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Biomedical subjects

D Robert

Publications and source records attributed to D Robert.

At least 73 records · Page 4Linked to original sources
PubMed2000

[Mandibular advancement orthoses used in the treatment of obstructive sleep apnea syndrome].

Mandibular advancement devices represent a therapeutic option for obstructive sleep apnea syndrome (OSAS). Clinical improvement has been proven in the different available studies, mainly on nocturnal respiratory events and quality of sleep. Less snoring have been noted by bed partners and objective studies have demonstrated decrease in snoring frequency and intensity. The effect of these ortheses on upper airways resistance syndrome is not yet well documented. The significant clinical improvement is secondary to the decrease in the occurrence of apneas and hypopneas. Polysomnographic improvement criteria with an apnea hypopnea index less than 10 per hour has been noted in certain cases. Although no improvement or even worsening was noted in other cases. Sleep architecture has also changed in these patients, with a decrease in the time spent in stages 1 and 2, and an increase in the time spent in stages 3 and 4 and rapid eye movement sleep. Micro-arousals are also decreased in number certainly with the decrease in the occurrence of respiratory events. Somnolence and loss of attention are improved; these have been evaluated subjectively or by a well known and approved somnolence scale. In some cases a test for vigilance was done.

Airway Resistance↗
PubMed2000

[The pectoralis myofascial flap in oropharyngeal and pharyngolaryngeal reconstruction in salvage surgery].

BACKGROUND: The pectoralis major myofascial (PMMF) flap is rapidly mobilized, reliable in a number of clinical situations calling for vascularized soft tissue coverage in the head and neck. Salvage surgery after radiation failures produce salivary fistula, skin flap necrosis, vascular rupture. Use of PMMF improves healing in such cases. METHODS: A retrospective review performed at the university hospital, Marseille, between August 1987 and August 1999, was undertaken in two groups of salvage surgery. Groupe 1: protection of great vessels and fistula prevention after total laryngectomy (TL) and pharyngolaryngectomy (PL). Groupe 2: intra oral and pharyngeal defects reconstruction. Outcomes were classified in three types: type 1 - no complications; type 2 - delayed healing; type 3 - complicated healing. In groupe 2, in six cases the amount of flap contraction was analysed by C.T. scan. RESULTS: 83 PMMF was performed. Groupe 1, 57 cases (TL 28 cases, PL 26 cases); groupe 2, oral cavity défect 9 cases; oropharyngeal défects; 17 cases. There was no flap necrosis or vascular rupture. The donor site complications rate was 9.2%. The overall complications follow up was; groupe 1; type 1: 66%; type 2: 32%; type 3: 2%. In the groupe 2, type 1: 81%; type 2: 19%; type 3: 0%. The flap contracture was 30%. The use of PMMF in salvage surgery must be indicated in all cases after TL or PL, and is an excellent alternative from soft tissue coverage of oropharyngeal defects.

Adult↗
PubMed1999

Inhomogeneous Lineshape Profiles of C(2)H(2) Perturbed by Xe.

Several infrared transitions of the nu(5) band of C(2)H(2) perturbed by Xe near 700 cm(-1) have been recorded using a tunable diode-laser spectrometer, equipped with a thermostatically regulated cell. The pressure and temperature regimes covered during the experiments are respectively ranging between 20 and 200 mbar and 170 and 350 K. The experimental profiles are accurately studied with a recently proposed lineshape model accounting for the collisional confinement narrowing of the Doppler spectral contribution, the inhomogeneous collisional broadening and shifting, and the exchange between the various speed classes of the Maxwell-Boltzmann distribution. The speed dependence of the collisional broadening is either ab initio calculated from a semiempirical potential or deduced from the experimental temperature dependence of the line broadening. It is shown that, for the considered range of temperature, this speed dependence does not significantly modify the lineshape, so that the usual hard and soft models conveniently account for most of the observed effects. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Effects of prone position on alveolar recruitment and oxygenation in acute lung injury.

