Evaluation of tests of central nervous system performance after hypoxemia for a model for cognitive impairment

A longitudinal study on the impact of high-altitude hypoxia on perceptual processes

This study aimed to explore the neural mechanisms underlying high-altitude (HA) adaptation and deadaptation in perceptual processes in lowlanders. Eighteen healthy lowlanders were administered a facial S1-S2 matching task that included incomplete face (S1) and complete face (S2) photographs combined with ERP technology. Participants were tested at four time points: shortly before they departed the HA (Test 1), twenty-five days after entering the HA (Test 2), and one week (Test 3) and one month (Test 4) after returning to the lowlands. Compared with those at sea level (SL), shorter reaction times (RTs), shorter latencies of P1 and N170, and larger amplitudes of complete face N170 were found in HAs. After returning to SL, compared with that of HA, the amplitude of the incomplete face P1 was smaller after one week, and the complete face was smaller after one month. The right hemisphere N170 amplitude was greater after entering HA and one week after returning to SL than at baseline, but it returned to baseline after one month. Taken together, the current findings suggest that HA adaptation increases visual cortex excitation to accelerate perceptual processing. More mental resources are recruited during the configural encoding stage of complete faces after HA exposure. The perceptual processes affected by HA exposure are reversible after returning to SL, but the low-level processing stage differs between incomplete and complete faces due to neural compensation mechanisms. The configural encoding stage in the right hemisphere is affected by HA exposure and requires more than one week but less than one month to recover to baseline.

Sensitivity of cognitive function tests to acute hypoxia in healthy subjects: a systematic literature review

Acute exposure to hypoxia can lead to cognitive impairment. Therefore, hypoxia may become a safety concern for occupational or recreational settings at altitude. Cognitive tests are used as a tool to assess the degree to which hypoxia affects cognitive performance. However, so many different cognitive tests are used that comparing studies is challenging. This structured literature evaluation provides an overview of the different cognitive tests used to assess the effects of acute hypoxia on cognitive performance in healthy volunteers. Less frequently used similar cognitive tests were clustered and classified into domains. Subsequently, the different cognitive test clusters were compared for sensitivity to different levels of oxygen saturation. A total of 38 articles complied with the selection criteria, covering 86 different cognitive tests. The tests and clusters showed that the most consistent effects of acute hypoxia were found with the Stroop test (where 42% of studies demonstrated significant abnormalities). The most sensitive clusters were auditory/verbal memory: delayed recognition (83%); evoked potentials (60%); visual/spatial delayed recognition (50%); and sustained attention (47%). Attention tasks were not particularly sensitive to acute hypoxia (impairments in 0%-47% of studies). A significant hypoxia level-response relationship was found for the Stroop test (p = 0.001), as well as three clusters in the executive domain: inhibition (p = 0.034), reasoning/association (p = 0.019), and working memory (p = 0.024). This relationship shows a higher test sensitivity at more severe levels of hypoxia, predominantly below 80% saturation. No significant influence of barometric pressure could be identified in the limited number of studies where this was varied. This review suggests that complex and executive functions are particularly sensitive to hypoxia. Moreover, this literature evaluation provides the first step towards standardization of cognitive testing, which is crucial for a better understanding of the effects of acute hypoxia on cognition.

Alteration of functional connectivity despite preserved cerebral oxygenation during acute hypoxia

Resting state networks (RSN), which show the connectivity in the brain in the absence of any stimuli, are increasingly important to assess brain function. Here, we investigate the changes in RSN as well as the hemodynamic changes during acute, global hypoxia. Mice were imaged at different levels of oxygen (21, 12, 10 and 8%) over the course of 10 weeks, with hypoxia and normoxia acquisitions interspersed. Simultaneous GCaMP and intrinsic optical imaging allowed tracking of both neuronal and hemodynamic changes. During hypoxic conditions, we found a global increase of both HbO and HbR in the brain. The saturation levels of blood dropped after the onset of hypoxia, but surprisingly climbed back to levels similar to baseline within the 10-min hypoxia period. Neuronal activity also showed a peak at the onset of hypoxia, but dropped back to baseline as well. Despite regaining baseline sO2 levels, changes in neuronal RSN were observed. In particular, the connectivity as measured with GCaMP between anterior and posterior parts of the brain decreased. In contrast, when looking at these same connections with HbO measurements, an increase in connectivity in anterior-posterior brain areas was observed suggesting a potential neurovascular decoupling.

