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B Louis

Publications and source records attributed to B Louis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Noninvasive estimate of work of breathing due to the endotracheal tube.

BACKGROUND: Although evidence suggests that secretions lining the inner wall of the endotracheal tube (ETT) often reduce its cross-sectional area, no data are available on the work of breathing as affected by the ETT. A noninvasive method is proposed for estimating the additional work of breathing necessitated by the ETT in patients whose lungs are mechanically ventilated. This method (the acoustic-Blasius method) involves (1) determining the inner geometry of the ETT using the acoustic reflection method and (2) using these geometric data to solve the Blasius equation that characterizes the ETT pressure drop-flow relation. METHODS: To evaluate the acoustic-Blasius method in vivo, the authors computed the work of breathing due to the ETT in four healthy persons breathing through an ETT connected to a pressure-support device and in five tracheally intubated patients receiving mechanical assistance in the pressure-support mode. For the tracheally intubated patients, the reference value was the work calculated from the ETT pressure drop measured between the two ends of the ETT using a pressure catheter. RESULTS: In the healthy participants and the tracheally intubated patients, there was close agreement between inspiratory work per cycle values estimated by directly measuring the ETT pressure drop and calculated using the acoustic-Blasius method: The difference was consistently less than 0.08 joules (< 10% of the reference value). CONCLUSIONS: The data show that the acoustic-Blasius method allows noninvasive quantification of the ETT-related work of breathing in situ.

Humans↗
PubMed1994

Pulmonary airway area by the two-microphone acoustic reflection method.

We noninvasively assessed airway dimensions from acoustic reflection data measured at the mouth. We recently described a two-transducer system for measurement of the nasal airway. Here we apply this approach to the measurement of the upper airway and trachea. We describe the theoretical implications of breathing on this kind of measurement and propose a new procedure that, unlike single- and dual-transducer systems used currently, does not require the use of He-O2 for inference of geometry of subglottic airways.

Algorithms↗
PubMed1994

Acoustic method to estimate the longitudinal area profile of endotracheal tubes.

A problem in mechanical ventilation is the accumulation of mucus secretions in the endotracheal tube (ETT), which tends to reduce the patent cross-sectional area. Here we characterized the extent and locus of the ETT obstruction using an acoustic reflection method recently modified to be applied at bedside. Experiments were conducted both in vivo in 10 intubated patients and in vitro in ETT with or without known constrictions of 1 to 3 mm over 5 cm, located at various distances from the ETT entry: 5, 10, 15, and 20 cm. Acoustic results were compared with the results obtained by an hydraulic reference method, which was the only method available to measure ETT obstruction in mechanically ventilated patients. In vivo acoustic results showed that area reductions were maximal near the tracheal extremity of the ETT, with a range from 2 to 36% (mean value 13 +/- 10%), when estimated relative to the area measured in an unused ETT of the same inner diameter (7 to 9 mm). Statistical analysis of the differences between acoustic reflection data and hydraulic data showed that the two methods did not differ significantly. In vitro acoustic results obtained in constricted ETT showed a highly significant correlation with the actual area (r = 0.97, p = 0.0001). Thus, reductions in ETT area may be detected, quantified, and located by the present acoustic reflection method, which therefore provides a means to avoid emergency extubation because of ETT obstruction.

Acoustics↗
PubMed1994

[Bronchial epidermoid carcinoma with unusual disclosure].

Dissemination has often occurred before the diagnosis of bronchopulmonary cancer. Pancreatic metastases are exceptional and are very rarely the revealing manifestation. The authors report a case of a tumour of the pancreas which led to the discover of an bronchogenic epidermoid carcinoma. The relationship between these two tumours lead to the proposed hypothesis of pancreatic metastasis of a bronchogenic carcinoma. Although this situation is rare, the preoperative work-up for bronchogenic carcinoma should include computed tomography of the pancreas if the abdominal echography does not allow complete visualization of the pancreas in cases with suggestive digestive disorders. If a tumour is observed in the pancreas, scan-guided needle biopsy should be performed to enable the histological examination.

Carcinoma, Bronchogenic↗
PubMed1993

Airway area by acoustic reflection: the two-microphone method.

