Biomedical subjects

N B Powell

Publications and source records attributed to N B Powell.

At least 37 records · Page 2Linked to original sources

PubMed1999

Overview of phase I surgery for obstructive sleep apnea syndrome.

It is well established that obstructive sleep apnea syndrome is associated with increased morbidity and mortality. Surgical therapy has been demonstrated to be a viable treatment option for cure. Thorough presurgical evaluation with the identification of the type of airway abnormality is mandatory to allow for the utilization of a surgical protocol that results in improved clinical outcomes. Phase I surgical protocol is designed to apply specific surgical procedures to alleviate the obstruction(s) present. Following a logical, stepwise surgical approach in airway reconstruction will minimize surgical interventions and avoid unnecessary operations. The incorporation of a risk-management protocol will minimize treatment complications while achieving cure.

Female↗

PubMed1999

Overview of phase II surgery for obstructive sleep apnea syndrome.

Maxillomandibular advancement is an extremely effective surgical procedure for the treatment of obstructive sleep apnea syndrome. When properly executed, it is associated with minimal morbidity and is well accepted by patients. It is a treatment option that achieves long-term care.

Aged↗

PubMed1998

Surgical management of the hypopharyngeal airway in sleep disordered breathing.

The etiology of sleep disordered breathing is collapse or obstruction of the upper airway during sleep. This obstruction may be localized to one or two areas or may encompass the entire upper airway passages to include the nasal cavity, nasopharynx, oropharynx, hypopharynx, and larynx. The presurgical evaluation, which includes polysomnography, a comprehensive head and neck physical examination, fiberoptic nasopharyngoscopy, and lateral cephalometric analysis is essential in directing surgical therapy in a site specific approach. The surgical procedures available to address hypopharyngeal and base of the tongue collapse include inferior sagittal mandibular osteotomy and gengioglossus advancement, hyoid myotomy and suspension, laser midline glossectomy, lingualplasty, partial glossectomy, and maxillomandibular advancement surgery. The Riley-Powell-Stanford Surgical Protocol has proven to be an effective and safe method for controlling upper airway collapse in sleep disordered breathing.

Airway Obstruction↗

PubMed1998

Long-term results of surgical management of sleep disordered breathing: are our patients really benefiting?

The etiology of sleep disordered breathing (SDB), which includes upper airway resistance syndrome (UARS) and obstructive sleep apnea syndrome (OSAS), is collapse or obstruction of the upper airway during sleep. Surgical management was the first treatment modality available for SDB. Since the introduction of the tracheotomy to treat OSAS, there have been numerous procedures discovered to address the various sites of obstruction of the upper airway. This article reviews the long-term surgical results and may improve one's insight into the successes of surgical therapy for SDB.

Airway Obstruction↗

PubMed1998

Radiofrequency volumetric tissue reduction for treatment of turbinate hypertrophy: a pilot study.

OBJECTIVES: Ideal treatment for nasal obstruction caused by turbinate hypertrophy remains in question. Medical therapy is often ineffective. Surgical procedures have associated morbidity including pain, bleeding, crusting, adhesion, infection, and dryness. Radiofrequency has recently been shown to be safe and effective in volumetric tissue reduction of the tongue in the animal model and of the palate in human beings. We prospectively evaluate the safety and effectiveness of radiofrequency volumetric tissue reduction (RFVTR) for the treatment of nasal obstruction caused by inferior turbinate hypertrophy. METHODS: Twenty-two consecutive patients with nasal obstruction and associated inferior turbinate hypertrophy refractory to medical therapy were evaluated for RFVTR. The study design limited the region of treatment to the anterior third of the inferior turbinate. The procedures were performed in an ambulatory facility with patients under local anesthesia. Clinical examinations, patient questionnaires, and visual analog scales were used to assess treatment outcomes. RESULTS: No adverse effects were encountered, including bleeding, crusting, dryness, infection, adhesion, or a worsening of obstruction. Mild edema was noted in all patients but was of short duration (24 to 48 hours). Posttreatment discomfort was well controlled with acetaminophen. Eight weeks after treatment, nasal breathing improved in 21 of 22 patients, with a 58.5% reduction in severity and a 56.5% decrease in the frequency of nasal obstruction. CONCLUSION: The results of this study demonstrate that RFVTR of the hypertrophic inferior turbinate is associated with minimal adverse effects. Furthermore, this new treatment modality achieves subjective improvement in patients with symptoms of nasal obstruction. However, because of the small sample size and short follow-up, future investigations are needed to fully evaluate the use of RFVTR in the treatment of nasal obstruction caused by turbinate hypertrophy.

