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Biomedical subjects

G Lawson

Publications and source records attributed to G Lawson.

At least 19 recordsLinked to original sources
PubMed2000

Composite hyoid-sternohyoid interposition graft in the surgical treatment of laryngotracheal stenosis.

This article reports six patients with severe laryngotracheal stenosis. The causes of stenosis were tracheotomy (two cases); prolonged endotracheal intubation (one case); laryngeal trauma (two cases); and surgery with postoperative chemo- and radiotherapy, addressing a thyroid gland follicular adenocarcinoma (one case). Two patients were already tracheotomized. The main postoperative complication was necrosis of the graft in a female patient who had previously undergone treatment for thyroid follicular adenocarcinoma. All patients were decannulated 6 months postoperatively. Five patients were then regularly followed up, but we lost contact with one patient. Comparison between pre- and postoperative pulmonary function testing revealed an increased maximum inspiratory flow (Vi max50) in five cases between 0.57 l/s and 2.18 l/s. A helical scan with 3-dimensional reconstruction of the cervical area in four patients confirmed the presence and preservation of the hyoid bone graft. Four patients remained satisfied with their postoperative voice quality, one patient was dissatisfied, and one patient was not followed up. This technique is effective in adults with severe laryngotracheal stenosis, restricted to the first tracheal rings, providing one takes into consideration the main contraindications of the procedure: past history of radiotherapy and thyroid surgery.

Adult↗
PubMed2000

Somatosensory evoked potentials as a means of assessing neurological abnormality in congenital talipes equinovarus.

Somatosensory evoked potentials (SSEPs) are a very sensitive measure of the functional integrity of the neuroaxis, including peripheral and central structures. When used in diagnostic mode they can provide additional information regarding the probable areas of dysfunction. SSEPs were recorded from 44 children (64 feet with congenital talipes equinovarus, CTEV), between the ages of 2 to 15 years, who had structural CTEV deformity previously treated by surgery, with no clinical evidence of neurological deficit. SSEPs were elicited after sequential and bilateral stimulation (0.1 ms/5 Hz/10 to 20 mA) of the posterior tibial nerve and the common peroneal nerve and were recorded cortically (P40). In half the children, additional recordings were conducted at the knee (N5), the first lumbar spinous process (N14), and the seventh cervical spinous process (N20). Eighteen children had abnormal responses, four children had non-reproducible responses, and 22 children had normal responses. Analysis of the data at different levels of the nervous system showed that eight children had abnormality at the spinal level. The surgical outcome was influenced by the neurological abnormality, with an excellent or good outcome in 34 of 36 feet with normal neurology and 19 of 28 feet where a deficit was present (p<0.05). These findings support the neurological theory as an etiological factor in CTEV deformity.

Adolescent↗
PubMed2000

MALDI-MS and colorimetric analysis of diisocyanate and polyol migrants from model polyurethane adhesives used in food packaging.

The identification of the migrants, into food simulants, from a series of polyurethane adhesives used in the manufacture of plastic film laminates for use in common food packaging is described. Commercial materials, based on four different model adhesive systems, were prepared by an industrial collaborator. The MALDI-MS fingerprint patterns of the three polyether and one polyester polyol components of these adhesives were obtained for reference purposes. The decrease in the level of diisocyanate as a migrant versus time after lamination was confirmed by colorimetric measurements. The migration of the standard polyol samples through polyethylene pouches into water at 70 degrees C has been demonstrated and also the attenuation effect for different polyols. Cured laminates in the form of pouches were used to carry out the migration experiments into distilled water, inside the pouch, at 70 degrees C over a period of 2 h. Comparison of the migration results from the food packaging laminates with those from the polyethylene film confirmed the migration of unreacted polyol components for the polyether-based systems. Cyclic oligomers from the polyol starting materials were identified as the migrants from the polyester-based adhesive.

Colorimetry↗
PubMed2000

Investigation of amine and polyol functionality in extracts of polyurethane wound management dressings using MALDI-MS.