Sauerstoff in der Akuttherapie

Sauerstoff (O₂) ist ein Arzneimittel und soll in der Akuttherapie bei Vorliegen einer Hypoxämie ärztlich verordnet und dokumentiert, regelmäßig überwacht und reevaluiert werden. Zur Überwachung dient in der Akutmedizin die Pulsoxymetrie, bei Risikopatienten sind arterielle Blutgase zu bestimmen. Sowohl eine Hypoxämie als auch eine Hyperoxämie sind bei akut Kranken zu vermeiden. Es sollten Zielbereiche der O₂-Sättigung (S_pO₂ [pulsoxymetrisch gemessene O₂-Sättigung]) festgelegt werden. Diese hängen vom Hyperkapnierisiko und vom Beatmungsstatus ab: spontan atmende Patienten ohne bzw. mit Hyperkapnierisiko: Ziel‑S_pO₂ = 92–96 % bzw. 88–92 %, beatmete Patienten: arterielle O₂-Sättigung zwischen 92 und 96 %. Die Zielbereiche gelten bis auf wenige Ausnahmen für alle Erwachsenen unabhängig von der Diagnose. Die O₂-Applikationssysteme werden nach Patientensicherheit und -komfort ausgewählt. Bei Beendigung der O₂-Gabe kann es bei vulnerablen Menschen zur Reboundhypoxämie kommen.

Acute mountain sickness and sleep disturbances differentially influence cognition and mood during rapid ascent to 3000 and 4050 m

The impact of acute mountain sickness (AMS) and sleep disturbances on mood and cognition at two altitudes relevant to the working and tourist population is unknown. Twenty unacclimatized lowlanders were exposed to either 3000 m (n = 10; 526 mmHg) or 4050 m (n = 10; 460 mmHg) for 20 h in a hypobaric chamber. AMS prevalence and severity was assessed using the Environmental Symptoms Questionnaire (ESQ) and an AMS‐C score ≥ 0.7 indicated sickness. While sleeping for one night both at sea level (SL) and high altitude (HA), a wrist motion detector was used to measure awakenings (Awak, events/h) and sleep efficiency (Eff, %). If Eff was ≥85%, individuals were considered a good sleeper (Sleep+). Mood and cognition were assessed using the Automated Neuropsychological Assessment Metric and Mood Scale (ANAM‐MS). The ESQ and ANAM‐MS were administered in the morning both at SL and after 20 h at HA. AMS severity (mean ± SE; 1.82 ± 0.27 vs. 0.20 ± 0.27), AMS prevalence (90% vs. 10%), depression (0.63 ± 0.23 vs. 0.00 ± 0.24) Awak (15.6 ± 1.6 vs. 10.1 ± 1.6 events/h), and DeSHr (38.5 ± 6.3 vs. 13.3 ± 6.3 events/h) were greater (p < 0.05) and Eff was lower (69.9 ± 5.3% vs. 87.0 ± 5.3%) at 4050 m compared to 3000 m, respectively. AMS presence did not impact cognition but fatigue (2.17 ± 0.37 vs. 0.58 ± 0.39), anger (0.65 ± 0.25 vs. 0.02 ± 0.26), depression (0.63 ± 0.23 vs. 0.00 ± 0.24) and sleepiness (4.8 ± 0.4 vs. 2.7 ± 0.5) were greater (p < 0.05) in the AMS+ group. The Sleep− group, compared to the Sleep+ group, had lower (p < 0.05) working memory scores (50 ± 7 vs. 78 ± 9) assessed by the Sternberg 6‐letter memory task, and lower reaction time fatigue scores (157 ± 17 vs. 221 ± 22), assessed by the repeated reaction time test. Overall, AMS, depression, DeSHr, and Awak were increased (p < 0.05) at 4050 m compared to 3000 m. In addition, AMS presence impacted mood while poor sleep impacted cognition which may deteriorate teamwork and/or increase errors in judgement at HA.