This report deals with noninvasive imaging of airway geometry based upon information contained in acoustic reflections measured at the mouth. Here we describe a new theoretical approach that enables development of a new miniaturized apparatus. Unlike the single-transducer systems used currently, this new strategy is based upon a two-transducer system that is a variant of that suggested originally by Shroeder (1967). We have developed, implemented, and tested computational algorithms necessary to reconstruct airway dimensions from acoustic reflection data using this two-transducer strategy.

Acoustics↗
PubMed1993

Interaction of oscillatory and steady turbulent flows in airway tubes during impedance measurement.

Measurement of input respiratory impedance is carried out by superimposing forced oscillations on spontaneous breathing. The latter thus acts as a quasi-steady unidirectional flow component, with effects on the measured impedance that are habitually neglected (linearity assumption). We examined the validity of that assumption in the case of a turbulent steady flow. We tested the validity of a fluid dynamics criterion previously proposed in water channel experiments for gas flow in a tube. This criterion states that oscillatory and continuous turbulent flow may or may not interact if the Stokes boundary layer (ls) is embedded within the viscous sublayer (lv), i.e., if lS+ = lS/lv < or = 10, implying Re7/8 < or = (100 alpha/square root of 2), for a fully developed hydraulically smooth turbulent flow in a tube (where alpha is Womersley parameter and Re is Reynolds number of the steady-flow component). Experiments were performed in long rigid circular and semicircular tubes by superimposing two independent well-defined flows: 1) laminar oscillatory flow obeying the linear transmission line model (frequency = 1.5-250 Hz, i.e., alpha = 6-80) and 2) fully developed turbulent flow characterized by Blasius resistance formula (Re = 3,000-16,000). Confirming the validity of the criterion above, we found that the real and the imaginary parts of the long-tube impedance did not differ from those measured in the absence of a steady-flow component, provided lS+ < or = 10. On the contrary, the real parts measured with and without the continuous component differed greatly as soon as lS+ > 10, both for circular and semicircular tubes and for outward as well as inward steady flows. We concluded that the proposed criterion is pertinent for predicting appropriate oscillation frequency for a given rate of spontaneous flow, such that oscillatory and turbulent flows do not interact. Application of the forced oscillation measurement technique during spontaneous breathing requires use of a range of oscillatory frequencies higher than the frequency range classically used during apnea.

Air Movements↗
PubMed1992

Use of the Blasius resistance formula to estimate the effective diameter of endotracheal tubes.

To early detect mucus deposition in endotracheal tubes (ETT), we propose using a geometric, flow-independent parameter, i.e., diameter of the ETT, based on a precise knowledge of ETT flow regime, instead of using the classic flow-dependent ETT resistance based on the empirical, nonlinear Rohrer equation. From the estimated slope of -0.24 derived from Moody diagrams characterizing the pressure-flow relationship in ETT of various inner diameters (D), we first assessed that the Blasius resistance formula slope of -0.25 could be applied to adult-size ETT, meaning that flow remains fully developed, turbulent, and hydraulically smooth (0.5 L/s less than or equal to V less than or equal to 1.4 L/s). Insertion into the ETT of a pressure catheter (external diameter: d) to stimulate in vivo measurements did not modify these results, provided the hydraulic diameter, D* = D - d, was substituted for D in the Blasius formula. The Blasius formula was then used to determine, from in vitro pressure and flow measurements in ETT before intubation and in ETT lined with dry mucus secretions, the effective diameter, shown here to be highly correlated to the actual diameter measured by volumetric water displacement. The effective ETT diameter was measured in eight patients at different stages after oral or nasal intubation. Compared with the actual ETT diameter measured before insertion, the effective diameter was slightly reduced (2.6 +/- 2.5%) during the first week of intubation and was strongly reduced (12.2 +/- 2.8%) during the second week.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1992

Immunophenotypic characterisation of human peritoneal and alveolar macrophages and of human blood monocytes differentiated in the presence of either GM-CSF or M-CSF or a combination of GM-CSF/M-CSF.

