Black Representation in the Primary Care Physician Workforce and Its Association With Population Life Expectancy and Mortality Rates in the US

Importance

Studies have suggested that greater primary care physician (PCP) availability is associated with better population health and that a diverse health workforce can improve care experience measures. However, it is unclear whether greater Black representation within the PCP workforce is associated with improved health outcomes among Black individuals.

Objective

To assess county-level Black PCP workforce representation and its association with mortality-related outcomes in the US.

Design, Setting, and Participants

This cohort study evaluated the association of Black PCP workforce representation with survival outcomes at 3 time points (from January 1 to December 31 each in 2009, 2014, and 2019) for US counties. County-level representation was defined as the ratio of the proportion of PCPs who identifed as Black divided by the proportion of the population who identified as Black. Analyses focused on between- and within-county influences of Black PCP representation and treated Black PCP representation as a time-varying covariate. Analysis of between-county influences examined whether, on average, counties with increased Black representation exhibited improved survival outcomes. Analysis of within-county influences assessed whether counties with higher-than-usual Black PCP representation exhibited enhanced survival outcomes during a given year of heightened workforce diversity. Data analyses were performed on June 23, 2022.

Main Outcomes and Measures

Using mixed-effects growth models, the impact of Black PCP representation on life expectancy and all-cause mortality for Black individuals and on mortality rate disparities between Black and White individuals was assessed.

Results

A combined sample of 1618 US counties was identified based on whether at least 1 Black PCP operated within a county during 1 or more time points (2009, 2014, and 2019). Black PCPs operated in 1198 counties in 2009, 1260 counties in 2014, and 1308 counties in 2019-less than half of all 3142 Census-defined US counties as of 2014. Between-county influence results indicated that greater Black workforce representation was associated with higher life expectancy and was inversely associated with all-cause Black mortality and mortality rate disparities between Black and White individuals. In adjusted mixed-effects growth models, a 10% increase in Black PCP representation was associated with a higher life expectancy of 30.61 days (95% CI, 19.13-42.44 days).

Conclusions and Relevance

The findings of this cohort study suggest that greater Black PCP workforce representation is associated with better population health measures for Black individuals, although there was a dearth of US counties with at least 1 Black PCP during each study time point. Investments to build a more representative PCP workforce nationally may be important for improving population health.

Rural-Urban Differences in the Utilization of Hospital-Based Care for Women of Reproductive Age

Background: To investigate rural-urban differences in hospital-based care utilization among women of reproductive age (18-44 years). Methods: Rural-urban differences were estimated for hospital outpatient visits, emergency department (ED) visits, hospitalizations, and associated expenditures both overall and by insurance status, by analyzing a nationally representative sample of women of reproductive age from the Medical Expenditure Panel Survey (2006-2015). Results: The study sample consisted of 48,114 women of reproductive age. Unadjusted results showed that rural women reported higher likelihood of hospital outpatient visits (rural vs. urban: 17.10% vs. 13.34%) although, among those using such care, fewer average visits (rural vs. urban: 2.00 vs. 2.56 visits). Rural women reported higher likelihood of ED visits (rural vs. urban: 18.13% vs. 15.11%) and more hospital stays (rural vs. urban: 0.13 vs. 0.11 stays). Adjusted results showed rural women had higher likelihood of outpatient care use (+2.5 percentage points; 95% confidence interval [CI] = 0.002-0.049) but fewer visits (-0.314 visits, 95% CI = -0.566 to -0.062). For the privately insured, rural women had greater likelihood of outpatient care (+3.1 percentage points, 95% CI = 0.001-0.060) and fewer ED visits (-0.031 visits, 95% CI = -0.061 to -0.003); for the publicly insured, rural women had more hospital stays (+0.045 stays, 95% CI = 0.009-0.083); for the uninsured, rural women had fewer outpatient visits among those using such care (-1.118 visits, 95% CI = -1.865 to -0.372) and shorter hospital stays overall (-0.093 nights, 95% CI = -0.181 to -0.005). Rural-urban expenditure differences were not significant between any insurance grouping. Conclusions: Rural-urban differences in hospital-based care utilization were observed, although somewhat heterogeneous by insurance status. Strengthening outpatient and preventive service access, particularly for publicly insured and uninsured rural women of reproductive age, is important for shifting care to lower cost settings and improving population health.

