Biomedical subjects

R Colton

Publications and source records attributed to R Colton.

15 recordsLinked to original sources

PubMed2000

Reactions of M(CO)5X (M = Mn, Re; X = Cl, Br) with (Ph2PCH2)3CCH3 (P3) and (Ph2P(CH2)2)3P (P3P'): synthetic, spectroscopic, electrochemical, and electrospray mass spectrometric studies.

The reactions of M(CO)5X (M = Mn, Re; X = Cl, Br) with (Ph2PCH2)3CCH3 (P3) and (Ph2P(CH2)2)3P (P3P') are investigated, and the products are characterized by IR, NMR (31P and 13C), and electrospray mass spectrometric (ESMS) techniques. With P3, the major products are fac-M(CO)3(eta 2-P3)X (syn and anti isomers) and cis,fac-M(CO)2(eta 3-P3)X, and with P3P', the major product for each metal is cis,mer-M(CO)2(eta 3-P3P')X, but cis-[M(CO)2(eta 4-P3P')]X and fac-[Re(CO)3(eta 3-P3P')]X are also characterized. Addition of MeI to those complexes containing pendant phosphine groups produces the corresponding phosphonium cations without affecting the remainder of the molecule. On the voltammetric time scale, electrochemical oxidation of cis,fac-Mn(CO)2(eta 3-P3)X yields the corresponding 17e cation cis,fac-[Mn(CO)2(eta 3-P3)X]+, but on the longer time scale of exhaustive electrolysis or chemical oxidation, the product is fac-[Mn(CO)3(eta 3-P3)]+. In contrast, the rhenium cation cis,fac-[Re(CO)2(eta 3-P3)X]+ is stable on the synthetic time scale, but upon oxidation of cis,fac-Re(CO)2(eta 3-P3)X with NOBF4, the final product is the 18e [Re(CO)(NO)(eta 3-P3)X]+. cis,mer-Mn(CO)2(eta 3-P3P')X is reversibly oxidized to cis,mer-[Mn(CO)2(eta 3-P3P')X]+ on the voltammetric time scale, but on the longer synthetic time scale, the product isomerizes to trans-[Mn(CO)2(eta 3-P3P')X]+, which can be reduced to trans-Mn(CO)2(eta 3-P3P')X. Upon voltammetric oxidation, the corresponding rhenium complexes show an initial irreversible response associated with the pendant phosphine group prior to the reversible oxidation of the metal on the synthetic time scale; spectroscopic data indicate formation of cis,mer-Re(CO)2(eta 3-P3P'O)X. The complex cis,mer-[Re(CO)2(eta 3-P3P'Me)X]+ shows only the reversible metal oxidation response. ESMS data are obtained directly for the methylated cationic complexes, and neutral complexes are either oxidized or adducted with sodium ions to produce cationic species.

Journal Article↗

PubMed1997

Lessons for the health care industry from America's experience with public utilities.

In the United States, the traditional public utilities, power and telecommunications, along with health care, are being deregulated and becoming increasingly competitive, especially on price. Regulation of the public utilities has occurred for the past century not simply because they have been monopolies, but, more importantly, because they are "industries affected with the public interest," that is industries which: 1. provide an essential service, 2. benefit from public prequisites, and 3. would cause great public harm if mismanaged. Consequently, the presence of competition in these industries does not negate the need for regulation. Regulation of these industries is best understood as being along the three sides of a "triangle of public interests"--quality, public accountability, and universal service. Examples are provided of these types of regulation in power and telecommunications, even in current "deregulatory" legislation. Health care reform activists in the United States have lately paid attention mostly to the first two legs of the triangle; they are encouraged to focus creatively on the third leg--universal health care.

Economic Competition↗

PubMed1996

Assessment of the infant airway with videorecorded flexible laryngoscopy and the objective analysis of vocal fold abduction.

