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PubMed1988

Intraluminal measurement of distance in the colorectal region employing rigid and flexible endoscopes.

Intraluminal measurements of distance cephalad to the anal verge in the colorectal region of 40 consecutive adult patients were performed employing rigid and flexible proctosigmoidoscopic techniques. In 2/40 (5%) patients, the measurements were identical. In 32/40 (80%) patients, measurements employing a flexible proctosigmoidoscope exceeded measurements employing a rigid instrument by at least 3 cm. The observations have relevance in the context of assessments of adequate distal margins and preservation of anal continence in patients requiring colorectal surgery via transabdominal, transsacral, transperineal, and/or transanal routes.

Colon↗
PubMed1995

Subtypes of Guanine-Nucleotide-Binding Regulatory Proteins at the Locus coeruleus Involved in Fentanyl-Induced Muscular Rigidity in the Rat.

Previous results from our laboratory have established that the G(o) subtype of guanine nucleotide (GTP)-binding regulatory protein at the locus coeruleus (LC) may participate in the elicitation of muscular rigidity by fentanyl. The present study further examined the involvement of other subtypes of GTP-binding regulatory proteins at the LC in this process, using Sprague-Dawley rats anesthetized with ketamine (120 mg/kg, i.p., with 30 mg/kg/h i.v. infusion supplements) and under mechanical ventilation. Intravenous administration of fentanyl (100 &mgr;g/kg) induced a significant increase in electromyographic signals recorded from the sacrococcygeus dorsi lateralis muscle. Power spectral analysis revealed that this was accomplished by a decrease in the mean power frequency and an increase in the root mean square values of the signals. The above responses were appreciably antagonized by pretreating animals with bilateral microinjection into the LC of pertussis toxin (80 or 160 fmol), N-ethylmaleimide (16 pmol) or 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (100 or 200 fmol); but not by cholera toxin (120 or 240 fmol), forskolin (240 or 480 pmol) or N-ethylmaleimide at a higher dose (32 pmol). These results suggest that, in addition to G(o) protein, fentanyl-induced muscular rigidity may also involve other pertussis toxin-sensitive GTP-binding regulatory proteins, possibly G(i) and G(p) subtypes, in the signal transduction processes following activation of &mgr;-opioid receptors at the LC. Copyright 1995 S. Karger AG, Basel

Journal Article↗
PubMed1992

Hoffmann half-frame external fixation rigidity and its relationship to universal joint slippage.

Hoffmann half-frame external fixation device configurations often fail under minimal loads secondary to joint slippage. In these experiments improved universal joints that were developed in an earlier study were tested on Hoffmann half-frame assemblies. The rigidity of selected half-frame configurations was tested in four modes (axial compression, torsion, medial-lateral and anterior-posterior four-point bending). These results were compared to those of an earlier, similar study looking at the standard Hoffmann half-frame. No changes in overall rigidity were noted, but significant increases in yield loads and loads to frame failure were achieved. Such improvements will increase the reliability and usefulness of the Hoffmann device to the orthopaedic community.

Equipment Design↗
PubMed1994

Flow and stress characteristics in rigid walled and compliant carotid artery bifurcation models.

Computer simulation of pulsatile non-Newtonian blood flow has been carried out in different human carotid artery bifurcation models. In the first part of the investigation, two rigid walled models are analysed, differing in the bifurcation angle (wide angle and acute angle bifurcation) and in the shape of both the sinus (narrow and larger sinus width) and the bifurcation region (small and larger rounding of the flow divider), in order to contribute to the study of the geometric factor in atherosclerosis. The results show a significant difference in the wall shear stress and in the flow separation. Flow recirculation in the sinus is much more pronounced in the acute angle carotid. An important factor in flow separation is the sinus width. In the second part of the study, flow velocity and wall shear stress distribution have been analysed in a compliant carotid artery bifurcation model. In the mathematical model, the non-Newtonian flow field and the idealized elastic wall displacement are coupled and calculated iteratively at each time step. Maximum displacement of approximately 6% of the diastolic vessel diameter occurs at the side wall of the bifurcation region. The investigation demonstrates that the wall distensibility alters the flow field and the wall shear stress during the systolic phase. Comparison with corresponding rigid wall results shows that flow separation and wall shear stress are reduced in the distensible wall model.

Arteriosclerosis↗
PubMed1983

Comparison of the rigid sigmoidoscope and the flexible sigmoidoscope in conjunction with colon x-ray for detection of lesions of the colon and rectum.

