Effects of Sustained Low-Level Elevations of Carbon Dioxide on Cerebral Blood Flow and Autoregulation of the Intracerebral Arteries in Humans

Cerebral blood flow velocity (CBFv) was measured by insonating the middle cerebral arteries of 4 subjects using a 2 Mhz transcranial Doppler. Ambient CO2 was elevated to 0.7% for 23 days in the first study and to 1.2% for 23 days in the same subjects in the second study. By non-parametric testing CBFv was elevated significantly by +35% above pre-exposure levels during the first 1-3 days at both exposure levels after which CBFv progressively readjusted to pre-exposure levels. Despite similar CBFv responses, headache was only reported during the initial phase of exposure to 1.2% CO2. Vascular reactivity to CO2 assessed by rebreathing showed a similar pattern with the CBFv increases early in the exposures being greater than those elicited later. An increase in metabolic rate of the visual cortex was evoked by having the subjects open and close their eyes during a visual stimulus. Evoked CBFv responses measured in the posterior cerebral artery were also elevated in the first 1-3 days of both studies returning to pre-exposure levels as hypercapnia continued. Cerebral vascular autoregulation assessed by raising head pressure during 10 deg head-down tilt both during the low-level exposures and during rebreathing was unaltered. There were no changes in the retinal microcirculation during serial fundoscopy studies. The time-dependent changes in CO2 vascular reactivity might be due either to retention of bicarbonate in brain extracellular fluid or to progressive increases in ventilation, or both. Cerebral vascular autoregulation appears preserved during chronic exposure to these levels of ambient CO2

Employed But Still Unhappy? On the Relevance of the Social Work Norm

In the modern welfare state, people who cannot make a living usually receive financial assistance from public funds. Accordingly, the so-called social work norm against living off other people is violated, which may be the reason why the unemployed are so unhappy. If so, however, labour market concepts based on the notion of promoting low-paid jobs that are subsidised if necessary with additional payments would appear far less favourable. It could be that people are employed, but still unhappy. Using German panel data, this paper examines the relevance of the social work norm and finds a significant disutility effect of living off public funds. Although this is true for employed people as well, the results show that the individual is generally better off having a job that requires additional assistance, than having no job at all. On the other hand, such policies as the recent German labour market reforms can trigger undesired side-effects, if policy-makers ignore the issue of the social work norm

Validation of a self-efficacy instrument and its relationship to performance of crisis resource management skills

Self-efficacy is thought to be important for resuscitation proficiency in that it influences the development of and access to the associated medical knowledge, procedural skills and crisis resource management (CRM) skills. Since performance assessment of CRM skills is challenging, self-efficacy is often used as a measure of competence in this area. While self-efficacy may influence performance, the true relationship between self-efficacy and performance in this setting has not been delineated. We developed an instrument to measure pediatric residents’ self-efficacy in CRM skills and assessed its content validity, internal structure, and relationship to other variables. After administering the instrument to 125 pediatric residents, critical care fellows and faculty, we performed an exploratory factor analysis within a confirmatory factor analysis as well as a known group comparison. The analyses specified four factors that we defined as: situation awareness, team management, environment management, and decision making. Pediatric residents reported lower self-efficacy than fellows and faculty in each factor. We also examined the correlation between self-efficacy and performance scores for a subset of 30 residents who led video recorded simulated resuscitations and had their performances rated by three observers. We found a significant, positive correlation between residents’ self-efficacy in situation awareness and environment management and their overall performance of CRM skills. Our findings suggest that in a specific context, self-efficacy as a form of self-assessment may be informative with regards to performance

Air pollution and the microvasculature: A cross-sectional assessment of in vivo retinal images in the population-based multi-ethnic study of atherosclerosis (MESA)

10.1371/journal.pmed.1000372PLoS Medicine711