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Biomedical subjects

N E Leatherman

Publications and source records attributed to N E Leatherman.

10 recordsLinked to original sources
PubMed1991

Psychological outcomes of a pulmonary rehabilitation program.

This study assessed physiologic, psychological, and cognitive functioning in outpatients with COPD. Sixty-four subjects, 53 to 82 years of age, participated in the 30-day exercise rehabilitation program. The program consisted of exercise, education and psychosocial counselling. Participants were assessed prior to beginning the program and at the end of 30 days. Assessments at both times included physiologic functioning (bicycle ergometry testing, pulmonary function tests, 12-min walk), psychological well-being (anxiety, depression, psychiatric symptoms, perceived well-being) and an abbreviated neuropsychological test battery. Results indicate significant improvement in physical endurance and pulmonary function, significant reductions in symptoms of depression and anxiety, and improvement in measures of general well-being and neuropsychological functioning. The study suggests that exercise rehabilitation of older adults with COPD contributes not only to improvements in physical functioning and endurance, but also to enhanced cognitive functioning and psychological well-being.

Aged↗
PubMed1990

Ventilatory muscle loads and the frequency-tidal volume pattern during inspiratory pressure-assisted (pressure-supported) ventilation.

Pressure support ventilation (PSV) is a new form of mechanical ventilatory support that assists a patient's spontaneous ventilatory effort with a clinician-selected amount of inspiratory pressure. In order to assess the muscle unloading effect and the ventilatory pattern response to increasing levels of this inspiratory pressure assist, we first utilized a computer respiratory system model with variable alveolar ventilation demands and impedances. From this model, we calculated ventilatory muscle loads (expressed either as the work/min or as the pressure time index) during simulated, unassisted breathing and during simulated breathing with levels of inspiratory pressure assist up to that which resulted in a VT of 800 ml and no work being performed by the muscles (defined as PSVmax for the model conditions being studied). The optimal ventilatory pattern (i.e., frequency-tidal volume) under each ventilation and impedance condition was defined as that which resulted in minimal muscle load. Under these model conditions, we found that PSVmax ranged from 5 to 41 cm H2O and that as the level of inspiratory pressure assist was increased from zero to PSVmax, there was a biphasic response of both the ventilatory muscle loading and the ventilatory pattern. Specifically, at low levels of inspiratory pressure assist, the model predicted that the applied pressure would only partially unload the ventilatory muscles. Continued muscle energy expenditure would thus still be required, whereas the ventilatory pattern would change little. Conversely, at higher levels of inspiratory pressure assist, the model predicted that the applied pressure would be sufficient to completely unload the ventilatory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1989

Mechanical loads on the ventilatory muscles. A theoretical analysis.

Two indices of the total mechanical load on the ventilatory muscles, i.e., the work per minute (W.min-1) and the inflation pressure time index (PTI), have been developed to better assess muscle energy demands and fatigue potential. However, the relationship of these two indices to the various individual determinants of load and to muscle energy demands and fatigue potential are not well understood. To investigate these relationships in a theoretical fashion, we first constructed a computer model to quantitate the magnitude and relative effects of changes in the ventilation component of load, i.e., alveolar ventilation demands (VA) and dead space volume (VD), and changes in the respiratory system impedance component of load, i.e., compliance (Crs) and resistance (Raw), on W.min-1 and PTI over a wide, clinically relevant, range of ventilatory conditions. From this analysis, we demonstrated that: (1) high mechanical loads could be developed over a wide range of circumstances (i.e., W.min-1 ranged from 0.29 kg.m.min-1 to 30.55 kg.m.min-1 and PTI ranged from 1.22 to 28.8 cm H2O as ventilation increased from 7 to 39 L.min-1 and impedances worsened from normal to a combined restricted and obstructed pattern); (2) each load determinant (i.e., VA, VD, Crs, and Raw) contributed substantially to these two indices of total mechanical load; (3) although impedance changes had comparable effects on W.min-1 and PTI, ventilation changes, as would be expected, had a greater effect on W.min-1 than on PTI.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Simulation↗
PubMed1987

Effects of microgravity on tissue perfusion and the efficacy of astronaut denitrogenation for EVA.

The prevention of astronaut decompression sickness (DCS) during extravehicular activity (EVA) from the Shuttle Orbiter entails basic questions about how the efficacies of pre-EVA denitrogenations are affected by physiological responses and adaptations to microgravity. Many of these questions may be answered, without requiring inflight decompression experiments, when suitable inflight measurements of N2 elimination from spacecrew breathing 100% O2 can be analyzed using an N2 elimination/DCS risk correlation which has been calibrated in ground-based studies. In order to pursue this approach in our laboratory, a potentially flight-applicable, breath-by-breath method for measuring N2 elimination from human subjects breathing 100% O2 for 2-3-h periods has been developed. The present report describes this development with particular emphasis on required methodological accuracy and its achievement in view of certain properties of mass spectrometer performance. A method for the breath-by-breath analysis of errors in measured N2 elimination profiles is also described.

Adaptation, Physiological↗
PubMed1987

A likelihood analysis of experiments to test altitude decompression protocols for shuttle operations.

The principle of maximum likelihood and the method of linear regression both are used to fit mathematical models to experimental data, but likelihood can be applied to binary data such as the outcome of a decompression, whereas linear regression cannot. Maximum likelihood was applied to 548 individual altitude exposures from 30 experimental pressure profiles tested by NASA and the Air Force. Twelve decompression models were studied including modified Haldane models and models which assume that stationary bubbles cause Type I decompression sickness. The data was best represented by a model in which a bubble in tissue is surrounded by a diffusion barrier, but this representation was statistically indistinguishable from a single tissue Haldane model with a halftime of 508 min. By providing a quantitative measure of the agreement between theory and data, the principle of maximum likelihood offers an opportunity for improving the understanding of decompression mechanisms and for developing safer and faster decompression procedures.

Altitude↗
PubMed1975

A design improvement in continuous blood sampling and analysis for glucose in rest and exercise.

In the past 15 yr attempts to sample blood continuously for glucose analysis with the AutoAnalyzer (Technicon Corp.) have been reasonably successful in resting subjects. However, they have sometimes required heparinization of the subjects so as to avoid clotting in the tubes of the system. To avoid the hazards of heparinization during exercise, a method is described for sampling and analyzing blood glucose continuously with the AutoAnalyzer, using a specially designed male Luer adaptor which fits into disposable Teflon catheters.

Blood Glucose↗