In vivo, circulating blood monocytes (Mo) migrate into the various tissues where they undergo terminal maturation into macrophages (M phi) with morphological and sometimes functional properties that are characteristic for the tissue in which they reside. This tissue-specific M phi heterogeneity results from the immediate microenvironment, but may also originate from genetically distinct Mo subpopulations. The in vitro transformation of Mo to M phi is thought to reflect the events of the in vivo maturation and thus is widely used as a model to analyse M phi development. To study the heterogeneity within the mononuclear phagocyte system, we have investigated the phenotypic characterisation of mature tissue M phi, blood Mo and Mo-derived M phi cultured in medium with either GM-CSF, M-CSF or a combination of both cytokines. Tissue peritoneal and alveolar M phi showed different antigenic specificities, particularly concerning the transferrin receptor and CD68 and CD14 antigens. M-CSF-derived M phi when compared to the other M ø populations also exhibited a significantly increased expression of transferrin receptor and CD68 antigen. In contrast, GM-CSF treated cells which exhibited a better long term survival, showed notably more positivity for CD11b and CD32 antigens. These results show that the phenotypic heterogeneity of the different M phi populations is limited and appears to result from discrepancies in the differentiation and/or activation of the cells. The location of the CD68 antigen, which is generally considered to be an intracellular protein, was investigated at the ultrastructural level and found to be exclusively situated at the outer cell membrane.

Antibodies, Monoclonal↗
PubMed1992

The promoter of the human cystic fibrosis transmembrane conductance regulator gene directing SV40 T antigen expression induces malignant proliferation of ependymal cells in transgenic mice.

Transgenic mice bearing a human cystic fibrosis transmembrane conductance regulator (CFTR) promoter-SV40 T antigen fusion transgene were generated in order to localize in vivo the potential oncogenesis linked to the tissue-specific activity of the promoter for the CFTR gene. Surprisingly, the only site of tumors resulting from expression of the reporter onc gene was ependymal cells lining the brain ventricles. SV40 T antigen expression in these cells led to a consistent pathology in the first weeks of age: ependymoma and consequent hydrocephaly. Tumor-derived cell lines were established, characterized and shown to originate from SV40 T antigen-induced ependymoma. No pathological alterations were found in other organs, such as lungs and pancreas, in which cystic fibrosis is pathologically manifest in humans. Such transgenic mice and derived cell lines may represent valid models for analysing (1) the role of SV40 T antigen in ependymoma formation and (2) CFTR function in ependymal cells.

Animals↗
PubMed1991

Long term cultures of human monocytes in vitro. Impact of GM-CSF on survival and differentiation.

In vitro differentiation of human monocytes (Mo) provides large amounts of mature and functionally competent macrophages (M phi) which may be used as potentially powerful anticancer agents for adoptive immunotherapy. Granulocyte macrophage-colony stimulating factor (GM-CSF) was evaluated for its ability to influence long term cultures of Mo-derived M phi. Large quantities of Mo isolated by leukapheresis and elutriation were cultured in non-adherent cell culture bags or in plastic flasks with or without GM-CSF. At various stages of differentiation, GM-CSF treated M phi were recovered and assayed for survival, morphology, surface antigens, functional properties and proliferation in comparison with control M phi. In the present paper, we demonstrate that GM-CSF at a concentration of 50 U/ml (5 ng/ml) promotes better cell survival and the differentiation of Mo into M phi displaying certain morphological differences as compared to control M phi such as an increased expression of Max-1 antigen, CR3 and Fc gamma II receptors, higher phagocytic properties and increased capacities of cytotoxicity and TNF secretion when the cells are further activated by IFN-gamma. Furthermore, GM-CSF treated cells exhibit a low-grade proliferation although the nature of the proliferating cells has not been entirely elucidated. We conclude that the GM-CSF treated M phi would be particularly suitable for adoptive immunotherapy.

Antibodies, Monoclonal↗
PubMed1991

Shunt effect of gas compression inside pneumotachographs during forced oscillations.