Adolescent↗

PubMed1998

Surgical management of obstructive sleep apnea syndrome.

This article discusses the history of operative management of obstructive sleep apnea syndrome and reviews a protocol for surgical intervention. An overview of diagnostic procedures and evaluation is also presented, and emerging technology for the management of this disorder is touched on.

Clinical Trials as Topic↗

PubMed1998

Differential binding of apo and holo human transferrin to meningococci and co-localisation of the transferrin-binding proteins (TbpA and TbpB).

Apo-transferrin (apo-hTf) and holo-transferrin (holo-hTf) were separately conjugated to 15-nm colloidal gold. Iron-restricted Neisseria meningitidis strain SD (B:15:P1.16) bound up to three-fold more holo-hTf than apo-hTf (p <0.001). The ability of meningococcal mutants lacking either transferrin-binding protein A (TbpA) or TbpB to discriminate between apo-hTf and holo-hTf was also investigated. There was no significant difference between the amount of gold-labelled apo-transferrin bound by the isogenic TbpA mutant (expressing TbpB) and the parent strain, whereas an isogenic TbpB mutant (expressing TbpA) bound significantly less gold-labelled apo-hTf. The isogenic TbpA and TbpB mutants and the parent strain all bound significantly more holo-hTf than apo-hTf, whereas the double 'knock-out' mutant failed to bind hTf irrespective of the iron-loading. In the isogenic mutants, TbpB was more effective in binding either apo- or holo-hTf than TbpA. Monoclonal antibodies against TbpA and TbpB were used to co-localise the transferrin-binding proteins on strain SD. The ratio of TbpA:TbpB was approximately 1:1. TbpA and TbpB were occasionally observed in close proximity to each other, but the two proteins were generally quite separate, which may indicate that they do not usually form a complex to act as a transferrin receptor.

Antibodies, Monoclonal↗

PubMed1998

Molecular cloning of a 32-kilodalton lipoprotein component of a novel iron-regulated Staphylococcus epidermidis ABC transporter.

Our previous studies identified two iron-regulated cytoplasmic membrane proteins of 32 and 36 kDa expressed by both Staphylococcus epidermidis and Staphylococcus aureus. In this study we show by Triton X-114 phase partitioning and tritiated palmitic acid labelling that these proteins are lipoproteins which are anchored into the cytoplasmic membrane by their lipid-modified N termini. In common with those of some other gram-positive bacteria, these highly immunogenic lipoproteins were released from the bacterial cell into the culture supernatants, with release being promoted by growth of the bacteria under iron-restricted conditions. Immunoelectron microscopy with a monospecific rabbit antiserum to the 32-kDa S. epidermidis lipoprotein showed that the majority of the antigen was distributed throughout the staphylococcal cell wall. Only minor quantities were detected in the cytoplasmic membrane, and exposure of the lipoprotein on the bacterial surface was minimal. A monoclonal antibody raised to the 32-kDa lipoprotein of S. aureus was used in immunoblotting studies to investigate the conservation of this antigen among a variety of staphylococci. The monoclonal antibody reacted with polypeptides of 32 kDa in S. epidermidis and S. aureus and of 40 kDa in Staphylococcus hominis. No reactivity was detected with Staphylococcus lugdunensis, Staphylococcus cohni, or Staphylococcus haemolyticus. The gene encoding the 32-kDa lipoprotein from S. epidermidis has been isolated from a Lambda Zap II genomic DNA library and found to be a component of an iron-regulated operon encoding a novel ABC-type transporter. The operon contains three genes, designated sitA, -B, and -C, encoding an ATPase, a cytoplasmic membrane protein, and the 32-kDa lipoprotein, respectively. SitC shows significant homology both with a number of bacterial adhesins, including FimA of Streptococcus parasanguis and ScaA of Streptococcus gordonii, and with lipoproteins of a recently described family of ABC transporters with proven or putative metal ion transport functions. Although the solute specificity of this novel transporter has not yet been determined, we speculate that it may be involved in either siderophore- or transferrin-mediated iron uptake in S. epidermidis.

