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Biomedical subjects

L M Collins

Publications and source records attributed to L M Collins.

At least 19 recordsLinked to original sources
PubMed2001

Mini-audits facilitate quality assurance in outpatient units.

PURPOSE: It has been shown that large-scale epidemiological studies are an unsatisfactory method of measuring quality of care in anesthesia. We performed a mini-audit of the outpatient surgery unit at Vancouver General Hospital to determine whether such methodology would be helpful in assessing and monitoring quality of care and in identifying areas where improvements could be made. METHODS: After institutional approval, we conducted a prospective quality assurance audit in a cohort of 462 consecutive outpatients. A measurement tool was developed using information from previous literature. Data recorded included demographics, type of surgery and anesthesia, duration of stay in the postanesthetic care unit (PACU) and any adverse events in the PACU. The effect of ethnicity on the above was also examined. RESULTS: The demographics and practice profiles of our unit were comparable to other units. The mean duration of stay in the PACU was 91 +/- 55.3 min and is twice as long as other units. The incidence of hypotension, hypothermia and excessive pain in the PACU were higher compared to other centres. The incidence of other adverse events was comparable to that reported by other centres. O2 supplementation was required more frequently in Caucasians (23% vs 9%; P <0.05) and postoperative bleeding occurred more frequently in Asiatics (46% vs 27%; P <0.05). CONCLUSION: A mini-audit was found to be helpful in assessing and monitoring quality of care and in identifying areas where improvements could be made.

Adult↗
PubMed2001

Regional anesthesia for laparoscopy.

A variety of laparoscopic procedures can be performed on patients under regional anesthesia. Diagnostic laparoscopy in elective and emergency patients, pain mapping, laparoscopy for infertility, and tubal sterilization are some examples. The key benefits of regional anesthesia include less emesis, less postoperative pain, shorter postoperative stay, improved patient satisfaction, and overall safety. Regional techniques, such as rectus sheath blocks, inguinal blocks, and caudal blocks, are useful adjuncts to general anesthesia and facilitate postoperative analgesia. Other techniques, such as spinal and epidural anesthesia, and combination of the two, are suitable as a sole anesthetic technique for laparoscopy. The physiologic changes during laparoscopy in the awake patient appear to be tolerated well under regional anesthesia. It is reasonable to assume that with advances in instrumentation and surgical techniques, the role of laparoscopy will increase in the future. The benefits conferred by regional anesthesia make it an attractive option to general anesthesia for many patients and procedures. Successful implementation of regional anesthesia is an important determinant of how anesthesiologists, surgeons, and surgical facilities cope with new challenges. In the future, it could be possible to provide "walk-in/walk-out" regional anesthesia with a real possibility of fast tracking patients through the recovery process after ambulatory surgery. For maximal patient safety, however, facilities offering regional anesthesia must have appropriately trained anesthesia personnel and the equipment necessary for monitoring and providing full resuscitation in the event of complications or a need to convert to general anesthesia.

Anesthesia, Conduction↗
PubMed2001

A comparison of two loudness balancing tasks in cochlear implant subjects using bipolar stimulation.

OBJECTIVE: In this study, the accuracy of independent measurement of the loudness of different electrodes in a cochlear implant (the "reference" method) was compared with the accuracy of measurements that depend on the results of previous measurements (the "adjacent" method) by evaluating the similarity between and the slopes of the loudness balance curves, and the variability in the measured loudness balance values. DESIGN: The two methods of loudness balancing differed only in the reference electrode used. In the adjacent method, the loudness of the test electrode was sequentially adjusted to match the loudness of an adjacent reference electrode, whereas in the reference method, the loudness of all test electrodes was adjusted to match that of a common reference electrode. Five subjects implanted with the Nucleus 22 device completed both methods of loudness balancing for all of their functioning electrodes. Each test/reference electrode pair was loudness balanced six times to assess the variability of the two methods. RESULTS: The loudness balance curves for the two methods were statistically correlated (p < 0.001) for all subjects. The slopes of the regression lines for the loudness balance curves were statistically different from zero (p < 0.05) for roughly half of the subjects for each method. A sign test indicated statistically different means for the basal set and apical set of measurements for only one subject for both methods. The variance in the measured values across electrodes for the reference method was significantly greater for three of the five subjects (p < 0.01). CONCLUSIONS: It was hypothesized that because of its dependence on previously measured values, the adjacent method could be susceptible to "drift," i.e., a shift in the overall loudness to which the electrodes are balanced. However, none of the statistical measures employed to test for drift indicated that the adjacent method was more susceptible to drift than the reference method, nor were the responses to the adjacent method more variable. Thus, based on these results, dependent measurements do not seem to be less accurate than independent measurements. The relatively higher variance for the reference method in some subjects may be due to the difficulty of comparing the loudness of stimuli that are far apart in pitch.