German S3 Guideline: Oxygen Therapy in the Acute Care of Adult Patients

BACKGROUND

Oxygen (O2) is a drug with specific biochemical and physiological properties, a range of effective doses and may have side effects. In 2015, 14% of over 55,000 hospital patients in the UK were using oxygen. 42% of patients received this supplemental oxygen without a valid prescription. Health care professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

A national S3 guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. A literature search was performed until February 1, 2021, to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for assessing the quality of evidence and for grading guideline recommendation, and a formal consensus-building process was performed.

RESULTS

The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O2 therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are based depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

This is the first national guideline on the use of oxygen in acute care. It addresses health care professionals using oxygen in acute out-of-hospital and in-hospital settings.

Oculometric Feature Changes During Acute Hypoxia in a Simulated High-Altitude Airdrop Scenario

BACKGROUND: Severe acute hypoxia results in a rapid deterioration of cognitive functioning and thus poses a risk for human operations in high altitude environments. This study aimed at investigating the effects of oxygen system failure during a high-altitude high-opening (HAHO) parachute jump scenario from 30,000 ft (9144 m) on human physiology and cognitive performance using a noncontact eye-tracking task.METHODS: Nine healthy male volunteers (ages 27-48) were recruited from the Norwegian Special Operations Commandos. Eye-tracking data were collected to derive information on cognitive performance in the context of rapid dynamic changes in pressure altitude while performing a modified King-Devick test. The baseline data was collected at 8000 ft (2438 m) while breathing 100% oxygen during decompression. For every test, the corresponding arterial blood gas analysis was performed.RESULTS: The study subjects endured severe hypoxia, which resulted in significant prolongations of fixation time (range: 284.1-245.6 ms) until 23,397 ft (131 m) and fixation size (range: 34.6-32.4 mm) until 25,389 ft (7739 m) as compared to the baseline (217.6 ± 17.8 ms and 27.2 ± 4.5 mm, respectively). The increase in the saccadic movement and decrease in the saccadic velocity was observed until 28,998 ft and 27,360 ft (8839 and 8339 m), respectively.DISCUSSION: This is the first study to investigate cognitive performance from measured oculometric variables during severe hypobaric hypoxia in a simulated high-altitude airdrop mission scenario. The measurement of altered oculometric variables under hypoxic conditions represents a potential avenue to study altered cognitive performance using noncontact sensors that can derive information and serve to provide the individual with a warning from impending incapacitation.Pradhan GN, Ottestad W, Meland A, Kåsin JI, Høiseth LØ, Cevette MJ, Stepanek J. Oculometric feature changes during acute hypoxia in a simulated high-altitude airdrop scenario. Aerosp Med Hum Perform. 2021; 92(12):928-936.

[Oxygen in the acute care of adults : Short version of the German S3 guideline]

Hintergrund

Sauerstoff (O₂) ist ein Arzneimittel mit spezifischen Eigenschaften, einem definierten Dosis-Wirkungs-Bereich und O₂ hat unerwünschte Wirkungen. Im Jahr 2015 wurden 14 % einer Stichprobe von britischen Krankenhauspatienten mit Sauerstoff behandelt, davon hatten nur 42 % eine Verordnung. Gesundheitspersonal ist häufig unsicher über die Relevanz einer Hypoxämie und es besteht ein eingeschränktes Bewusstsein für die Risiken einer Hyperoxämie. In den letzten Jahren wurden zahlreiche randomisierte, kontrollierte Studien zur Sauerstofftherapie veröffentlicht.

Methoden

Im Rahmen des Leitlinienprogramms der Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften e. V. (AWMF) wurde unter Beteiligung von 10 Fachgesellschaften diese S3-Leitlinie auf Basis einer Literaturrecherche bis zum 01.02.2021 entwickelt. Zur Literaturbewertung wurde das System des Oxford Centre for Evidence-Based Medicine (CEBM; „The Oxford 2011 Levels of Evidence“) verwendet. Die Bewertung der Evidenzqualität erfolgte anhand des Grading of Recommendations Assessment, Development and Evaluation (GRADE) und die Leitlinienempfehlungen wurden formal konsentiert.

