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Biomedical subjects

E Dahan

Publications and source records attributed to E Dahan.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effects of different mechanical treatments on nasal resistance assessed by rhinometry.

The goal of this study was to compare the effectiveness of three treatments aiming to reduce nasal airflow resistance (NR): an external nasal strip device (Respir+), an internal nasal mechanical dilator (Nozovent), and a topical decongestant (Pernazène). NR was estimated by active posterior rhinometry at both a 0.5 L/s flow (NRF) and a 1 cm H2O pressure (NRP), under four conditions: in the basal state, with Respir+, with Nozovent, and after treatment with Pernazène. The efficacy of each treatment was assessed by the percentage changes in NRF and NRP (%NRF and %NRP, respectively). The study was performed in 15 healthy subjects. The efficacy of the treatments was significantly different, depending on whether it was evaluated by NRF or by NRP (p<0.02), with %NRF and %NRP values, respectively, equal to the following: 88+/-20% and 91+/-14% with Respir+, 58+/-17% and 70+/-13% with Nozovent, and 55+/-29% and 69+/-22% with Pernazène. NRF remained unchanged with Respir+, whereas it significantly decreased with Nozovent and Pernazène (p<0.0001). No significant difference was observed between the effects of the two latter treatments. These results demonstrate that Nozovent, which involves no risk of side effects or drug interactions, is an effective treatment to improve nasal breathing. Nozovent might therefore be recommended as an alternative to topical decongestants, for certain subjects presenting with nasal obstruction.

Administration, Intranasal↗
PubMed1998

Nasal airflow resistance measurement: forced oscillation technique versus posterior rhinomanometry.

This study was designed to determine whether nasal airflow resistance (Rn) which is nonlinear during tidal breathing, can be assessed by the forced oscillation (FO) technique. Rn values obtained by the FO technique and extrapolated to 0 Hz (Rn,FO) were compared to those assessed by posterior rhinomanometry at maximal tidal inspiratory flow (Rn,m), at a 0.5 L x s(-1) flow (Rn,F), and at a 1 hPa transnasal pressure (Rn,P). All Rn estimates were derived from the same inspiratory and expiratory nasal flow and transnasal pressure signals obtained during tidal nasal breathing whilst a forced flow was applied at the nose via a rigid nasal mask in 23 healthy volunteers, of whom 14 had additional measurements after vasoconstrictor treatment. In the basal state, no significant difference, and significant correlations (p<0.0001) were found between Rn,FO and the other Rn estimates. Only the regression line of Rn,FO versus Rn,m was not significantly different from the identity line. After nasal decongestion, Rn,P became significantly higher than the other Rn estimates (p<0.005). The regression line of Rn,FO versus Rn,m remained nonsignificantly different from the identity line. Similar results were observed regarding the percentage values of the different Rn estimates after decongestant treatment. This study shows that, despite its nonlinearity, Rn can be assessed by the FO technique, and that Rn,FO and Rn,m could be indifferently used as physiological indices of nasal patency. As the FO technique is more difficult to implement than the conventional rhinomanometry, its interest in rhinology appears not to be obvious.

Adrenergic alpha-Agonists↗
PubMed1997

Nasal cavity geometry measured by acoustic rhinometry and computed tomography.

