Biomedical subjects

G Lawson

Publications and source records attributed to G Lawson.

At least 19 recordsLinked to original sources

PubMed2006

An ultra-clean firn core from the Devon Island Ice Cap, Nunavut, Canada, retrieved using a titanium drill specially designed for trace element studies.

An electromechanical drill with titanium barrels was used to recover a 63.7 m long firn core from Devon Island Ice Cap, Nunavut, Canada, representing 155 years of precipitation. The core was processed and analysed at the Geological Survey of Canada by following strict clean procedures for measurements of Pb and Cd at concentrations at or below the pg g(-1) level. This paper describes the effectiveness of the titanium drill with respect to contamination during ice core retrieval and evaluates sample-processing procedures in laboratories. The results demonstrate that: (1) ice cores retrieved with this titanium drill are of excellent quality with metal contamination one to four orders of magnitude less than those retrieved with conventional drills; (2) the core cleaning and sampling protocols used were effective, contamination-free, and adequate for analysis of the metals (Pb and Cd) at low pg g(-1) levels; and (3) results from 489 firn core samples analysed in this study are comparable with published data from other sites in the Arctic, Greenland and the Antarctic.

Air Pollutants↗

PubMed2003

Voice prostheses: long-term follow-up retrospective study (three- to sixteen-year follow-up of 22 patients).

BACKGROUND: Thirty-five patients using tracheoesophageal voice with a 3- to 16-year follow-up were investigated. We analyzed functional voice outcome, voice prosthesis (VP) lifespan, and VP-related complications. METHODS: Between 1987 and 2001, 81 patients underwent total laryngectomy (TL). The 35 currently surviving patients (31 men, 4 women) were studied for VP lifespan and VP-related complications encountered up to 16 years after surgery. For voice rehabilitation, the 35 laryngectomies of our study required 178 prostheses. Short- and long-term voice results of 22 patients were compared by objective voice examination: maximum phonation time (MPT), intensity range (Int.), fundamental frequency (F0), frequency analysis (FA), and voice handicap index (VHI). RESULTS: Long-term results are: F0=131 (range: 30-250); Int=22.5 dB (range: 17-35 dB); MPT=4 sec (range: 2-12 sec); FA=3 (range: 1-4); VHI=38/120 (range: 8-73). Short- vs long-term outcome comparison shows the following values: F0: 93 vs 135 Hz; Int: 25 vs 24 dB; FA: 1 vs 3; and MPT: 21 vs 4 sec. The mean VP lifespan is 165.5 days for Provox (range: 2 days-30 months); 143.5 days for Blom-Singer (range: 10 days-24 months); and 195 days for VoiceMaster (6-7 months). Postoperative complications involved 12 cases of periprosthetic leakage (6.74%); 31 granulomas (17.4%); 3 partial stenoses of the tracheoesophageal tract (1.6%); and 1 temporarily removed VP (0.5%). CONCLUSIONS: Complications are generally resolved during standard office-setting examination. The commercially available VPs are complementary, used according to the diverse characteristics of each VP.

Acoustics↗

PubMed2003

Use of a laryngeal mask during medialization laryngoplasty.

OBJECTIVES: In certain instances medialization thyroplasty under local anesthesia is awkward for the patient and complicates surgery. Moreover, for certain operations such as for sulcus vergeture or presbyphonia, subjective auditory appreciation of vocal improvement under operating room conditions is not efficient. In those various instances, we therefore perform thyroplasty under general anaesthesia using a laryngeal mask, and under fibrerscopic control. MATERIAL AND METHOD: A joint connecting the laryngeal mask to the ventilation tube is angled and comprises a small valve through which a fiberscope is slipped. We have used this method since April 99 for 11 surgery procedures. RESULTS AND CONCLUSION: To date, we have not encountered intraoperative complications that have required intubating the patient in order to continue surgery. It can, however, occur that a change in head posture during surgery displaces the mask. In that event, surgery must be momentarily interrupted in order to re-position the mask. The vocal results met expectations.

Adolescent↗

PubMed2002

Laser-assisted surgery addressing snoring long-term outcome comparing CO2 laser vs. CO2 laser combined with diode laser.

Our study encompasses 61 patients (49 men--80.3%; 12 women--19.7%) treated from September 1998 through August 2001. Mean follow-up covers 25 months (range: 7-43 months). Our CO2-LAUP technique involves vaporizing the palatine mucosa along a rectangular surface from the palatal dimple to the base of the uvula; trimming the palatine arches under the velum; and resecting the uvula. For 22 patients, we employed intravelar diode laser coagulation in the expectation of reducing the postoperative pain whilst achieving the same therapeutic effectiveness. There is no pain difference between the CO2-LAUP technique versus that combining intravelar diode laser coagulation with CO2 laser uvula resection and trimming of the palatine arches. Mean maximal pain reaches 6.93 +/- 3.55 with CO2 laser and 6.95 +/- 3.64 with CO2 laser plus diode laser. Similarly, both techniques involve the same mean algesic period of 22 days with the day of maximal pain at 1 week after surgery. Associating base of tongue vaporization significantly increases the algesic period (p = 0.042). No long-term complications were observed in relation to intravelar coagulation or LAUP, whether combined or not with base of tongue vaporization. In terms of patients satisfaction, no significant difference exists between the various surgical techniques of the velum alone. The satisfaction rate reaches 5.26 +/- 3.92 with CO2 laser and 5.82 +/- 2.67 with the CO2 laser plus diode laser. Satisfaction is statistically identical when base of tongue vaporization is included in the procedure.