Accurate diagnosis of upper airway abnormalities by flexible laryngoscopy in infants is hampered by rapid laryngeal motion and lack of patient cooperation. This study evaluates the added role of videorecorded flexible laryngoscopy and the objective measurement of vocal fold abduction in improving the diagnosis of upper airway abnormalities in infants. Seventy-eight infants had videorecorded flexible laryngoscopy performed as part of their evaluation of a suspected airway disorder. These recordings were reviewed by three otolaryngologists for confirmation of the clinical diagnosis. From the video image, the maximum angle of vocal fold abduction was measured with image analysis software. Of 78 patients 40 had supraglottic or glottic abnormalities, 9 had nasal or nasopharyngeal obstruction, 9 had subglottic abnormalities (diagnosed subsequent to videolaryngoscopy), and 15 patients had normal findings on examination. Of those with laryngeal abnormalities, laryngomalacia was the most common diagnosis (23 of 78). Vocal fold paralysis was present in 4 patients. A separate group (9 of 78) of patients was identified as having symmetric bilateral limitation of vocal fold abduction. Laryngeal dyskinesia was diagnosed in these 9 patients. The mean values of maximal vocal fold abduction were as follows: (1) normals, 59.5 degrees; (2) laryngomalacia, 57.0 degrees; (3) paralysis, 26.6 degrees; and (4) incomplete abduction with laryngeal dyskinesia, 27.6 degrees. Videolaryngoscopy is a valuable tool for documentation, parent education, and analysis of infant laryngeal abnormalities. Repeat viewing of the video examination and frame-by-frame analysis improve the diagnostic accuracy. Using this approach, we have calculated the anterior glottic abduction angle in the normal and abnormal infant larynx. In addition, we have identified a group of infants with incomplete abduction of the vocal folds that appears to be different from that found in vocal cord paralysis.

Airway Obstruction↗

PubMed1995

Physiological characteristics of the supported singing voice. A preliminary study.

The purpose of this study was to develop a definition of the supported singing voice based on physiological characteristics by comparing the subjects' concepts of a supported voice with objective measurements of their supported and unsupported voice. This preliminary report presents findings based on data from eight classically trained singers. Subjects answered questions about their concepts of the characteristics of the supported singing voice and how it is produced. Samples of the supported and unsupported singing voice produced at low, medium, and high pitches at a comfortable loudness level were collected for acoustic, spectral, airflow, electroglottographic, air volume, and stroboscopic analyses. Significant differences between the supported and unsupported voice were found for sound pressure level (SPL), peak airflow, subglottal pressure (Ps), glottal open time, and frequency of the fourth formant (F4). Mean flow and F2 frequency differences were sex and pitch related. Males adjusted laryngeal configuration to produce supported voice, whereas glottal configuration differences were greater in females. Breathing patterns were variable and not significantly different between supported and unsupported voice. Subjects in this study believe that the supported singing voice is resonant, clear, and easy to manage and is produced by correct breath management. Results of data analysis show that the supported singing voice has different spectral characteristics from and higher SPL, peak airflow, and Ps than the unsupported voice. Singers adjust laryngeal and/or glottal configuration to account for these changes, but no significant differences in breathing activity were found.

Acoustics↗

PubMed1995

Endoscopic microsuture repair of vocal fold defects.

The presence of a nonvibratory segment of vocal folds after microlaryngeal surgery is often a cause of poor voice result. The etiology of a nonvibratory segment is due to full thickness epithelial defect followed by secondary wound closure and scar contracture. To reduce scar contracture and nonvibratory segment of the vocal folds, primary repair with a 6-0 chromic endo-knot suture technique was used to close defects and approximate microflaps of the vocal folds. This was done in 18 patients with epithelial defects after resection of benign vocal fold lesions. The pathologic findings included severe polypoid degeneration (n = 7), fusiform laryngeal polyps (n = 5), sulcus vocalis (n = 2), cyst (n = 2), and keratosis (n = 2). Voice was improved in all patients after surgery. Comparison of vocal fold vibration before and after surgery showed improvements in configuration, amplitude, and mucosal wave. Vocal folds that were sutured all had good vibratory characteristics; none had a nonvibrating segment at the site of suture placement. Voice and healing after microsuture technique were near normal by Day 10 and return of mucosal wave was often complete by Day 14. Endoscopic microsuture closure of microflaps of the vocal folds edge is safe and affords the surgeon an opportunity for primary repair with improved functional result.

Endoscopy↗

PubMed1994

The integration of voice science, voice pathology, medicine, public speaking, acting, and singing.

The integration of voice science, voice pathology, medicine, public speaking, acting, and singing has been central to evolution in all fields. The Voice Foundation Symposia have played a seminal and central role in fostering integration among disciplines. The result has been an improvement in the knowledge and practice in each field. And the future promises to be even more informative and exciting.