Adult↗
PubMed2001

A comparison of inclusive and restrictive strategies in modern missing data procedures.

Two classes of modern missing data procedures, maximum likelihood (ML) and multiple imputation (MI), tend to yield similar results when implemented in comparable ways. In either approach, it is possible to include auxiliary variables solely for the purpose of improving the missing data procedure. A simulation was presented to assess the potential costs and benefits of a restrictive strategy, which makes minimal use of auxiliary variables, versus an inclusive strategy, which makes liberal use of such variables. The simulation showed that the inclusive strategy is to be greatly preferred. With an inclusive strategy not only is there a reduced chance of inadvertently omitting an important cause of missingness, there is also the possibility of noticeable gains in terms of increased efficiency and reduced bias, with only minor costs. As implemented in currently available software, the ML approach tends to encourage the use of a restrictive strategy, whereas the MI approach makes it relatively simple to use an inclusive strategy.

Confidence Intervals↗
PubMed2000

The prolonged duration of rocuronium in Chinese patients.

We compared the potency and duration of action of rocuronium in Chinese and Caucasian patients during general anesthesia. Thirty-six women (18 Caucasian and 18 Chinese) and 36 children (18 Caucasian and 18 Chinese) were evaluated during the administration of propofol/fentanyl anesthesia. Patients in each age group were randomized into three subgroups to receive single doses of 0.06, 0. 12, or 0.18 mg/kg rocuronium (adults) or 0.12, 0.18, or 0.24 mg/kg rocuronium (children). Neuromuscular blockade was assessed by electromyography of the adductor pollicis after train-of-four (TOF) stimulation of the ulnar nerve. Dose response curves were constructed when maximum neuromuscular depression of the first twitch of the train (T(1)) was obtained. A second bolus dose of rocuronium was then administered to a total dose of 0.6 mg/kg. The times of spontaneous recovery to T(1) 10%, 25%, and 90% of control and to TOF 0.25, 0.50, and 0.70 were recorded. For both adults and children, recovery occurred later in Chinese than in Caucasian patients (P<0.05 for T(1) of 10%, 25%, 75%, and 90% and TOF to 0.7). The 50% effective dose was smaller in Chinese adults (125+/-63 vs. 159+/-66 microg/kg) and Chinese children (171+/-43 vs. 191+/-46 microg/kg) than in Caucasian adults and children, but the difference was not statistically significant. In adults, time to 25% T(1) recovery was 43+/-13 min in Chinese patients and 33+/-10 min in Caucasian patients (P<0.05). The corresponding values were more rapid for children: 30+/-10 and 24+/-6 min (P<0.05). We conclude that the recovery from rocuronium neuromuscular blockade was longer in Chinese compared with Caucasian patients and in adults compared with children.

Adolescent↗
PubMed2000

Investigating perceptual features of electrode stimulation via a multidimensional scaling paradigm.

To achieve the most effective speech processing for individuals with cochlear implants, it is important to understand the perceptual features associated with the stimulation parameters. In general, when electrodes are stimulated in order from apex to base, the pitch of the perceived sound changes in an orderly fashion from low to high. Some deviations from this assumed order have been documented. Also, pitch is the dominant perceptual attribute of a sound when the stimuli associated with different electrodes have been accurately loudness balanced. In this study, the results of a multidimensional scaling (MDS) paradigm were compared to the results of a pitch-ranking procedure for six subjects implanted with multichannel cochlear prostheses. Results indicate that there may be multiple percepts that change with electrode location. Not surprisingly, the dominant percept is strongly correlated with pitch. The results also indicate that the structure of the second percept is consistent across subjects, although not interpretable using the data measured in this study. Furthermore, results indicate that MDS data can be used to pinpoint indiscriminable electrodes more accurately than pitch data. The results of this study may have importance for the design of the next generation of speech processors.

