval the speaker was moved cw or ccw in the presence of a masking noise at 73 db SPL. Practiced young adults (2F, 1 M) judged azimuth "same" or "different"; minimum discriminable angle (MDA) was taken as P(c) = .70, corrected for false alarms (judgments "s" or "d" with no movement). Standard azimuths relative to S were at the 8 cardinal points. MDAs were best at 0 degree (c. 4.5 degrees) but were still relatively good (c. 8.5 degrees) at 180 degrees. In general, MDAs were poorer in the rear quadrants. One S excelled at MDA and exhibited the lowest false alarm rate. The effect of the masker, and random selection of standard and azimuth and of comparison stimuli at every trial, help explain the rather large MDAs compared with the minimum audible angles in the literature. The rather large determination at 90 degrees azimuth as determined by Mills (1958) was not found in these data.

Adult↗
PubMed2006

The multimodal world of medical monitoring displays.

A vision of the future of intraoperative monitoring for anesthesia is presented-a multimodal world based on advanced sensing capabilities. I explore progress towards this vision, outlining the general nature of the anesthetist's monitoring task and the dangers of attentional capture. Research in attention indicates different kinds of attentional control, such as endogenous and exogenous orienting, which are critical to how awareness of patient state is maintained, but which may work differently across different modalities. Four kinds of medical monitoring displays are surveyed: (1) integrated visual displays, (2) head-mounted displays, (3) advanced auditory displays and (4) auditory alarms. Achievements and challenges in each area are outlined. In future research, we should focus more clearly on identifying anesthetists' information needs and we should develop models of attention in different modalities and across different modalities that are more capable of guiding design.

Anesthesia, General↗
PubMed2005

Evaluation of a fall detector based on accelerometers: a pilot study.

As falls and fall-related injuries remain a major challenge in the public health domain, reliable and immediate detection of falls is important so that adequate medical support can be delivered. Available home alarm systems are placed on the hip, but have several shortcomings. A fall detector based on accelerometers and placed at head level was developed, as well as an algorithm able to distinguish between activities of daily living and simulated falls. Accelerometers were integrated into a hearing-aid housing, which was fixed behind the ear. The sensitivity of the fall detection was assessed by investigation into the acceleration patterns of the head of a young volunteer during intentional falls. The specificity was assessed by investigation into activities of daily living of the same volunteer. In addition, a healthy elderly woman (83 years) wore the sensor during the day. Three trigger thresholds were identified so that a fall could be recognised: the sum-vector of acceleration in the xy-plane higher than 2 g; the sum-vector of velocity of all spatial components right before the impact higher than 0.7 m s(-1); and the sum-vector of acceleration of all spatial components higher than 6 g. The algorithm was able to discriminate activities of daily living from intentional falls. Thus high sensitivity and specificity of the algorithm could be demonstrated that was better than in other fall detectors worn at the hip or wrist at the same stage of development.

Acceleration↗
PubMed2004

Signal verification of middle latency auditory evoked potentials by automated detection of the brainstem response.

BACKGROUND: The midlatency components of auditory evoked potentials (AEPs) are gradually suppressed with increasing concentrations of anesthetics. Thus, they have been proposed as a monitor of anesthetic depth. However, undetected malfunction or disconnection of headphones and undetected hearing loss also result in suppressed midlatency AEPs that in turn may be misinterpreted as signs of deep anesthesia. As the brainstem component of the AEP is minimally influenced by anesthetics, its presence or absence can be used to verify that the recorded signal is a true AEP rather than an artifact. In this study, an online-capable procedure for detection of the brainstem component of the AEP was developed. METHODS: One hundred and ninety perioperatively recorded AEPs (binaural stimuli, 500 sweeps) were selected from a database with electroencephalographic and concomitant AEP stimulus information. Identical electroencephalogram regions were used to produce nonstimulus synchronized averaged signals (500 sweeps, "non-AEP"). The 190 AEPs and 190 "non-AEPs" were used to develop a detector of the brainstem component of AEPs. AEPs and "non-AEPs" were wavelet transformed (discrete wavelet decomposition, biorthogonal 2.2 mother-wavelet), and the coefficient with the best separation of the two classes of signals was selected. Receiver operating characteristic curve analysis was performed to determine the optimum threshold value for this coefficient. RESULTS: The third coefficient of the third level was selected. In AEP signals, retransform of this coefficient produces a peak that resembles peak V of the brainstem response. The developed detector of the brainstem component of AEP had a sensitivity of 97.90% and a specificity of 99.48%. CONCLUSIONS: This detector of the AEP brainstem component can be used to verify that the signal reflects the response to an auditory stimulus. An alternative approach, used in the Danmeter AEP monitor, is based on the signal-to-noise ratio of the midlatency components of the AEP. Because the midlatency components of AEP are suppressed by anesthesia, a false alarm "low AEP/no AEP" is generated during deep anesthesia. This, in turn, may suggest disconnection of headphones or technical problems whenever anesthesia is deep. This disadvantage has been overcome by our detector, which is based on the identification of the brainstem component of AEP.