Cardiovascular outcomes in hospitalized patients with COVID-19 and history of cancer: a CORONA-VTE analysis

Background

In hospitalized patients with COVID-19, active cancer has been identified as a potential risk factor for adverse cardiovascular outcomes, including thrombosis. However, the impact of COVID-19 on outcomes in patients with a remote history of cancer is poorly understood. We evaluated hospitalized patients with a history of remote cancer and COVID-19 to examine whether a history of cancer contributes to 30-day major adverse cardiovascular outcomes among patients with COVID-19.

Methods

Using a retrospective cohort of 1114 patients from CORONA-VTE (Registry of Arterial and Venous Thromboembolic Complications in Patients With COVID-19), we looked at 399 hospitalized patients diagnosed with polymerase chain reaction (PCR)-confirmed COVID-19 within a large heath care network that consists of two large academic medical centers and several community hospitals. Twenty-six patients with active cancer or receiving cancer treatment within 1-year of COVID-19 diagnosis and five patients with unknown cancer history were excluded. We assessed 46 patients with a history of cancer and 322 patients without any history of cancer. The primary endpoint was the frequency of adjudicated major adverse cardiovascular outcomes, defined as myocardial infarction, stroke, pulmonary embolism, deep vein thrombosis, and mortality.

Results

Among the 46 hospitalized patients with COVID-19 and a history of cancer, 23.9% were non-white and 43.48% women. Compared to patients without any history of cancer, patients with a history of cancer were older (median 59.0 vs. 75.5 years, p<0.001) and had higher BMI (median 26.4 vs. 29.6 kg/m2, p<0.05). Patients with a history of cancer had higher rates of underlying CVD than those without (42.4% vs. 23.2%). Rates of major adverse cardiovascular events were similar in patients with and without a history of cancer (28.3% vs. 23.6%, respectively). Those with a history of cancer had a higher mortality rate (28.9% vs. 11.2%, p<0.05). Acute Respiratory Distress Syndrome (ARDS) and preexisting CVD were independently associated with mortality in this patient cohort (OR 19.7, 95% CI 7.5–51.7 and OR 2.9, 95% CI 1.2–6.9). History of remote cancer was not independently associated with mortality (OR 2.39, 95% CI 0.93–6.15, p=0.07).

Conclusion

Our findings indicate that a history of remote cancer is not independently associated with increased mortality in hospitalized COVID-19 patients. These data suggest that the cause of death among hospitalized patients with COVID-19 and history of cancer is most likely multifactorial, with a strong contribution from cardiovascular disease.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Janssen Pharmaceuticals

Determinants of rural-urban differences in health care provider visits among women of reproductive age in the United States

BACKGROUND

Rural health disparities and access gaps may contribute to higher maternal and infant morbidity and mortality. Understanding and addressing access barriers for specialty women's health services is important in mitigating risks for adverse childbirth events. The objective of this study was to investigate rural-urban differences in health care access for women of reproductive age by examining differences in past-year provider visit rates by provider type, and quantifying the contributing factors to these findings.

METHODS AND FINDINGS

Using a nationally-representative sample of reproductive age women (n = 37,026) from the Medical Expenditure Panel Survey (2010-2015) linked to the Area Health Resource File, rural-urban differences in past-year office visit rates with health care providers were examined. Blinder-Oaxaca decomposition analysis quantified the portion of disparities explained by individual- and county-level sociodemographic and provider supply characteristics. Overall, there were no rural-urban differences in past-year visits with women's health providers collectively (65.0% vs 62.4%), however differences were observed by provider type. Rural women had lower past-year obstetrician-gynecologist (OB-GYN) visit rates than urban women (23.3% vs. 26.6%), and higher visit rates with family medicine physicians (24.3% vs. 20.9%) and nurse practitioners/physician assistants (NPs/PAs) (24.6% vs. 16.1%). Lower OB-GYN availability in rural versus urban counties (6.1 vs. 13.7 providers/100,000 population) explained most of the rural disadvantage in OB-GYN visit rates (83.8%), and much of the higher family physician (80.9%) and NP/PA (50.1%) visit rates. Other individual- and county-level characteristics had smaller effects on rural-urban differences.