OBJECTIVE: To investigate the effects of prone position (PP) on alveolar recruitment and oxygenation in acute respiratory failure. DESIGN: Prospective physiologic study. SETTING: Medical ICU two in a university hospital. PATIENTS: Twelve adult patients intubated and mechanically ventilated with medical primary acute lung injury/adult respiratory distress syndrome (ALI/ARDS) in whom PP was indicated. MEASUREMENTS AND RESULTS: We constructed the static inflation volume-pressure curves (V-P) of the respiratory system in the 12 patients and differentiated between lung and chest wall in ten of them. We determined the difference between end-expiratory lung volume on positive end-expiratory pressure (PEEP) and relaxation volume of the respiratory system on zero PEEP (delta FRC). The recruited alveolar volume was computed as the delta FRC times the ratio of static elastance of the respiratory system to the lung. These measurements together with arterial blood gases determination were made in supine position (SP1), after 1 h of PP and after 1 h of supine repositioning (SP2) at the same level of PEEP. The PaO2/FIO2 ratio improved from SP1 to PP (136 +/- 17 vs 204 +/- 24 mm Hg; p < 0.01). An PP-induced alveolar recruitment was found in five patients. The change in oxygenation correlated to the recruited volume. The static elastance of the chest wall decreased from 4.62 +/- 0.99 cmH2O/l in SP1 to 6.26 +/- 0.54 cmH2O/l in PP (p < 0.05) without any correlation to the change in oxygenation. CONCLUSIONS: Alveolar recruitment may be a mechanism of oxygenation improvement in some patients with acute hypoxemic respiratory failure. No correlation was found between change in oxygenation and chest wall elastic properties.

Adult↗
PubMed1999

Facet diagrams for quantum similarity data.

The objective of this work is to demonstrate that an appropriate treatment of quantum similarity matrices can reveal hidden data grouping related to relevant structural features and even to biological properties of interest. Classical scaling is used here to extract the information contained in the similarity relationships between the elements of a molecular set. Facet theory is invoked to relate, in a qualitative way, the spatial regions to structural characteristics as well as to properties of interest. Two application examples are discussed: the Cramer steroid set and a benzene, toluene and xylene derivatives set.

Benzene↗
PubMed1999

Quantitative voice analysis in the assessment of bulbar involvement in amyotrophic lateral sclerosis.

Bulbar and pseudobulbar symptoms are diagnostic criteria of amyotrophic lateral sclerosis (ALS). One of the earliest symptoms of bulbar involvement is voice deterioration. Until now voice assessment in ALS patients has been done mainly by perceptual analysis. The objective parameters, including acoustic measures, one aerodynamic measure and the maximal phonation time, have been measured only in a few small series of patients. The first purpose of this prospective study was to determine which vocal parameters discriminate ALS patients with bulbar involvement from control patients. The second was to identify sensitive parameters for early detection of voice deterioration due to bulbar involvement in pre-symptomatic ALS patients. The voices of 63 female ALS patients, including 40 with bulbar symptoms (sALS patients) and 23 without bulbar symptoms (aALS patients), were studied using an objective voice analysis system that allows simultaneous analysis of acoustic and aerodynamic parameters. Measurements were compared with those obtained in 40 normal female subjects (control patients). Five of eight acoustic parameters were significantly different among the three groups: jitter, coefficient of variation for frequency, shimmer, number of harmonics, and maximum phonatory frequency range. Three aerodynamic parameters, phonatory airflow, cycle-to-cycle variation for phonatory airflow, and coefficient of variation for phonatory airflow were significantly different between sALS patients and control patients. No aerodynamic parameter allowed discrimination between aALS patients and control patients. This study shows that acoustic parameters are more sensitive than aerodynamic parameters for early detection of bulbar involvement. Nevertheless, the measurements used can predict bulbar involvement in 73% of those in the sALS group, but only in 52% of those in the aALS group.

Aged↗
PubMed1999

Tympanal hearing in the sarcophagid parasitoid fly Emblemasoma sp.: the biomechanics of directional hearing.

In Diptera, tympanal hearing has evolved at least twice in flies that belong to two different families, the tachinids and the sarcophagids. Common to these flies is their parasitoid reproductive strategy, both relying on the acoustic detection and localization of their hosts, singing insects, by means of tympanal hearing organs. In the present study, the external anatomy of the unusual hearing organs of the sarcophagid fly Emblemasoma sp. is described. The sarcophagid ears bear numerous anatomical similarities with those of ormiine tachinids: they are located on the ventral prosternum and possess a pair of scolopidial mechanoreceptive sense organs. A striking difference, however, resides in the lack of a well-defined presternum in the sarcophagid tympanal system. Instead, a deep longitudinal fold, the tympanal fold, spans both hemilateral tympanal membranes across the midline of the animal. Measured using laser Doppler vibrometry, the tympanal mechanical response in the sound field reveals asymmetrical deflection shapes that differ from those of tachinids. Lacking a central fulcrum, the sarcophagid tympanal complex presents different vibrational modes that also result in interaural coupling. The evolutionarily convergent, yet distinct, solutions used by these two small auditory systems to extract directional cues from the sound field and the role of tympanal coupling in this process are discussed.