A series of 1007 patients was randomly divided into two groups, one a group of 499 patients who underwent rigid sigmoidoscopy and the other a group of 508 patients who had flexible sigmoidoscopy. Contrast barium enema studies were subsequently performed in all patients. Eighteen per cent of the patients had a neoplasm. We concluded that, given the amount of colon surveyed by rigid and flexible sigmoidoscopy in conjunction with contrast barium enema, there was no difference in the rate of detection between the two endoscopic techniques.

Barium Sulfate↗
PubMed1994

Comparison of a rigid laryngoscope with the ultrathin fibreoptic laryngoscope for tracheal intubation in infants.

The flexible ultrathin fibreoptic laryngoscope allows placement of endotracheal tubes as small as 2.5 mm internal diameter. The purpose of this study was to document the safety and efficacy of intubation using an ultrathin fibreoptic laryngoscope. Proved safety and efficacy would justify the routine use of fibreoptic laryngoscopy in normal infants to maintain skills needed for management of the difficult infant airway. In this prospective study, 40 infants < 24 mo of age scheduled for elective surgery were randomly divided into two equal groups. After inhalation induction of anaesthesia, in 20 infants the trachea was intubated using direct rigid laryngoscopy, and in 20 using the ultrathin fibreoptic laryngoscope (size 1.8 mm OD) Olympus LFP. Time to successful intubation was recorded, as well as blood pressure, heart rate, end-tidal CO2 and oxygen saturation. Airway trauma in the operating room, the post-anaesthesia care unit, and on the first postoperative day was recorded. The intubation times using rigid laryngoscopy were less than those using fibreoptic laryngoscopy (13.6 +/- 0.9 sec (mean +/- SEM) vs 22.8 +/- 1.7 sec; P < 0.01). Oxygen saturation and end-tidal CO2 readings were not different between the two groups. After intubation, blood pressure and heart rate increased equally in both groups, returning to normal within one to two minutes. There was no difference in the airway trauma between groups. We conclude that the ultrathin fibreoptic laryngoscope is a safe and effective method for tracheal intubation in infants and may be used routinely in order to maintain fibreoptic airway skills.

Anesthesia, Inhalation↗
PubMed2005

[An unexpected difficult intubation. Bonfils rigid fiberscope].

A solution to managing intubation difficulties during anaesthesia induction is described in this article. After two attempts at laryngoscopy had failed, endotracheal intubation was achieved by the combined use of a laryngoscope and the Bonfils rigid fiberscope. The successful technique involved two anaesthesiologists, one who displaced the patient's tongue to the left ventral part of the mouth with a laryngoscope and cleared the airway by suctioning, and one who accomplished the intubation using the Bonfils rigid fiberscope by following the blade of the laryngoscope to the larynx. After securing a good view of the vocal cords, the tube was successfully inserted into the trachea. The entire procedure of intubation was accomplished within 20 s.

Algorithms↗
PubMed2002

[Fantoni translaryngeal tracheotomy (TLT) with rigid endoscopic control].

RATIONALE: The incidence of translaryngeal tracheotomy (TLT)-associated peri- and postoperative complications should be assessed prospectively. METHODS: TLT was carried out in operation-theatre under rigid endoscopic control. Peri- and postoperative complications, decanulement and late sequelae were assessed in ENT-patients. In patients of other wards only perioperative complications were evaluated. RESULTS: 41 patients (26 ENT-patients, 15 patients of other wards) were tracheotomised by TLT. Perioperatively, we observed 3 technical problems (accidental pulling through of the tracheostomy tube). In 2 of these cases TLT could be completed without problems, in 1 case TLT was converted to surgical tracheotomy. Postoperatively, we could find no complications in 26 ENT-patients. Decanulation took place after 7 days on average. We found no tracheocutaneous fistulas or tracheostenoses, scars were unobtrusive. CONCLUSIONS: TLT with rigid endoscopy is a simple percutaneous tracheotomy-technique with a low complication rate.

Adult↗
PubMed2001

Stabilization of posture by precision touch of the index finger with rigid and flexible filaments.

