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Biomedical subjects

A M Koontz

Publications and source records attributed to A M Koontz.

7 recordsLinked to original sources
PubMed2001

An autoregressive modeling approach to analyzing wheelchair propulsion forces.

Biomechanical signals collected during wheelchair propulsion are often analyzed by computing averages and/or peak values over several strokes. Due to the complex nature of the signals, this type of analysis may not be specific to identifying factors that may predispose a wheelchair user to joint pain/injury. Hence, a new technique is introduced that uses a system identification approach, autoregressive (AR) modeling, to analyze wheelchair propulsion force waveforms. In this application an AR method was used to create a model force waveform based on current and past values of digital pushrim force data. The feasibility of the AR modeling method over point-wise methods to detect asymmetry among force waveforms was tested with a group of 20 wheelchair users. Subjects propelled at a constant 0.9 m/s on a roller system during which 20 s of force data were collected from the SMART(Wheel)s, force and torque sensing pushrims. Both methods showed that the wheelchair users as a group propelled evenly, however, individual analysis using the AR model error estimates indicated that twenty-five percent demonstrated significant asymmetry in their force waveforms. If only point-wise means and variances of the applied bilateral forces were considered, most subjects would have appeared symmetrical. Thus, the AR modeling approach is more sensitive to detecting anomalies in propulsion technique.

Adult↗
PubMed2001

Comparison of three different models to represent the wrist during wheelchair propulsion.

Due to the high incidence of secondary wrist injury among manual wheelchair users, recent emphasis has been placed on the investigation of wheelchair propulsion biomechanics. Accurate representation of wrist activity during wheelchair propulsion may help to elucidate the mechanisms contributing to the development of wrist injuries. Unfortunately, no consensual wrist biomechanical model has been established. In order to determine if different methodologies obtain similar results, this investigation created and compared three different wrist models: 1) a fixed joint center placed between the styloids (midstyloid joint center); 2) a joint center with 2 degrees of freedom computed from de Leva's joint center data; and 3) a floating joint center. Results indicate that wrist flexion and extension angles are highly consistent between models, however, radial and ulnar deviation angles vary considerably. Mean maximum right flexion angles were found to be 3.5 degrees, 2.2 degrees, and 5.0 degrees for the midstyloid, de Leva, and floating joint center models, respectively. Extension angles were 22.3 degrees, 23.6 degrees, and 23.6 degrees, respectively. Mean maximum right radial deviation angles for the midstyloid, de Leva, and floating joint center models were 26.0 degrees, 26.9 degrees, and 45.1 degrees, respectively, and ulnar deviation angles were found to be 30.5 degrees, 38.8 degrees, and 10.2 degrees, respectively. This information is useful when comparing kinematic studies and further supports the need for consensual methodology.

Biomechanical Phenomena↗
PubMed1988

Racial differences in pregnancy outcomes.

Black mothers in the United States are twice as likely as their white counterparts to experience a wide variety of adverse pregnancy outcomes, including prematurity, low birth weight, and infant and fetal death. Although blacks have higher proportions of births with maternal risk factors such as young age, high birth order, low education, and unmarried mothers, these differences do not account for their higher rates of adverse outcomes; the reasons for the excess remain largely unknown. To develop effective interventions to reduce the racial disparities in pregnancy outcome, we must further our understanding of the mechanisms underlying premature onset of labor and intrauterine growth.

Black or African American↗
PubMedDate not supplied

Serving women in need: nurse-midwifery practice in the United States.