Animals↗
PubMed1999

Mosquito hearing: sound-induced antennal vibrations in male and female Aedes aegypti.

Male mosquitoes are attracted by the flight sounds of conspecific females. In males only, the antennal flagellum bears a large number of long hairs and is therefore said to be plumose. As early as 1855, it was proposed that this remarkable antennal anatomy served as a sound-receiving structure. In the present study, the sound-induced vibrations of the antennal flagellum in male and female Aedes aegypti were compared, and the functional significance of the flagellar hairs for audition was examined. In both males and females, the antennae are resonantly tuned mechanical systems that move as simple forced damped harmonic oscillators when acoustically stimulated. The best frequency of the female antenna is around 230 Hz; that of the male is around 380 Hz, which corresponds approximately to the fundamental frequency of female flight sounds. The antennal hairs of males are resonantly tuned to frequencies between approximately 2600 and 3100 Hz and are therefore stiffly coupled to, and move together with, the flagellar shaft when stimulated at biologically relevant frequencies around 380 Hz. Because of this stiff coupling, forces acting on the hairs can be transmitted to the shaft and thus to the auditory sensory organ at the base of the flagellum, a process that is proposed to improve acoustic sensitivity. Indeed, the mechanical sensitivity of the male antenna not only exceeds the sensitivity of the female antenna but also those of all other arthropod movement receivers studied so far.

Acoustic Stimulation↗
PubMed1999

[Mandibular advancement orthotic for treatment of obstructive sleep apnea].

Mandibular advancement devices represent a therapeutic option for obstructive sleep apnea syndrome (OSAS). Clinical improvement has been proved in the different available studies, mainly on nocturnal respiratory events and quality of sleep. Less snoring have been noted by bed partners and objective studies have demonstrated decrease in snoring frequency and intensity. The effect of these ortheses on upper airways resistance syndrome is not yet well documented. The significant clinical improvement is secondary to the decrease in the occurrence of apneas and hypopneas. Polysomnographic improvement criteria with an apnea hypopnea index less than 10 per hour has been noted in certain cases. Although no improvement or even worsening was noted in other cases. Sleep architecture has also changed in these patients, with a decrease in the time spent in stages 1 and 2, and an increase in the time spent in stages 3 and 4 and rapid eye movement sleep. Microarousals are also decreased in number certainly with the decrease in the occurrence of respiratory events. Somnolence and loss of attention are improved; these have been evaluated subjectively or by a well known and approved somnolence scale. In some cases a test for vigilance was done.

Humans↗
PubMed1998

Oxygen tolerance in patients with acute respiratory failure.

OBJECTIVE: To search for a threshold of pulmonary oxygen toxicity in patients with acute respiratory failure. DESIGN: Retrospective study over a 10-year period. SETTING: Three intensive care units of two university hospitals. PATIENTS AND PARTICIPANTS: Seventy-four patients with acute respiratory failure ventilated continuously with a FIO2 > or = 0.9 for at least 48 h were selected. INTERVENTIONS: Information regarding status, scoring, diagnosis and therapeutic interventions upon admission and ICU course were extracted from the patients' charts. MEASUREMENTS AND RESULTS: We found that total exposure [mean (standard error of the mean)] to a FIO2 of 0.9 (TE 90) or more was 5.6 (1.1) days in the 17 survivors (S) versus 5.9 (0.5) days in the 57 non-survivors (D) (NS). Total exposure time to a FIO2 more than 0.5 (TE 50) was 16.5 (2.6) days in S and 11.2 (1) days in D (p < 0.05). The PaO2/FIO2 ratio became significantly higher in S only 5 days after beginning FIO2 of 0.9 or more. Hypoxemia was not frequent at the time of death, whereas in 70% of the non-survivors there were at least three organ failures in the last 48 h. In univariate analysis, the duration of exposure to FIO2 of 0.9 or more was not different in survivors and non-survivors, and the average total duration of exposure to FIO2 of more than 0.5 was even longer in survivors. In multivariate analysis, exposure shorter than 10 days to FIO2 more than 0.5 and exposure longer than 4 days to a FIO2 of 0.9 or more were significantly associated with death. However, despite a larger exposure to a FIO2 of 0.9 or more during the last 5 years of the study, the trend moved towards a higher survival rate during this period compared with the first 5 years of the study. CONCLUSIONS: Thus, our data provide circumstantial evidence that the lungs of patients with acute respiratory failure might exhibit some relative resistance to prolonged oxygen exposure. Therefore, it might be worthwhile carrying out a prospective study of different FIO2 strategies in such patients.

