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Biomedical subjects

C Mariette

Publications and source records attributed to C Mariette.

53 records · Page 3Linked to original sources
PubMed1996

A new correction technique for measuring respiratory impedance through an endotracheal tube.

Measurement of respiratory impedance (Zrs) in intubated patients requires corrections for flow-dependent resistance and air compression inside the endotracheal tube (ET). The purpose of this study was to test a new correction technique for these effects. We therefore studied 110 patients in two conditions: breathing normally (C1), or breathing through an ET placed at the mouth (C2). In C1, we measured pressure and flow signals at the mouth, and in C2, at the ET inlet, during application of a pseudorandom forced excitation (4-32 Hz). In C1, respiratory impedance was calculated directly as Z1. In C2, pressure data were first corrected for the flow-dependent resistance of the ET, and respiratory impedance was then corrected both for gas compression inside the set-up and ET inertance (impedance Z2). Strong linear relationships were found between the reference and corrected estimates of the resistance at 6 Hz, the frequency dependence of resistance and the resonant frequency. The mean normalized distance between Z1 and Z2 observed in the patients over the 4-32 Hz frequency range was about 14% for resistance and 12% for reactance (-9% and -4%, respectively, when considering the algebraic value of the distance). This slight underestimation of both components of impedance might be due to an overcorrection of pressure for the flow-dependent resistance of the ET. We conclude that, in intubated patients, newly tested corrections for the mechanical contribution of the endotracheal tube may yield a fair estimate of respiratory impedance when pressure is measured at the inlet of the endotracheal tube.

Airway Resistance↗
PubMed1995

Prevalence of anti-R-13 antibodies in human Trypanosoma cruzi infection.

Infection with Trypanosoma cruzi develops in three phases: acute, indeterminate or asymptomatic, and chronic phase (with cardiac or digestive manifestations). Moreover, transmission may occur from infected mothers to newborn, the so-called congenital form. In the present study, humoral responses against T. cruzi total extract and against the 13 amino acid peptide named R-13 derived from the parasite ribosomal P protein, previously described as a possible marker of chronic Chagas heart disease, were determined in chagasic patients and in blood bank donors from endemic areas. While in sera from acute phase, only IgM anti-T.cruzi response was observed, both IgM and IgG anti-T. cruzi antibodies were detected in sera from congenitally infected newborns. The percentage of positive response in sera from blood bank donors was relatively high in endemic regions. Antibodies against the R-13 peptide were present in a large proportion of cardiac chagasic patients but were totally lacking in patients with digestive form of Chagas' disease. Furthermore, anti-R-13 positive responses were detected in congenitally infected newborns.

Acute Disease↗
PubMed1993

Influence of signal processing on estimation of respiratory impedance.

Respiratory impedance was estimated between 4 and 30 Hz by spectral analysis of the mouth flow and pressure signals measured in spontaneously breathing subjects when applying a pseudorandom pressure excitation at the mouth. The signals were submitted to antialiasing low-pass filtering followed by digital preprocessing before the calculation of spectra by a fast Fourier transform algorithm. The effectiveness of signal preprocessing in eliminating the leakage error due to breathing noise was illustrated in both a mechanical analogue and a patient. Five preprocessing techniques that combined high-pass filtering and windowing were then compared in 32 randomly selected patients by examining the influence of these techniques on 1) the values of impedance at 5, 10, and 20 Hz, and 2) the parameters of linear models fitting the real (Zr) and imaginary (Zi) parts of impedance for coherence values higher than a preset threshold. The impedance values and derived parameters were either the mean of the estimates separately obtained in the three data recordings (PA) or the single estimate obtained from average spectra (SP). Small but significant differences between filtering and windowing, as well as between SP and PA, were evidenced for the Zr, whereas Zi was only slightly sensitive to the type of averaging technique. We conclude that the signal preprocessing and data averaging techniques selected in this study have similar effects on spectral estimation of respiratory impedance.

Airway Resistance↗
PubMed1989

Four and six parameter models of forced random noise respiratory impedance in normals.

Total respiratory impedance has been measured between 3-42 Hz by the forced random noise technique, in 15 subjects breathing either air or a helium oxygen mixture in three experimental conditions: at basal state, and then with a resistor or a tube added at the mouth. Impedance is modelled, either by a 4-parameter model (M4), derived from the series model (resistance, inertance, compliance) by making resistance a linear function of frequency; or by a 6-parameter model (M6) including a central compartment (airway resistance and gas inertance), and a tissue compartment (resistance, inertance and compliance in series) placed in parallel with alveolar gas compliance. The additive resistance is perfectly evaluated by both models, whereas the additive inertance is not accurately estimated by the model M6, the fitting of which combines the real and imaginary parts of impedance. Resistance extrapolated at zero frequency on the one hand, inertance of M4 and central inertance of M6 of the other, are highly correlated. However, changes in some parameters of both models according to the experimental conditions are difficult to explain on physiological grounds. We conclude that the model M6 cannot be easily and accurately identified over such a limited frequency range, at least in normals, while the model M4 yields a simplified description of impedance which may be sufficient for diagnostic purposes.

