PubMed Health⌕ Search

Biomedical subjects

L Beydon

Publications and source records attributed to L Beydon.

At least 19 recordsLinked to original sources
PubMed2003

Effects of positive end-expiratory pressure increments can be predicted by computer simulation based on a physiological profile in acute respiratory failure.

OBJECTIVE: We examined whether computer simulation predicts airway pressures after increments of positive end-expiratory pressure (PEEP) in acute respiratory failure. DESIGN AND SETTING: Prospective, nonrandomized comparative trial in an intensive care unit of a university hospital. PATIENTS: Twelve consecutive acute respiratory failure patients. INTERVENTIONS. PEEP increments from 0 to 2.5, 5, 7.5, 10, and 15 cm H(2)O. MEASUREMENTS AND RESULTS: A physiological profile comprising values for compliance, respiratory resistance and CO(2 )elimination as a function of tidal volume was established from a recording of ordinary breaths prior to increments of PEEP. Airway pressures and CO(2 )elimination were measured 30 s after resetting, pressures also after 10 min. Values from simulation of the resetting, based on the profile, were compared to measured values. The profiles indicated vast differences in physiology between the 12 subjects. Errors of simulation of airway pressures were nonsignificant or trivial up to PEEP levels of 10 cm H(2)O (95% of errors <3 cm H(2)O). After 10 min plateau pressure averaged 1.5 cm H(2)O lower than 30 s after resetting. At increments to PEEP 7.5, 10, and 15, CO(2 )elimination fell by on average 4%, 8%, and 11%, respectively. As tidal volume and respiratory rate was unchanged this was not predicted. CONCLUSIONS: On the basis of a simple lung model, simulation predicted effects of moderate increments of PEEP on airway pressures in patients with complex physiology.

Acute Disease↗
PubMed2002

Effects of positive end-expiratory pressure on dead space and its partitions in acute lung injury.

OBJECTIVE: A large tidal volume (VT) and lung collapse and re-expansion may cause ventilator-induced lung injury (VILI) in acute lung injury (ALI). A low VT and a positive end-expiratory pressure (PEEP) can prevent VILI, but the more VT is reduced, the more dead space (VD) compromises gas exchange. We investigated how physiological, airway and alveolar VD varied with PEEP and analysed possible links to respiratory mechanics. SETTING: Medical and surgical intensive care unit (ICU) in a university hospital. DESIGN: Prospective, non-randomised comparative trial. PATIENTS. Ten consecutive ALI patients. INTERVENTION: Stepwise increases in PEEP from zero to 15 cm H2O. MEASUREMENTS AND RESULTS: Lung mechanics and VD were measured at each PEEP level. Physiological VD was 41-64% of VT at zero PEEP and increased slightly with PEEP due to a rise in airway VD. Alveolar VD was 11-38% of VT and did not vary systematically with PEEP. However, in individual patients a decrease and increase of alveolar VD paralleled a positive or negative response to PEEP with respect to oxygenation (shunt), respectively. VD fractions were independent of respiratory resistance and compliance. CONCLUSIONS: Alveolar VD is large and does not vary systematically with PEEP in patients with various degrees of ALI. Individual measurements show a diverse response to PEEP. Respiratory mechanics were of no help in optimising PEEP with regard to gas exchange.

Adult↗
PubMed2002

[Potential advantages a new syringe pump system].

OBJECTIVES: To evaluate what could be the benefit in terms of alarm suppression, of a new syringe pumps system, which allows automatic relay without alarms. PATIENTS AND METHODS: We have prospectively recorded the nature and the mode of relay of all syringe pumps for administration of drugs to patients in two ICU. The perfusion regimen was studied in 61 patients over the complete duration of their stay in two ICU. Alarms were also recorded in one ICU room, over 13 days consecutive. The records were processed off-line with an automatic detection-recognition system in order to assess the origin of each alarm. Accordingly, the amount of alarm corresponding to monitor, ventilator and syringe pumps was computed. RESULTS: We found that syringe pumps, which would provide automatic relays without alarm, would suppress 17% of alarms in ICU and automatize 65% of the relay procedures, which are usually performed often in emergency, on response to the end of perfusion alarm. CONCLUSION: New syringe pumps allow both reduction of alarms in ICU and a better management of nurse workload. Indeed syringe relay can be planned in advance.

Equipment Failure↗
PubMed2001

[Electroencephalographic effects of sevoflurane in pediatric anesthesia: a prospective study of 20 cases].