OBJECTIVE: Nurse-midwifery practices in the United States were examined to study the relationship between certified nurse-midwives' (CNMs) demographic, work setting, and practice characteristics in terms of clientele, practice size, and practice type. Factors that might influence the ability of CNMs to serve populations at risk for poor outcomes were given particular attention. METHODOLOGY: A total of 2,405 responses to a 1998 mailed survey of 6,365 nurse-midwives ever-certified by the American College of Nurse-Midwives were analyzed. RESULTS: Study results indicated that CNMs continue to serve a population who are, based on a social risk profile, disproportionately at risk for poor pregnancy outcomes, including women who are uninsured (16%), immigrant (27%), adolescent (29%), and women of color (50%). It was also found that clientele varied according to practice settings: CNMs working in non-hospital, nonprofit settings served a clientele that was 65% nonwhite, 44% immigrant, 40% adolescent, and 29% uninsured; these CNMs received 61% of their client payments from Medicaid. CNMs working in private offices or for managed care organizations were less likely to serve women with these characteristics. CONCLUSION: Study results, taken in conjunction with research that documents the safety of nurse-midwifery practice, reinforce policy recommendations that support expanded access to nurse-midwifery services. Findings also indicate a need for further research in the areas of CNM workload and productivity in managed care settings and the association between CNM race and ethnicity and the race and ethnicity of their clients.

Ethnicity↗
PubMedDate not supplied

Perceptions of risks of smoking and heavy drinking during pregnancy: 1985 NHIS findings.

As part of the Health Promotion and Disease Prevention Questionnaire administered in the 1985 National Health Interview Survey, nearly 20,000 respondents ages 18-44 answered questions about their awareness of the risks of smoking and heavy drinking during pregnancy. In reference to smoking, interviewers asked about miscarriage, stillbirth, prematurity, and low birth weight; in reference to heavy drinking, they asked about miscarriage, mental retardation, low birth weight, and birth defects, as well as fetal alcohol syndrome. For each of these adverse outcomes, a majority of subjects acknowledged increased risk because of smoking or heavy drinking during pregnancy. The range was 66-80 percent of respondents for the four questions on smoking, with the perceived association to smoking strongest for low birth weight. Approximately 84 percent of respondents associated heavy drinking with increased risk for each of the suggested pregnancy outcomes. Smoking seemed to be perceived to pose a lesser risk to pregnancy than heavy drinking. This relative lack of awareness of the pregnancy risks of smoking was more apparent among respondents with less education and more pronounced among blacks than whites. Women were more likely than men to express some opinion on these pregnancy-related questions and were more cognizant than men of the risks. On this limited survey, Americans ages 18-44 were not very knowledgeable about fetal alcohol syndrome. Among the 55 percent who had heard of fetal alcohol syndrome, fewer than one in four correctly identified it as a set of birth defects when offered three possible definitions. It will be interesting to correlate responses to these "knowledge" questions with NHIS data still forthcoming on reported actual smoking and drinking behavior among women respondents who were recently pregnant.

Adolescent↗
PubMedDate not supplied

Pregnancy and infant health: progress toward the 1990 objectives.

Assuring all infants a healthy start in life and enhancing the health of their mothers are goals of the Public Health Service's health promotion and disease prevention initiative. The 13 priority objectives selected for the pregnancy and infant health area of the initiative focus on lowering infant, neonatal, and perinatal mortality rates, reducing the number of low-birth-weight infants, improving the health care of pregnant women and infants through regionalized perinatal care systems and comprehensive primary care services, encouraging early prenatal care and healthy lifestyles in pregnancy, and targeting the factors and populations associated with health risk. Although considerable progress has been made in this century in lowering the infant mortality rate, infants continue to die at a higher rate than members of any other age category under 60 years, and black infants die at almost twice the rate of white infants. To lower these high mortality rates, the private, public, and voluntary sectors have cooperated in new approaches to perinatal and infant health that have already produced some encouraging results. Recent data, for example, indicate that the priority objective of universal screening of newborns for treatable metabolic disorders has already been achieved and that the target for neonatal and infant mortality rates could be reached earlier than 1990. Substantial challenges, however, lie ahead if the current racial and ethnic differentials evident in the rates for prenatal care registration, low-birth-weight babies, and maternal and infant mortality are to be eliminated.

Female↗