Light touch of the index finger with a stationary surface at non-mechanically supportive force levels (<100 g) greatly attenuates the body sway of standing subjects. In three experiments, we evaluated the properties of finger contact and of the contacted object necessary to produce postural stabilization in subjects standing heel-to-toe with eyes closed, as well as how accurately hand position can be controlled. Experiment 1 involved finger contact with flexible filaments of different bending strengths, a flat surface, and an imagined spatial position. Contact with the flat surface was most effective in attenuating sway; the flexible filaments were much less effective but still significantly better than imagined contact. Experiment 2 compared the effectiveness of finger contact with a flexible filament, a rigid filament of the same diameter, a flat surface, and an imagined spatial position. The rigid filament and flat surface conditions were equally effective in attenuating body sway and were greatly superior to contact with the flexible filament, which was superior to imagined contact. Experiment 3 included five conditions: arms by sides; finger "contact" with an imagined spatial position; finger contact with a flat surface; finger contact with a flexible filament attempting to maintain it bent; and contact with the flexible filament attempting not to bend it. The arms by sides and finger "contact" with an imagined position conditions did not differ significantly; all three conditions involving actual finger contact showed significantly less center of pressure and hand sway, but contact with the flat surface was most effective in attenuating both postural and hand displacement. In all three experiments, the level of force applied in fingertip contact conditions was far below that necessary to provide mechanical stabilization. Our findings indicate that: (1) stimulation of a small number of receptors in the fingertip is adequate to allow stabilization of sway, (2) fingertip force levels as low as 5-10 g provide some stabilization, (3) contact with a stationary spatial referent is most effective, and (4) independent control of arm and torso occurs when finger contact is allowed.

Adult↗
PubMed2004

Vesicle fluctuation analysis of the effects of sterols on membrane bending rigidity.

Sterols are regulators of both biological function and structure. The role of cholesterol in promoting the structural and mechanical stability of membranes is widely recognized. Knowledge of how the related sterols, lanosterol and ergosterol, affect membrane mechanical properties is sparse. This paper presents a comprehensive comparison of the effects of cholesterol, lanosterol, and ergosterol upon the bending elastic properties of 1-palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine giant unilamellar vesicles. Measurements are made using vesicle fluctuation analysis, a nonintrusive technique that we have recently improved for determining membrane bending rigidity. Giving a detailed account of the vesicle fluctuation analysis technique, we describe how the gravitational stabilization of the vesicles enhances image contrast, vesicle yield, and the quality of data. Implications of gravity on vesicle behaviour are also discussed. These recent modifications render vesicle fluctuation analysis an efficient and accurate method for determining how cholesterol, lanosterol, and ergosterol increase membrane bending rigidity.

Computer Simulation↗
PubMed1997

Effect of blood storage on erythrocyte/wall interactions: implications for surface charge and rigidity.

In this report, we study, under flow conditions, the interactions of stored erythrocytes with an artificial surface: a microelectrode whose charge density ranges from -15 to +27 microC/cm2. Interactions consist of red cells slowly circulating on the microelectrode and exerting a real contact with the electrode. Interaction is detected and measured by transient fluctuations of the electrolyte resistance obtained by impedance measurement of the microelectrode. Effects of aging induced by storage of whole blood at 4 degrees C show that the surface charge of erythrocytes rapidly decreases when blood is stored for more than 6 days under our experimental conditions. In comparison with trypsin-treated erythrocytes, an eight day storage induces a 60% decrease in the surface charge of red cells. After two weeks of storage, red cells are no longer negatively charged, presumably because of removal of sialic acid. Cells rigidity is significant after 6 days of storage and influences the electrical contact. Membrane rigidity increase could arise from the surface charge decrease. Finally the surface charge decrease could be importance in the use of stored blood.

Blood Preservation↗
PubMed2005

Neuronavigational neuroendoscopic surgery. Frameless free-hand maneuvering of a handy rigid-rod neuroendoscope on visualized three-dimensional computerized image guidance: trajectory to the prepontine cistern in cadaver study.

BACKGROUND: Considering the separate benefits of neuronavigation and neuroendoscopy, neuroendoscopic surgery with the aid of neuronavigation systems will play an increasingly important role in the future. Bearing this in mind, the present research project was conducted to facilitate neuronavigational neuroendoscopic surgery along the pathway to the prepontine cistern using cadaver heads. MATERIALS AND METHODS: A computer-aided, frameless image-guided stereotactic navigation system and a new type of handy rigid-rod neuroendoscope were used. The ideal entry point and the safest trajectory to the prepontine cistern through the foramen of Monro were defined in two formalin-fixed cadaver heads and clinical brain MRI data. Then, maneuvering of the neuroendoscope with the aid of the neuronavigation system was performed. RESULTS: Straight trajectories from the entry point to the prepontine cistern could be designed. For the registration accuracy of the tip of the neuroendoscope, the virtual image registered a mean error distance of 5.42 mm away from the reference point along the axis of vertical line. However, free-hand maneuvering enabled the neuroendoscope to be finely manipulated without damaging brain tissues. Neuroendoscopic anatomical views of the interpeduncular and prepontine cistern were also acquired. CONCLUSION: Interactive use of free-hand maneuvering of the handy rigid-rod neuroendoscope together with frameless neuronavigation systems plot the way to true neuronavigational neuroendoscopic surgery in a safe and reliable manner. This pairing of the most recent technological neurosurgical options with better understanding of neuroendoscopic anatomy enables the neurosurgeon to acquire broader treatment options for central nervous system diseases.