ATP-Binding Cassette Transporters↗

PubMed1998

Radiofrequency volumetric tissue reduction of the palate in subjects with sleep-disordered breathing.

STUDY OBJECTIVES: To evaluate pain, swallowing, speech, edematous response, tissue shrinkage, sleep, snoring, and safety (energy limits and adverse effects) following radiofrequency (RF) treatment to the palate in 22 subjects with sleep-disordered breathing. DESIGN: This investigation is a prospective nonrandomized study. Polysomnography, radiographic imaging, and infrared thermography, along with questionnaires and visual analog scales, were used to evaluate the effects of RF treatment to the palate. SETTING: Treatments were delivered on an outpatient basis at Stanford University Medical Center. PATIENTS: Twenty-two healthy patients (18 men), with a mean age of 45.3+/-9.1 years, were enrolled. All were snorers seeking treatment and met predetermined criteria: a respiratory disturbance index < or = 15, oxygen saturation > or = 85%, and a complaint of daytime sleepiness. INTERVENTION: RF was delivered to the submucosa of the palate with a custom-fabricated electrode for a mean duration of 141+/-30 s with a mean of 3.6+/-1.2 treatments per patient. Reduction of their snoring scores determined the end point of the study. RESULTS: Neither speech nor swallowing was adversely affected. Pain was of short duration (0 to 48 h) and was controlled with acetaminophen. There were no infections. Although there was documented edema at 24 to 48 h, there were no clinical airway compromises. Polysomnographic data showed improvement in esophageal pressure measurements of the mean nadir and the 95th percentile nadir (p=0.031, p=0.001) respectively, as well as the mean sleep efficiency index (p=0.002). Radiographic imaging showed a mean shrinkage of 5.5+/-3.7 mm (p< or =0.0001). Subjective snoring scores fell by a mean of 77% (8.3+/-1.8 to 1.9+/-1.7, p=0.0001) accompanied by improved mean Epworth sleepiness scores (8.5+/-4.4 to 5.2+/-3.3, p=0.0001). CONCLUSION: The results of this investigation allowed the formulation of safety parameters for RF in this defined population with mild sleep-disordered breathing. There was a documented tissue reduction and improvement in symptoms in all subjects. However, given the small sample size and short-term follow-up, these results should be confirmed by further investigation.

Ambulatory Surgical Procedures↗

PubMed1997

Obstructive sleep apnea surgery: risk management and complications.