Ergebnisse

Die Leitlinie enthält 34 evidenzbasierte Empfehlungen zu Indikation, Verordnung, Überwachung und Abbruch der Sauerstofftherapie in der Akutversorgung. Die Indikation für Sauerstoff ist hauptsächlich die Hypoxämie. Hypoxämie und Hyperoxämie sollten aufgrund der Assoziation mit einer erhöhten Sterblichkeit vermieden werden. Die Leitlinie empfiehlt Zielbereiche der Sauerstoffsättigung für die Sauerstoff-Akuttherapie ohne Differenzierung zwischen verschiedenen Diagnosen. Zielbereiche sind abhängig vom Hyperkapnierisiko und Beatmungsstatus. Die Leitlinie bietet einen Überblick über verfügbare Sauerstoffzufuhrsysteme und enthält Empfehlungen für deren Auswahl basierend auf Patientensicherheit und -komfort.

Fazit

Dies ist die erste nationale Leitlinie zum Einsatz von Sauerstoff in der Akutmedizin. Sie richtet sich an medizinisches Fachpersonal, das Sauerstoff außerklinisch und stationär anwendet, und ist bis zum 30.06.2024 gültig.

Current Alzheimer disease research highlights: evidence for novel risk factors

Alzheimer disease (AD) is the most common type of dementia characterized by the progressive cognitive and social decline. Clinical drug targets have heavily focused on the amyloid hypothesis, with amyloid beta (Aβ), and tau proteins as key pathophysiologic markers of AD. However, no effective treatment has been developed so far, which prompts researchers to focus on other aspects of AD beyond Aβ, and tau proteins. Additionally, there is a mounting epidemiologic evidence that various environmental factors influence the development of dementia and that dementia etiology is likely heterogenous. In the past decades, new risk factors or potential etiologies have been widely studied. Here, we review several novel epidemiologic and clinical research developments that focus on sleep, hypoxia, diet, gut microbiota, and hearing impairment and their links to AD published in recent years. At the frontiers of AD research, these findings and updates could be worthy of further attention.

[German S3 Guideline - Oxygen Therapy in the Acute Care of Adult Patients]

BACKGROUND

 Oxygen (O₂) is a drug with specific biochemical and physiologic properties, a range of effective doses and may have side effects. In 2015, 14 % of over 55 000 hospital patients in the UK were using oxygen. 42 % of patients received this supplemental oxygen without a valid prescription. Healthcare professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

 A S3-guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. Literature search was performed until Feb 1st 2021 to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used and for assessing the quality of evidence and for grading guideline recommendation and a formal consensus-building process was performed.

RESULTS

 The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O₂ therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

 This is the first national guideline on the use of oxygen in acute care. It addresses healthcare professionals using oxygen in acute out-of-hospital and in-hospital settings. The guideline will be valid for 3 years until June 30, 2024.

Microsaccades in Applied Environments: Real-World Applications of Fixational Eye Movement Measurements

Across a wide variety of research environments, the recording of microsaccades and other fixational eye movements has provided insight and solutions into practical problems. Here we review the literature on fixational eye movements-especially microsaccades-in applied and ecologically-valid scenarios. Recent technical advances allow noninvasive fixational eye movement recordings in real-world contexts, while observers perform a variety of tasks. Thus, fixational eye movement measures have been obtained in a host of real-world scenarios, such as in connection with driver fatigue, vestibular sensory deprivation in astronauts, and elite athletic training, among others. Here we present the state of the art in the practical applications of fixational eye movement research, examine its potential future uses, and discuss the benefits of including microsaccade measures in existing eye movement detection technologies. Current evidence supports the inclusion of fixational eye movement measures in real-world contexts, as part of the development of new or improved oculomotor assessment tools. The real-world applications of fixational eye movement measurements will only grow larger and wider as affordable high-speed and high-spatial resolution eye trackers become increasingly prevalent.