Polyurethane (PU) foams used in wound management are produced by a reaction between aromatic diisocyanates and polyether polyols. There is concern that residues of these starting materials, which may contain aromatic amine functionality, may leach from the finished polymer during in vivo applications. Furthermore, oligomers and additives may be leached from the PU system after the polymerization process is complete. Finished polymers have, therefore, been extracted with a range of solvents, such as water, diethyl ether and dilute HCl. The extracts were subjected to MALDI-MS (matrix-assisted laser desorption ionization mass spectrometry) analysis in an attempt to determine the amine and polyol functionality. Direct MALDI-MS analysis of the wound dressing extracts indicated the presence of components based on the polyols [corrected] used in the formulation of the foam. The spacing between the peaks identified the base monomer used in the polyol. MALDI-MS analysis of the fluorescamine derivatives of model amine compounds has demonstrated the anticipated increase in mass (278 for monoamines and 278 and 556 for diamines). Similar results were obtained from the derivatization of model polyols with phenyl isocyanate, where the mass shift (n x 119) was a direct measure of the number of active hydroxyl groups. Fluorescamine labelling of PU foams shows the colour change which could be [corrected] indicative of the presence of an amine, but the subsequent MALDI-MS analysis was unable to demonstrate the anticipated increase in mass.

Amines↗
PubMed2000

Positron emission tomography with fluorodeoxyglucose for suspected head and neck tumor recurrence in the symptomatic patient.

OBJECTIVE: To analyze the impact of positron emission tomography with fluorodeoxyglucose (FDG-PET) in the treatment of patients suspected of having head and neck cancer recurrence. STUDY DESIGN: Prospective and consecutive inclusion of 44 patients presenting with clinical symptoms suggestive of head and neck tumor recurrence. METHODS: FDG-PET was compared with combined computed tomography (CT) plus magnetic resonance imaging (MRI) procedures for the differential diagnosis between tumor recurrence and benign post-therapeutic changes. For FDG-PET, the potential additional value of semiquantitative indexes was studied. The impact on patient treatment (i.e., their ability to accurately select patients for panendoscopic exploration) was analyzed retrospectively for both CT+MRI and PET workups. RESULTS: The diagnostic accuracy was found higher for PET than for combined CT+MRI: sensitivity ranged from 96% to 73%, specificity from 61% to 50%, and accuracy from 81% to 64% for PET and CT+MRI, respectively. The accuracy of FDG-PET was the highest (94%) in patients included more than 12 weeks after the end of therapy. In 15 discordant cases, PET was correct in 11 and CT+MRI in 4. Patient selection for panendoscopic exploration and biopsy was correct in 79% and 50% of patients with FDG-PET and CT+MRI, respectively. Quantification of FDG uptake had no additional value over visual analysis alone, although we found that a SUVlbm (standardized uptake value corrected for lean body mass) threshold of 3 could be helpful in patients scanned less than 12 weeks after the end of therapy. CONCLUSION: FDG-PET has a major additional diagnostic value to CT+MRI for the evaluation of the symptomatic patient suspected of having head and neck cancer recurrence. PET could have a direct impact on management by correctly selecting patients in whom a panendoscopic exploration with biopsy is indicated.

Adult↗
PubMed2000

Microsurgery of sulcus vergeture with carbon dioxide laser and injectable collagen.

