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Biomedical subjects

B Grenier

Publications and source records attributed to B Grenier.

At least 19 recordsLinked to original sources
PubMed2001

Charge ordering and spin dynamics in NaV(2)O(5).

We report high-resolution neutron inelastic scattering experiments on the spin excitations of NaV(2)O(5). Below T(c), two branches with distinct energy gaps are identified. From the dispersion and intensity of the spin excitation modes, we deduce the precise zigzag charge distribution on the ladder rungs and the corresponding charge order: Delta(c) approximately 0.6. We argue that the spin gaps observed in the low-T phase of this compound are primarily due to the charge transfer.

Journal Article↗
PubMed2000

[Comparison of two measurement methods: the Bland and Altman assessment].

Bland-Altman analysis for comparison of two methods of clinical measurement is frequently used in scientific publications. This article is more appropriate than the conventional linear regression analysis. This paper gives an overview of the principles for the use of Bland-Altman analysis as well as the specific terminology attached to it. The Bland-Altman comparison analysis is mainly a tool for clinical interpretation. The bias and the agreement limits provide the variation of the values of the technique compared to the other. The difference between the two methods of measurement is plotted against the average obtained with each of the two techniques. Bland-Altman analysis can also be used to check the repeatability of a measurement technique within the same subject and to determine a repeatability coefficient. With an adaptation of the calculation of the agreement limits, the average of multiple measurements for each subject with two measurement techniques can be used for the Bland-Altman analysis.

Regression Analysis↗
PubMed2000

Single-breath CO2 analysis as a predictor of lung volume change in a model of acute lung injury.

OBJECTIVE: To examine the utility of single-breath CO2 analysis as a measure of lung volume change in a model of acute lung injury. SETTING: Animal laboratory in a university-affiliated medical center. DESIGN: Prospective, animal cohort study comparing 21 variables derived from single-breath CO2 analysis with lung volume measurements determined by nitrogen washout. SUBJECTS: Seven lambs with saline lavage-induced acute lung injury. METHODS: Animals were treated with repetitive saline lavage to achieve a uniform degree of acute lung injury (PaO2 < 100 torr [13.32 kPa] on FiO2 of 1.0). Twenty-one derived components of the CO2 expirogram were evaluated as predictors of lung volume change. Lung volume was manipulated by 3-cm H2O incremental increases in positive end-expiratory pressure from 0 to 21 cm H2O and ranged between 90 and 765 mL. MEASUREMENTS AND MAIN RESULTS: Fifty-five measurements of lung volume were available for comparison with derived variables from the CO2 expirogram. Stepwise linear regression identified five variables that were most predictive of lung volume change: a) dynamic lung compliance; b) the slope of phase III; c) the slope of phase II divided by the mixed expired CO2 concentration; d) airway deadspace; and e) PaO2/FIO2 ratio. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 = .94, p < .0001). The bias and precision of the calculated lung volume were 10.9 and 55.9, respectively. The mean percentage difference for the lung volume estimate derived from the single-breath CO2 analysis station was 3.3%. CONCLUSIONS: Our data indicate that analysis of the CO2 expirogram can yield accurate information about lung volume in animals with saline lavage-induced acute lung injury. Specifically, five variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in lung volume in healthy lambs with an adjusted coefficient of determination of 0.94. We hope to further define the utility of this technique by prospective application of this methodology in the clinical setting.

Animals↗
PubMed1999

Capnography monitoring during neurosurgery: reliability in relation to various intraoperative positions.

