A controlled trial of an environmental tobacco smoke reduction intervention in low-income children with asthma.

STUDY OBJECTIVES: To determine the effectiveness of a cotinine-feedback, behaviorally based education intervention in reducing environmental tobacco smoke (ETS) exposure and health-care utilization of children with asthma. DESIGN: Randomized controlled trial of educational intervention vs usual care. SETTING: The pediatric pulmonary service of a regional pediatric hospital. PARTICIPANTS: ETS-exposed, Medicaid/Medi-Cal-eligible, predominantly minority children who were 3 to 12 years old and who were seen for asthma in the hospital's emergency, inpatient, and outpatient services departments (n = 87). INTERVENTION: Three nurse-led sessions employing behavior-changing strategies and basic asthma education and that incorporated repeated feedback on the child's urinary cotinine level. MEASUREMENTS: The primary measurements were the urinary cotinine/creatinine ratio (CCR) and the number of acute asthma medical visits. The secondary measurements were number of hospitalizations, smoking restrictions in home, amount smoked, reported exposures of children, and asthma control. RESULTS: The intervention was associated with a significantly lower odds ratio (OR) for more than one acute asthma medical visit in the follow-up year, after adjusting for baseline visits (total visits, 87; OR, 0.32; p = 0.03), and a comparably sized but nonsignificant OR for one or more hospitalization (OR, 0.34; p = 0.14). The follow-up CCR measurement and the determination of whether smoking was prohibited inside the home strongly favored the intervention group (n = 51) (mean difference in CCR adjusted for baseline, -0.38; p = 0.26; n = 51) (60; OR [for proportion of subjects prohibiting smoking], 0.24; p = 0.11; n = 60). CONCLUSIONS: This intervention significantly reduced asthma health-care utilization in ETS-exposed, low-income, minority children. Effects sizes for urine cotinine and proportion prohibiting smoking were moderate to large but not statistically significant, possibly the result of reduced precision due to the loss of patients to active follow-up. Improving ETS reduction interventions and understanding their mechanism of action on asthma outcomes requires further controlled trials that measure ETS exposure and behavioral and disease outcomes concurrently.

Black-white differences in cigarette smoking uptake: progression from adolescent experimentation to regular use.

BACKGROUND: More U.S. adolescents and young adults have initiated cigarette smoking in recent years. Blacks have been less likely than whites to start smoking, and the gap has widened recently. Reasons accounting for this large black-white difference remain unclear. METHODS: A multiple logistic regression analysis was performed using a cohort of 2,467 adolescent smoking experimenters ages 11-18, within the 1989-1993 Teenage Attitudes and Practices Survey, a nationally representative survey. RESULTS: Among experimenters (1989), 25.7% of whites and 10.3% of blacks had progressed to current smoking (1993). The unadjusted odds ratio (OR) of progression for blacks (vs whites) was 0.33 [95% confidence interval (CI) 0.23, 0.48]. Adjustment for factors significantly predictive of progression (most parsimonious model) modified the black-white OR to 0.36 (CI 0.24, 0.55), while the full model yielded a black-white OR of 0.39 (CI 0.24, 0.66). CONCLUSIONS: The observed black-white difference in smoking progression was only partly explained by the factors evaluated, and some additional factor(s) must be important. Understanding the black-white difference in the progression from experimentation to current smoking may help prevent uptake among all adolescents.

Problems with serum IgM as a screening test for congenital infection.

The purpose of this study was to determine the usefulness of the total serum IgM level as a screening test for congenital infection in asymptomatic or mildly symptomatic infants. A retrospective medical record review was performed on 168 infants in whom the serum IgM was measured as a screen for congenital infection. The indications for testing, the yield of testing, and the adequacy of follow-up of abnormal values were examined. Only one infant was diagnosed with a congenital infection which was not specifically suspected prior to screening; this was a case of congenital cytomegalovirus (CMV). Inappropriate screening was frequently performed in infants in whom indications for specific evaluation were present. Appropriate follow-up testing was performed in only 30% (seven of 23) of the infants with elevated serum IgM who received their pediatric care at our institution. Because of the low yield (< 1%) and lack of follow-up shown in this study, as well as poor sensitivity, serum IgM was not a useful screening test for congenital infection in our institution.

Effect of stenosis inlet geometry on shear rates of blood flow in the upstream region.

Abnormal shear rates of blood flow have been implicated in the processes of thrombosis, atherosclerosis, and restenosis after angioplasty. However, no study has quantitated the effect of stenosis inlet geometry on the shear rates in the region upstream to the stenosis. To quantitate this effect, we measured the velocity profiles of blood flow at Reynolds numbers 175 and 350 upstream to different axisymmetric model stenoses in an excised canine aorta. Two 40% and two 75% stenoses were tested, one each with a 45-degree inlet angulation and one each with a 90-degree angulation. For the velocity measurements we used a specially developed external single-channel Doppler ultrasound system capable of resolving blood flow velocity at 91 microns radial intervals across the aorta. We found that increasing the severity of stenosis narrowing and angulation resulted in a significant decrease in shear rate at the endothelial surface (40%/45-degree stenosis: 189 +/- 46 sec-1 vs 75%/90-degree stenosis: 49 +/- 12 sec-1 at Reynolds number 350; p < 0.002) and a significant increase in the maximum shear rate within the vessel lumen (189 +/- 46 sec-1 vs 295 +/- 8 sec-1, respectively; p < 0.05) in the region immediately upstream to the stenosis. These effects were less pronounced for Reynolds number 175. We conclude that stenosis inlet geometry has a significant impact on the flow conditions in the region immediately upstream to the stenosis, which is dependent on the Reynolds number. This may be an important determinant of thrombosis and atherogenesis in this particular region.

Intravascular ultrasound imaging of blood: the effect of hematocrit and flow on backscatter.

This study evaluates two key parameters influencing the ultrasonic backscatter from blood--hematocrit and flow rate--at 30 MHz in an in vitro flow system. A range of hematocrits from 0 to 50% was studied at a constant flow rate; various flow rates between stagnation and physiologic levels were studied at a constant hematocrit. The relation between backscatter intensity and hematocrit was a convex function with a maximum between a hematocrit of 10% and 20%. In the flow rate studies, the blood backscatter intensity was a maximum at a flow rate of 0 and rapidly decreased at higher flow rates. These in vitro results suggest that blood backscatter intensity is minimally dependent on hematocrit in the physiologic range. However, a dramatic increase in backscatter intensity occurs with stagnant flow, presumably the result of red blood cell aggregation. Clinically, blood backscatter intensity may provide an index for risk of thrombus formation.