BACKGROUND: Hypoxemia, hypertension, airway obstruction, and death have been associated with surgery for obstructive sleep apnea syndrome (OSAS). Patient analysis was undertaken to identify potential factors that could affect risk-management outcome. METHODS: One hundred eighty-two consecutively treated patients with OSAS undergoing 210 procedures were evaluated. Fifty-four factors were analyzed. RESULTS: Group characteristics included a mean age of 48.2 years, a mean respiratory disturbance index of 42.3, and a mean low oxyhemoglobin desaturation (LSAT) of 77.5%. Surgery included a combination of uvulopalatopharyngoplasty (162 patients; 77%) and maxillofacial procedures (173 patients; 82%). Patients with a respiratory disturbance index greater than 40 and an LSAT less than 80% (117 patients; 64%) were maintained on nasal continuous positive airway pressure. Thirty-nine patients (18.6% had difficult intubations. There was a positive correlation (p > 0.001) of difficult intubations, neck circumference (> 45.6 cm) and skeletal deficiency (Sella-Nasion-Point B < 75 degrees). All tubes were removed with the patient awake in the operating room with two transient episodes of airway obstruction. One hundred forty-eight of the patients (70.5%) required postoperative intravenous antihypertensive medications. Patients with a preoperative history of hypertension had a significantly increased risk (p > 0.01) of requiring intraoperative and postoperative intravenous antihypertensive medications. The mean hospital stay was 2.2 days (SD +/- 0.9). Analgesia was achieved with intravenous morphine sulfate or meperidine HCl (intensive care unit) and oral oxycodone (non-intensive care unit). There were no significant oxyhemoglobin desaturations, irrespective of severity of OSAS or obesity (mean LSAT day 1, 94.8% (SD +/- 2.4); mean LSAT day 2, 95.5% (SD +/- 1.6)). Complications included postoperative bleeding (n = 4), infection (n = 5), seroma (n = 3), arrhythmia (n = 4), angina (n = 1), and loss of skeletal fixation (n = 1). CONCLUSION: Intraoperative airway risks can be reduced by use of fiberoptic intubation in patients with increased neck circumference and skeletal deficiency. Patients with OSAS are at a significantly increased risk for hypertension. Nasal continuous positive airway pressure eliminated the postoperative risk of hypoxemia, which allowed the use of adequate parenteral or oral analgesics.

Female↗

PubMed1997

Radiofrequency volumetric reduction of the tongue. A porcine pilot study for the treatment of obstructive sleep apnea syndrome.

STUDY OBJECTIVE: To investigate, in an animal model, the feasibility of radiofrequency (RF) volumetric tongue reduction for the future purpose of determining its clinical applications in obstructive sleep apnea syndrome (OSAS). DESIGN: The study was performed in three stages, one in vitro bovine stage and two in vivo porcine stages. The last stage was a prospective investigation with histologic and volumetric analyses to establish outcomes. SETTING: Laboratory and operating room of veterinary research center. PARTICIPANTS: A homogeneous population of porcine animal models, including seven in stage 2 and 12 in stage 3. INTERVENTION: RF energy was delivered by a custom-fabricated needle electrode and RF generator to the tongue tissue of both the in vitro and in vivo models. MEASUREMENTS AND RESULTS: Microultransonic crystals were used to measure three-dimensional changes (volumetric reduction). Lesion size correlated well with increasing RF energy delivery (Sperman correlation coefficient of 0.986; p = 0.0003). Histologic assessments done serially over time (1 h through 3 weeks) showed a well-circumscribed lesion with a normal healing progression and no peripheral damage to nerves. Volumetric analysis documented a very mild initial edematous response that promptly tapered at 24 h. At 10 days after RF, a 26.3% volume reduction was documented at the treatment site (circumscribed by the microultrasonic crystals). CONCLUSION: RF, in a porcine animal model, can safely reduce tongue volume in a precise and controlled manner. Further studies will validate the use of RF in the treatment of OSAS.

Animals↗

PubMed1996

Blocking of iron uptake from transferrin by antibodies against the transferrin binding proteins in Neisseria meningitidis.