Between January 1989 and June 1998, we operated on 45 patients for sulcus vergeture. The studied population encompassed 38 women (84%) and 7 men (16%). The median age was 36 (range 12 to 71 years). The surgical technique is based on a concept of Cornut and Bouchayer according to which the dissection of the epithelium adherent to the deep subepithelial plane improves the vocal fold vibration. Dissection is performed with a single-pulsed carbon dioxide laser at 2 to 3 W with a pulse duration of 0.1 second. We use the Super-pulse microwave. The Acuspot micromanipulator provides a spot size of 250 microm at 350-mm focal length. When the vocal fold is atrophic, surgery is completed with a bovine or autologous collagen injection; the median injected quantity is 0.3 mL (range 0.1 to 0.4 mL). The epithelial microflap is redraped with fibrin glue. Voice therapy is indispensable for correcting the associated hyperkinetic dysphonia. The median postoperative follow-up period is 5 months (range 1 to 18 months). In terms of median values, the maximum phonation time improved from 9 to 13 seconds, the phonation quotient improved from 296.5 to 228.5 mL/s, and the spectral analysis distribution improved by 1 class. Stroboscopic examination reveals an improvement of the vibratory symmetry, amplitude, and wave. Subjectively, the patients describe an improved ability for vocal effort and the regression or disappearance of vocal fatigue. Although the timbre is improved, the voice often remains breathy and hoarse.

Adult↗
PubMed2000

In vitro evaluation of sedative drug losses during extracorporeal membrane oxygenation.

Sedative agents are routinely administered to critically ill patients, both on and off extracorporeal membrane oxygenation (ECMO), to enable patients to be comfortable and facilitate patient management. It has been observed empirically in our paediatric intensive care unit that doses of sedative drugs required to achieve desired levels of sedation in ECMO patients are far greater than those used in non-ECMO patients. These differences could not simply be accounted for by differences in patient types, clinical status or sedation levels. We therefore undertook an in vitro evaluation of drug binding in ECMO circuits. This study investigated how the polyvinyl chloride (PVC) and silicone rubber components of neonatal ECMO circuits affect drug delivery in patients through drug sorption. Phase 1 investigated drug uptake by the two polymers in static solutions of known concentrations of four commonly used sedative drugs: lorazepam, midazolam, diazepam and propofol. Phase 2 involved the setting up of a complete neonatal ECMO circuit, injecting the drug solutions pre reservoir at a flow rate of 350 ml/min and collecting samples post-oxygenator for analysis. Phase 1 results revealed significant uptake of drugs with losses in the range 40-98% and in the order propofol > diazepam > midazolam > orazepam. Phase 2 results were similar and in the first 40 min of running an ECMO circuit only 10% of propofol passed through the circuit. These results may help to explain observed clinical phenomena and raise important issues regarding drug dosing in ECMO patients.

Biocompatible Materials↗
PubMed1999

Use of injectable autologous collagen for correcting glottic gaps: initial results.

We report our results pertaining to the use of injectable autologous collagen for the correction of dysphonia resulting from a glottic gap. To date 20 cases have been treated, 13 of which were for unilateral vocal fold immobility and 7 for sulcus vergeture and/or scar. Collagen is extracted from the skin. Approximately 5 cm2 is necessary to yield 2 ml. Injection must take place in the deep layer of Reinke's space. No patient suffered from any local or general intolerance. The phonatory glottic gap was totally or partially closed. In the paralysis group, the improvements were the following: the median maximum phonation time improved from 5.8 seconds to 11 seconds, the median mean flow rate from 0.13 ml/s to 0.09 ml/s, the median glottic gap from 8.4 to 4.5 ml/dB per s, the median intensity range from 21 to 29 dB, and the median frequency range from 141 to 195 Hz. The spectral analysis layout classification improved from 2 to 3.

Adult↗
PubMed1999

A new technique for laser-assisted uvulopalatoplasty: decision-tree analysis and results.