Acoustic Stimulation↗
PubMed2004

Rapid population decline in red knots: fitness consequences of decreased refuelling rates and late arrival in Delaware Bay.

Most populations of migrant shorebirds around the world are in serious decline, suggesting that vital condition-dependent rates such as fecundity and annual survival are being affected globally. A striking example is the red knot (Calidris canutus rufa) population wintering in Tierra del Fuego, which undertakes marathon 30,000 km hemispheric migrations annually. In spring, migrant birds forage voraciously on horseshoe crab eggs in Delaware Bay in the eastern USA before departing to breed in Arctic polar deserts. From 1997 to 2002 an increasing proportion of knots failed to reach threshold departure masses of 180-200 g, possibly because of later arrival in the Bay and food shortage from concurrent over-harvesting of crabs. Reduced nutrient storage, especially in late-arriving birds, possibly combined with reduced sizes of intestine and liver during refuelling, had severe fitness consequences for adult survival and recruitment of young in 2000-2002. From 1997 to 2002 known survivors in Delaware Bay were heavier at initial capture than birds never seen again, annual survival of adults decreased by 37% between May 2000 and May 2001, and the number of second-year birds in wintering flocks declined by 47%. Population size in Tierra del Fuego declined alarmingly from 51,000 to 27,000 in 2000-2002, seriously threatening the viability of this subspecies. Demographic modelling predicts imminent endangerment and an increased risk of extinction of the subspecies without urgent risk-averse management.

Age Factors↗
PubMedDate not supplied

Automatic detection of atrial fibrillation and flutter by wave rectification method.

Rapid detection of atrial flutter or fibrillation is needed in intensive care or home ECG monitoring with alarm generation, and in portable monitors with warningfunction, etc. Detection and assessment of these atrial abnormalities is necessary in computerized morphological analysis as well, to decide whether parameter measurements should be rejected, restricted to QRS and/or T wave only, or limited to those leads where atrial flutter orfibrillation waves are less expressed. A method for the detection and measurement of atrial flutter and fibrillation in the T-P segments of the ECG is proposed. An atrial flutter/ fibrillation parameter (AFF) is defined as the mean value of the differentiated filtered and rectified signal in these segments. The AFF has been measured in 329 patients from an annotated atrial flutter-fibrillation database. A threshold of AFF=0.35% with respect to the maximum signal excursion was chosen by a heuristic algorithm, to separate patients with atrial arrhythmia. The accuracy of the method was 91.8 %. The positive and negative detection errors of the AFF classification are discussed.

Atrial Fibrillation↗
PubMed2001

The systematic discrepancy between A' for overall recognition and remembering: a dual-process account.

Signal detection accounts of recognition assume that all item endorsements arise from the assessment of a single continuous indication of memory strength, even when subjects claim to categorically separate items accompanied by contextual recollection from those that are not (viz., remembering vs. knowing). Dissociations of these response types are held to occur because the former require a higher response criterion for item strength than does the latter. Meta-analytic and individual subject data suggest that when the A' metric is used, accuracy for remembering can systematically deviate from that of overall responding for individual subjects. This occurs because, unlike the symmetric and rigid receiver-operating characteristic (ROC) implied under A', empirical ROCs are asymmetric and plastic. A dual-process model predicted that the magnitude of the deviation would vary as a systematic function of the proportion of overall recognition accompanied by subjective remember reports for individual subjects. The predictions were confirmed using multiple regression on Monte Carlo and experimental data sets and were also shown to generalize to the double equal-threshold, single high-threshold [i.e., H - FA; (H - FA)/(1 - FA)], and the equal variance signal detection d' corrections. The unequal variance signal detection model was also shown to mirror the data, but only under the post hoc assumption that every subject adopts a very similar remember criterion placement rule. The results demonstrate that the systematic failure of tightly constrained models of recognition constitutes valuable regression data for more complex models and simultaneously highlights why single-point measures of accuracy are unsuitable as summaries across conditions or groups. Furthermore, the results show that remember rates carry unique information regarding the underlying processes governing individual subject performance that cannot be gleaned from the overall hit and false alarm rates in isolation.