Neisseria meningitidis, when cultured in iron-restricted environments, synthesises new outer-membrane proteins, many of which are necessary for their survival and growth. Some of these proteins e.g. transferrin-binding proteins 1 and 2 (Tbp1 and Tbp2), are required for the acquisition of iron from transferrin and are examples of important iron-regulated meningococcal surface antigens which are not expressed after growth in common laboratory media. The antigenicity and antigenic heterogeneity of these proteins have been extensively studied, and the bactericidal activity of antibodies directed to them have been studied. In this work we analysed the ability of such antibodies to inhibit transferrin binding and to block iron uptake from human transferrin. Antisera from mice immunized with either meningococcal outer membrane vesicles, purified Tbp1/2 complexes, or purified Tbp2, were incorporated in radiolabeled-iron uptake assays. Uptake was blocked by more than 80% in the homologous strains, but blocked much less efficiently in some heterologous strains, correlating well with inhibition of transferrin binding and with an inhibitory effect on bacterial growth. Inhibition of iron uptake from citrate was unaffected which suggests that this effect is due to antibodies against the components of the transferrin binding system, specially Tbp2. Our results support the importance of these proteins and their suitability to be considered in the development of effective vaccines against serogroup B meningococci.

Antibodies, Bacterial↗

PubMed1996

Cell surface properties of Clostridium difficile: haemagglutination, relative hydrophobicity and charge.

Five well characterised strains of Clostridium difficile of differing virulence and two Escherichia coli strains, a verotoxigenic O157:H7 isolate and a urinary isolate, were examined for cell surface hydrophobicity and charge, and haemagglutinating ability. Phase partition in hexadecane or octan-1-ol was similar for C. difficile and E. coli, as was retention by hydrophobic interaction chromatography (HIC), indicating moderate hydrophobicity. The salt agglutination test showed E. coli to be hydrophobic and C. difficile to be hydrophilic. Relative hydrophobicity determined by HIC when charge effects were not nullified, i.e., to reflect more closely conditions in vivo, showed C. difficile to bind less well. Growth of C. difficile in caecal emulsions to simulate conditions in vivo did not alter the cell surface hydrophobicity. The phase partition method for charge determination indicated that E. coli and C. difficile had a net negative charge, although this was weaker for C difficile than E. coli. However, although E. coli exhibited a net negative charge as determined by immuno-gold electronmicroscopy (IGEM), in keeping with the results of the phase partition method, C. difficile was shown to be predominantly positively charged by IGEM, and by movement in a charged field as determined by paper electrophoresis and a novel method based on light microscope observation. A cell-wall deficient mutant of C. difficile was weakly positively charged, showing that most of the charge resides in the cell wall.

Cell Membrane↗

PubMed1995

Clear cell odontogenic carcinoma. A clinicopathologic analysis.

Clear cell odontogenic tumor is a rare neoplasm of the jaws that histologically may be confused with metastatic renal cell carcinoma. A review of 17 cases revealed that these tumors are aggressive, with a tendency to recur locally after surgery; they also may metastasize both regionally and distantly. There is a marked female predilection, and most cases are discovered during the fifth to seventh decades of life. Seventy percent occur in the mandible, appearing as poorly marginated radiolucencies. We conclude that this tumor is malignant and should be referred to as clear cell odontogenic carcinoma; it requires an aggressive surgical approach.

Adenocarcinoma, Clear Cell↗

PubMed1995

Obstructive sleep apnea. Trends in therapy.

The National Commission on Sleep Disorders Research, in its report to Congress, concluded that the primary care community generally does not understand sleep disorders. Obstructive sleep apnea carries a risk of substantial morbidity and mortality. Excessive daytime sleepiness results from fragmented sleep and microarousals associated with apneic events. It causes poor work performance and increases the incidence of automobile accidents due to driving while drowsy. The commission estimates that the loss of productivity in the United States from excessive daytime sleepiness is more than $20 billion per year. Obstructive sleep apnea is strongly associated with hypertension, myocardial infarction, and stroke. Risk factors for obstructive sleep apnea include male sex, obesity, older age, craniofacial anomalies, and familial risk. Treatment is based on documenting the disorder by polysomnography. Medical management of the syndrome includes weight loss and nasal continuous positive airway pressure. A network of follow-up and support is necessary to maintain compliance. Surgical treatment is reserved for those for whom nasal airway pressure treatment fails. A surgical protocol is presented that demonstrates efficacy equal to nasal airway pressure treatment. Primary care physicians should assume the responsibility of identifying patients at risk for obstructive sleep apnea and refer them appropriately.