Adult↗
PubMed2001

Rigid gas-permeable contact lens fitting in LASIK patients for the correction of multifocal corneas.

BACKGROUND: Laser in situ keratomileusis (LASIK) has recently become the most commonly performed refractive surgery procedure. Results are promising in correcting low to moderate myopia. Most complications occur during the surgeon's learning curve. One of the complications is a decentration of the ablated area that causes monocular diplopia and a nocturnal halo phenomenon due to a multifocality of the corneal surface overlying the entrance pupil. The corneal shape is significantly altered after LASIK. We evaluate the efficacy of rigid gas-permeable contact lens designs and fitting techniques used in eight eyes with multifocal LASIK ablations to correct haloes and impaired night vision complaints. METHODS: We used large-diameter tetra-curved rigid gas-permeable (RGP) contact lenses for visual recovery in eight eyes of seven LASIK patients. We used the power on the transition zone of the corneal topographic map, 0.2 mm outside the ablated refractive area, for selection of the back optic zone radius of the RGP contact lenses. Procedures for lens fitting are described. Visual acuity (high-contrast logarithm of the minimum angle of resolution, LogMAR) was measured before- and 6 months after contact lens fitting. RESULTS: Large-diameter tetra-curve RGP lenses with a mean diameter of 11.85 (SD 0.16) mm were successfully used in LASIK patients with multifocal corneas. Mean best spectacle-corrected visual acuity was +0.3 LogMAR (SD 0.19; in Snellen equivalent, 20/40) and improved significantly with the contact lenses to +0.08 LogMAR (SD 0.11; in Snellen equivalent, 20/25, P=<0.01). During the follow-up period of 16.7 months, the average daily wearing time of the lenses was 12.5 h. Contact lenses with a standard geometry were not useful due to excessive movement and inadequate centration. CONCLUSIONS: Contact lenses with large diameters, in combination with selection of the back optic zone radius 0.2 mm peripheral of the refractive ablation zone, facilitate contact lens fitting to restore best-corrected visual acuity in LASIK patients with multifocal corneas.

Adult↗
PubMed2005

VASP-dependent regulation of actin cytoskeleton rigidity, cell adhesion, and detachment.

Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) proteins are established regulators of actin-based motility, platelet aggregation, and growth cone guidance. However, the molecular mechanisms involved essentially remain elusive. Here we report on a novel mechanism of VASP action, namely the regulation of tensile strength, contractility, and rigidity of the actin cytoskeleton. Compared to wild-type cells fibroblasts derived from VASP-deficient mice have thicker and more stable actin stress fibres. Furthermore focal adhesions are enlarged, myosin light chain phosphorylation is increased, and the rigidity of the filament-supported plasma membrane is elevated about three- to fourfold, as is evident from atomic force microscopy. Moreover, fibronectin-coated beads adhere stronger to the surface of VASP-deficient cells. The resistance of these beads to mechanical displacement by laser tweezers is dramatically increased in an F-actin-dependent mode. Cytoskeletal stabilization coincides with slower cell adhesion and detachment, while overall adhesion is increased. Interestingly, many of these effects observed in VASP (-/-) cells are recapitulated in VASP-overexpressing cells, hinting towards a balanced stoichiometry necessary for appropriate VASP function. Taken together, our results suggest that VASP regulates surface protrusion formation and cell adhesion through modulation of the mechanical properties of the actin cytoskeleton.

Actins↗
PubMed2001

Biochemical analysis of elastic and rigid cuticles of Cirsium horridulum.