UNLABELLED: In neurosurgery, estimation of PaCO2 from PETCO2 has been questioned. The aim of this study was to reevaluate the accuracy of PETCO2 in estimating PaCO2 during neurosurgical procedures lasting >3 h and to measure the effect of surgical positioning on arterial to end-tidal CO2 gradient (P[a-ET]CO2) over time. One hundred four neurosurgical patients classified into four groups (supine [SP], lateral [LT], prone [PR], sitting [ST]) were included in a prospective study. PaCO2, PETCO2, and P(a-ET)CO2 were measured after induction of anesthesia (T0), after positioning (T1), each following hour (T2, T3, T4), and at the end of the procedure after return to the SP position (T5). Data are expressed as the mean +/- SD, and statistical analysis used linear regression, the Bland-Altman method, and analysis of variance. The mean durations of positioning and surgery were 4.1+/-1 h and 3.7+/-1.3 h, respectively. We performed 624 simultaneous measurements of PaCO2 (33+/-5 mm Hg) and PETCO2 (27+/-4 mm Hg), leading to a mean P(a-ET)CO2 of 6+/-4 mm Hg. P(a-ET)CO2 of the LT group (7+/-3 mm Hg) was larger (compared with the SP, PR, and ST groups) because of a lower PETCO2 (26+/-4 mm Hg). Negative P(a-ET)CO2 (PETCO2 > PaCO2) occurred 22 times, only in the SP (n = 9) and ST groups (n = 13). Changes in opposite directions of PETCO2 and PaCO2 between two successive measurements were found in 26% of the cases. Correlation coefficients in the four groups (PaCO2 versus PETCO2) were not in good agreement (0.46 to 0.62; P < 0.001). The mean bias was between 5 and 7 mm Hg. The superior (13-15 mm Hg) and inferior (-5 to 0 mm Hg) limits of agreement were too large to expect PETCO2 to replace PaCO2. In conclusion, during neurosurgical procedures of >3 h, capnography should be performed with regular analysis of arterial blood gases for optimal ventilator adjustment. IMPLICATIONS: This study, which aimed to reevaluate the ability of PETCO2 to estimate PaCO2 during neurosurgical procedures according to surgical position, indicates that PETCO2 cannot replace PaCO2 for the following reasons: scattering of individual values; occurrence of negative arterial to end-tidal CO2 gradient (P[a-ET]CO2; PaCO2 and PETCO2 variations in opposite directions; large changes in P(a-ET)CO2 between two samples; and instability of P(a-ET)CO2 over time.

Adult↗
PubMed1998

Paediatric day case anaesthesia: estimate of its quality at home.

The aim of this clinical audit was to evaluate the home recovery and complications of 104 daycase anaesthetized children, as well as parent satisfaction. A questionnaire, explained at the time of preoperative visit, was given to parents at hospital discharge and returned by mail. Opioids were administered in 19% of the children whereas regional anaesthesia was performed in 28% of cases. In the recovery room, 8% of them suffered pain. At home, pain was the main problem (25%) and vomiting and agitation were found in 9% and 6% of the cases respectively. Parents reported anxiety in 45% of cases, and 14% called their general practitioner. Nevertheless, 94% were satisfied with the anaesthetic. A clinical audit is useful in detecting management deficiencies. Quality of home recovery may be improved by: wider use of perioperative analgesia, systematic prescription of take-home analgesia, designation of a hospital practitioner for advice, and closer collaboration with general practitioners.

Adult↗
PubMed1998

Single-breath CO2 analysis as a predictor of lung volume in a healthy animal model during controlled ventilation.

OBJECTIVE: To examine the utility of single-breath CO2 analysis as a measure of lung volume. DESIGN: A prospective, animal cohort study comparing 21 parameters derived from single-breath CO2 analysis with lung volume measurements determined by nitrogen washout in animals during controlled ventilation. SETTING: An animal laboratory in a university-affiliated medical center. SUBJECTS: Seven healthy lambs. INTERVENTIONS: The single-breath CO2 analysis station consists of a mainstream capnometer, a variable orifice pneumotachometer, a signal processor and computer software with capability for both on- and off-line data analysis. Twenty-one derived components of the CO2 expirogram were evaluated as predictors of lung volume. Lung volume was manipulated by 3 cm H2O incremental increases in positive end-expiratory pressure from 0 to 21 cm H2O, and ranged between 147 and 942 mL. MEASUREMENTS AND MAIN RESULTS: Fifty-five measurements of lung volume were available for comparison with derived variables from the CO2 expirogam. Stepwise linear regression identified four variables that were most predictive of lung volume: a) dynamic lung compliance; b) the slope of phase 3; c) the slope of phase 2 divided by the mixed expired CO2 tension; and d) airway deadspace. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 =.94, p < .0001). The bias and precision of the calculated lung volume was .00 and 51, respectively. The mean percent difference for the lung volume estimate derived from the single-breath CO2 analysis station was 0.79%. CONCLUSIONS: Our data indicate that analysis of the CO2 expirogram can yield accurate information about lung volume. Specifically, four variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in lung volume in healthy lambs with an adjusted coefficient of determination of .94. Prospective application of this technology in the setting of lung injury and rapidly changing physiology is essential in determining the clinical usefulness of the technique.