CONCLUSION

Although there were no overall rural-urban differences in past-year visit rates, the lower OB-GYN availability in rural areas appears to affect the types of health care providers seen by women. Whether rural women are receiving adequate specialized women's health care services, while seeing a different cadre of providers, warrants further investigation and has particular relevance for women experiencing high-risk pregnancies and deliveries.

Regional Variations in Maternal Mortality and Health Workforce Availability in the United States

BACKGROUND

Skilled, high-quality health providers and birth attendants are important for reducing maternal mortality.

OBJECTIVE

To assess whether U.S. regional variations in maternal mortality rates relate to health workforce availability.

DESIGN

Comparison of regional variations in maternal mortality rates and women's health provider rates per population and identification of a relationship between these measures.

SETTING

U.S. health system.

PARTICIPANTS

Women of child-bearing age and women's health providers, as captured in federal data sources from the Centers for Disease Control and Prevention, Census Bureau, and Health Resources and Services Administration.

MEASUREMENTS

Regional-to-national rate ratios for maternal mortality and women's health provider availability, calculated per population for women of reproductive age. Provider availability was examined across occupations (obstetrician-gynecologists, internal medicine physicians, family medicine physicians, certified nurse-midwives), in service-based categories (birth-attending and primary care providers), and across the entire women's health workforce (all studied occupations).

RESULTS

Maternal deaths per population increased nationally from 2009 to 2017 and, in 2017, were significantly higher in the South and lower in the Northeast (P < 0.001) than nationally. The occupational composition and per-population availability patterns of the women's health workforce varied regionally in 2017. The South had the lowest availability in the nation for nearly every health occupation and category studied, and the Northeast had the highest. This exploratory analysis suggests that subnational levels of provider availability across a region may be associated with higher maternal mortality rates.

LIMITATIONS

No causal relationship was established. Nationally representative maternal mortality and health workforce data sources have well-known limitations. Low numbers of observations limit statistical analyses.

CONCLUSION

Regional variations in maternal mortality rates may relate to the availability of birth-attending and primary care providers.

PRIMARY FUNDING SOURCE

None.

The geographic alignment of primary care Health Professional Shortage Areas with markers for social determinants of health

Background

The Health Resources and Services Administration (HRSA), an agency within the U.S. Department of Health and Human Services (HHS), works to ensure accessible, quality, health care for the nation’s underserved populations, especially those who are medically, economically, or geographically vulnerable. HRSA-designated primary care Health Professional Shortage Areas (pcHPSAs) provide a vital measure by which to identify underserved populations and prioritize locations and populations lacking access to adequate primary and preventive health care–the foundation for advancing health equity and maintaining health and wellness for individuals and populations. However, access to care is a complex, multifactorial issue that involves more than just the number of health care providers available, and pcHPSAs alone cannot fully characterize the distribution of medically, economically, and geographically vulnerable populations.

Methods and findings

In this county-level analysis, we used descriptive statistics and multiple correspondence analysis to assess how HRSA’s pcHPSA designations align geographically with other established markers of medical, economic, and geographic vulnerability. Reflecting recognized social determinants of health (SDOH), markers included demographic characteristics, race and ethnicity, rates of low birth weight births, median household income, poverty, educational attainment, and rurality. Nationally, 96 percent of U.S. counties were either classified as whole county or partial county pcHPSAs or had one or more established markers of medical, economic, or geographic vulnerability in 2017, suggesting that at-risk populations were nearly ubiquitous throughout the nation. Primary care HPSA counties in HHS Regions 4 and 6 (largely lying within the southeastern and south central United States) had the most pervasive and complex patterns in population risk.

Conclusion

HHS Regions displayed unique signatures with respect to SDOH markers. Descriptive and analytic findings from our work may help inform health workforce and health care planning at all levels, and, by illustrating both the complexity of and differences in county-level population characteristics in pcHPSA counties, our findings may have relevance for strengthening the delivery of primary care and addressing social determinants of health in areas beset by provider shortages.