OBJECTIVE: To study electroencephalographic (EEG) changes in children during induction of anaesthesia with 8% sevoflurane. PATIENTS: Twenty patients were consecutively included (ASA I-II; aged: 13-101 months). MATERIAL AND METHOD: Prospective study; approved by the Ethics Committee; written informed consent obtained from parents; anaesthesia induced with 8% sevoflurane in oxygen; no premedication was given; to collect the EEG data, non-invasive electodes were installed before induction; EEG was recorded continuously and stored on a computer for later analyses (descriptive analysis). RESULTS: Myoclonics movements were observed during induction of anaesthesia in two boys. Myoclonics movements stopped spontaneously without therapy. Epileptiform EEG activity (spikes and poly-spikes, burst suppression) was observed. In the 18 others cases, during sevoflurane induction, EEG changed rapidly with an increase in the range of beta activity (> 13 Hz) (n = 15) and in slow (< 8 Hz) and delta activity (< 4 Hz). In 14 patients, at time of laryngoscopy, the EEGs showed monophasic slow data activity (sharp high-voltage slow waves). Periods of EEG isoelectrical (burst suppression) were seen without spikes in four cases. CONCLUSION: At 2 MAC, epileptiform EEG activity has been observed during sevoflurane anaesthesia. In a short group of patients, this raises the question of avoiding sevoflurane in patients who have a history of epilepsy.

Anesthetics, Inhalation↗
PubMed2001

Analysis of the French health ministry's national register of incidents involving medical devices in anaesthesia and intensive care.

This study details all incidents involving medical devices used in anaesthesia and intensive care reported to the relevant authorities in France in 1998. There were 1004 reports during that year. Incidents were classified as serious (harmful to patients) in 11% of cases; death resulted in 2% of cases. Equipment for ventilation and infusion, and monitors of all kinds, accounted for most of the reports, representing 37%, 30% and 12%, respectively, of all reports. The leading causes of failure varied according to the category of device. User errors, quality control problems during production of the device and design faults were the three main causes. The problems identified during the study period enabled the faulty medical devices to be improved in 12-44% of cases. We conclude that post-marketing vigilance is a useful way of improving the quality of medical devices.

Anesthesiology↗
PubMed2001

Doppler study of middle cerebral artery blood flow velocity and cerebral autoregulation during a simulated ascent of Mount Everest.

OBJECTIVE: To explore cerebral hemodynamics in 8 healthy volunteers in a hypobaric chamber up to the altitude of Mount Everest after a progressive stepwise decompression to 8,848 m. METHODS: Physiological, clinical, and transcranial Doppler data were collected after at least 3 days at 5,000, 6,000, and 7,000 m and within 4 hours of reaching 8,000 m and returning to sea level. RESULTS: Three subjects were excluded at 8,000 and 8,848 m because of acute neurological deficits. Heart rate increased; mean arterial pressure remained stable; PaO2 and PaCO2 decreased with altitude; hemoglobin (Hb) and hematocrit (Ht) increased; arterial O2 content decreased over 6,000 m; middle cerebral artery blood flow velocity (MCAv) increased only during acute exposure to 8,000 m; and the corresponding pulsatility (PI) and resistivity indices (RI) decreased over 5,000 m. PI and RI correlated with heart rate. The transient hyperemic response (THR) of MCAv to common carotid compression was depressed at 8,000 m. CONCLUSIONS: At 8,000 m, the increase in MCAv seemed to reflect the normal hemodynamic response to acute hypoxia. The decrease of THR at this altitude could be an indication of impaired cerebral autoregulation. The role of impaired cerebral autoregulation in the genesis of acute neurologic deficits, observed at 8,000 m and above in 3 subjects, remains speculative.

Adult↗
PubMed2000

[Performance studies of 6 new anesthesia ventilators: bench tests].

OBJECTIVE: To assess the pneumatic performances of six new anaesthesia ventilators. STUDY DESIGN: Bench test study. MATERIAL: The study included one ventilator operated by an electric motor: ABT 5300 (Kontron); four ventilators of "bellows-in-bottle" category: ADU version 97 (Datex-Ohmeda); Aestiva 3000 (Datex-Ohmeda), Kion (Siemens), the two versions of Julian (Dräger); and an original ventilator devised for quantitative, or self-regulating target controlled inhalation anaesthesia, with a totally closed circuit, made of four ventilating chambers: PhysioFlex (Dräger). METHODS: The bench test included a passive lung model with adjustable compliance and resistances, and flow and pressure gauges. The accuracy of volume and pressure measurements was tested in various conditions of resistance and compliance. RESULTS: Pneumatic performance and accuracy were satisfactory, even in severe ventilatory conditions. All the ventilators, except ABT 5300 and Julian 1, have a compliance compensation system permitting to deliver and to maintain a constant tidal volume under various conditions of downstream load, particularly under maximal load condition. Variations of tidal volume with the increase of the fresh gas flow are negligible. CONCLUSION: Recent technological progress has improved pneumatic performance of anaesthesia ventilators and the marketed models are more homogeneous at present. Ergonomics and training for the use of the machine are becoming major criteria for the global assessment and the choice of a ventilator.

Airway Resistance↗
PubMed2000

[Equipment surveillance of implantable catheter ports (1996-1998). Members of Sub-Commissions 4a and 4b for Equipment Surveillance].

We analyse all incident reports to the French Health Ministry over the 1996-1998 period, concerning implantable catheter ports. They represent 7% of all reports in the field of anaesthesia and intensive care. Two hundred eleven reports have been analysed. There were 93 catheter ruptures with 77 intravascular migrations. In more than 50% of cases, a pinch-off syndrome mechanism was responsible of these ruptures and a displacement of the O'ring was involved in 25%. Additional minor complications were reported and discussed in regard to literature. We conclude that implantable catheter ports may lead to serious incidents which are preventable in most cases.

