Biomedical subjects
Publications and source records attributed to S L Smith.
A patient was referred for superior vena cava (SVC) stenting prior to surgical biopsy of a mediastinal mass. A technically satisfactory insertion was followed 6 months later by cardiac tamponade with two legs of the Wallstent having perforated the wall of the SVC.
To investigate changes in spatial orientation ability and walking performance following space flight, 7 astronaut subjects were asked pre- and post-flight to perform a goal directed locomotion paradigm which consisted of walking a triangular path with and without vision. This new paradigm, involving inputs from different sensory systems, allows quantification of several critical parameters, like orientation performance, walking velocities and postural stability, in a natural walking task. The paper presented here mainly focuses on spatial orientation performance quantified by the errors in walking the previously seen path without vision. Errors in length and reaching the corners did not change significantly from pre- to post-flight, while absolute angular errors slightly increased post-flight. The significant decrease in walking velocity and a change in head-trunk coordination while walking around the corners of the path observed post-flight may suggest that during re-adaptation to gravity the mechanisms which are necessary to perform the task have to be re-accomplished.
The authors examined the association between anxiety state and various sociodemographic factors, as well as measures of general health, mood, and stress in a community-dwelling, geriatric population. A survey questionnaire designed for the study was completed by 123 randomly selected subjects. Univariable linear regression analysis showed anxiety state to have an inverse association with age (beta = -0.29, P = 0.0001) and general health measures (P = 0.0001), and to have a direct relationship with depression (beta = 0.78, P = 0.0001), life stress events (beta = 0.98, P = 0.01), and medical comorbidity (beta = 1.04, P = 0.01). Gender differences in anxiety state were not found. The results provide a framework to begin understanding those factors that contribute to anxiety states in late life. This study revealed anxiety and depression to be highly correlated even in elderly subjects who reported low levels of anxiety and depressive symptoms.
The precise neuromuscular control needed for optimal locomotion, particularly around heel strike and toe off, is known to he compromised after short duration (8- to 15-day) space flight. We hypothesized here that longer exposure to weightlessness would result in maladaptive neuromuscular activation during postflight treadmill walking. We also hypothesized that space flight would affect the ability of the sensory-motor control system to generate adaptive neuromuscular activation patterns in response to changes in visual target distance during postflight treadmill walking. Seven crewmembers, who completed 3- to 6-month missions, walked on a motorized treadmill while visually fixating on a target placed 30 cm (NEAR) or 2 m (FAR) from the subject's eyes. Electronic foot switch data and surface electromyography were collected from selected muscles of the right lower limb. Results indicate that the phasic features of neuromuscular activation were moderately affected and the relative amplitude of activity in the tibialis anterior and rectus femoris around toe off changed after space flight. Changes also were evident after space flight in how these muscles adapted to the shift in visual target distance.
Complement components C3 and C4 have been isolated from the serum of the nurse shark (Ginglymostoma cirratum) and of the channel catfish (Ictalurus punctatus). As in the higher vertebrates, the fish C4 proteins have three-chain structures while the C3 proteins have two-chain structures. All four proteins have intra-chain thioesters located within their highest molecular mass polypeptides. N-terminal sequence analysis of the polypeptides has confirmed the identity of the proteins. In all cases except the catfish C3 alpha-chain, which appears to have a blocked N-terminus, sequence similarities are apparent in comparisons with the chains of C3 and C4 from higher vertebrates. We have confirmed that the activity/protein previously designated C2n is the nurse shark analogue of mammalian C4. This is the first report of structural evidence for C4 in both the bony and cartilaginous fish.
Paraesophageal herniation of the stomach is a rare complication following laparoscopic Nissen fundoplication. We retrospectively reviewed our experience with 720 patients undergoing laparoscopic Nissen fundoplications. Seven patients were found to have postoperative paraesophageal hernias requiring reoperation. The clinical presentation, diagnostic workup, operative treatment, and outcome were evaluated. There were no deaths or procedure-related complications. Clinical presentation was recurrent dysphagia in four, nonspecific abdominal symptoms in one, and acute abdomen in one. One additional patient was asymptomatic. Preoperatively the correct diagnosis was able to be confirmed in four of six patients by barium esophagogram. Four patients underwent successful laparoscopic repair. Two patients had a thoracotomy including one conversion from laparoscopy to thoracotomy. One patient had a lap-arotomy to reduce an intrathoracic gastric volvulus. At a mean follow-up of 2.5 months no patient had further complications. Paraesophageal herniation is a rare complication following laparoscopic Nissen fundoplication and a definitive diagnosis is often difficult to establish. Early dysphagia after surgery should alert the surgeon to this complication. Redo laparoscopic surgery is feasible but an open procedure may be necessary.