OBJECTIVE: Report a new technique of laser-assisted uvulopalatoplasty (LAUP) for snoring performed as a one-stage procedure. STUDY DESIGN: A decision-tree was used in a prospective study of 89 patients from April 1994 to May 1997. It included a fiberscopy and Muller's maneuver, rhinomanometry, pH monitoring, computed tomography scan to measure the pharyngeal lumen, pulse oximetry, and polysomnography in case of sleep apnea syndrome was suspected. METHODS: The authors performed their LAUP technique on 43 patients (48.5%) whose snoring was mainly caused by the velum. This technique consists of scarifying the velum by vaporizing the mucosa and the submucosa along a rectangle extending from the palatal dimple to the uvula and having a width of 1.5 to 2 cm. Vaporization of the palatal arches follows without exceeding the junction of the anterior and posterior pillars in height. The uvula is cut if necessary, preserving a length of at least 0.5 cm. The other patients underwent different procedures according to the cause of snoring. RESULTS: There was no significant difference between LAUP and uvulopalatoplasty (UPPP) regarding pain. No permanent phonatory disorders and no regurgitation occurred. Satisfaction evaluated on a scale ranging from 0 to 10 was equivalent for the two techniques: mean value = 7.68 (+/-2.18) for LAUP and 8.60 (+/-2.27) for UPPP. The mean follow-up was 17 months (range, 1-37 mo). Satisfaction was also identical for all techniques. CONCLUSION: Our LAUP technique combined with other procedures according to a decision-tree is efficient and safe.

Adult↗
PubMed1999

Carbon dioxide laser microsurgery of benign vocal fold lesions: indications, techniques, and results in 251 patients.

Two hundred fifty-one carbon dioxide laser-assisted cases of microphonosurgery are reported. Our series includes 167 women (66.5%) and 84 men (33.5%), with a mean age of 41 (+/-11) years. Single lesions represent 67.8% (n = 170) of the cases, with 20% (n = 50) being nodules, 18% (n = 44) Reinke's edema, 9% (n = 23) polyps, 8% (n = 19) sulci and related lesions, 6% (n = 16) mucosal cysts, 4% (n = 10) scars, 2% (n = 4) granulomas, and 2% (n = 4) vascular corditis. The cases with 2 or 3 lesions represented 32% (n = 81). Carbon dioxide laser-assisted microphonosurgery is efficient, provided the working parameters are strictly adhered to: micromanipulator micropoint providing a 250-microm laser beam for a 400-mm working distance; 0.1-second single pulses; and maximum power of 3 W with the superpulse wave. Glutaraldehyde-cross-linked collagen remains our filling material of choice in cases of vocal fold atrophy. Fibrin glue is useful for covering the resection area and for setting the microflaps. Microphonosurgery cannot be dissociated from speech therapy, the planning and duration of which, in relation to the procedure, depend on the nature of the initial lesion. Twenty to 30 sessions are usually adequate, but 6 months may be necessary in the case of sulcus vergetures. Our operating technique is derived from the microphonosurgery procedures with cold instruments. In addition to the classic advantage with regard to hemostasis, the carbon dioxide laser micropoint seems to make the dissection of microflaps easier.

Adult↗
PubMed1999

Carbon dioxide laser debulking for obstructing endolaryngeal carcinoma: a 10-year experience.

The results of the carbon dioxide (CO2) laser debulking procedure for obstructing endolaryngeal carcinoma were analyzed in terms of efficiency, complications, secondary tracheotomy rate, and peristomal recurrence rate in a series of 50 patients consecutively managed at our department. The CO2 laser was used to reestablish a safe airway without resorting to tracheotomy and without performing a transoral resection. Our series included 42 patients in a pre-definitive treatment group (group 1) and 8 patients in a palliation group (group 2). Complications included death, pneumonia from inhalation, and cutaneous burns in 2 patients, 1 patient, and 1 patient, respectively. Thirty-two percent of patients required a repeat laser treatment to maintain the airway. Overall success rates of 92.8% and 87.5% were achieved in group 1 and group 2 patients, respectively. None of the variables under analysis could predict the success of the CO2 laser debulking procedure. The overall incidences for secondary tracheotomy were 4.7% and 0% in group 1 and group 2 patients, respectively. Peristomal recurrence was not encountered in patients managed with definitive therapy with curative intent.

Adult↗
PubMed1999

Correcting vocal fold immobility by autologous collagen injection for voice rehabilitation. A short-term study.