The cuticle is a complex structure of soluble lipids, lipid polymers and polysaccharides. In addition to its functions to reduce water loss and provide a protective barrier, its mechanical properties may be significant to plant growth and development. We investigated the cuticle of Cirsium horridulum Michx. because of its involvement in the thigmonastic contraction of staminal filaments. The staminal filaments and portions of the style are surrounded by a highly elastic cuticle in contrast to the rigid cuticle of the corolla and leaves. Our aim was to determine if the biochemical composition affected the elasticity of the cuticle. We discovered that the ratio of carbohydrates to lipids is 1:7 in floral parts but 2:1 in leaf cuticle. Esterified cutin components represented about 80% of the cuticle and di-hydroxyhexadecanoic acids were the major monomers of cutin, regardless of origin. The cutin of elastic tissues is characterized by a higher content of tri-hydroxy monomers than the cutin of rigid tissues. The data suggest that hydroxyl groups enhance the hydrophilic character of the cuticle and contribute to cuticular elasticity.

Asteraceae↗
PubMed1998

Respiratory muscle rigidity in a preterm infant after use of fentanyl during Caesarean section.

UNLABELLED: Fentanyl is in many neonatal intensive care units the sedative of choice. One side-effect is, however, the possibility of muscle and/or chest wall rigidity. A pregnant woman with a critical pulmonary valve stenosis had a balloon dilatation at 26 weeks of gestation. She was put on propranolol, but went into a severe cardiac failure. In week 31, she developed pregnancy induced hypertension. Periodically absent diastolic flow in the umbilical cord was demonstrated. A Caesarean section was performed using fentanyl as analgesia. A boy weighing 1440 g, had a 1 min Apgar score of 3 without respiratory movements. Mask ventilation was tried, but chest wall expansion was not achieved despite using high pressures. He was intubated and positive pressure ventilation attempted, with the same result. Despite the use of high pressures up to 60-70 cm H2O, no chest movement could be achieved. An intravenous line was established in order to give naloxone and pancuronium. Just before the drugs were given, chest wall movements were achieved and the heart rate normalized. CONCLUSION: This is the first report on chest wall rigidity in a neonate after administration of fentanyl to the mother during Caesarean section.

Adult↗
PubMed2006

Rigid sigmoidoscopy: a potential hazard for cross-contamination.

BACKGROUND: Rigid sigmoidoscopy using a disposable or nondisposable sigmoidoscope is a common outpatient procedure. It has been assumed that the nondisposable bellows and light head of the sigmoidoscope remain free from enteric organisms so that the procedure is sterile if a disposable or nondisposable (metal) sigmoidoscope shaft is used. The aim of this study was to identify the presence of organisms within the bellows or light head of the sigmoidoscope. METHODS: Of 21 patients undergoing rigid sigmoidoscopy with a disposable instrument, bacterial cultures were taken from the inside of sterile Jackson-Pratt bulbs in 12 patients, with the bulbs being used to simulate the nondisposable insufflation bellows. In an additional nine patients, swabs were taken for culture from the inside of the nondisposable light head. RESULTS: Enteric gram-negative Escherichia coli and mixed anaerobic organisms were cultured from the Jackson-Pratt bulbs in two cases, and gram-positive organisms were cultured in another case. Gram-negative organisms, including Bacillus, Proteus mirabilis, Klebsiella, and Enterococcus faecalis, were cultured from the inside of the light head in two cases. CONCLUSION: Sigmoidoscopy using a disposable instrument is not a sterile procedure and may pose a risk of patient-to-patient cross-contamination by potentially harboring organisms in the bellows or light head.

Cross Infection↗
PubMed2002

Elastic stabilization alone or combined with rigid fusion in spinal surgery: a biomechanical study and clinical experience based on 82 cases.

The authors report their experience with the treatment of lumbar instability by a kind of spine stabilization. The elastic stabilization, which follows a new philosophy, is obtained by an interspinous device, and should be used alone in degenerative disc disease, recurrent disc herniation and in very low grade instability, or in association with rigid fusion for the prevention of pathology of the border area. In collaboration with bioengineers, we carried out an experimental study on a lumbar spine model in order to calculate stresses and deformations of lumbar disc during simulation of motion, in physiological conditions and when elastic stabilization is combined with rigid fusion. Results suggest that elastic stabilization reduces stresses on the adjacent disc up to 28 degrees of flexion. Based on this preliminary result, we began to use elastic stabilization alone or combined with fusion in 1994. To date, we have performed 82 surgical procedures, 57 using stabilization alone and 25 combined with fusion, in patients affected by degenerative disc disease, disc herniation, recurrence of disc herniation or other pathologies. Clinical results are satisfactory, especially in the group of patients affected by recurrent disc herniation, in whom the elastic device was used alone.

Adult↗