The Afghan osteotomy was combined with external fixation on 19 patients (23 extremities) with late-onset tibia vara. The average weight was 258 lb and all patients weighed >95th percentile. The average preoperative deformity was 28.2 degrees. The average intraoperative correction was 27.6 degrees. Average healing time was 141 days. The mean follow-up was 2.7 years. Based on radiographic correction, at long-term follow-up, there were 15 excellent, two fair, and six poor results. The quality of the initial correction was the only significant variable, and it was borderline (p = 0.0587). Complications included loss of alignment, peroneal nerve palsy, superficial pin tract infection, deep infection, and fracture. This method offers a technically simple procedure with a relatively low complication rate. It allows early mobilization and provides the ability to manipulate the correction postoperatively. An excellent long-term outcome is predicated on achieving an acceptable initial correction as determined by intraoperative mechanical axis radiographs.
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OBJECTIVE: The objective of this study was to examine whether inappropriate cardiovascular responses to stressors may underlie symptoms in Gulf War veterans with chronic fatigue. METHODS: Psychophysiological stress testing was performed on 51 Gulf War veterans with chronic fatigue (using the 1994 case definition of the Centers for Disease Control and Prevention) and 42 healthy veterans. Hemodynamic responses to cold pressor, speech, and arithmetic stressors were evaluated using impedance cardiography. RESULTS: Veterans with chronic fatigue had diminished blood pressure responses during cognitive (speech and arithmetic) stress tests due to unusually small increases in total peripheral resistance. The cold pressor test, however, evoked similar blood pressure responses in the chronic fatigue and control groups. Low reactivity to cognitive stressors was associated with greater fatigue ratings among ill veterans, whereas an opposite relation was observed among healthy veterans. Self-reported neurocognitive decline was associated with low reactivity to the arithmetic task. CONCLUSIONS: These results suggest a physiological basis for some Gulf War veterans' reports of severe chronic fatigue. A greater deficit with responses processed through cerebral centers, as compared with a sensory stimulus (cold pressor), suggests a defect in cortical control of cardiovascular function. More research is needed to determine the specific mechanisms through which the dissociation between behavioral and cardiovascular activities identified in this study may be contributing to symptoms in Gulf War veterans.
OBJECTIVE: To describe the current practice of neonatal nurse practitioners in assessing skeletal health and preventing and treating metabolic bone disease in very-low-birth-weight infants. DESIGN: Descriptive, retrospective survey. PARTICIPANTS: Neonatal nurse practitioners in the continental United States were systematically randomly selected. A 64% response rate was obtained (112). MAIN OUTCOME MEASURES: Responses to questions about assessing skeletal health and preventing and treating metabolic bone disease in very-low-birth-weight infants. RESULTS: Current practice of neonatal nurse practitioners includes assessing skeletal health of very-low-birth-weight infants on the 7th (47.3%) or 14th (19.6%) day of life, with subsequent assessments every 7 (63.3%) or 14 (18.8%) days. Neonatal nurse practitioners (85.1%) estimate the incidence of metabolic bone disease at less than 15%. Neonatal nurse practitioners initiate total parenteral nutrition (99%), provide parenteral calcium and phosphorous in ratios of 1.3-1.7:1 (9%), and add powdered fortifier (90.1%) and liquid fortifier (25.2%) to expressed breast milk. All respondents use formulas made for premature infants. Physical therapy is used by 46.8% of neonatal nurse practitioners. CONCLUSIONS: Neonatal nurse practitioners underestimate the incidence of metabolic bone disease. Parenteral calcium and phosphorous are given but in quantities that differ from the recommended ratio. Most neonatal nurse practitioners use formulas made for premature infants and add powdered fortifier to expressed breast milk. Although physical therapy is prescribed, more research on its effect on bone mineralization is warranted before this practice is recommended without reservation.
Since the mid-1980s, quality management has infused the healthcare industry with a newborn commitment to improving the quality and efficiency of its service delivery processes. Increasing industry competition has served to sharpen the focus on quality. For health services companies such as Blue Cross and Blue Shield of Massachusetts, a relative latecomer to the managed care marketplace, the challenges of getting quickly up to speed were significant. This article describes the simultaneous efforts of the company to develop a substantial new presence in the managed care marketplace, while also applying the basic principles of quality assurance and continuous quality improvement to its organizational transformation.