Female↗

PubMed2001

Factors modulating the epithelial response to toxicants in tracheobronchial airways.

As one of the principal interfaces between the organism and the environment, the respiratory system is a target for a wide variety of toxicants and carcinogens. The cellular and architectural complexity of the respiratory system appears to play a major role in defining the focal nature of the pulmonary response to environmental stressors. This review will address the biological factors that modulate the response of one of the major target compartments within the respiratory system, the tracheobronchial airway tree. Individual airway segments respond uniquely to toxic stress and this response involves not only the target cell population, e.g. epithelium, but also other components of the airway wall suggesting a trophic interaction within all components of the airway wall in maintaining steady state and responding to injury. A number of biological factors modulate the nature of the response, including: (1) metabolic potential at specific sites for activation and detoxification; (2) the nature of the local inflammatory response; (3) age of the organism at the time of exposure; (4) gender of the exposed organism; (5) history of previous exposure; and (6) species and strain of the organism exposed.

Aging↗

PubMed2001

Improving the functional outcome of Tucker's reconstructive laryngectomy.

BACKGROUND: The goal of reconstructive laryngectomy addressing glottic carcinoma, as described by Tucker, is twofold: achieve local control and preserve as much as possible the physiological laryngeal function. METHODS: The study consisted of long-term assessment of oncological, deglutitory, and vocal outcome in 34 patients following Tucker's reconstructive laryngectomy. Postoperative follow-up included fiberscopic examination, videoradiography, and voice assessment after speech rehabilitation. RESULTS: The 5-year overall survival rate was 92% +/- 5%. Fiberscopic examination and videoradiography contributed to observing and understanding the rehabilitation process and impairment to its progress. Two main compensatory movements were identified: the anticipatory backward movement of the tongue base (50%) and the anticipatory upward laryngeal motion (15%). Both movements occurred simultaneously at the beginning of the pharyngeal stage of the swallow (35%). The median duration prior to tracheostomy tube removal was 14 days. Swallowing of solids resumed on day 9 (median), and liquid intake (water and soup) resumed on day 12 (median). The median duration of hospitalization was 16 days. Following speech rehabilitation, the latest follow-up visit measured as follows: the mean conversational voice intensity at 64 dB (range, 57-79 dB); the mean maximum intensity at 87 dB (range, 78-96 dB); the minimum intensity at 54 dB (range, 45-65 dB); the mean maximum phonation time at 16 seconds (range, 10-29 seconds); and the mean phonation quotient at 284 mL/second (range, 205-341 mL/second). According to our classification, voice spectral analysis revealed 19 class-III patients, 12 class-II patients, and three class-I patients. CONCLUSION: Tucker's reconstructive laryngectomy is reliable in terms of both the oncological and functional outcome. Fiberscopic examination and videoradiography are two complementary methods for assessing postoperative deglutition.

Adult↗

PubMed2001

Medialization framework surgery for voice improvement after endoscopic cordectomy.

Seven dysphonic patients who had previously undergone total or extended cordectomy underwent laryngeal framework medialization. A minimum 6-month period between cordectomy and framework surgery was enforced to allow the vocal cord to scar and form a fibrous "neocord", to evaluate the voice recovery achieved by speech therapy alone and avoid the risk of operating on a patient with undiagnosed early recurrence. The operation is performed with fiberscopic control under general anesthesia. These operating conditions are required because undermining the fibrous tissue at the inner side of the thyroid ala is a lengthy and laborious procedure. This step is necessary to ensure easy placement of the implant. Caution must be taken to avoid tearing the fibrous tissue, with consequent risk of prosthesis extrusion. The cartilage window is left intact. Whereas cartilage implants remain indicated for minor gaps, we advocate Friedrich's implant for wider gaps. The vocal outcome revealed an increased median maximum phonation time from 5 s (range 2-12 s) to 7.5 s (range 3-23 s); a reduced phonation quotient from 516.5 ml/s (range 235-1000 ml/s) to 222 ml/s (range 146-595 ml/s); a slightly increased modal intensity from 61.5 dB (range 57-75 dB) to 67 dB (range 46-68 dB); an improved intensity range from 24.5 dB (range 16-36 dB) to 30 dB (range 16-62 dB); a steady fundamental frequency from 150 Hz (range 132-290) to 152 Hz (range 125-200); and an increased median spectral analysis class from 2 (range 1-3) to 3 (range 2-4). Subjectively, the patients noted that, throughout the day, phonation required less effort and induced less vocal fatigue.

Durapatite↗

PubMed2001

[Laryngitis revealing bacterial tracheitis in a five-year-old child].

CASE REPORT: We report the case of a five-year-old boy with clinical features of croup and left lower lobe pneumonia. Response to inhaled adrenaline and dexamethasone was incomplete and he developed respiratory distress. Direct laryngoscopy performed in the operating room showed mild glottic and subglottic inflammation. On bronchoscopy, there was thick pus coming from the left lower lobe. He was intubated for three days and regular toilet brought back thick pus. Tracheal fluid culture grew Haemophilius influenzae. COMMENTS: We suggest that he had bacterial tracheitis but that the tracheal involvement was not prominent at the time of diagnosis. CONCLUSION: Laryngoscopy and bronchoscopy in specialized surroundings should be considered for each child with croup unresponsive to conventional treatment, especially in case of lower respiratory tract involvement.

Administration, Inhalation↗

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↗