Humans↗

PubMed1994

Obstructive sleep apnea and the hyoid: a revised surgical procedure.

Obstructive sleep apnea syndrome results from a loss of muscular activity of pharyngeal dilators and airway collapse at the hypopharynx-base of tongue or the oropharynx-soft palate. The hyoid arch and its muscle attachments strongly affect hypopharyngeal airway patency and resistance. On the basis of these concepts and previous experience, a modified hyoid suspension procedure is presented. Fifteen consecutively treated surgical patients underwent an isolated modified hyoid suspension procedure to correct hypopharyngeal obstruction. Oropharyngeal-palatal obstruction had previously been corrected or was thought not to be a component of the obstruction. Treatment outcomes were based on objective polysomnographic data and subjective clinical correction of excessive daytime sleepiness. The polysomnographic data included analysis of the respiratory disturbance index and lowest oxyhemoglobin desaturation. On the basis of these criteria, 12 of 15 patients (75%) had correction of their excessive daytime sleepiness and marked improvement in their sleep disorder breathing. The mean preoperative respiratory disturbance index was 44.7 +/- 22.6, and the lowest oxyhemoglobin desaturation was 82% +/- 6%. The postoperative respiratory disturbance index and lowest oxyhemoglobin desaturation were 12.8 +/- 6.9 and 86% +/- 5%, respectively. The modified hyoid suspension procedure appears to offer significant adjunctive treatment for hypopharyngeal obstruction in obstructive sleep apnea syndrome.

Adult↗

PubMed1993

Neisseria meningitidis transferrin-binding protein 1 expressed in Escherichia coli is surface exposed and binds human transferrin.

A gene library of Neisseria meningitidis B15 P1.16 DNA was established in lambda Zap II and clones containing DNA encoding transferrin binding protein 1 (TBP-1) identified following hybridisation with a 63-bp DNA probe based on the codon assignment for the first 21 N-terminal amino acids of TBP-1. Sequencing of the cloned DNA demonstrated that all of the intergenic DNA (i.e. upstream of tbp-1 running through to the 3' end of the transferrin-binding protein 2 gene) and approx. 15% of tbp-1 had been cloned. The complete gene was generated using a polymerase chain reaction, with the primer for the 3' end being based on tbp-A of N. gonorrhoeae, and the approx. 2.9-kb DNA product cloned into pGem-3Z. The expressed protein (approx. 100 kDa) reacted with antiserum to an N-terminal peptide of TBP-1. In addition, the native product was surface-expressed by Escherichia coli and bound human transferrin.

Amino Acid Sequence↗

PubMed1993

Obstructive sleep apnea syndrome: a surgical protocol for dynamic upper airway reconstruction.

A surgical protocol for dynamic upper airway reconstruction in the treatment of obstructive sleep apnea syndrome is presented. Two hundred thirty-nine consecutively treated patients were evaluated. All patients underwent a presurgical evaluation that included a physical examination, fiberoptic pharyngoscopy, cephalometric analysis, and polygraphic monitoring. The goal of the presurgical evaluation was to document sleep apnea and isolate the area of obstruction. The treatment was then directed to the obstructive site. The surgical protocol included two phases. Phase 1 was a conservative approach and included uvulopalatopharyngoplasty and/or mandibular osteotomy with genioglossus advancement-hyoid myotomy and suspension. Polysomnography was repeated at 6 months and patients with unsuccessful surgical results were offered maxillary-mandibular advancement osteotomy. Results were based on the postoperative polysomnograms, and included assessing changes in both sleep architecture and sleep-disordered breathing. The surgical results were compared with results in patients who were using nasal continuous positive airway pressure. The surgical success rate for the 239 patients entered into phase 1 therapy was 61% (145 patients). Twenty-four patients who failed phase 1 treatment elected phase 2 treatment. The surgical success rate of this phase was 100%.

Cephalometry↗