Computer access and Internet use by urban and suburban emergency department customers.

BACKGROUND: Patients are increasingly using the Internet (43% in 2000 vs. 70% in 2006) to obtain health information, but is there a difference in the ability of urban and suburban emergency department (ED) customers to access the Internet? STUDY OBJECTIVE: To assess computer and Internet resources available to and used by people waiting to be seen in an urban ED and a suburban ED. METHODS: Individuals waiting in the ED were asked survey questions covering demographics, type of insurance, access to a primary care provider, reason for their ED visit, computer access, and ability to access the Internet for health-related matters. RESULTS: There were 304 individuals who participated, 185 in the urban ED and 119 in the suburban ED. Urban subjects were more likely than suburban to be women, black, have low household income, and were less likely to have insurance. The groups were similar in regard to average age, education, and having a primary care physician. Suburban respondents were more likely to own a computer, but the majority in both groups had access to computers and the Internet. Their frequency of accessing the Internet was similar, as were their reasons for using it. Individuals from the urban ED were less willing to schedule appointments via the Internet but more willing to contact their health care provider via e-mail. The groups were equally willing to use the Internet to fill prescriptions and view laboratory results. CONCLUSION: Urban and suburban ED customers had similar access to the Internet. Both groups were willing to use the Internet to access personal health information.

Cerebral oxygenation in awake rats during acclimation and deacclimation to hypoxia: an in vivo electron paramagnetic resonance study.

Exposure to high altitude or hypobaric hypoxia results in a series of metabolic, physiologic, and genetic changes that serve to acclimate the brain to hypoxia. Tissue Po(2) (Pto(2)) is a sensitive index of the balance between oxygen delivery and utilization and can be considered to represent the summation of such factors as cerebral blood flow, capillary density, hematocrit, arterial Po(2), and metabolic rate. As such, it can be used as a marker of the extent of acclimation. We developed a method using electron paramagnetic resonance (EPR) to measure Pto(2) in unanesthetized subjects with a chronically implanted sensor. EPR was used to measure rat cortical tissue Pto(2) in awake rats during acute hypoxia and over a time course of acclimation and deacclimation to hypobaric hypoxia. This was done to simulate the effects on brain Pto(2) of traveling to altitude for a limited period. Acute reduction of inspired O(2) to 10% caused a decline from 26.7 ± 2.2 to 13.0 ± 1.5 mmHg (mean ± SD). Addition of 10% CO(2) to animals breathing 10% O(2) returned Pto(2) to values measured while breathing 21% O(2,) indicating that hypercapnia can reverse the effects of acute hypoxia. Pto(2) in animals acclimated to 10% O(2) was similar to that measured preacclimation when breathing 21% O(2). Using a novel, individualized statistical model, it was shown that the T(1/2) of the Pto(2) response during exposure to chronic hypoxia was approximately 2 days. This indicates a capacity for rapid adaptation to hypoxia. When subjects were returned to normoxia, there was a transient hyperoxygenation, followed by a return to lower values with a T(1/2) of deacclimation of 1.5 to 3 days. These data indicate that exposure to hypoxia results in significant improvements in steady-state oxygenation for a given inspired O(2) and that both acclimation and deacclimation can occur within days.

Modeling of the response of ptO2 in rat brain to changes in physiological parameters.

It is known that oxygen tension in tissue (ptO2) will change in response to an alteration of physiological parameters including: pCO2 in arterial blood, blood flow, capillary density, oxygen carrying capacity, and p50 of hemoglobin. We have used modeling to compute the change of PtO2 in response to changes of each physiological parameter and related these changes to experimental data. The oxygen distribution in a Krogh cylinder was computed assuming a linear decrease of hemoglobin saturation from the arterial to the venous end of the capillary. Parameters of the model were used to compute the baseline cerebral PtO2 expressed as the mean value of the PtO2 over the whole cylinder. These parameters were adjusted to derive PtO2 values close to those measured at the relevant experimental conditions. Then each desired parameter was varied to calculate the change in PtO2 related to this parameter. Effects of different factors on cerebral PtO2 were modeled and compared with experimental values obtained with various experimental interventions including: changing CBF, modifying p50 with the allosteric modifier RSR13, modification of capillary density, and hemoglobin content. An acceptable agreement of the computed and the experimental changes of the cerebral PtO2 was obtained for these experimental conditions.

Monitoring angiogenesis in brain using steady-state quantification of DeltaR2 with MION infusion.

An MRI method for quantification of cerebral blood volume (CBV) in time-course studies of angiogenesis is described. Angiogenesis was stimulated by acclimation to hypoxia. The change in relaxation rate, R2, which is relatively sensitive to the microvasculature, was quantified before and after infusion of a superparamagnetic vascular contrast agent (MION). The DeltaR2 was measured in serum and brain parenchyma with a multiecho sequence. In vitro and in vivo calibration curves of MION concentration vs. R2 were approximated by a linear function. CBV was 3.14 +/- 0.32% (mean +/- SE, n=13) and 6.42 +/- 0.54% (n=4) before and after acclimation. A second acclimated group was hemodiluted to control for polycythemia. CBV was not significantly different between hemodiluted and nonhemodiluted groups. In animals where NMR measurements were taken before and after acclimation, there was a 120% increase in CBV. The NMR technique was validated using quantitative morphometrics, which showed an increase of 147% in CBV with acclimation. We found a linear correlation between MRI and the morphometric results for CBV, as well as demonstrating a quantitative equivalence for relative changes in CBV. This article describes a simple, repeatable method of imaging brain microvascular volume using a plasma-based contrast agent that can be applied to longitudinal studies of angiogenesis.