Aged↗
PubMed2000

Developmental pathways to alcohol abuse and dependence in young adulthood.

OBJECTIVE: To determine if people who were diagnosed with alcohol abuse or dependence (AAD) at age 21 had different developmental patterns of alcohol use in adolescence than non-AAD individuals. METHOD: An ethnically diverse urban sample of 808 children was surveyed at age 10 in 1985 and followed prospectively to age 21 in 1996. AAD at age 21 was assessed following DSM-IV criteria. Latent Transition Analysis (LTA) was used to identify four statuses of alcohol use (nonuse, initiation only, current use only, heavy episodic drinking), as well as transition probabilities between these four statuses from elementary school to middle school and from middle school to high school among the AAD and non-AAD group. RESULTS: The prevalence of alcohol use statuses during elementary school was similar in the two groups. Differences in alcohol use emerged in middle school and became more pronounced in high school. In middle school, AAD individuals were more likely to have initiated or been current drinkers than non-AAD individuals. However, the two groups did not differ in the prevalence of heavy episodic drinking in middle school. In high school, most AAD individuals were in the heavy episodic drinking status (54%), while most non-AAD individuals were in the initiation only (33%) or current use only (34%) statuses. CONCLUSIONS: These findings suggest preventive intervention targets for different developmental periods. Alcohol abuse and dependence at age 21 may be prevented by delaying alcohol initiation, by reducing current use in middle school and by reducing heavy episodic drinking in high school.

Adolescent↗
PubMed1999

Effects of stimulus level on electrode-place discrimination in human subjects with cochlear implants.

Effects of stimulus level on discrimination of one stimulation site from another were examined in 15 human subjects with Nucleus-22 cochlear implant systems. Bipolar stimulation was used in all cases with electrodes in the bipolar pair separated by 1.5 mm (center to center). Subjects were first tested at a medium loudness level, using an adaptive tracking procedure, to determine the regions of the electrode array where electrode-place discrimination was best and the regions where it was poorest. Electrode-place discrimination was then tested at three regions distributed throughout the array, which included the regions of best and poorest discrimination. At each region, electrode-place discrimination was tested at three levels: 25%, 50%, and 75% of the dynamic range. For each of these nine conditions (3 sites x 3 levels), the test-electrode pairs were loudness balanced with the reference-electrode pairs. A two-interval forced-choice same-different procedure was then used to determine discriminability of the reference-electrode pair from the nearest, apical, test-electrode pair. If P(C)max was <0.707 at all three levels, additional testing was done using the next, more apical, electrode pair as the test-electrode pair. A tendency toward better discrimination at more apical regions of the array was observed. Electrode pairs with poor discrimination typically had smaller dynamic ranges than those with good discrimination. There was a weak tendency toward better discrimination at higher levels of stimulation. However, effects of level on electrode-place discrimination were less pronounced and less consistent than previously observed effects of level on temporal discriminations. These results suggest interactions between current spread and the condition of the implanted cochlea as underlying mechanisms.

Adult↗
PubMed1999

Using computational auditory models to predict simultaneous masking data: model comparison.

In order to develop improved remediation techniques for hearing impairment, auditory researchers must gain a greater understanding of the relation between the psychophysics of hearing and the underlying physiology. One approach to studying the auditory system has been to design computational auditory models that predict neurophysiological data such as neural firing rates [15], [1]. To link these physiologically-based models to psychophysics, theoretical bounds on detection performance have been derived using signal detection theory to analyze the simulated data for various psychophysical tasks [20]. Previous efforts, including our own recent work using the Auditory Image Model, have demonstrated the validity of this type of analysis; however, theoretical predictions often continue to exceed experimentally-measured performance [9], [21]. In this paper, we compare predictions of detection performance across several computational auditory models. We also reconcile some of the previously observed discrepancies by incorporating appropriate signal uncertainty into the optimal detector.

Computer Simulation↗
PubMed1999

Investigation of the effects of temporal and spatial interactions on speech-recognition skills in cochlear-implant subjects.

