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Biomedical subjects

H Simpson

Publications and source records attributed to H Simpson.

155 records · Page 9Linked to original sources
PubMedDate not supplied

Observations on the limitations of two apnea/respiration monitors commonly used in the home.

The performance of two types of respiration monitor was studied with regard to detection of central apnea and individual breaths. Each monitor detected central apnea more frequently than routine intermittent nursing observation. Both false alarms, when the monitor failed to detect breathing movements (false positive for apnea), and false respiration signals, when the monitor failed to detect the absence of breathing movements (false negative for apnea) were found. The latter sometimes prevented alarms. It was found that a trial period of monitoring under the controlled conditions described permitted adjustments to be made which eliminated or minimized these sources of error. This should be considered when the monitors are issued for use in the home. It is important that persons issuing the monitors be aware of their limitations.

Apnea↗
PubMedDate not supplied

Manipulation of microcantilever oscillations.

Experimental observation of self-sustaining oscillations via a delayed feedback system is presented for a rectangular silicon microcantilever. The system is modeled as one and two-dimensional damped oscillator and the resulting delay differential equations are studied in frequency and time domain. The shortcomings of each model are outlined, and an improved formulation of the dynamics of the cantilever is presented.

Journal Article↗
PubMedDate not supplied

Force-displacement behaviour of biological tissue during distraction osteogenesis.

Limb lengthening and bone transport treatments are used frequently, and complications during treatment are common. Knowledge of the origin of tensile forces which resist distraction and the force-displacement response of biological tissues during extension would assist in reducing complication rates. Two tibial diaphyseal lengthenings carried out using an Ilizarov fixator were monitored by a displacement transducer to determine extension of the lengthening tissue (the regenerate bone), and by force transducers to determine tensile forces in the tissues that resist extension. The position of the force vector within a cross-section of the limb at the regenerate (provided by CT) was used to determine the origin of these forces. The muscle groups and adjacent fascia resisting extension were the gastrocnemius in one subject and the anterior and peroneal compartments in the other. In response to distraction, these tissues had relatively high stiffness (> 200 N/mm), less "immediate" displacement (< 35% of long term non-recoverable displacement) and inconsistent force relaxation properties (0-90%). In contrast, when the force vector was located in the vicinity of the regenerate, tissue exhibited lower stiffness (< 50 N/mm) and more immediate displacement (> 65% of long term nonrecoverable displacement), but also exhibited inconsistent force relaxation (0-67%).

Adaptation, Physiological↗
PubMedDate not supplied

Use of the preoperative levels of CEA in patients with colorectal cancer.

BACKGROUND/AIMS: Preoperative carcinoembryonic antigen has been considered useful as a prognostic factor and recurrence indicator of colorectal neoplasms. However, its diagnostic ability related to some parameters such as resectability or tumor staging has been less studied. The aim of this study was to evaluate the use of this marker as a diagnostic test for these parameters of colorectal cancer. METHODOLOGY: In a sample of 283 patients operated on for colorectal carcinoma data were retrospectively recorded corresponding to preoperative carcinoembryonic antigen, type of surgery performed (curative vs. non-curative), tumor intramural spread, lymph node involvement, distant metastasis, TNM stage, tumoral differentiation, survival time and survival time free of disease. Bivariate analysis between carcinoembryonic antigen and the rest of the parameters was performed. Also, the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy (efficiency) of the marker considered as a diagnostic test, were analyzed in relation to the tumoral resectability and tumoral spread. RESULTS: Preoperative level of serum carcinoembryonic antigen was statistically significantly associated with type of surgery performed (p < 0.001); tumoral intramural spread (p = 0.001); lymph node involvement (p < 0.001); presence of distant metastasis (p < 0.001); TNM staging (p < 0.001); overall survival period (p < 0.001) and disease-free survival time (p = 0.04). There was no relation between carcinoembryonic antigen and the degree of tumoral differentiation. The carcinoembryonic antigen's greatest sensitivity corresponded with the prediction for the type of the surgery performed and with the existence of distant metastasis, 80% and 70.9%, respectively. The negative predictive value was also high (> 90% in both cases). When considering the intramural spread, the specificity was 82% and its positive predictive value 93.1%. CONCLUSIONS: Preoperative levels of serum carcinoembryonic antigen, considered as a diagnostic test, are useful as predictors of resectability and tumor spread in colorectal carcinoma.

Adult↗
PubMedDate not supplied

Maximum voluntary cough: an indication of airway function.

Maximum voluntary coughing produces a flow-volume profile which incorporates the characteristics of a maximum expiratory flow-volume curve (MEFV). The cough flow-volume curve also has transient spikes of supramaximal flow, interspersed with portions of zero flow when the glottis is closed. The peak flow rates of the supramaximal flow transients during cough decrease in a linear fashion as lung volume goes down from total lung capacity to residual volume. Cough flow-volume curves have been recorded from forty-two subjects between the ages of 7 and 56 yr. The rate of change of cough peak flow shows a positive correlation with airway conductance measured plethysmographically in children. The ratio of forced expiratory flow to cough peak flow (the cough ratio) expresses the maximum expiratory flow rate during forced expiration as a proportion of that which can be achieved with a cough. The cough ratio declines during adult life, because although there is a fall in cough peak flow with age there is a proportionally greater fall in MEFV-equivalent flow. These investigations explore the information to be gained from cough flow-volume curves by examining the cough in a heterogeneous group of individuals.

Adolescent↗
PubMedDate not supplied

Toward a chronopsy: Part III. Automatic monitoring of rectal, axillary and breast surface temperature and of wrist activity; effects of age and of ambulatory surgery followed by nosocomial infection.

Data of core and breast surface temperature and motor activity collected automatically with ambulatory devices, reveal circadian rhythms of different prominence in these various potential chronobiologic markers. Chronobiologic serial sections further allow the study of any alterations of the circadian rhythm parameters following ambulatory surgery. An approach using miniaturized instrumentation and methods of time series analysis may signal the danger of postoperative complications and, if it prompts timely preventive measures, may increase the safety of ambulatory surgery in particular.

Ambulatory Surgical Procedures↗