OBJECTIVE: To determine the significance of cross-sectional areas obtained by acoustic rhinometry. DESIGN: Comparison of data obtained by acoustic rhinometry and computed tomography (CT). SETTING: Outpatient clinic. PATIENTS: Nine adults with nasal obstruction due to turbinate hypertrophy. MAIN OUTCOME MEASURES: Acoustic rhinometry and CT were performed after nasal decongestion. The acoustic area-distance curve was analyzed based on 3 notches (A1, A2, and A3) corresponding to 3 local minimal areas. Computed tomographic measurements were made in the coronal plane at 0.5-cm intervals, and the narrowest sections in the anterior (S1), middle (S2), and posterior (S3) parts of the nasal cavity were selected. Mean specific section areas and volumes were computed by integration of the acoustic area-distance curves using the same procedure for the 2 methods. RESULTS: Significant correlations were found between acoustic and CT areas in the anterior nasal cavity (A1 vs S1, P < .001; A2 vs S2, P < .005). Acoustic and CT anterior volumes from A1 to A2 and from S1 to S2 were significantly correlated with each other (P < .005). No correlation was found between acoustic and CT areas measured at the posterior part of the nose (A3 vs S3). A weak correlation was evidenced between acoustic and CT posterior volumes from A2 to A3 and from S2 to S3 (P < .05). CONCLUSIONS: Acoustic rhinometry may be particularly well suited to the evaluation of anterior nasal geometry during clinical studies. At the posterior part of the nose, acoustic measurements may be of limited clinical relevance.

Acoustics↗
PubMed1997

Assessment of high-frequency neonatal ventilator performances.

OBJECTIVE: To assess the efficacy and reliability of neonatal high-frequency ventilators. DESIGN: Bench evaluation of neonatal high-frequency ventilators. SETTING: Physiology department and university hospital neonatal intensive care unit. INTERVENTIONS: HFV-Babylog 8000 (Dräger Medical), OHF 1 (Dufour), and SensorMedics 3100A (Sensor-Medics) ventilators were connected to a neonatal test-lung. Tidal volume, peak-to-peak pressure amplitude, and mean airway pressure were measured for several ventilator settings, endotracheal tube sizes, and lung compliances. MEASUREMENTS AND RESULTS: Increasing peak-to-peak pressure resulted in a linear increase in tidal volume delivery in the 0-30% range of maximum amplitude. No significant increase in tidal volume was observed with the HFV-Babylog 8000 when pressure amplitude was above 50%. The maximum tidal volume delivered was substantially smaller with the HFV-Babylog 8000 than with the OHF 1 or SensorMedics 3100A. Tidal volume increased with endotracheal tube size with all three ventilators. Increasing test-lung compliance resulted in lower tidal volumes only with OHF 1. Decreasing mean airway pressure was responsible for a decrease in tidal volume delivery with HFV-Baby-log 8000. CONCLUSION: We found that under our test conditions two of the three ventilators delivered adequate tidal volumes at the usual frequency of 15 Hz, regardless of the size of the endotracheal tube and of the mechanical properties of the respiratory system. When lung compliance increased or mean airway pressure decreased, both of which are common events during the recovery phase of hyaline membrane disease, we found that the intrinsic properties of two of the ventilators tested were responsible for a decrease in tidal volume. This decrease may account for some cases of heretofore unexplained hypercapnia.

Critical Care↗
PubMed1997

Choice of lens and dioptric power in pediatric pseudophakia.

PURPOSE: To evaluate lens choice and dioptric power in pediatric eyes having posterior chamber intraocular lens (IOL) implantation. SETTING: Oxford Eye Center and the St. John Eye Hospital, Johannesburg, South Africa. METHODS: This retrospective study evaluated the refractive development in 156 pseudophakic eyes of 99 children aged 1 month to 8 years who had surgery between June 1983 and April 1994. The children were divided into three groups based on age at time of IOL implantation: Group A (68 eyes), 1 to 18 months; Group B (32 eyes), 19 to 36 months; Group C (48 eyes), 3 to 8 years. Poly(methyl methacrylate) posterior chamber IOLs with an overall diameter between 10.5 and 12.0 mm were used. The dioptric power was 3.00 to 6.00 diopters (D) less than that needed to achieve emmetropia. RESULTS: In Group A, the mean growth in axial length was 3.59 mm +/- 1.80 (SD) and the mean change in refraction was 6.39 +/- 3.68 D. In Group B, the respective means were 0.75 +/- 0.85 mm and 2.73 +/- 1.40 D and in Group C, 0.76 +/- 0.69 mm and 2.60 +/- 1.84 D. CONCLUSIONS: The younger the child at time of implantation, the greater the myopic shift. To reduce the necessity of IOL exchange, these eyes should be undercorrected, with the residual refractive error corrected by spectacles that are adjusted throughout life according to refractive development. This leads to initial hypermetropia that gradually moves to emmetropia or moderate myopia in adulthood.