Determination of the frequency response of pneumotachographs is needed whenever they are used to measure high-frequency flows, such as in the forced oscillation method. When screen and capillary pneumotachographs are calibrated using an adiabatic compression in a closed box as a reference impedance, they can be adequately described by a series of inertial-resistive elements. However, this type of reference impedance strongly differs from the actual respiratory impedance (ZL). We studied the frequency response of pneumotachographs up to 250 Hz in reference to the impedance of a compressible gas oscillating in a long tube, taken as a more generalizable model of actual ZL. We found that, with this device, the series resistance-inertance models fail to describe the frequency response of the pneumotachograph. However, when compressible effects in the pneumotachograph are taken into account by adding to the resistive models a compliance (Cpn) corresponding to the compression in half of the inner volume of the pneumotachograph, the agreement with experiments becomes satisfactory. Gas compression-related phenomena were demonstrated to be negligible only when the parameter omega Cpn magnitude of ZL is much smaller than 1 (omega pulsation). Results obtained in normal humans have shown that such a correction is required above 100 Hz. Similar correction at lower frequency might also be necessary in cases of large respiratory impedance (e.g., babies, subjects with pathological lungs, and intubated subjects).

Humans↗
PubMed1990

[The treatment of bone and joint infections in developing countries].

One hundred eighteen patients--with 151 osteitis and 33 septic arthritis--were treated in a second category hospital in Sahel (Africa) between 1987 and 1988. A very simple and inexpensive treatment was used; this is of great importance in developing countries, with poor general hygiene and limited reserves of antibiotics. There is no special equipment required, excepted basic instruments for bone surgery. The results were: a) out of a total of 119 patients, 103 cures: 87.3% 7 amputations: 6% 7 failures: 6% 1 death (among the amputees) 1 lost to follow-up b) out of 151 osteitis, 134 cures: 88.7% c) out of 33 arthritis, 21 cures: 63.6%. This series shows that amputation is no longer necessary if the treatment is long enough. Amputation is indicated exceptionally in young patients, even in the poor conditions of the developing countries.

Adolescent↗
PubMed1984

[Epithelioid sarcoma. Apropos of 3 cases].

The authors present two cases of epithelioid sarcoma of the hand and one of the foot with clinical interest. This recently described tumor (Enzinger, 1970), is relatively rare. It occurs in the hand, forearm, pretibial region and foot and affects principally young adults. It should be emphasized, and this is borne out in the literature, that this tumor may appear perfectly benign and often has a course of long duration. The difficulty of clinical and especially of histologic diagnosis as well as the difficulty of determining the boundaries of extension of the tumor make it necessary to carry out radical surgery (amputation or rarely block excision). Every author agrees that local excision is to be condemned, there being an 85% recurrence rate. Spread of the tumor is by way of the fascial planes and tendon sheaths. Lymphatic and pulmonary metastases occur particularly when there is vascular invasion.

Adult↗
PubMed1984

Dissolution of biliary duct stones without papillotomy in a patient with Billroth II resection and Crohn's disease.

A patient with a Billroth II resection and Crohn's disease subsequently developed obstructive jaundice and biliary sepsis. Three hepatic duct stones were demonstrated by ERC. After overcoming the obstruction by means of temporary retrograde internal drainage, perfusion of glyceryl-1-monooctanoate-carnosine and bile-acid-EDTA solution (2) was combined with sucralfate instillation into the blind loop via a duodenal tube. During successful treatment of the cholangiolithiasis, no deterioration of Crohn's disease was seen. Secondary effects such as abdominal pain or diarrhoea, were treated symptomatically.

Aged↗
PubMed1983

Epithelioid sarcomas. Three cases.

The authors present two cases of epithelioid sarcoma of the hand and one of the foot with clinical interest. This recently described tumor (Enzinger, 1970), is relatively rare. It occurs in the hand, forearm, pretibial region and foot and affects principally young adults. It should be emphasized, and this is borne out in the literature, that this tumor may appear perfectly benign and often has a course of long duration. The difficult of clinical and especially of histologic diagnosis as well as the difficulty of determining the boundaries of extension of the tumor makes it necessary to carry out radical surgery (amputation or rarely block excision). Every author agrees that local excision is to be condemned, there being an 85% recurrence rate. Spread of the tumor is by way of the fascial planes and tendon sheaths. Lymphatic and pulmonary metastases occur particularly when there is vascular invasion.

Adult↗