We report on a short-term clinical study of injectable autologous collagen (Vocalogen) used to correct dysphonias arising from vocal fold immobility. The collagen is extracted from skin taken from the lower abdominal quadrant area or from just above the bikini line. About 30 cm2 of skin are required to provide 2 mL of injectable collagen. The histologic examination of the preparation before injection disclosed the presence of elastin fibers and some clusters of epithelial cells, beside the collagen fibers. The collagen is naturally reticulated, and the molecule is preserved in its entirety. The technique is exactly the same as that reported for bovine collagen: injection into Reinke's space, under general anesthesia, monitored by direct microlaryngoscopy. The amount injected is also similar: 1.5 mL for correction of glottic insufficiency in which the immobile vocal fold is in the intermediate position. Eight patients were injected, and the average follow-up was 4.5 months. Voice assessments made before and after the treatment included stroboscopy, subjective and perceptual judgments, and aerodynamic and acoustic measurements. The functional results were similar to those obtained with bovine collagen. No complications arose. The probability of any hypersensitivity reaction, always a possibility to be feared with bovine collagen, is negligible with the autologous collagen. Long-term results are as yet unknown, but from the fact that the collagen molecular structure is intact and there is little risk of foreign body response, it would be expected that autologous preparations would be more stable than bovine collagen; this appears to be the case in cosmetic applications. Autologous collagen could be employed for the same indications as bovine collagen, provided that a delay of 45 days (the time required to prepare the injectable collagen) is acceptable. The amount of collagen required is also a limiting factor, since the patient's own skin is the starting donor material.

Aged↗
PubMed1999

Palliative treatment for tracheal stenoses using carbon dioxide laser and the Gianturco stent. Long-term results.

Between September 1992 and March 1998, the self-expandable Gianturco prosthesis was inserted in 23 patients suffering from tracheal stenosis. After radial incision and dilation of the stenosis as described by Shapshay, the positioning of the stent was performed during an endoscopic procedure under optical control. The prosthesis used was a double-ring stent 50 mm long and 20 mm in diameter. The follow-up period ranged between 0.5 and 67 months with an average of 31 +/- 18 months. Pulmonary function tests showed an average improvement of the peak expiratory flow (50%) from preoperative results of 1.06 +/- 0.60 L/s to short-term postoperative results of 2.08 +/- 0.78 L/s and long-term postoperative results of 2.11 +/- 0.78 L/s. The mean peak inspiratory flow (50%) improved from 1.43 +/- 0.85 L/s to 2.40 +/- 1.29 L/s at short term and to 2.56 +/- 1.20 L/s at long term. Eight patients out of the 23 had to undergo a second endoscopic procedure: 3 patients for granuloma vaporization; 1 patient to change a malpositioned stent; 2 patients to add a second stent because of insufficient tracheal enlargement; and 2 patients to resect mucosal membranes between the 2 stent rings and to place a second stent. Optical control of the accurate positioning and use of this model of Gianturco prosthesis helped to avoid the severe complications described in the literature (migration, extrusion, fracture, wall erosion. and hemorrhage). The follow-up must particularly target the prevention of granulomas. The self-expandable Gianturco prosthesis can be advocated for long-term palliative treatment of tracheal stenoses that are inoperable by an external surgical approach.

Aged↗
PubMed1999

Transoral laser microsurgery is the recommended treatment for early glottic cancers.

Medical terminology frequently mistakes the instrument for the surgical procedure: endoscopic excision of laryngeal cancers existed long before laser came into use. Lasing obeys the same rules as those of suspension laryngoscopy: if adequate laryngeal exposure is not attained, then the procedure is at risk of being incomplete and of providing few satisfactory results. Because a certain degree of literary anarchy exists in terms of definitions for the different cordectomy types, the Nomenclature Committee of the European Laryngological Society has proposed a classification. This categorization is a synthesis and a compromise between members of the Society who had developed and used, for several years, a personal classification. The proposed classification has two aims: to better understand each surgeon's technique in function of the tumoral extent; and to compare more rigorously the postoperative results. This classification includes the following procedures: Subepithelial cordectomy or decortication (Type I); Subligamentous cordectomy (Type II); Transmuscular cordectomy (Type III); Total or complete cordectomy (Type IV); Extended cordectomy encompassing the contralateral vocal fold (Type Va); encompassing the arytenoid (Type Vb); encompassing the ventricular fold (Type Vc); encompassing the subglottis (1 cm) (Type Vd).