Data Interpretation, Statistical↗
PubMed2006

Tinnitus as an alarm bell: stress reaction tinnitus model.

Stress is a significant factor influencing the clinical course of tinnitus. Auditory system is particularly sensitive to the effects of different stress factors (chemical, oxidative, emotional, etc.). Different stages of reaction (alarm, resistance, exhaustion) lead to different characteristics of tinnitus and different therapeutic approaches. Individual characteristics of stress reaction may explain different aspects of tinnitus in various patients with different responses to treatment, despite similar audiological and etiological factors. A model based on individual reactions to stress factors (stress reaction tinnitus model) could explain tinnitus as an alarm signal, just like an 'alarm bell', informing the patient that something potentially dangerous for subject homeostasis is happening. Tinnitus could become a disabling symptom when the subject is chronically exposed to a stress factor and is unable to switch off the alarm. Stress signals, specific for each patient, have to be identified during the 'alarm' phase in order to prevent an evolution toward the 'resistance' and 'exhaustion' phases. In these phases, identification of stressor is no more sufficient, due to the organization of a 'paradoxical auditory memory' and a 'pathologically shifted attention to tinnitus'. Identification of stress reaction phase requires accurate otolaryngology and anamnesis combined with audiological matching tests (Feldman Masking Test, for example) and psychometric questionnaires (Tinnitus Reaction and Tinnitus Cognitive Questionnaires).

Adult↗
PubMed2003

Role of obesity and leptin in the pubertal process and pubertal growth--a review.

The prevalence of obesity is increasing alarmingly to epidemic proportions in children and adolescents, especially in industrialized countries. The finding that overweight children, especially girls, tend to mature earlier than lean children has led to the hypothesis that the degree of body fatness may trigger the neuroendocrine events that lead to the onset of puberty. Obese children have high leptin levels, and these may play a role in their earlier onset of puberty. Leptin receptors have been identified in the hypothalamus, gonadotrope cells of the anterior pituitary, and ovarian follicular cells, as well as Leydig cells. Leptin accelerates gonadotropin-releasing hormone (GnRH) pulsatility in hypothalamic neurons, and it has a direct effect on the anterior pituitary. Leptin administration at low doses may have a permissive, threshold effect on the central networks that regulate gonadotropin secretion. However, at high levels, such as those in obese people, it can have an inhibitory effect on the gonads. Children with obesity also have increased adrenal androgen levels, which may be involved in the accelerated growth of these children before puberty. Recent data indicate that leptin has a specific role in stimulating the activity of enzymes essential for the synthesis of adrenal androgens. Children with exogenous obesity frequently show an increase in height velocity with tall stature for age despite low growth hormone levels. Our group has shown that leptin acts as a skeletal growth factor, with a direct effect on skeletal growth centers, in the mice mandibular condyle, a model of endochondral ossification. In summary, obesity is associated with early puberty. Elevated leptin levels might have a permissive effect on the pubertal process and pubertal growth.

Adolescent↗
PubMed2006

Binaural detection with narrowband and wideband reproducible noise maskers. III. Monaural and diotic detection and model results.

A single-interval, yes-no, tone-in-noise detection experiment was conducted to measure the proportion of "tone present" responses to each of 25 reproducible noise-alone and tone-plus-noise waveforms under narrowband (100 Hz), wideband (2900 Hz), monotic, and diotic stimulus conditions. Proportions of "tone present" responses (estimates of the probabilities of hits and false alarms) were correlated across masker bandwidths and across monotic and diotic conditions. Two categories of models were considered; one based on stimulus energy or neural counts, and another based on temporal structure of the stimulus envelope or neural patterns. Both categories gave significant correlation between decision variables and data. A model based on a weighted combination of energy in multiple critical bands performed best, predicting up to 90% of the variance in the reproducible-noise data. However, since energy-based models are unable to successfully explain detection under a roving-level paradigm without substantial modification, it is argued that other variations of detection models must be considered for future study. Temporal models are resistant to changes in threshold under roving-level conditions, but explained at most only 67% of the variance in the reproducible-noise data.