Comprehensive Revenue and Expense Data Collection Methodology for Teaching Health Centers: A Model for Accountable Graduate Medical Education Financing

BACKGROUND

Despite considerable federal investment, graduate medical education financing is neither transparent for estimating residency training costs nor accountable for effectively producing a physician workforce that matches the nation's health care needs. The Teaching Health Center Graduate Medical Education (THCGME) program's authorization in 2010 provided an opportunity to establish a more transparent financing mechanism.

OBJECTIVE

We developed a standardized methodology for quantifying the necessary investment to train primary care physicians in high-need communities.

METHODS

The THCGME Costing Instrument was designed utilizing guidance from site visits, financial documentation, and expert review. It collects educational outlays, patient service expenses and revenues from residents' ambulatory and inpatient care, and payer mix. The instrument was fielded from April to November 2015 in 43 THCGME-funded residency programs of varying specialties and organizational structures.

RESULTS

Of the 43 programs, 36 programs (84%) submitted THCGME Costing Instruments. The THCGME Costing Instrument collected standardized, detailed cost data on residency labor (n = 36), administration and educational outlays (n = 33), ambulatory care visits and payer mix (n = 30), patient service expenses (n =  26), and revenues generated by residents (n = 26), in contrast to Medicare cost reports, which include only costs incurred by residency programs.

CONCLUSIONS

The THCGME Costing Instrument provides a model for calculating evidence-based costs and revenues of community-based residency programs, and it enhances accountability by offering an approach that estimates residency costs and revenues in a range of settings. The instrument may have feasibility and utility for application in other residency training settings.

Apparatus for measuring Seebeck coefficient and electrical resistivity of small dimension samples using infrared microscope as temperature sensor

An apparatus for measuring the Seebeck coefficient (α) and electrical resistivity (ρ) was designed to operate under an infrared microscope. A unique feature of this apparatus is its capability of measuring α and ρ of small-dimension (sub-millimeter) samples without the need for microfabrication. An essential part of this apparatus is a four-probe assembly that has one heated probe, which combines the hot probe technique with the Van der Pauw method for "simultaneous" measurements of the Seebeck coefficient and electrical resistivity. The repeatability of the apparatus was investigated over a temperature range of 40 °C-100 °C using a nickel plate as a standard reference. The results show that the apparatus has an uncertainty of ±4.9% for Seebeck coefficient and ±5.0% for electrical resistivity. The standard deviation of the apparatus against a nickel reference sample is -2.43 μVK(-1) (-12.5%) for the Seebeck coefficient and -0.4 μΩ cm (-4.6%) for the electrical resistivity, respectively.

Trend analysis of medical publications about LGBT persons: 1950-2007

Although there are currently at least 6 million lesbian, gay, bisexual, and transgender (LGBT) persons in the United States, there are no prior studies analyzing how this group is represented in the medical literature. An examination of published LGBT topics over a 57-year period was performed using OvidSP. A total of 21,728 publications was analyzed for topic using information from the title, keywords, subject headings, and abstracts. Several trends became apparent. The largest proportion of LGBT publications (31.78%) was devoted to HIV/AIDS and other sexually transmitted infections (STIs), yet there was an overall lack of emphasis on general health topics or common causes of mortality. Further analysis showed that if publications on HIV/AIDS or STIs addressed sexual orientation, they were more likely to be about LGBT persons than heterosexuals. Overall, the volume and range of medical publications on LGBT persons may not be reflective of the health care needs of this population.

The effect of patient age on perceived resuscitation outcomes by practitioners

BACKGROUND

When health care practitioners assist patients with decisions about advance directives, the risks and benefits of resuscitation options are often discussed. Whether practitioners have accurate perceptions about in-hospital resuscitation success rates is not known, nor is the effect of patient age on these perceptions. Age on its own has not been definitively associated with decreased inpatient survival after resuscitation. The goal of this study was to compare perceived resuscitation success rates with the actual observed rates at our hospital and to assess the effect of patient age on the perceived rates.

METHODS

A survey-based observational study of on-duty hospital-based faculty, internal medicine resident physicians, and critical care nurses was performed over a week-long recruitment period to estimate their perception of in-hospital resuscitation success rates for patients of different ages. The survey response rate was 100%.

