Automatic characterization of events on SpO2 signal: comparison of two methods.

Two methods based on trend extraction have been designed to provide automatic analysis of physiological data recorded on adult patients hospitalized in intensive care unit. We focused our work on the characterization of events occurring on SpO2 signal, this signal being used to detect vital problems. Our aim was to recognize events related to technical or vital problems to assist medical staff in his decision process. Our results show that both methods are able to detect and distinguish between probe deconnection, transient hypoxia and desaturation events.

Alarms in the intensive care unit: how can the number of false alarms be reduced?

Many alarms, as they now exist in most monitoring systems, are not usually perceived as helpful by the medical staff because of the high incidence of false alarms. This paper gives an overview of the problems related to their current design and the objectives of monitoring. The current approaches used to improve the situation are then presented from two main standpoints: organizational and behavioural on the one hand, and technical on the other.

Towards symbolization using data-driven extraction of local trends for ICU monitoring.

We propose a methodology for the extraction of local trends from a stream of data. It has been designed to suit the needs of interpretation-oriented visualization and symbolization from ICU monitoring data. After giving implementation details for efficient computation of local trends, we propose the use of a characteristic analysis span for each variable. This characteristic span is obtained from a set of criteria that we compare and evaluate in regard of analysis of ICU monitoring data gathered within the Aiddaig project. The processing results in a rich visual representation and a framework for the local symbolization of the data stream based on its dynamics.

Multicentric study of monitoring alarms in the adult intensive care unit (ICU): a descriptive analysis.

OBJECTIVES: To assess the relevance of current monitoring alarms as a warning system in the adult ICU. DESIGN: Prospective, observational study. SETTINGS: Two university hospital, and three general hospital, ICUs. PATIENTS: Hundred thirty-one patients, ventilated at admission, from different shifts (morning, evening, night) combined with different stages of stay, early (0-3 days), intermediate (4-6 days) and late (> 6 days). INTERVENTIONS: Experienced nurses were asked to record the patient's characteristics and, for each alarm event, the reason, type and consequence. MEASUREMENTS AND MAIN RESULTS: The mean age of the patients included was 59.8 +/- 16.4 and SAPS1 was 15.9 +/- 7.4. We recorded 1971 h of care. The shift distribution was 78 mornings, 85 evenings and 83 nights; the stage distribution was 88 early, 78 intermediate and 80 late. There were 3188 alarms, an average of one alarm every 37 min: 23.7% were due to staff manipulation, 17.5% to technical problems and 58.8% to the patients. Alarms originated from ventilators (37.8%), cardiovascular monitors (32.7%), pulse oximeters (14.9%) and capnography (13.5%). Of the alarms, 25.8% had a consequence such as sensor repositioning, suction, modification of the therapy (drug or ventilation). Only 5.9% of the alarms led to a physician's being called. The positive predictive value of an alarm was 27% and its negative predictive value was 99%. The sensitivity was 97% and the specificity 58%. CONCLUSIONS: The study confirms that the level of monitoring in ICUs generates a great number of false-positive alarms.

Introduction of knowledge bases in patient's data management system: role of the user interface.

As the number of signals and data to be handled grows in intensive care unit, it is necessary to design more powerful computing systems that integrate and summarize all this information. The manual input of data as e.g. clinical signs and drug prescription and the synthetic representation of these data requires an ever more sophisticated user interface. The introduction of knowledge bases in the data management allows to conceive contextual interfaces. The objective of this paper is to show the importance of the design of the user interface, in the daily use of clinical information system. Then we describe a methodology that uses the man-machine interaction to capture the clinician knowledge during the clinical practice. The different steps are the audit of the user's actions, the elaboration of statistic models allowing the definition of new knowledge, and the validation that is performed before complete integration. A part of this knowledge can be used to improve the user interface. Finally, we describe the implementation of these concepts on a UNIX platform using OSF/MOTIF graphical interface.

INFORM: European survey of computers in intensive care units.