Adult↗
PubMedDate not supplied

[Essay on pain].

The classical conception of pain, considering it as pertaining to a specific sensation, called pain or nociceptive sensation, ie capable of differentiating between all informations those which are detrimental to the organism, is unsatisfactory. The organization of somesthetic pathways allows to say that this pain sensation, associated with temperature sensation, stems from the most archaic nervous sensation: that of the most primitive organisms, for whom contact provokes a flight reaction. This leads to consider the presence of a "contact" sensation, thermic as well as mechanical, "existential" so to speak, far different from touch sensation which is a discriminatory sensation. Pain appears at one end of a chain, the other end corresponding to cutaneous contacts. These latter contacts are pleasurable or very pleasurable, as typified by sexual contacts. Beyond pain, the archaic nervous function is the origin of a whole defense and protection system for the organism. Pain constitutes the subjective alarm mechanism, triggered off in case of lesion or break of the primitive envelope or of its by-products. This existential sensation, with pain as its most blatant manifestation, has held a central place in the course of evolution: our organism could in this way become aware of its own existence. For all of us it plays an important role in the organization and structuring of our personality.

Afferent Pathways↗
PubMed2002

[Hearing screening with automatic evaluation of TEOAE and a new method of automatic evaluation of early auditory evoked potentials. Optimization and field trial].

BACKGROUND AND OBJECTIVE: To make a rational decision as to which screening test might be adequate as a universal newborn hearing screening, different methods have to be tested under "real-life" conditions. In addition, a good reference is required as "golden standard." PATIENTS/METHODS: In the study presented here, an ABR with a novel algorithm for threshold-estimation was optimized and compared to TEOAE (Echoscreen) and DPOAE (GSI 60) in a three-step protocol using a standard click-evoked ABR (Evoselect) as reference of sensitivity and specificity. RESULTS: 26 ears were found to be hearing-impaired. All of them were also detected by each of the screening method (sensitivity 100%). Specificity in the final "step 2" of the study was around 87.7/92.3% for Echoscreen, 82.4/84.4% for DPOAE and 82.4/89.1 for Evoflash (left/right, respectively). Differences were not at all significant (X2-test, p > > 0.05). In summary, results were somewhat inferior to those found by other authors, probably due to more difficult conditions in the "real-life" setting. CONCLUSIONS: A higher rate of false-alarm shows that a two-step screening is necessary. Therefore, increased resources for diagnostic procedures are required.

Adolescent↗
PubMed2005

A direct brainstem-amygdala-cortical 'alarm' system for subliminal signals of fear.

We examined whether consciously undetected fear signals engage a collateral brainstem pathway to the amygdala and prefrontal cortex in the intact human brain, using functional neuroimaging. 'Blindsight' lesion patients can respond to visual fear signals independently from conscious experience, suggesting that these signals reach the amygdala via a direct pathway that bypasses the primary visual cortex. Electrophysiological evidence points to concomitant involvement of prefrontal regions in automatic orienting to subliminal signals of fear, which may reflect innervation arising from brainstem arousal systems. To approximate blindsight in 22 healthy subjects, facial signals of fear were presented briefly (16.7 ms) and masked such that conscious detection was prevented. Results revealed that subliminal fear signals elicited activity in the brainstem region encompassing the superior colliculus and locus coeruleus, pulvinar and amygdala, and in fronto-temporal regions associated with orienting. These findings suggest that crude sensory input from the superior colliculo-pulvinar visual pathway to the amygdala may allow for sufficient appraisal of fear signals to innervate the locus coeruleus. The engagement of the locus coeruleus could explain the observation of diffuse fronto-temporal cortical activity, given its role in evoking collateral ascending noradrenergic efferents to the subcortical amygdala and prefrontal cortex. This network may represent an evolutionary adaptive neural 'alarm' system for rapid alerting to sources of threat, without the need for conscious appraisal.

Adult↗
PubMed1992

Basic biochemical investigations as rationale for the design of original antimalarial drugs. An example of phospholipid metabolism.