RESULTS

Patient survival to hospital discharge following in-hospital resuscitation during a three-year period at New Hanover Regional Medical Center was 29.22% for patients < 70 years old and 20.13% for patients > or = 70. The perceived in-hospital resuscitation success rates were 38.76% for patients < 70 and 21.24% for patients > or = 70. This corresponds to a statistically significant overestimation of resuscitation success rates for patients < 70 years old (p < 0.001), although predictions were fairly accurate for patients > or = 70. When posed with one of two clinical scenarios where the only different variable was patient age, participants were statistically more likely to predict success for the younger patient. Subgroup analysis showed general agreement in the estimates between the three major types of practitioners, and factors such as length of experience in their current position and time since their last Advanced Cardiac Life Support (ACLS) recertification course did not have a significant impact on these perceptions.

CONCLUSIONS

Practitioners may overestimate resuscitation success rates in patients younger than 70. Disseminating information about ACLS success rates to clinicians, and what factors affect or do not affect these rates, seems essential.

Pelvic pain as an unusual first presentation of a demyelinating disease

Pelvic pain as the presenting symptom of demyelinating disease is rare. We report on a 49-year-old female patient that initially had symptoms of pain and anesthesia in the perineum. Symptoms later evolved to include both lower and upper extremity weakness and were associated with enhancing spinal cord lesions on MRI. Recognizing that the patient's disease was localized only to the spinal cord led to an eventual serological diagnosis of neuromyelitis optica (Devic's disease), a demyelinating syndrome that is now considered distinct from multiple sclerosis and that primarily affects the spinal cord and optic nerves. Pelvic pain is an unusual first presentation of this illness. Additionally, this case illustrates the challenges of establishing a diagnosis of neuromyelitis optica. Recognizing the distinct clinical features of this rare illness, referring specifically from a spinal cord or ophthalmological etiology, is essential for its rapid diagnosis, and hence for initiation of appropriate therapy.

Comparison of a commercially available clinical information system with other methods of measuring critical care outcomes data

PURPOSE

To compare the quality of data recorded by a commercially available clinical information system (CIS) to other commonly used methods for obtaining large amounts of patient data.

MATERIALS AND METHODS

Five sets of clinical patient data were chosen as a cross-section of all the data collected by a CIS in our intensive care unit (ICU): 1) Length of stay in the ICU, 2) Vital signs, 3) Days of mechanical ventilation, 4) medications, and 5) diagnoses. Data generated by our ICU CIS was compared with other parallel data sets commonly used to obtain the same data for clinical research.

RESULTS

When compared with our CIS, the hospital database recorded a length of stay at least 1 day longer than the actual length of stay 53% of the time. A search of 139,387 sets of vital signs showed less than 0.1% rate of suspected artifact. When compared to direct observation, our CIS correctly recorded days of mechanical ventilation in 23 of 26 patients (88%). Two other data sets, medical diagnoses and medications given showed significant differences with other commonly used databases of the same information collected outside the ICU (billing codes and pharmacy records respectively

CONCLUSIONS

Compared to other commonly used data sources for clinical research, a commercially available CIS is an acceptable source of ICU patient data.

Tetracyclines inhibit activated B cell function

Tetracyclines have recently been shown to exert a number of pleiotropic anti-inflammatory and immunomodulatory activities, independent of their antibiotic properties. These include the ability to inhibit metalloproteinases (MP), a class of enzymes involved in crucial cellular functions such as the shedding of soluble mediators and their receptors from the cell surface, as well as interaction with, and remodeling of, the extracellular matrix. Here we report that doxycycline at therapeutic concentrations (1--5 microg/ml) significantly suppresses Ig secretion and class switching by in vitro activated murine B cells. Suppression of Ig secretion correlates with a decrease in levels of mRNA for the terminal B cell differentiation-associated genes Blimp-1 and mad-4, as well as to a reduction in expression of the plasma cell markers Syndecan-1 and J chain. Inhibition of class switching occurs at the recombination stage and is also induced by other MP inhibitors, including tetracycline analogs lacking antibiotic activity and the chemically unrelated hydroxamate KB8301. These novel, direct effects of MP inhibitors on B lymphocytes suggest an intrinsic role for MP in B cell activation and likely explain some of the observed in vivo immunomodulatory properties of tetracyclines. Moreover, these findings have significant implications for tetracycline therapy in Ig-mediated autoimmune or allergic diseases and raise questions about the use of doxycycline-inducible transgenic systems for the study of B cell function.