The aims of this study were (a) to survey and evaluate the impact of information technology applications in High Dependency Environments (HDEs) on organizational, psychological and cost-effectiveness factors, (b) to contribute information and design requirements to the other workpackages in the INFORM Project, and (c) to develop useful evaluation methodologies. The evaluation methodologies used were: questionnaires, case studies, objective findings (keystroke) and literature search and review. Six questionnaires were devised covering organizational impact, cost-benefit impact and perceived advantages and disadvantages of computerized systems in HDE (psychological impact). The general conclusion was that while existing systems have been generally well received, they are not yet designed in such a developed and integrated way as to yield their full potential. Greater user involvement in design and implementation and more emphasis on training emerged as strong requirements. Lack of reliability leading to parallel charting was a major problem with the existing systems. It proved difficult to assess cost effectiveness due to a lack of detailed accounting costs; however, it appeared that in the short term, computerisation in HDEs tended to increase costs. It is felt that through a better stock control and better decision making, costs may be reduced in the longer run and effectiveness increased; more detailed longitudinal studies appear to be needed on this subject.

INFORM: integrated support for decisions and activities in intensive care.

Many medical decision support systems that have been developed in the past have failed to enter routine clinical practice. Often this is because the developers have failed to analyse in sufficient detail the precise user requirements, because they have produced a system which takes too narrow a view of the patient, or because the decision support facilities have not been sufficiently well integrated into the routine clinical data handling activities. In this paper we discuss how the AIM-INFORM project is setting out to deal with these issues, in the context of the provision of decision support in the intensive care unit.

INFORM: development of information management and decision support systems for High Dependency Environments.

The long-term aim in the INFORM Project is to develop, evaluate and implement a new generation of Information Systems for hospital High Dependency Environments (HDE-Intensive Care Units, Neonatal Units, Burns Units. Operating and Recovery Rooms, and other specialised areas). The distinguishing feature of the HDE is the very large amount of data that is collected through monitors and paper records about the state of critically ill patients; this has made the role of the staff a technical one in addition to a caring one. The INFORM System will integrate Decision Support with on-line, off-line and observed patient data and, in addition, will incorporate and integrate unit management features. In the Exploratory Phase of the Project, functional requirements have been set out. These are based on four components: conceptual model of the HDE; evaluation of existing HDE Information Systems; development of a novel software architecture using a Knowledge-Based Systems (KBS) methodology, and based on a critical review of KBS applied to the HDE: monitoring of appropriate leading-edge technological developments. The conceptual model has two components: a patient-related information model, and a department-related cost model. The patient-related model is identifying key and difficult areas of decision making. A key aspect of INFORM is integration of clinical Decision Support for these areas into the Information System through a layered software architecture. The lower layers are concerned with monitoring and alarming and the higher levels with patient assessment and therapy planning. The functionality and interconnection of these layers are being determined.

Use of capnography in diagnosis of pulmonary embolism during acute respiratory failure of chronic obstructive pulmonary disease.

In chronic obstructive pulmonary disease (COPD) patients, there is a difference between PaCO2 and end-tidal partial pressure of CO2 (PetCO2). This gradient P(a-et)CO2 is due to ventilation/perfusion mismatching and deadspace, and is usually abolished by forced and prolonged expiration. We hypothesized that this gradient might not be canceled by forced expiration in the case of acute respiratory failure (ARF) related to pulmonary embolism (PE). Forty-four adult COPD patients were prospectively entered into this study; they were suspected of having ARF related to PE on the basis of clinical and biological data on admission. Maximum expired partial pressure of CO2 (PemCO2) was measured in mechanically ventilated and sedated patients by an interrupt of mechanical support. CO2 concentration was recorded during the following prolonged and passive expiration. The test was considered valid if an expiratory plateau was obtained. PemCO2 was measured in triplicate. Simultaneously, PaCO2 was measured and the ratio, R = [( 1-PemCO2]/PaCO2) x 100, was calculated. Pulmonary angiography was performed on the same day for all patients. Results showed that 17 patients had PE (PE+) and 17 had no PE (PE-). The two groups were comparable regarding mean age, severity of underlying chronic respiratory disease, PaCO2, PaO2, and hemodynamic data on admission. P(a-em)CO2 and R were significantly different in PE+ and PE- patients at 12 +/- 6.9 torr compared to 1 +/- 2.4 torr and at 28 +/- 14.8% compared to 2 +/- 6.2% (p less than .001), respectively. The positive predictive value of the test was 74%, but the negative predictive value 100% and the specificity was 65%, but sensitivity was 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer-assisted evaluation of respiratory data in ventilated critically ill patients.

