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Biomedical subjects

D Laurent

Publications and source records attributed to D Laurent.

At least 109 records · Page 6Linked to original sources
PubMed1980

Computer determination of thoracic gas volume using plethysmographic "thoracic flow".

Plotting a line to the variables obtained during a panting maneuver, i.e. thoracic volume and mouth pressure, is the conventional way of computing plethysmographic thoracic gas volume (TGV). This procedure is reliable if the magnitude of the thoracic volume changes is large compared to the drift on the signal; this is one of the major problems in volumetric plethysmography. We propose replacing the thoracic volume signal (Vt) by its time derivative (Vt) and similarly mouth pressure (Pm) with its time derivative (Pm). Drift is thus ruled out, and the magnitude of Vt is preserved when the subject fails to carry out noticeable changes in thoracic volume during the panting, since even then the speed of these changes in thoracic volume remains high. The use of Vt and Pm appeared to be necessary when a minicomputer was connected to a pressure-compensated flow plethysmograph to obtain an automatic calculation of TGV. A regression-line technique applied to signals obtained during the panting was used to find the slope of the relation and thus TGV. However, this slope can only be predicted with less than 5% error if the correlation coefficient is very high (i.e., above 0.99). The analysis of 121 recordings from patients showed that the mean r was only 0.954 when Vt and Pm were used. It increased to 0.993 with Vt and Pm. For the same recordings the comparison of hand-calculated TGV and computer-derived TGV showed a much better agreement for the Vt-Pm method (standard error of the estimate (SEE) = 0.14 liter) than for the Vt-Pm method (SEE = 0.34 liter). These results emphasize that, in contrast to the manual technique, the computer does not adequately handle even a small drift of the thoracic signal. The proposed time-derivative method is therefore useful for a hand calculation, but essential to a reliable computer determination of thoracic gas volume

Diagnosis, Computer-Assisted↗
PubMed1980

A computerized data-handling system in hypertension management.

An inexpensive, easy to use, computerized data-handling system is described for managing patients with hypertension. It has been in operation for 2 1/2 years in a clinic that functions with nurse specialists and physicians working as a team. Data entry and retrieval are performed by nurse specialists. Computer entries have been made for over 1,030 new patients who had 5,873 clinic revisits and 1,800 laboratory visits. Several kinds of outputs are generated that assist physicians in patient management. Most useful are those on the laboratory flow sheet, which itemizes all or selected laboratory results by date, and the blood pressure and selected laboratory data flow sheets, which chronologically list pertinent patient data necessary for management.

Academic Medical Centers↗
PubMed1980

[Assessment of left ventricular function in patients with aortic regurgitation using dynamic investigation (author's transl)].

To assess accurately left ventricular function (LVF) in patients with aortic regurgitation (AR pts), isometric exercise (IE) was used in association with postextrasystolic potentiation (PESP) during diagnostic heart catheterization including left cineventriculography in 16 pts with pure moderate or severe AR. The results were compared with those observed in 8 control pts (C pts). IE resulted in a significant increase in heart rate by 15 p. cent and in an increase in mean aortic pressure by 29 p. cent (p < 0.001). During IE, LV end diastolic pressure (EDP) remained unchanged in C pts and in 6 AR pts whereas this value was increased by 49 p. cent (p < 0.01) in 7 AR pts without a significant change in LV end diastolic volume. Ejection fraction (EF) was decreased in each AR pt (mean 14 p. cent; p < 0.001) and remained unchanged in C pts. A negative correlation was evidenced between the decrease in EF and the increase in LVEDP (r = 0.76). PESP resulted in a increase in EF in both C pts and AR pts (+ 25 and + 29 p. cent respectively; p < 0.001). PESP under IE resulted in a lower increase in EF than PESP under basal conditions (+ 19 and + 24 p. cent respectively) mainly due to the increase in after load provided by IE. Dynamic investigation of the LVF in AR pts is a physiological method of investigation easy to perform which may assess both LV contractile reserve and cardiac reserve. Such a method of investigation may help to select AR pts for surgery.