Repair of sulfur mustard-induced DNA damage in mammalian cells measured by a host cell reactivation assay

DNA damage is thought to be the initial event that causes sulfur mustard (SM) toxicity, while the ability of cells to repair this damage is thought to provide a degree of natural protection. To investigate the repair process, we have damaged plasmids containing the firefly luciferase gene with either SM or its monofunctional analog, 2-chloroethyl ethyl sulfide (CEES). Damaged plasmids were transfected into wild-type and nucleotide excision repair (NER) deficient Chinese hamster ovary cells; these cells were also transfected with a second reporter plasmid containing RENILLA: luciferase as an internal control on the efficiency of transfection. Transfected cells were incubated at 37 degrees C for 27 h and then both firefly and RENILLA: luciferase intensities were measured on the same samples with the dual luciferase reporter assay. Bioluminescence in lysates from cells transfected with damaged plasmid, expressed as a percentage of the bioluminescence from cells transfected with undamaged plasmid, is increased by host cell repair activity. The results show that NER-competent cells have a higher reactivation capacity than NER-deficient cells for plasmids damaged by either SM or CEES. Significantly, NER-competent cells are also more resistant to the toxic effects of SM and CEES, indicating that NER is not only proficient in repairing DNA damage caused by either agent but also in decreasing their toxicity. This host cell repair assay can now be used to determine what other cellular mechanisms protect cells from mustard toxicity and under what conditions these mechanisms are most effective.

The efficiency of maternal transfer of lead and its influence on plasma IgE and splenic cellularity of mice

Exposure to the well known environmental toxicant lead is typically assessed by blood and/or bone levels and has been implicated in the onset of a variety of diseases affecting multiple human systems. However, there are conflicting data regarding the efficiency of in utero versus lactational transfer of lead to offspring, and the immunomodulatory effects of lead in early life have not been well defined. Pregnant BALB/c mice were exposed to lead acetate in their drinking water beginning at approximately day 15 of gestation, and cross-fostering of exposed/nonexposed litters was performed at parturition. Significant increases of blood lead levels of all exposed offspring were found at 1 week of age with evidence for both transplacental and lactational transfer. Additionally, mice exposed to lead continuously beginning at approximately 6 days prior to birth showed significant decreases in their blood lead levels 2 weeks after weaning, despite continued exposure as adults. This result suggests maternal transfer of lead is more efficient than oral adult exposure and that substantial lead transfer occurs both transplacentally and lactationally. The incidence of childhood atopic responses including asthma has risen considerably in recent years, particularly within areas containing higher levels of environmental pollutants. Plasma IgE levels of 2-week-old neonates exposed to lead before and/or after birth were measured as an index of atopy. Neonates exposed to lead transplacentally and/or lactationally had significantly higher plasma IgE levels, a biomarker of atopy, and lower splenic white blood cell numbers than age-matched controls. These results resemble the lag in immunocompetency and increase in serum IgE noted in atopic children and suggest a role for environmental toxicants and non-allergen-specific immunology in the prevalence of atopy and asthma in children.

Hypothermia causes a reversible, p53-mediated cell cycle arrest in cultured fibroblasts

Normal human fibroblasts grown in cell culture undergo a reversible growth arrest when incubated at 28 degrees C. During incubation at 28 degrees C, levels of p53 and p21 rise in these cells and cell cycle analysis shows that they have undergone a cell cycle arrest. To examine the importance of p53 in mediating this arrest, mouse embryo fibroblasts that are either wild-type or that are defective in p53 were also subjected to hypothermia. Only those cells with wild-type p53 undergo a cell cycle arrest, indicating that p53 has a role in mediating this response. Because many tumor cells have defective p53, this suggests that hypothermia may increase the selective toxicity of chemotherapeutic agents for tumor cells.