In intensive care unit, a lot of data are currently available but remain unused by nurses and residents because of complexity of analysis. We have developed a system for interpretation of respiratory data (RESPAID) in order to improve monitoring of patients under respiratory support and also to provide a high level of information. RESPAID is a real-time system which interprets quantitative and qualitative aspects of the usual respiratory data at different levels of information. Initial knowledge base was built from data given by four specialists in intensive care. Major attention was paid to different aspects of the system: monitor interface, user interface and time representation. Data are issued from standard respirators and/or monitors used in the intensive care unit. Informations provided by RESPAID are alarm identification, ventilator settings modification and proposal for physiological evolution of the patient or suspected complication. RESPAID runs on IBM PCAT3 with 1st class shell. It is currently in clinical validation procedure.

Carbon dioxide mandatory ventilation (CO2MV): a new method for weaning from mechanical ventilation. Description and comparative clinical study with I.M.V. and T. tube method in COPD patient.

We describe a new technique specially designed for weaning from mechanical ventilation: carbon dioxide mandatory ventilation (CO2MV). CO2MV is based on feedback between end tidal expired partial pressure of carbon dioxide and ventilatory mode, controlled or spontaneous. In order to evaluate its real interest we performed a randomized prospective study, CO2MV vs Intermittent Mandatory Ventilation (IMV) and T. Tube Method (TTM). Fourty-two adult patients with chronic obstructive pulmonary disease entered this study at the end of acute respiratory failure requiring mechanical ventilatory support. We observed a better stability of arterial blood gas during weaning with CO2MV and an increase in success rate (CO2MV 13/14 - IMV 5/14 - TTM 10/14). From this study CO2MV seems available for weaning of COPD patients. Nevertheless, further studies are required to appreciate its real clinical interest.

Decrease of angiotensin-converting enzyme activity after plasma exchange.

We measured sequential changes in serum angiotensin-converting enzyme (ACE) in 12 ICU patients undergoing plasma exchange (PE) with plasma substitutes (albumin-Polygelin). A dramatic decrease in serum ACE activity was observed after each of the 51 PE procedures. Repeated PE procedures resulted in almost a total depletion of serum ACE, which returned to normal ranges in 4 to 10 days. No ACE change was observed during hemodialysis or hemofiltration. ACE activity increased after PE with fresh frozen plasma replacement. ACE changes were compared with IgG, antithrombin III, and fibronectin changes. Extraction ratio comparisons were consistent, with a loss in removed plasma accounting for 50% to 70% of the observed ACE decrease. Plasma zinc levels were not modified after PE. Mixing experiments with increasing volumes of plasma substitutes showed ACE inhibition by Polygelin. In vivo infusion of Polygelin had the same effect. The renin-induced aldosterone response studied in six exchanged patients was consistent with a relative hyperreninemic hypoaldosteronism after repeated PE. These findings may be of clinical relevance during acute hypovolemia and dehydration after PE or Polygelin infusion and in patients with impaired lung endothelial function.

[New method of weaning from respiratory assistance. Ventilation based on carbon dioxide]. / Nouvelle technique de sevrage de l'assistance ventilatoire. Ventilation asservie au gaz carbonique.

The authors describe a new device for weaning from mechanical ventilation, based on continuous measurement of end-expiratory concentration of CO 2 (FCO 2 ET). The spontaneous or controlled mode of ventilation is automatically determined by the level of FCO 2 ET in relation to preselected maximum and minimum thresholds. The authors call this device "CO 2MV".

[Definition and realization of a microprocessor system for monitoring during artificial ventilation (author's transl)]. / Un système informatisé de monitorage ventilatoire. Définition et réalisation.

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.

[Determination of global diffusion of CO2 and its partial components under assisted respiration. Technical problems and practical value in respiratory resuscitation]. / Détermination sous ventilation assistée de la ductance globale du CO2 et de ses composantes partielles. Problèmes techniques et intérêt pratique en réanimation respiratoire.

A study of partial CO2 ductance has been performed in patients under assisted ventilation. The authors propose methods for simultaneous measurement of paCO2, PAECO2, PECO2 and PICO2. This methodology is used in patients presenting different conditions accounting for respiratory resuscitation: barbiturate poisoning with healthy lungs, bronchial stasis, acute lung involvement, obstructive bronchopneumopathy and pulmonary embolism.