Ultrasound imaging of the heart can provide an important source of diagnostic data to the cardiologist, but conventional echocardiography requires considerable expertise, and is extremely time-consuming. Computer-based analysis is therefore very attractive and, in the light of decreasing hardware costs in recent years, has become increasingly viable in practice. This paper describes the specification and implementation of a computer-based tool which supports the clinician in the analysis of echocardiograms, exploiting the clinical judgement and inherent skill of the clinician. The design of the system has focused particularly on the provision of a powerful user interface for ease of interaction, flexibility in system functionality, and extensive interactive capabilities to maximize reliability and convenience of use. This paper will describe the principal features of the system and illustrate its use in the clinical environment.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
OBJECTIVE: To describe (1) short-term postnatal weight loss and gain patterns in infants with very low and extremely low birth weights and (2) the variables that may affect these weight change patterns. DESIGN: Descriptive, retrospective review. SETTING: University hospital in the intermountain western United States. SUBJECTS: Sixty-two charts of infants admitted to a university neonatal intensive care unit from July 1990 through November 1992 were reviewed. Infants who weighed 1000 grams or less were categorized as extremely low birth weight (ELBW) and infants weighing 1001 to 1500 grams were categorized as very low birth weight (VLBW). Each group was comprised of 31 infants. Fifty percent of the sample were male, and 50% were female. Eighty-five percent of the sample were Anglo-American, and 15% were non-Anglo-American. MEASURES: Data were collected on a three-part data collection tool and included demographic and treatment variables. RESULTS: A significant difference was found in the maximum percent weight lost between the two groups, with the ELBW group losing a mean of 14.77% of birth weight and the VLBW group losing a mean of 11.35% of birth weight (t = 2.45, p < 0.05). The day the infants reached their nadir weight was significantly different between the two groups. The ELBW group reached their nadir on day of life 7, and the VLBW group reached their nadir on day of life 6 (t = 2.00, p < 0.05). No significant difference was noted in the time to return to birth weight between the two groups, with a mean of 15 days to return to birth weight. Factors associated with postnatal weight changes were intraventricular hemorrhage, use of diuretics and steroids, day of life when nadir weight occurred, and maximum percent of weight lost. Many of the independent variables were significantly interrelated to each other (r = -0.90 to r = 0.91, p < 0.01 to p < 0.001). However, only the variables that correlated with time to return to birth weight were entered into the regression analysis. These variables included number of days diuretics were given before return to birth weight, maximum percent of weight lost, and day of life the infants reached their nadir weight. Number of days diuretics were given before return to birth weight correlated significantly with time to return to birth weight (r = 0.77, F = 26.66, p < 0.0001) although maximum percent of weight lost and day of life the infants reached their nadir weight had a minimal effect. CONCLUSIONS: Further research into the effects of diuretic therapy on weight changes in this population of infants may lead to interventions to minimize the negative effects of diuretics on return to birth weight. In addition, the older growth charts may not be applicable to this population of infants. Generation of new growth charts that provide growth curves based on these data could be useful in developing nutritional therapies that would promote growth and possibly decrease the length of hospital stay for these infants.
During locomotion, angular head movements act in a compensatory fashion to oppose the vertical trunk translation that occurs during each step in the gait cycle. This coordinated strategy between head and trunk motion serves to aid gaze stabilization and perhaps simplifies the sensory coordinate transformation between the head and trunk, allowing efficient descending motor control during locomotion. Following space flight, astronauts often experience oscillopsia during locomotion in addition to postural and gait instabilities, suggesting a possible breakdown in head-trunk coordination. The goal of the present investigation was to determine if exposure to the microgravity environment of space flight induces alteration in head-trunk coordination during locomotion. Astronaut subjects were asked to walk (6.4 km/h, 20 s trials) on a motorized treadmill while visually fixating on a centrally located earthfixed target positioned either 2 m (FAR) or 30 cm (NEAR) from the eyes. In addition, some trials were also performed during periodic visual occlusion. Head and trunk kinematics during locomotion were determined with the aid of a video-based motion analyzing system. We report data collected preflight (10 days prior to launch) and postflight (2 to 4 hours after landing). The coherence between pitch head and vertical trunk movements during gaze fixation of both FAR and NEAR targets was significantly reduced following space flight indicating decreased coordination between the head and trunk during postflight locomotion. Astronauts flying on their first mission showed greater alterations in the frequency spectra of pitch head movements as compared to their more experienced counterparts. These modifications in the efficacy of head movement control may account for the reported disruption in gaze performance during locomotion and may contribute to postflight postural and gait dysfunction.