A critical appraisal of quantitative spectro-temporal analysis of the signal-averaged ECG: predicting arrhythmic events after myocardial infarction

The objective of this study was to determine if spectro-temporal analysis of the signal-averaged ECG (SAECG) predicts spontaneous sustained ventricular tachyarrhythmias and sudden death in patients prospectively followed after myocardial infarction (MI). A SAECG was recorded in 177 patients 9 +/- 5 days after MI. Spectro-temporal analysis of the SAECG involved incrementing a Hanning window every 3 ms beginning 20 mg before the end of the QRS complex and extending into the ST segment. Quantitative analysis was performed using a cross-correlation function to create a normality factor. A normality factor < 0.3 was deemed abnormal. The SAECG was abnormal in 41% of patients using time-domain analysis and 44% of patients using spectro-temporal analysis. There was no correlation between an abnormal SAECG in the time domain and the frequency domain. Patients with inferior wall MI were more likely to have an abnormal spectro-temporal map (odds ratio 2.26, P < 0.05). Time-domain analysis of the SAECG (relative risk (RR) 2.6) was a statistically significant univariate predictor of arrhythmic events. Spectro-temporal analysis of the SAECG was only weakly (RR 1.8) and not significantly (P = 0.15) associated with the spontaneous occurrence of these arrhythmias. When both time-domain analysis and spectro-temporal analysis of the SAECG were abnormal, the relative risk for an arrhythmic event was increased by 3.3-fold. Quantitative spectro-temporal analysis of high frequency signals within the SAECG cannot by itself predict the occurrence of spontaneous ventricular arrhythmias in patients after MI.

Vestibulo-ocular reflex gain as a measure of vestibular function in guinea pigs while in a recompression chamber: apparatus design and effects of nitrogen narcosis

There are several mechanisms whereby alteration of barometric pressure can produce vertigo in divers or aviators. Development of a reliable measure of vestibular function in an animal model is the first requirement for further study of these mechanisms. This report presents the development of a rotatory table device capable of evoking the vestibulo-ocular reflex (VOR) of a guinea pig while in a hyperbaric chamber. To assess the reproducibility of this response, eight animals were monitored by electronystagmography during rotations at three table velocities (62.4, 83.3, and 100 degrees/s). Two test sessions were performed on each animal with a 6-hour interval between sessions. The VOR gain was calculated by dividing the average peak velocity of the slow phase component of the nystagmus by the peak stimulus velocity. At least eight observations per test speed were averaged; calibration of eye movement was performed prior to each session by forced ocular abduction. Multifactorial analysis of variance revealed no significant differences (p > .05) between the differing rotation speeds nor between test sessions for individual animals. However, there was a significant difference in VOR gain between animals (p < .002). The VOR gain was then measured, using the same techniques, in another group of seven animals before, during, and after an air dive to the equivalent of 200 feet of seawater (7.06 atmospheres absolute) to assess the effects of nitrogen narcosis. Pre- and post-dive VOR gains were significantly greater than those measured at depth (p < .05). These results are consistent with the slow processing model of nitrogen narcosis and the controversial theory that central nervous system depressants decrease the VOR gain. The results also demonstrate the ability of this inexpensive apparatus to provide a sensitive measure of pressure-induced changes of vestibular function in guinea pigs.

Effects of position changes on transcutaneous carbon dioxide tension in neonates with respiratory distress

Routine neonatal care includes frequent position changes. Recent research has concluded that positions other than supine may result in beneficial physiologic responses. Specifically, several studies suggest that neonates may ventilate more effectively in a prone rather than in a supine position. This study tested the hypothesis that transcutaneous carbon dioxide tension (TcPCO2) would be lower in the prone than in the supine position in neonates with respiratory distress. Fourteen ventilated infants were studied. TcPCO2 was measured and recorded in prone, supine, and right-side-lying positions for each subject. There were no statistically significant differences in mean TcPCO2 values between the three positions (F = .45; df 2,39; P = .64). The relationship between TcPCO2 and PaCO2 values was stable (r = .88) during the studies. The results indicate that changing a neonate's position does not significantly alter transcutaneous carbon dioxide tension.