The future of antimalarial chemotherapy is particularly alarming in view of the spread of parasite cross-resistances to drugs that are not even structurally related. Only the availability of new pharmacological models will make it possible to select molecules with novel mechanisms of action, thus delaying resistance and allowing the development of new chemotherapeutic strategies. We reached this objective in mice. Our approach is hunged on fundamental and applied research begun in 1980 to investigate the phospholipid (PL) metabolism of intraerythrocytic Plasmodium. This metabolism is abundant, specific and indispensable for the production of Plasmodium membranes. Any drug able to interfere with this Plasmodium membranes. Any drug able to interfere with this metabolism blocks parasitic development. The most effective interference yet found involves blockage of the choline transporter, which supplies Plasmodium with choline for the synthesis of phosphatidylcholine, its major PL, this is a limiting step in the pathway. The drug sensitivity threshold is much lower for the parasite, which is more dependent on this metabolism than host cells. The compounds show in vitro activity against P. falciparum at 1 to 10 nM. They show a very low toxicity against a lymphoblastoid cell line, demonstrating a total absence of correlation between growth inhibition of parasites and lymphoblastoid cells. They show antimalarial activity in vivo, in the P. berghei or P. chabaudi/mouse system, at doses 20- to 100-fold lower than their acute toxicity limit. The bioavailability of a radiolabeled form of the product seemed to be advantageous (slow blood clearance and no significant concentration in tissues). Lastly, the compounds are inexpensive to produce. They are stable and water-soluble.

Animals↗
PubMed1996

Acute pain after thoracic surgery predicts long-term post-thoracotomy pain.

OBJECTIVE: Long-term pain is a common sequela of thoracotomy, occurring in approximately 50% of patients 2 years after thoracic surgery. Despite this alarming statistic, little is known about the factors responsible for the transition of acute to chronic pain. The aim of the present study is to identify predictors of long-term post-thoracotomy pain. DESIGN: Follow-up was for 1.5 years for patients who had participated in a prospective, randomized, controlled trial of preemptive, multimodal analgesia. SETTING: Subjects were recruited from a tertiary care center. PATIENTS: Thirty patients who had undergone lateral thoracotomy were followed up by telephone, administered a structured interview, and classified according to long-term pain status. MAIN OUTCOME MEASURES: Present pain status was measured by a verbal rating scale (VAS). Measures obtained within the first 48 h after surgery were compared between patients with and without pain 1.5 years later. These include VAS pain scores at rest and after movement, McGill Pain Questionnaire data, patient-controlled morphine consumption (mg), and pain thresholds to pressure applied to a rib contralateral to the thoracotomy incision. RESULTS: Fifty-two percent of patients reported long-term pain. Early postoperative pain was the only factor that significantly predicted long-term pain. Pain intensity 24 h after surgery, at rest, and after movement was significantly greater among patients who developed long-term pain compared with pain-free patients. A significant predictive relationship was also found at 24 and 48 h using the McGill Pain Questionnaire. Cumulative morphine was comparable for the two groups. Pain thresholds to pressure applied to a rib contralateral to the incision did not differ significantly between the groups. CONCLUSION: Aggressive management of early postoperative pain may reduce the likelihood of long-term post-thoracotomy pain.

Acute Disease↗
PubMed1999

Odor identification, consistency of label use, olfactory threshold and their relationships to odor memory over the human lifespan.

The purpose of this study was to investigate olfactory threshold, odor identification, consistency of label use and their relationships to odor memory in the context of semantic/episodic memory across the human lifespan. A total of 137 subjects aged 4-90 years were tested with several olfactory test procedures. We found that olfactory sensitivity was well developed in children despite the finding that their odor naming and odor memory were inferior to that of adults. In the elderly population, olfactory functions gradually declined, with odor memory and odor identification demonstrating the most significant decline. Semantic encoding was differentially related to odor memory over the human age span. Whereas consistency of label use was the main predictor for odor memory in children and young adults, olfactory identification ability was the main predictor in the elderly study group. We also calculated response bias for the separate age groups and found no differences between children, young adults and elderly. However, with age false alarm rates increased. We conclude that children possess equal olfactory sensitivity compared with adults; however, due to limitations in linguistic capabilities and familiarity to odorants, odor memory and odor identification performance was limited. Additionally, our data indicate major alterations of olfactory processing in advanced age with substantial losses in odor memory and odor identification performance.

Adolescent↗