Endoscopy↗
PubMed1998

Saturation of ecosystems with toxic metals in Sudbury basin, Ontario, Canada.

Mining and resource recovery activities have not been kind to ecosystems in the Sudbury basin, Ontario. The combination of logging, smelting, fires and erosion resulted in an unusual anthropogenic ecosystem of denuded barren land with lifeless lakes, or a micro-desert. Since the 1970s, however, the concerted efforts made to reduce the emissions and rehabilitate parts of the degraded ecosystem have resulted in improvements in water quality, and recoveries in phytoplankton, zooplankton, zoobenthos and fish communities but have had little impact on toxic metal concentrations in many lakes. We show that most of the catchments in the Sudbury basin have become saturated with Cu and Ni, and some with Zn and Pb. It is estimated that mobilization of metals stored in soils and glacial overburden by surface runoff, groundwater drainage and wind re-working of tailings can sustain the high concentrations of Cu and Ni in many lakes for well over 1000 years. Strategies to immobilize the pollutant metals in the watershed rather than further emission controls may be required for dealing with high levels of toxic metals in surface waters of the saturated ecosystems.

Copper↗
PubMed1998

A new epiglottoplasty procedure for the treatment of intractable aspiration.

Intractable aspiration may require diversion of the airway from the pharynx. The epiglottoplasty procedure involves suturing the epiglottis onto the perimeter of the larynx without creating resistance to the natural lines of force of the epiglottic cartilage. The procedure starts by an anterior subhyoid pharyngotomy. The epiglottis is released from the pre-epiglottic space and the thyroepiglottic ligament is sectioned. The disinsertion is completed in the laryngeal lumen by sectioning the epiglottis on each side by following its edges. The pharyngoepiglottic folds are preserved so as to serve as the rotational axis for the freed epiglottis. The petiole of the epiglottis is anchored to the posterior commissure and the free edge of the epiglottis above the ala and the angle of the thyroid cartilage, while the lateral sides of the suprahyoid epiglottis are sutured to the superior part of the arytenoids. This procedure was performed successfully in three patients with intractable aspiration.

Aged↗
PubMed1997

CO2 laser in the diagnosis and treatment of early cancer of the vocal fold.

A total of 74 patients underwent cordectomy using CO2 laser for either diagnosis or treatment of an early cancer of the vocal fold. Type I cordectomy consisted in the resection of the entire epithelium, while leaving the vocal ligament intact. Type II cordectomy involved removal of the vocal fold from the vocal process to the anterior commissure and passing through the inferior thyroarytenoid muscle. Type IIIA required vocal fold resection along the internal side of the thyroid ala, while type IIIB included removal of the anterior commissure. Type I cordectomies were carried out with an Acuspot micromanipulator, which provided a 250-micron-diameter beam for a working distance of 400 mm, and in the shot-by-shot cutting mode with 3 W power superpulse. This cordectomy was carried out in 39 patients and a dysplasia or an early carcinoma were detected in 45.9% of cases. Type II and type III procedures were performed with the Microslad micromanipulator having a 700-micron-diameter beam in the continuous cutting mode, 7 W power superpulse. Fifteen cases were treated by type II cordectomy, of which 3 T1aN0M0 cases underwent postoperative radiotherapy due to insufficient resections and 2 cases with T1bN0M0 tumors later underwent reconstructive laryngectomy. A type III cordectomy was used for 14 cases of T1aN0M0 carcinomas and 3 cases of severe dysplasia. The margins of resection were found to be positive histologically in 23.5% of these cases, making frozen section examinations mandatory at time of surgery. Results of all procedures showed that voice was best after a type I cordectomy where only the epithelium was resected. In the type II and type III cordectomies, the quality of voice depended on the development of a fibrous fold and the absence of anterior synechia in the healed larynx.

Adult↗