Continuous-wave Doppler for the noninvasive evaluation of aortic blood velocity and rate of change of velocity: evaluation in dogs

A new continuous-wave Doppler device is described, which has the capability of measuring peak aortic blood velocity and acceleration noninvasively in the ascending aorta of patients. To test the accuracy of the device, blood velocity and acceleration in the ascending aorta were compared with measurements obtained using an electromagnetic flowmeter in 16 open-chest anesthetized dogs. The Doppler probe was hand held directly on the aorta. Aortic flow was measured with a cuff electromagnetic flow transducer placed at the root of the aorta. Isoproterenol and propranolol, sometimes in combination with lidocaine, were administered intravenously to augment or reduce left ventricular contractile performance. Values of peak velocity, measured with the Doppler, corresponded closely to values measured with the electromagnetic flowmeter (r = 0.95). Values of peak acceleration also corresponded closely with the electromagnetic flow measurements (r = 0.96). The results indicate that valid measurements of blood acceleration in the ascending aorta, as well as blood velocity, can be obtained with continuous-wave Doppler.

Noninvasive evaluation of left ventricular performance based on peak aortic blood acceleration measured with a continuous-wave Doppler velocity meter

Peak aortic blood acceleration is recognized to be a sensitive index of global left ventricular performance. In the present study peak acceleration was assessed noninvasively in patients with a continuous-wave Doppler velocity meter. Peak aortic blood velocity and peak blood acceleration were measured by placing the ultrasonic transducer at the suprasternal notch. Measurements were obtained in 36 patients undergoing diagnostic cardiac catheterization. Peak velocity and acceleration were measured at rest just before left ventriculography. In patients with ejection fractions greater than 60%, peak acceleration was 19 +/- 5 m/sec/sec. In patients with ejection fractions of 41% to 60%, peak acceleration was lower, at 12 +/- 2 m/sec/sec (p less than .001). In patients with ejection fractions of 40% or less, peak acceleration (8 +/- 2 m/sec/sec) was markedly lower than in patients with ejection fractions greater than 60% (p less than .001). Peak acceleration showed a good linear correlation with ejection fraction (r = .90), and a better power fit (r = .93). These results indicate that peak acceleration, measured noninvasively with a continuous-wave Doppler velocity meter, is a useful indicator of global left ventricular performance.

Real-time orthogonal mode scanning of the heart. I. System design

A necessary percursor to real-time three-dimensional echocardiographic imaging is the ability to obtain multiple planes of acoustic data simultaneously. A new ultrasound imaging technique facilitates the display of two real-time orthogonal B-mode images (O-mode). The O-mode technique uses a novel two-dimensional transducer and system processor to interrogate the two perpendicular planes simultaneously, yielding sector arcs that share one origin. It permits simultaneous display of two sector arcs on a single monitor either side by side or in a two-dimensional projection designed to convey the three-dimensional nature of the acoustic data. Clinical results from the first 50 patients undergoing O-mode evaluation indicate that image quality in the two simultaneously obtained planes is equal to that of a single plane when the system is operating in its conventional format. These data confirm the feasibility of real-time multiplane imaging. The system design offers the potential for the future addition of more simultaneous planes and, thus, the possibility of real-time three-dimensional ultrasound imaging.

Visual evoked potential and pupillary signs. A comparison in optic nerve disease

We measured the pupil cycle time, the relative afferent pupillary defect, and the pattern-reversal visual evoked potential (VEP) in 41 patients with unilateral anterior ischemic optic neuropathy (AION) and 24 patients with unilateral optic neuritis. We speculated that the relative afferent pupillary defect would match the VEP amplitude and that the pupil cycle time would correspond to the VEP latency. We found a correlation between the relative afferent pupillary defect and VEP amplitude in patients with AION, but not in patients with optic neuritis. We also found that the pupil cycle time and VEP latency were weakly correlated, but only in patients with optic neuritis. In these two groups of patients with unilateral optic neuropathy, the most sensitive objective indicator of disease was the relative afferent pupillary defect. The least sensitive indicator was the pupil cycle time.

[Electroophthalmological characteristics in ischemic retinopathy (author's transl)]

In the ERG the b-wave and the oscillatory potentials are reduced or nonrecordable in ischemic retinopathy. The photopic b-wave appeared to be more sensitive than the scotopic b-wave. In the EOG the slow oscillation is reduced. These clinical observations are in accordance with the results of experimental studies in rhesus monkeys.