Forward masking was investigated as a measure of spectral and temporal interactions. Such interactions may adversely affect speech recognition in cochlear-implant subjects. Seven subjects, implanted with the Nucleus 22 device, performed a forward-masking task. They also performed an electrode-discrimination task in order to measure spectral interactions without temporal interactions. Correlation analysis indicated a significant relationship between data obtained in the two tasks (p < 0.1). The two tasks were also correlated with the subjects' scores from five measures of speech recognition. Forward masking and electrode discrimination were strongly correlated with measures requiring consonant and phoneme recognition, respectively. These results indicate that the relationship between forward masking and speech recognition may be due, in part, to a lack of spectral resolution. The data also indicate that consonants may be more readily masked than vowels. Forward-masking data measured for all clinically programmed electrodes in three of the seven subjects were used with a model of the spectral maxima sound processor (SMSP) to estimate the number of electrodes stimulated during a consonant that might be masked by prior presentation of a vowel. These results suggest that temporal interactions across electrodes may be a factor in speech-recognition abilities of some cochlear-implant subjects.

Adult↗
PubMed1998

Analysis of the performance of a model-based optimal auditory signal processor.

Traditionally, psychophysical data have been predicted either by constructing models of the peripheral auditory system or by applying signal detection theory (SDT). Frequently, the theoretical detection performance predicted by SDT is greater than that observed experimentally and a nonphysiologically based "internal noise" source is often added to the system to compensate for the discrepancy. A more appropriate explanation may be that traditional SDT approaches either incorporate little or no physiology or make simplifying assumptions regarding the density functions describing the physiological data. In the work presented here, an integrated approach, which combines SDT and a physiologically based model of the human auditory system, is proposed as an alternate method of quantifying detection performance. To validate this approach, the predicted detection performance for a simultaneous masking task is compared to predictions obtained from traditional methods and to experimental data. Additionally, the sensitivity of the integrated method is thoroughly investigated. The results suggest that by combining SDT with a physiologically based auditory model, thereby capitalizing on the strengths of each individual method, the previously observed discrepancies can be partially explained as the result of physical processes inherent in the auditory system rather than unspecified "internal noise" and more accurate predictions of psychophysical behavior can be obtained.

Auditory Perception↗
PubMed1998

Deep venous thrombosis.

Deep venous thrombosis (DVT) is an important clinical condition accounting for 600,000 hospitalized patients in North America per year. Signs and symptoms of DVT are nebulous and often absent. Pulmonary embolus is often a coexisting condition and is most often caused by DVT. Both require anticoagulation and possibly thrombolytic therapy. There is a long list of risk factors that predispose a patient to DVT including cancer, cardiac disease, and hereditary conditions. This article examines predisposing factors, diagnostic tools, treatment, and sequela of DVT.

Anticoagulants↗
PubMed1997

Comparison of electrode discrimination, pitch ranking, and pitch scaling data in postlingually deafened adult cochlear implant subjects.

The goal of this study was to investigate the relationship between variation in electrode site of stimulation and the perceptual dimensions along which such stimuli vary. This information may allow more effective use of electrode place when encoding speech information. To achieve this goal, two procedures which measure pitch in subjects implanted with the Nucleus/Cochlear Corporation multichannel device were performed. Estimates of electrode discriminability that can be obtained from these procedures were compared to a more direct measure of electrode discriminability that was obtained in a previous study [Collins et al., Assoc. Res. Otolaryng. Abstracts, No. 642 (1994)]. In the first task, subjects performed a pitch ranking procedure similar to that used in previous studies [Townshend et al., J. Acoust. Soc. Am. 82, 106-115 (1987); Nelson et al., J. Acoust. Soc. Am. 98, 1987-1999 (1995)]. Estimates of the pitch percept elicited by stimulation of each electrode as well as the discriminability of the electrodes were generated from the data using two different statistical analyses. In the second task, subjects performed a pitch scaling procedure similar to one used in a previous study [Busby et al., J. Acoust. Soc. Am. 95, 2658-2669 (1994)]. Again, two different statistical analyses were performed to generate estimates of the pitch percept corresponding to stimulation of each electrode and to generate estimates of electrode discriminability. In general, the estimates of the relationships between the pitch percepts obtained from the two procedures were not identical. In addition, the estimates of electrode discriminability were not equivalent to the electrode discrimination measures obtained from the same subjects during the previous study. Signal detection theory has been used to model the decision processes required by each of the procedures described above [e.g., Jesteadt and Bilger, J. Acoust. Soc. Am. 55, 1266-1276 (1974)]. However, these models do not predict the differences that were observed between the data sets obtained during this study. An alternate model is proposed which may explain the data obtained from these subjects. This model is based on the assumption that the percept that is elicited by electrical stimulation of an electrode is multidimensional, as opposed to unidimensional in nature. Therefore, the perceived signal is more appropriately modeled using a multidimensional random vector, where each element of the vector represents the perceived value of one of the dimensions of the signal.