Congresses as Topic↗

PubMed1994

Aerodynamic and stroboscopic findings before and after microlaryngeal phonosurgery.

Acoustic, aerodynamic, and laryngo-video-stroboscopy (LVS) studies were done on 50 patients before and after microlaryngeal surgery for benign vocal fold lesions. Perceptual pre- and postratings were also obtained. After microlaryngeal surgery, statistically significant differences between pre- and posttreatment conditions included postoperative findings of (a) a lowering of mean flow rate, (b) an increase in glottal efficiency, and (c) an increase in maximum sound pressure level. There was no significant improvement in maximum phonation time. Stroboscopy findings showed changes of glottal configuration, linearity of the vocal fold edge, amplitude of vocal fold vibration, excursion of the mucosal wave, and periodicity. Acceptable perceptual voice quality appeared to depend on a straight vocal fold edge, good vibratory amplitude, and good mucosal wave. Improved understanding of vocal function after phonosurgery should help us refine surgical principles and techniques. The combined use of LVS and phonatory function measures is advocated.

Glottis↗

PubMed1994

Diagnosis and treatment of persistent dysphonia after laryngeal surgery: a retrospective analysis of 62 patients.

Sixty-two patients with persistent or recurrent dysphonia after laryngeal surgery underwent interdisciplinary voice evaluation, laryngostroboscopy, and objective measurements of vocal function. The causes of persistent dysphonia were attributed to vocal fold scarring (n = 22), residual mass lesion (n = 8), residual inflammation (n = 13), recurrent mass (n = 4), and hyperfunctional voice disorder (n = 7). Laryngoscopy often showed excessive ventricular compression and anterior-to-posterior laryngeal compression. Ventricular dysphonia was often a compensatory gesture in response to poorly mobile vocal fold membranes. Stroboscopy was able to document a number of abnormalities which included abnormalities of laryngeal configuration, vibratory asymmetry, reduction of amplitude, and mucosal wave. Using a diversified approach consisting of medical therapy, voice therapy, and repeat surgery, better vocal function was able to be restored in the majority of patients. An interdisciplinary approach to the dysphonic patient after laryngeal surgery was most useful in defining the pathology and refining a treatment rehabilitation program.

Adult↗

PubMed1992

Dysphonia in the aging: physiology versus disease.

A chart review from 151 dysphonic patients over the age of 60 was done to define aging related voice disorders. Overwhelmingly, patients suffered from dysphonia due to disease processes associated with aging rather than to physiologic aging alone. These include: 1. central neurological disorders affecting laryngeal function (e.g., stroke, Parkinson's disease, essential tremor, Alzheimer's disease); 2. benign vocal fold lesions (e.g., Reinke's edema, benign and dysplastic epithelial lesions); 3. inflammatory disorders (e.g., laryngitis sicca, medication effect); 4. laryngeal neoplasia; and 5. laryngeal paralysis. Typical laryngeal findings of vocal fold bowing and breathiness consistent with presbylarynges were present in only six patients. Presbylarynges is not a common disorder and should be a diagnosis of exclusion made only after careful medical and speech evaluation.

Aged↗

PubMed1991

Functional staging for vocal cord paralysis.

Phonatory function can be reliably tested after vocal paralysis. After a review of 116 cases, 55 patients underwent objective testing. The clinical history of vocal ability and aspiration were found to be significantly correlated with measurements of phonatory mean flow rate (MFR), maximum phonation time (MPT), and maximum decibel output (SPL). A four-stage classification system, based on clinical and objective measurements, has been formulated. In stage I, measures of vocal parameters approached those of normals with MFR = 155 cc/sec, MPT = 12 sec, and SPL = 92 dB. Patients with stage IV disability have high MFR (480 cc/sec), but low MPTs (less than 3 sec) and low SPL values (76 dB). Factors such as sex, age, weight loss, and the presence of malignancy affect the degree of vocal function deficit. Post-therapy recordings indicated an improvement in vocal function by an increase in MPT and SPL, with a decrease in MFR. Measurements of MFR, PT, and SPL are good objective indicators available to the clinician. Functional staging can be applied to assessment and treatment of vocal cord paralysis.

Adult↗

PubMed1989