Cataract↗
PubMed1997

Extended screening by PCR for seven cry-group genes from field-collected strains of Bacillus thuringiensis.

An extended multiplex PCR method was established to rapidly identify and classify Bacillus thuringiensis strains containing cry (crystal protein) genes toxic to species of Lepidoptera, Coleoptera, and Diptera. The technique enriches current strategies and simplifies the initial stages of large-scale screening of cry genes by pinpointing isolates that contain specific genes or unique combinations of interest with potential insecticidal activities, thus facilitating subsequent toxicity assays. Five pairs of universal primers were designed to probe the highly conserved sequences and classify most (34 of about 60) genes known in the following groups: 20 cry1, 3 cry2, 4 cry3, 2 cry4, 2 cry7, and 3 cry8 genes. The DNA of each positive strain was probed with a set of specific primers designed for 20 of these genes and for cry11A. Twenty-two distinct cry-type profiles were identified from 126 field-collected B. thuringiensis strains. Several of them were found to be different from all published profiles. Some of the field-collected strains, but none of the 16 standard strains, were positive for cry2Ac. Three standard and 38 field-collected strains were positive by universal primers but negative by specific primers for all five known genes of cry7 and cry8. These field-collected strains seem to contain a new gene or genes that seem promising for biological control of insects and management of resistance.

Animals↗
PubMed1996

Pulmonary clearance and lung function: influence of acute tobacco intoxication and of vitamin E.

Cigarette smoking increases the alveolar epithelial permeability to small solutes, as assessed by the pulmonary clearance of aerosolized 99mTc-labeled diethylenetriaminepentaacetate. The involvement of lipid peroxidation in this increased clearance was tested in eight asymptomatic young smokers by investigating the effects of a 3-wk supplementation with oral vitamin E (1,000 IU/day) on pulmonary clearance according to a protocol designed as a single-blind crossover study. Indexes of acute tobacco intoxication (exhaled CO, carboxyhemoglobin, and urinary cotinine) and lung function parameters [including Krogh factor (KCO)] were also studied. Under control conditions, pulmonary clearance was abnormally increased (2.93 +/- 0.78%/min), whereas KCO was in the normal range. Pulmonary clearance correlated strongly with expired CO (P < 0.04), HbCO (P < 0.005), urinary cotinine (P < 0.003), and KCO (P < 0.004). Supplementation with vitamin E, a highly efficient antioxidant, neither decreased the pulmonary clearance nor altered the above correlations. However, the strong correlations observed between pulmonary clearance and indexes of acute tobacco intoxication, which reflect the amount of inhaled smoke and the resultant oxidant stress, do not allow exclusion of the involvement of lipid peroxidation in the pulmonary clearance increase observed in smokers.

Adult↗
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

Laparoscopic cholecystectomy minimally impairs postoperative cardiorespiratory and muscle performance.

Surgery elicits a subjective feeling of postoperative fatigue, at least partly related to an impairment in cardiorespiratory function and muscle performance. Laparoscopic surgery is reported to impair the patient's condition minimally. The aim of this study was to assess exercise performance in patients scheduled for elective laparoscopic cholecystectomy. Nine patients assessed as having American Society of Anesthesiologists (ASA) grade I were enrolled in the study. Subjective feelings of fatigue (measured on a visual analogue scale), and heart rate, systemic arterial pressure oxygen consumption and carbon dioxide production responses to graded exercise testing, were assessed before operation and on days 3 and 10 after operation. There were no significant differences in any of these measurements, at rest or during exercise, between the preoperative and postoperative values. Uncomplicated laparoscopic cholecystectomy does not impair postoperative cardiorespiratory and muscle performance or induce significant postoperative fatigue in patients with ASA I, allowing rapid recovery.