Chi-Square Distribution↗
PubMed1997

Light dosimetry for photodynamic therapy in the esophagus.

BACKGROUND AND OBJECTIVE: Photodynamic therapy (PDT) is an efficient technique to treat superficial early cancers in the pharynx, esophagus, and tracheo-bronchial tree. However, the lack of selectivity of some of the clinically used photosensitizers can result in significant damage to the healthy tissue during the treatment. In the esophagus, this may lead to medical complications such as stenosis and fistula. Insufficient selectivity may be compensated to some extent by accurate light dosimetry. Here, we present an approach to safer and more efficient PDT by improved light dosimetry in the esophagus. STUDY DESIGN/MATERIALS AND METHODS: This includes the utilization of a suitable light distributor, the estimation of the radiant energy density in the tissue, and the knowledge of the esophagus morphology. The light distributor presently used in the clinic is described and several techniques to study light propagation in the esophageal wall have been investigated and are discussed. Thickness of different histological layers of the esophageal wall have been measured ex vivo and are presented. RESULTS: Under these conditions and based on a simple model of the light distribution in the tissue, some basic and clinically useful notions of light dosimetry can be drawn. These notions, associated with measured value of tissue optical properties at the wavelengths of interest with the presently used photosensitizers, are discussed regarding the particular morphology of the esophageal wall. In particular, the importance of the illumination wavelength from the safety point of view is shown. CONCLUSION: The proposed approach allows for improved safety and efficacy of PDT in the esophagus, particularly in the clinical tests of new photosensitizers.

Esophagus↗
PubMed1997

Three-dimensional optical phantom and its application in photodynamic therapy.

BACKGROUND AND OBJECTIVE: A technique to manufacture a stable, reproducible three-dimensional optical phantom is presented. This phantom reproduces the tissue's optical properties as well as the geometry and, to some extent, the mechanical properties of the organ concerned. Easy to make and to handle, this phantom is a useful tool for numerous medical applications involving light interaction with biological tissues. STUDY DESIGN/MATERIALS AND METHODS: The phantom is based on a transparent two-component silicone, which is molded into the desired shape and cured at room temperature. Specific optical properties are obtained by adding scatterers (Al2O3 particles or polystyrene microspheres) and absorbers (dyes or pigments). A method to measure the radiant energy fluence rate in the phantom is described. This method is based on a small isotropic optical detector. RESULTS: A three-dimensional phantom of the bronchial tree is presented. This phantom is used for testing new light distributors designed for photodynamic therapy of the bronchi. CONCLUSION: The proposed technique allows one to produce a stable three-dimensional phantom with accurately predictable optical properties.

Equipment Design↗
PubMed1997

Prone position in mechanically ventilated patients with severe acute respiratory failure.