Catheters, Indwelling↗
PubMed2000

[Perfusion instruments: analysis of product surveillance in 1998 and its on-the-job training. Subcommittee 4b for Product Surveillance].

OBJECTIVES: To analyze retrospectively the data base of the French national vigilance reporting system concerning infusion devices during the year 1998. METHODS: Each report has been reviewed and classified, except implantable catheter ports. RESULTS: The study included 309 reports. Among them, 28% concerned infusion pumps and 72% single use devices, i.e. catheters, infusion lines, taps, connectors, etc. We observed six deaths and 23 severe incidents. Only 25% of devices could be formally investigated by manufacturers. The origins of incidents were very different between infusion pumps and single use devices. The first showed simple failures, software errors, maintenance omissions or errors, and problems related to obsolescence of the device. The second revealed manufacturer quality insurance failures, design and utilization errors, and problems related to the technique itself rather than device. DISCUSSION: Our findings are similar to the few data available in international literature. They address the need to obtain an adequacy between the performances of devices which vary with generations of devices and the clinical risks: newest and safest devices should be preferred for the infusion of the most critical drugs.

Catheterization↗
PubMed2000

Cerebral hemodynamics during arterial and CO(2) pressure changes: in vivo prediction by a mathematical model.

The aim of this work was to analyze changes in cerebral hemodynamics and intracranial pressure (ICP) evoked by mean systemic arterial pressure (SAP) and arterial CO(2) pressure (Pa(CO(2))) challenges in patients with acute brain damage. The study was performed by means of a new simple mathematical model of intracranial hemodynamics, particularly aimed at routine clinical investigation. The model was validated by comparing its results with data from transcranial Doppler velocity in the middle cerebral artery (V(MCA)) and ICP measured in 44 tracings on 13 different patients during mean SAP and Pa(CO(2)) challenges. The validation consisted of individual identification of 6 parameters in all 44 tracings by means of a best fitting algorithm. The parameters chosen for the identification summarize the main aspects of intracranial dynamics, i.e., cerebrospinal fluid circulation, intracranial elastance, and cerebrovascular control. The results suggest that the model is able to reproduce the measured time patterns of V(MCA) and ICP in all 44 tracings by using values for the parameters that lie within the ranges reported in the pathophysiological literature. The meaning of parameter estimates is discussed, and comments on the main virtues and limitations of the present approach are offered.

Adolescent↗
PubMed1999

Correlation between cerebral oxygen saturation measured by near-infrared spectroscopy and jugular oxygen saturation in patients with severe closed head injury.

UNLABELLED: Near-infrared spectroscopy has been used to monitor cerebral oxygen saturation during cerebral circulatory arrest and carotid clamping. However, its utility has not been demonstrated in more complex situations, such as in patients with head injuries. The authors tested this method during conditions that may alter the arteriovenous partition of cerebral blood in different ways. METHODS: The authors compared changes in measured cerebral oxygen saturation and other hemodynamic parameters, including jugular venous oxygen saturation, in nine patients with severe closed head injury during manipulation of arterial carbon dioxide partial pressure and after mean arterial pressure was altered by vasopressors. RESULTS: The Bland and Altman representation of cerebral oxygen saturation versus jugular oxygen saturation showed a uniform scatter. Values for changing arterial carbon dioxide partial pressure were: bias = 1.1%, 2 SD = +/-21%, absolute value; and those for alterations in mean arterial pressure: bias = 3.7%, 2 SD = +/-24%, absolute value. However, a Bland and Altman plot of changes in cerebral oxygen saturation versus changes in jugular oxygen saturation had a negative slope (alteration in arterial carbon dioxide partial pressure: bias = 2.4%, 2 SD = +/-17%, absolute value; alteration in mean arterial pressure: bias = -4.9%, 2 SD = +/-31%, absolute value). Regression analysis showed that changes in cerebral oxygen saturation were positively correlated with changes in jugular venous oxygen saturation during the carbon dioxide challenge, whereas correlation was negative during the arterial pressure challenge. CONCLUSIONS: Cerebral oxygen saturation assessed by near-infrared spectroscopy does not adequately reflect changes in jugular venous oxygen saturation in patients with severe head injury. Changes in arteriovenous partitioning, infrared-spectroscopy contamination by extracerebral signal, algorithm errors, and dissimilar tissue sampling may explain these findings.

Administration, Inhalation↗
PubMed1999

[Accessory anesthetic breathing systems: verification before use].

Accessory or ancillary anaesthesia breathing systems can be defined as all those connected to the fresh gas outlet of the anaesthetic apparatus and used instead of the circle system associated with the ventilator, which is the main circuit. They include: the Mapleson systems, the systems with a nonrebreathing valve and the disposable systems with a carbon dioxide absorber. They can be a cause of major accidents when not checked before and monitored during use. This technical note describes techniques of preanaesthetic checking and monitoring during anaesthesia.

Anesthesia, Closed-Circuit↗