Blood Pressure↗
PubMed1994

Serious occurrences in the natural history of advanced climatic keratopathy.

BACKGROUND: Climatic or chronic actinic keratopathy is an important corneal degeneration occurring after prolonged climatic exposure. The advanced stages of disease are confined generally to tropical or arid localities (including the Arctic) with high levels of sunlight. After many years of disease evolution, the advent of stage 3 keratopathy often presages a rapid downhill course. The instability of advanced climatic keratopathy has received little attention. METHODS: Eighteen patients with advanced climatic keratopathy are described from the Transvaal region in South Africa and from Saudi Arabia. Patients with rapid disease progression, spontaneous sterile ulceration, and secondary microbial keratitis are described. RESULTS: The rapid progression characteristic of stage 3 climatic keratopathy is illustrated. Severe, focal, sterile ulceration of the devitalized corneal degeneration may be common. Secondary infection may occur, leading to rapid dissolution of the climatic keratopathy material. Corneal perforation may ensue. The occurrence of yellow or brown fragments of the climatic keratopathy within or adjacent to the corneal inflammatory infiltrate indicates the predisposing cause of the infection, as usually also with examination of the opposite eye. CONCLUSIONS: These observations emphasize the inherent instability of advanced climatic keratopathy, which frequently takes a relentless downhill course. In rural populations of the developing world, climatic keratopathy is an important cause of blindness. Disease pathogenesis, treatment, and prevention deserve greater study.

Adult↗
PubMed1994

Vitamin E does not prevent exercise-induced increase in pulmonary clearance.

It has been observed that sustained exercise results in a prolonged increase in alveolar epithelial permeability, as assessed by the pulmonary clearance rate of aerosolized 99mTc-labeled diethylenetriaminepentaacetate (Lorino et al. J. Appl. Physiol. 67: 2055-2059, 1989). The involvement of lipid peroxidation in this increased permeability was tested in seven nonsmoking volunteers by comparing the exercise-induced increases in pulmonary 99mTc-diethylenetriaminepentaacetate clearance before and after a 3-wk supplementation with oral vitamin E (1,000 IU/day), according to a protocol designed as a single-blind crossover study. The 60-min exercise was performed on a treadmill at a constant load corresponding to 80% of maximal O2 uptake. Administration of vitamin E, a very important antioxidant, did not reduce the exercise-induced increase in lung clearance, suggesting that the exercise-induced increase in lung epithelial permeability does not primarily result from the occurrence of lipid peroxidation in the alveolar membrane. This result thus corroborates the hypothesis of an alteration of the intercellular tight junctions due to the mechanical effects of hyperventilation.

Administration, Oral↗
PubMed1993

Early-stage avascular necrosis of the femoral head: MR imaging for prognosis in 31 cases with at least 2 years of follow-up.

Thirty-one cases of stage 1 or 2 osteonecrosis (ON) of the hip in 27 patients were studied with T1-weighted coronal magnetic resonance (MR) imaging. Three quantitative parameters were measured on the contiguous MR sections, corresponding to the 2-cm-wide median portion of the femoral head: the angle filled by ON (alpha), the percentage of weight-bearing femoral cortex involved with ON (WB), and the percentage of femoral head surface involved with ON. The clinical and radiologic courses were assessed after at least 2 years of follow-up (mean, 46 months). Core decompression was performed in 12 cases of ON. Values were strikingly lower in the group with good clinical or radiologic outcome versus poor outcome, with very little overlapping. WB was the more reliable parameter. Outcome of hips treated with versus without core decompression appeared closely related with these MR parameters and not with the treatment procedure. Thus, a quantitative approach to determination of extent and location of the lesion on the initial MR image appears accurate for use in the prediction of long-term outcome of ON. Effectiveness of core decompression should be reevaluated on this basis.