The purpose of this study was to characterize changes in oxygenation, expressed as PaO2/F(I)O2, when patients with severe acute respiratory failure (PaO2/F(I)O2 < 150), unrelated to left ventricular failure to atelectasis, were turned to and from a supine to prone position at 1- and 4-h intervals. Ventilator settings were unchanged. Thirty-two consecutive patients were studied 1 h before, 1 and 4 h during and 1 h after placing in a prone position with PaO2/F(I)O2 of 103 +/- 28, 158 +/- 62, 159 +/- 59, and 128 +/- 52, respectively (ANOVA, p < 0.001). After 1 h in a prone position, improvement of PaO2/F(I)O2 by 20 mm Hg or more was considered a positive response. Seven patients studied had no response (22%), hereafter referred to as nonresponders, and 25 had a positive response (78%), hereafter referred to as responders. Among the seven nonresponders, two did not tolerate the prone position and were returned supine before the end of the 4-h trial. With the remaining five, PaO2/F(I)O2 evolution was 83 +/- 29, 77 +/- 19, 83 +/- 33, and 81 +/- 47, respectively. For two of the 25 responders, measurements are missing after returning to the supine position. In 10 of the 23 responders (43%) who completed the 4 h prone trial, the PaO2/F(I)O2 returned to its starting value when patients were repositioned supine: 117 +/- 24, 164 +/- 44, 156 +/- 55, and 110 +/- 34, respectively (ANOVA, p < 0.01). In 13 of the 23 (57%) improvement persisted: 105 +/- 27, 187 +/- 58, 189 +/- 49, and 157 +/- 49, respectively (ANOVA, p < 0.001). Repeated improvements after turning to a prone position were frequently observed. Side effects in the 32 patients after a total of 294 periods in a prone position included minor skin injury and edema, two instances of apical atelectasis, one catheter removal, one catheter compression, one extubation, and one transient supraventricular tachycardia.

Adolescent↗
PubMed1997

Forewing asymmetries during auditory avoidance in flying locusts

Flying locusts orient to sounds in their environment. Sounds similar to those produced by echolocating bats cause a flying locust to change its flight path. We used high-speed cinematography and videography to study changes in body posture and wing kinematics of tethered locusts in response to stimulation with bat-like sounds. Locusts showed both negative and positive phonotaxis to this stimulus. Within a few wingbeats of stimulus onset (between 126 and 226ms), locusts deflected their abdomens to one side, and the angle of the left and right forewings with respect to the dorsal&shy;ventral body axis became asymmetrical during the downstroke. This forewing asymmetry, in which the forewing on the inside of the turn became more depressed, ranged from 20 to 45&deg; (37&plusmn;9.7&deg;, mean &plusmn; s.d.) and was correlated with the direction and magnitude of abdomen deflection, a measure of steering in tethered, flying locusts. Hindwing stroke angle asymmetries were minimal or non-existent after stimulation. Coincident with changes in forewing asymmetry and abdomen deflection was a decrease in stroke amplitude (19&plusmn;6.5&deg;) of the forewing on the inside of the attempted turn. Motor patterns from forewing first basalar (M97) muscles showed an asymmetry in the timing of left and right depressor activation that ranged from 10.4 to 1.6ms (4.23&plusmn;2.85ms). The number of spikes per depressor burst increased to a maximum of three spikes in the muscle on the inside of the attempted turn, and depressor frequency (wingbeat frequency) increased by approximately 2Hz (2.17&plusmn;0.26Hz). We suggest that the asymmetry in forewing first basalar activity is causally related to the asymmetry in the timing of the initiation of the downstroke, resulting in an asymmetry in the ranges of the stroke angles of the forewings, which would impart a roll torque to the locust. This would augment the steering torques generated by concurrent changes in the angle of attack of the fore- and hindwings and changes in abdomen position to effect rapid avoidance manoeuvres.

Journal Article↗
PubMed1997

[Medialization of paralysed vocal cord by expansive polytetrafluoroethylene implant (Gore-Tex)].

We report a technique for medialization of a paralyzed vocal cord using a Gore-Tex (expanded polytetrafluoroethylene) implant inserted under local anesthesia via a cervical incision. Gore-Tex is an expanded form of Teflon. It is used in vascular surgery (vessel repair) and esthetic surgery (particularly to increase lip volume). In esthetic surgery, the development of inflammatory processes difficult to control have been observed with teflon and appear to be less frequent with Gore-Tex due to the absence of free particles in the expanded form. The minimally invasive technique is simple and reproducible and can be performed under local anesthesia. We report a series of 9 cases operated from October 1995 to October 1997. During this period, this technique predominated (two other patients had Teflon injections). Excepting one case of extrusion of the implant material, vocal results were very satisfactory, based on both subjective and objective analysis of vocal parameters. The contribution of this technique in comparison with the reference endoscopic techniques (Teflon, collagen) and surgical techniques (silicone, cartilage) is discussed. Early results would suggest that Gore-Tex implantation can be used in the more severe forms due to vocal cord paralysis in the lateral position.

Adult↗