Adult↗
PubMed1997

Electrode discrimination and speech recognition in postlingually deafened adult cochlear implant subjects.

This study investigated the relationship between electrode discrimination and speech recognition in 11 postlingually deafened adult cochlear implant subjects who were implanted with the Nucleus/Cochlear Corporation multichannel device. The discriminability of each electrode included in a subject's clinical map was measured using adaptive and fixed-level discrimination tasks. Considerable variability in electrode discriminability was observed across subjects. Two subjects could discriminate all electrodes, and discrimination performance by the remaining nine subjects varied from near perfect to very poor. In these nine subjects, the results obtained from the discrimination tasks were used to create a map that contained only discriminable electrodes, and subjects' performance on speech recognition tasks using this experimental map was measured. Four different speech recognition tests were administered: a nine-choice closed-set medial vowel recognition task, a 14-choice closed-set medial consonant recognition task, the NU6 Monosyllabic Words Test [T. W. Tillman and T. Carhart, Tech. Rep. No. SAM-TR-66-55, USAF School of Aerospace Medicine, Brooks Air Force Base, Texas (1966)] scored for both words and phonemes correct, and the Central Institute for the Deaf (CID) Everyday Sentences test [H. Davis and S. R. Silverman, Hearing and Deafness (Holt, Rinehart, and Winston, New York, 1978)]. Seven of the nine subjects tested with the experimental map showed significant improvement on at least one speech recognition measure, even though the experimental map contained fewer electrodes than the original map. Three subjects' scores improved significantly on the CID Everyday Sentences test, three subjects' scores improved significantly on the NU6 Monosyllabic Words test, and five subjects' scores improved significantly on the NU6 Monosyllabic Words test scored for phonemes correct. None of the subjects' scores improved significantly on either the vowel or consonant tests. No significant correlation was observed between electrode discrimination ability and speech recognition scores or between electrode discrimination ability and improvement in speech recognition scores when programmed with the experimental map. The results of this study suggest that electrode discrimination tasks may be used to improve speech recognition of some cochlear implant subjects, and that each electrode site does not necessarily provide perceptually distinct information.

Adult↗
PubMed1996

Prenatal cocaine alters dopamine transporter binding in postnatal day 10 rat striatum.

The effect of in utero cocaine exposure on the postnatal binding of the radiolabeled dopamine (DA) uptake inhibitor [3H]GBR 12935 to the DA uptake complex was examined in male rats. One set of pregnant Sprague-Dawley rats was given subcutaneous (s.c.) injections of cocaine (40 mg/kg) or 0.9% saline from gestational day (GD) 8-21. Another set of animals received bilateral s.c. Silastic implants, each containing 60 mg cocaine base dissolved in polyethylene glycol (PEG) or PEG only, from GD 18-21. The density of [3H]GBR 12935 binding to the DA transporter in striatum and mesencephalon was assessed by quantitative autoradiography on postnatal day (PND) 1, 10, 30, and 60. Both treatment methods resulted in a decrease of [3H]GBR 12935 binding in dorsal lateral striatum of cocaine-exposed offspring on PND 10. There were no significant differences in [3H]GBR 12935 binding between offspring of cocaine and vehicle-treated dams at any other time points examined. Thus, prenatal cocaine exposure by either daily injection from GD 8-21 or continuous infusion from GD 18-21 resulted in a transient decrease in DA transporter binding in the dorsal lateral striatum that was apparent on PND 10.

Animals↗