Adult↗
PubMed1991

Irrigation, aspiration, and polishing cannula.

Aspiration of the lens cortex and capsule polishing are two important aspects of modern extracapsular cataract surgery. In this report we describe simple but useful modifications to the widely used Simcoe irrigation/aspiration cannula. The modifications consist of enlarging the aspiration port diameter from 0.3 mm to 0.4 mm and altering the terminal segment of the cannula to a sandblasted capsule polisher. The 0.4 mm diameter aspiration port reduces the incidence of capsular entrapment and allows a more efficient aspiration of cortex of varying textures. The modifications eliminate the need for a separate capsule polishing instrument and allow simultaneous lens material aspiration and capsular cleanup. These modifications can be used for any irrigation/aspiration cannula whether manually or machine operated.

Cataract Extraction↗
PubMed1990

Pseudophakia in children: precautions, technique, and feasibility.

Intraocular lens implantation in young children can yield satisfactory results when the surgical techniques are modified and adapted to the child's eye. Between June 1983 and July 1988, 84 posterior chamber lenses were implanted in 80 children aged 2 months to 8 years. An elective posterior capsulotomy followed by an anterior vitrectomy was performed in all cases prior to the lens insertion. This step allowed a permanent clear visual axis which in turn has facilitated visual rehabilitation of the pseudophakic eye. The best results occurred in the developmental cataract group followed by the traumatic cataract group; the poorest visual outcome occurred in patients with unilateral congenital cataracts. Amblyopia treatment and alternative methods of correcting pediatric aphakia are discussed.

Aphakia↗
PubMed1989

Factors affecting relapse in node-negative breast cancer. A multivariate analysis including the labeling index.

Between 1975 and 1982, 167 patients with carcinoma of the breast without axillary lymph node metastases were studied. The thymidine labeling index (LI), representing the percentage of cells in the DNA synthesis phase, was measured in all these patients. High LI values were more frequently encountered in young patients (P = 0.05), in low estrogen receptor (ER) tumor content (P = 0.007) and in high grade tumors (P = 0.0002). The overall 8-year relapse-free survival (RFS) was 68%. Univariate analysis demonstrated that RFS was influenced by histological grading (P = 0.03), ER (P = 0.03), PR (P = 0.02) and LI (P = 0.01). Multivariate analysis using the Cox regression model selected the LI as the single significant prognostic factor with regard to RFS (P = 0.037). These results emphasize the important role of cell proliferation kinetics in defining node-negative breast cancer patients with a high risk of relapse.

Adult↗
PubMed1989

Implantation in the posterior chamber without capsular support.

The relatively high incidence of complications of anterior chamber implants has encouraged ophthalmologists to implant in the posterior chamber, even in eyes without posterior capsules. A new surgical technique for implantation of posterior chamber lenses in the ciliary sulcus is described. Twenty posterior chamber lenses were implanted in eyes which had had intracapsular cataract extraction, with a follow-up ranging from three to 14 months (mean 7.4 months). Although no serious complications occurred in this small series, the safety and viability of this technique will be established with a longer follow-up.

Adult↗
PubMed1989

Ciliary sulcus reconstruction for posterior implantation in the absence of an intact posterior capsule.

Secondary implantation of a posterior chamber intraocular lens in an aphakic eye devoid of an intact posterior capsule requires a special surgical approach. When lens capsule remnants remain in the periphery, the ciliary sulcus can be reconstructed to accommodate a posterior chamber lens. The fibrotic lens or capsular residues that often remain adherent to the posterior surface of the iris are divided with sharp intraocular scissors, and a shelf is created that is sufficient to support the lens haptics. A series of 28 cases, including 16 involving young children, demonstrates the feasibility and the favorable visual results obtainable with this surgical technique.

Adolescent↗