Adult↗
PubMed1979

[Evaluation of the viral contamination of the sea water after the emission of an effluent into the sea (author's transl)].

Research of virus in the sea water has been made by the concentrated method of adsorption-elution on glass powder. --This method has enabled us to strike the balance on the concentration of virus in the sea water, from the emission to the bank. The frequency of isolation of virus in the bathing zone considered as healthy is very high. The concentration of virus is practically constant in the length of an axis, 200 m distant in comparison with the bank.--The increase of particles of virus in the sea, in the estuary of the emission, reflects in the same way in the bathing zone, 5 m away from the bank. The phenomenon of dilution of the effluent in the sea water doesn't seem to play a part.

Bathing Beaches↗
PubMed1979

Evaluation of left ventricular performance in aortic stenosis, aortic regurgitation and mitral regurgitation from the stroke work/left ventricular mass ratio.

Evaluation of left ventricular performance in aortic stenosis, aortic regurgitation and mitral regurgitation from the stroke work/left ventricular mass ratio. Europ. J. Cardiol., 10/4, 279--294. 132 patients with a pure valvular dysfunction affecting a single orifice, namely aortic stenosis, aortic or mitral regurgitation, were studied. All patients, including 20 control subjects, underwent hemodynamic examination of both right and left heart chambers including left cineangiography. Using the stroke work index/myocardial mass ratio (SWI/MLV), for which the limits in normal subjects are narrow (0.81 +/- 0.03 . g-1) it was possible to divide these patients into three groups: Group I (SWI/MLV greater than 0.87 gm . g-1) characterized by a proportionately greater increase in stroke work index than myocardial mass (hyperfunctioning ventricle). Group II (0.87 gm . g-1 greater than or equal to SWI/MLV greater than or equal to 0.75 gm . g-1) characterized by a parallel increase in stroke work index and myocardial mass (normally functioning ventricle). Group III (SWI/MLV less than 0.75 gm . g-1) for which the increase in myocardial mass was proportionately greater than that of the stroke work index (hypofunctioning ventricle). As one progresses from group I to III, there is a concomitant fall in ventricular function with decreased mean velocity of circumferential fiber shortening (VCF), ejection fraction (EF) and increased enddiastolic volume (EDV) together with the hypertrophy of the left ventricle during the last stage. We conclude that the SWI/MLV ratio is an easy to calculate index, independent of the unerlying dysfunction, which evaluates left ventricular function by taking into account the myocardial mass.

Adult↗
PubMed1979

[Endomyocardial biopsy results and left ventricular function in primary myocardiopathies (author's transl)].

Endomyocardial biopsies (EMB) of the left ventricle (LV) were performed during cardiac catheterization in 27 patients with apparently primary myocardiopathies (PMC). The results of optical and electron microscopy were compared with ventricular performance indices calculated from hemodynamic and cinematographic data from the left ventricle. The telediastolic pressure of the LV increases with the spread of fibrosis (r = 0.68) suggesting that it disturbs the filling of this cavity. Systolic effort is reduced as this fibrosis increases (r = 0.56), and it contributes to the changes in the pumping function of the LV, but the contractile power of the LV is altered in a less evident and less constant manner. The association of cell and fibro-elastic tissue degeneration is always accompanied by a drop in ventricular performance (p less than 0.0001). Apart from its diagnostic role, which is limited but may be of great value, the EMB can help to clarify the physiopathology of PMC and to formulate a prognosis based on more solid grounds.

Biopsy↗
PubMed1978

Impedance of the arterial system in terms of Fourier harmonic analysis of the pulse wave.