Animals↗
PubMed1998

Normal blood-glucose concentration which range for what?

Two definitions of normality ("isolated" or "correlated") are considered. The boundaries of "isolated" normality were determined by a statistical procedure, whereas the "correlated" approach was related to a clinical or predictive definition. In the latter case, the biological variations were considered abnormal if they implied a hazard with some significant future ailment as a risk factor. In this pragmatic approach, the upper limit of normal/abnormal variations is the point beyond which medical strategy is related to the most expected benefit when applied to a definite population or to an individual patient. The capacity of a diagnostic test to discriminate between patients with a defined risk and those without risk depends strictly on the value of the parameter chosen. In medical care for the prevention of vascular complications in diabetic patients or with foetal risks in pregnant women, the limits of the so-called normal range of glycaemia and other parameters should be determined according to the objective of the preventive and/or therapeutic measures to be prescribed.

Blood Glucose↗
PubMed1997

[Must we justify our medical decisions?].

To provide an equal or better health care with limited resources, is an inescapable constraint for health care providers. Every physician and clinical decision maker must now account for economical and technical resources that are to be invested in diagnostic and therapeutic procedures, in public as well as in private medical practice. Every medical decision must be endorsed in relation with the expected benefits and risks for the patient and/or the society. Methods and protocols must provide a definite efficiency and rely on a better management of resources allowed to health services and facilities. Words, concepts and basic principles of medical decision analysis are inescapable tools to cope with uncertainty, to evaluate medical decisions according to their expected consequences, objective and subjective, for a definite patient in a bedside situation, as for a larger community. In a context of economic constraint, rational decision analysis is a prerequisite for a better quality of care, optimizing expected results, personal preferences and expenses of financial, technical and human resources in order to save time, risks and suffering.

Health Care Rationing↗
PubMed1997

[What should medical decision be based on?].

Medical decision making is basically related to three criteria: 1) estimated effectiveness in terms of objective and subjective results: 2) equity related to the concept of justice in the societal context; 3) legitimacy according to the willingness to pay of the society, its resource availability and the fraction of its income that is allowed to be spent for health care. A worsening dilemma is unescapable between a utilitarian medical project, and the traditional hippocratic rule of rescue no matter what the cost may be. Every care taker should be involved to give a clear account of medical decision in order to generate and adopt some acceptable view for a reliable implementation with respect to equity and justice.

Decision Making↗
PubMed1997

Noninvasive determination of cardiac output in a model of acute lung injury.