Airway Resistance↗
PubMed1986

Real-time detection of ventilatory maneuvers by a microcomputer.

The SYTER software system was built around an Apple II microcomputer to automatically process the data yielded by three ventilatory tests: analysis of lung elasticity during an expiratory maneuver, plethysmographic measurement of airway resistance during a panting maneuver, and similar measurements of lung volumes. A volume signal is displayed to the operator throughout each test to help control the maneuver. The various stages of the test are recognized in real time by routines written in assembling language, so that significant data are displayed and stored during the maneuver. This paper describes the algorithms used to perform waveform analysis, and presents illustrative displays obtained in the Lung Function Laboratory.

Airway Resistance↗
PubMed1985

On line determination of airway resistance by plethysmography and microcomputer.

On line determination of airway resistance is carried out by an Apple II connected to a flow body plethysmograph. Recognition of the panting maneuver is performed in real time. Linear drift of plethysmographic volume V is eliminated by taking the derivatives V and Vm of V and mouth flow Vm. Linear regression of V on Vm yields an estimate R of airway resistance, at a volume close to functional residual capacity FRC. The values of FRC is given by linear regression of V on Pm, the derivative of mouth pressure. No significant difference has been found between the estimates of the specific conductance sG calculated by linear regression and by spectral analysis of V and Vm. As variability of sG can be kept below 10%, the regression technique appears to be reliable for routine patient testing and pharmacological studies.

Airway Resistance↗
PubMed1985

A microcomputer-based system for real-time calculation of airway conductance in awake guinea pigs.

Bronchial responsiveness to various drug stimuli is currently studied by constructing cumulative dose-response curves of specific respiratory conductance (SG). Airway conductance can be measured in guinea pigs by the plethysmographic technique, during the rapid transition from expiration to inspiration (TEI). Since the drug action assigns a strict timing to the experiment, conventional methods of measuring SG prove inconvenient and often lack accuracy. A computerized data acquisition system has therefore been developed to recognize TEI and calculate SG in real time. This paper describes the significant features of the program DOREMI, and gives an illustrative example of the system in use.

Airway Resistance↗
PubMedDate not supplied

[Laparoscopic fundoplication: current data].

Laparoscopic fundoplication is as effective as its open counterpart, allowing reduced morbidity, shorter hospital stay and recovery, lower consumption of analgesics, and very low mortality, with no significant differences in early functional outcome. Rate of early recurrence is similar after partial and total fundoplication, but but the partial approach has a significantly reduced rate of reoperation for failure, mainly due to postoperative dysphagia. Long-term follow-up is required to evaluate dysphagia and quality-of-life.

Deglutition Disorders↗
PubMedDate not supplied

[Complications following oesophagectomy: mechanism, detection, treatment and prevention].

Oesophageal surgery remains a relatively morbid operation with potentially devastating complications that can be minimized by prevention, early recognition, and appropriate management. Anastomotic leak, conduit necrosis, and pulmonary failure are the most serious complications. The management of complications following oesophagectomy is reviewed in the following section.

Esophagectomy↗
PubMedDate not supplied

[Surgical management of post-operative peritonitis].

Post-operative peritonitis usually results from intra-operative or delayed injury to a digestive organ; it is accompanied by a high mortality rate. Prognosis is directly related to early diagnosis and appropriate re-intervention. Clinical and laboratory signs of gravity impose prompt re-operation. Imaging exams such as CT will aid in diagnosis and guide the therapeutic approach. Treatment specifically adapted to the etiologic cause must be thorough and complete from the start.

Early Diagnosis↗
PubMedDate not supplied

[Apprenticeship in laparoscopic surgery: Tools and methods for the surgeon in training].

The introduction of laparoscopic approaches to surgery has been responsible for increased morbidity and has necessitated the development of a system of apprenticeship training in and out of the operating room for surgeons making their debut in the laparoscopic arena. This study, based on published data in the surgical literature, aims to evaluate the tools currently available for both teaching and evaluating competence in laparascopic surgery. Video simulators currently being used for teaching laparoscopic skills do not permit an objective evaluation of skill acquisition. Virtual reality simulators have the advantage of permitting an apprenticeship in laparoscopic surgical technique and a simultaneous assessment of the acquisition of surgical dexterity. This new technology should enable a better preparation of young surgeons for the operating room of the future.

Animals↗