The results obtained by analysis of pulse waves by means of Fourier harmonics in healthy subjects and patients with aortic insufficiency show good agreement between input impedance of the aorta and the initial segment of the femoral bed in both groups. This means that in this region there is no marked increase in impedance, which provides a favourable background for energy transfer (blood content) in the distal direction. Impedance in healthy subjects increases in vessels of the lower extremity. In patients with aortic insufficiency there is a marked decrease in amplitude of all higher harmonic frequencies. This practically means that the second harmonic is no longer the main accumulator of energy of the pulse wave as in healthy subjects, and the same is also true, to a proportionate degree, for the third, fourth and fifth harmonics.

Aortic Valve Insufficiency↗
PubMed1978

Pulmonary gas exchange during venoarterial bypass with a membrane lung for acute respiratory failure.

In patients with fulminating pulmonary edema not responsive to conventional therapy, venoarterial membrane lung bypass can provide assistance if decreased systemic blood pressure prevents use of high-level positive end-expiratory pressure ventilation. In 10 patients with acute respiratory failure, partial venoarterial bypass provided a rapid and marked improvement of systemic oxygenation. Measurement of pulmonary blood flow (PBF) and intrapulmonary shunting (QS/QP) during bypass via prolonged left heart catheterization showed that left ventricular PaO2 was increased through a rapid and profound reduction of QS/QP. During the first days of bypass, derecruitment of pulmonary vessels is probably the mechanism of improved pulmonary oxygenation. When low pulmonary arterial pressures (PAP) are sustained, resorption of pulmonary edema is favored. Despite the beneficial effects of bypass, death occurred in every case due to diffuse interstitial fibrosis and/or parenchymal damage. The absence of healing, due to prolonged circulatory exclusion, may be detrimental despite immediate improvement. Because of this possibility, venovenous or mixed perfusion should be more extensively explored.

Acute Disease↗
PubMed1978

[Evaluation of the contractile reserve of the myocardium by post-extrasystolic potentiation in aortic insufficiency].

Calculations were made of the indices of ventricular performance during the ejectional phase in 10 patients with a normal left ventricle and in 24 patients with aortic aneurysm, both under basal conditions and in the presence of extrasystoles produced incidentally during left biplanar cineventriculography. The fact that these indices were constantly raised implies the presence of post-extrasystole potentiation associated with an increase in contractility without significant changes in load. This technique, which provides a dynamic study of the behavior of the left ventricle in aortic incompetence allows us to assess the contractile reserve, and thus to give a more accurate prediction of the potential for recovery after operation.

Aortic Aneurysm↗
PubMed1978

[Physiopathological study of coupled electric stimulation].

The charges of left ventricular function provoked by coupled electrical stimulation were studied in 17 patients with severe chronic aortic incompetence and 9 controls. These results were compared with those obtained after isolated extrasystole in 24 cases of aortic incompetence and 10 controls, and during paired electrical stimulation in 12 cases of aortic incompetence. Left ventricular function increased uniformly after post-extrasystolic potentiation whatever the mode of stimulation. The preload did not change significantly, the increased ventricular function being mainly due to increased contractility. Coupled electrical stimulation mobilised the greatest contractility reserve (ejection fraction : +32 % in controls and +37 % in aortic incompetence and averaged circumferentiel fibre shortening +55 % in controls and +47 % in aortic incompetence). The contractility reserve is inversely proportional to the initial ejection fraction except when its value is less than 35 %. The myocardial response then becomes variable so that left ventricles with probable irreversible hypocontractility may be distinguished from those whose ventricular funciton would improve after surgical correction.

Adult↗
PubMed1977

[Centro-pontine myelinolysis associated with diffuse lesions of the white matter. Water-electrolyte disturbances associated with diuretic therapy].

The authors report a case of centropontine myelinosis associated with demyelinising lesions of the tectum mesencephali, the cerebellum, the central grey nuclei and the white matter of the hemispheres. This case is compared with similar observations already studied in the literature. From an aetiological standpoint, attention is drawn to the apparent causative role of diuretic therapy which had resulted in severe water and electrolyte disturbances.

Adult↗