OBJECTIVE: To examine the utility of single breath CO2 analysis as a noninvasive measure of cardiac output in a model of acute lung injury. SETTING: An animal laboratory in a university-affiliated medical center. DESIGN: A prospective, animal cohort study comparing 21 parameters derived from single breath CO2 analysis with cardiac output determined by an ultrasonic flow probe. SUBJECTS: Six adult sheep with saline lavage-induced acute lung injury. INTERVENTIONS: Animals were treated with repetitive saline lavage to achieve a uniform degree of acute lung injury (PaO2 of < 100 torr [< 13.32 kPa] on an FIO2 of 1.0). Cardiac output was manipulated by successive injections of an hydraulic constrictor placed around the inferior vena cava and measured using an ultrasonic flow probe. Twenty-one derived components of the CO2 expirogram were evaluated as predictors of cardiac output. MEASUREMENTS AND MAIN RESULTS: Thirty-eight measurements of cardiac output were available for comparison with derived variables from the CO2 expirogam. Stepwise linear regression identified four variables for the equation predicting cardiac output: a) PaO2/FIO2 ratio; b) the angle between the slope lines for phases II and III divided by the tidal volume; c) mixed expired CO2 tension; and d) physiologic deadspace to tidal volume ratio. The multivariate equation was highly statistically significant and explained 80% of the variance (adjusted R2 = .80, p < .0001). The blas and precision of the calculated cardiac output were .00 and .38, respectively. The mean percent difference for the cardiac output estimates derived from the single breath CO2 analysis station was -0.01%. CONCLUSIONS: Our results indicate that changes in cardiac output can be determined using components of the CO2 expirogram with a high degree of reliability in animals with induced acute lung injury. Specifically, the use of four parameters derived from a plot of expired CO2 concentration vs. expired volume predict changes in cardiac output in adult sheep with induced lung injury with an adjusted coefficient of determination of .80. Prospective application of this technology in the clinical setting with the rapidly changing physiology that is characteristic of the acutely ill patient will be essential in determining the clinical usefulness of single breath CO2 analysis as a noninvasive measure of cardiac output.

Acute Disease↗
PubMed1996

[Severe hyperthermia caused by sudden withdrawal of continuous intrathecal administration of baclofen].

Baclofen is used for the treatment of post-traumatic spasticity. It carries a risk of overdose as well as of an acute withdrawal syndrome. We report two cases of severe hypertonia and hyperthermia (> 42 degrees C), occurring after accidental discontinuation of intrathecal infusion of baclofen. Both hypertonia and hyperthermia ceased when administration of baclofen was resumed. In parallel, the patients developed transient life-threatening alterations of hepatic (cytolysis), haematologic (coagulopathy) and cardiorespiratory functions for some days. It is concluded that the occurrence of such a withdrawal syndrome should be prevented, especially in patients with chronic intrathecal administration and first symptoms should be recognized without delay. Relationships with other malignant hyperthermias are discussed.

Adult↗
PubMed1996

High-frequency oscillatory ventilation in pediatric patients.

High-frequency oscillatory ventilation (HFOV) offers the potential to maintain adequate gas exchange without imposing the large pressure swings and tidal volumes associated with ventilatory-induced lung injury. This article reviews the studies evaluating the use of HFOV to treat pediatric respiratory failure, discusses the complications associated with HFOV, and details an approach to the practical application of HFOV in the non-neonatal pediatric population.

Adolescent↗
PubMed1995

[Chronic cervico-brachial neuralgia treated by cervical epidural injection of corticosteroids. Long-term results].

OBJECTIVE: To assess long-term results of a single cervical epidural corticosteroid injection (CECI) in patients suffering from chronic cervicobrachial neuralgia (CCBN). STUDY DESIGN: Open prospective study. PATIENTS: A CECI was performed in 29 patients suffering for more than 12 months from a non-compressive and non-surgical CCBN with permanent pain for at least three months non relieved by an adequately conducted medical treatment. METHODS: The cervical epidural space was injected (C7-T1, 18 G needle) with an increasing volume (maximum 10 mL) of isotonic saline solution to exacerbate patient's cervicobrachial pain. The patients then received an equivalent volume of 0.5% lidocaine plus triamcinolone acetonide (10 mg.mL-1). The pain decrease was estimated on a visual analogic scale (VAS), in comparison to intensity of pain rated at 100 mm before CECI. RESULTS: The mean volume injected into the epidural space was 6 +/- 2 mL. It increased pain in 26 out of 29 patients. After 3 months, a success rate of 83% was obtained, with a pain rate of 12 mm on VAS. Concerning mid- and long-term results, pain relief remained stable for at least 24 months (mean follow-up: 48 +/- 18 months). Simultaneously, the need for analgesics decreased significantly. CONCLUSION: A single CECI in patients suffering from non-compressive and non-surgical CCBN results in long-lasting pain relief.

Administration, Topical↗