EEG signals during mouth breathing in a working memory task

Background: Continuous mouth breathing results not only morphological deformations but also poor learning outcomes. However, there were few studies that observed correlations between mouth breathing and cognition. This study aimed at investigating the changes in brain activity during mouth breathing while the participant simultaneously performed a cognitive task using electroencephalography (EEG).Methods: Twenty subjects participated in this study, and EEG electrodes (32 channels, 250-Hz sampling rate) were placed on their scalp. Brain waves during a resting state and n-back tasks (0-back and 2-back) and physiological parameters such as SpO2, ETCO2, and the airway respiratory rate were measured. The pre-processed EEG signals were analyzed based on their frequencies as delta waves (0.5 ∼ 4 Hz), theta waves (4 ∼ 8 Hz), alpha waves (8 ∼ 13 Hz), beta waves (13 ∼ 30 Hz) and gamma waves (30 ∼ 50 Hz) using fast Fourier transform (FFT).Results: When compared with nose breathing, theta and alpha powers were lower during mouth breathing at rest and alpha wave presented low power at 0-back and 2-back tasks. Furthermore, beta and gamma waves exhibited low powers at 2-back task. However, the behavioral results (accuracy and response time) have no significant difference between two breathing methods (mouth and nose). Mouth breathing showed different brain activity patterns, compared to nose breathing, and these changes are related to cognitive regions.Conclusion: The reason for this change seems to relate to the decreased oxygen saturation during mouth breathing, suggesting that when cognitive abilities are required, mouth breathing can act as one of the variables that cause different outcomes in brain activities.

Caudwell Xtreme Everest: A prospective study of the effects of environmental hypoxia on cognitive functioning

Background

The neuropsychological consequences of exposure to environmental hypobaric hypoxia (EHH) remain unclear. We thus investigated them in a large group of healthy volunteers who trekked to Mount Everest base camp (5,300 m).

Methods

A neuropsychological (NP) test battery assessing memory, language, attention, and executive function was administered to 198 participants (age 44.5±13.7 years; 60% male). These were studied at baseline (sea level), 3,500 m (Namche Bazaar), 5,300 m (Everest Base Camp) and on return to 1,300 m (Kathmandu) (attrition rate 23.7%). A comparable control group (n = 25; age 44.5±14.1 years; 60% male) for comparison with trekkers was tested at/or near sea level over an equivalent timeframe so as to account for learning effects associated with repeat testing. The Reliable Change Index (RCI) was used to calculate changes in cognition and neuropsychological function during and after exposure to EHH relative to controls.

Results

Overall, attention, verbal ability and executive function declined in those exposed to EHH when the performance of the control group was taken into account (RCI .05 to -.95) with decline persisting at descent. Memory and psychomotor function showed decline at highest ascent only (RCI -.08 to -.56). However, there was inter-individual variability in response: whilst NP performance declined in most, this improved in some trekkers. Cognitive decline was greater amongst older people (r = .42; p < .0001), but was otherwise not consistently associated with socio-demographic, mood, or physiological variables.

Conclusions

After correcting for learning effects, attention, verbal abilities and executive functioning declined with exposure to EHH. There was considerable individual variability in the response of brain function to sustained hypoxia with some participants not showing any effects of hypoxia. This might have implications for those facing sustained hypoxia as a result of any disease.

Low intensity exercise does not impact cognitive function during exposure to normobaric hypoxia

Exposure to hypoxia is associated with cognitive impairment, mediated by cerebral deoxygenation. This can be problematic for individuals who perform mental tasks at high altitude. Eight healthy men completed two experimental trials consisting of 5h of exposure to normobaric hypoxia (12.5% O2). In one of the experimental trials (Hypoxia) subjects remained resting in a seated position the entire 5h; in the other experimental trial (Hypoxia and Exercise) subjects rested 2h, cycled for 1h at constant wattage (workload equivalent to 50% of altitude adjusted VO2max), then rested the last 2h. Cerebral oxygenation was measured continuously via near-infrared spectroscopy and cognitive performance was assessed by Trail Making Test A and B. Cerebral oxygenation and cognitive performance both were impaired during exposure to hypoxia. In the Hypoxia and Exercise trial, subjects experienced further declinations in cerebral oxygenation without concomitant decreases in cognitive function. These data demonstrate that cognitive function declines during exposure to normobaric hypoxia and this decline is not exacerbated by low intensity exercise.

Lung disease as a determinant of cognitive decline and dementia

Almost 40 million people currently live with dementia but this is estimated to double over the next 20 years; despite this, research identifying modifiable risk factors is scarce. There is increasing evidence that cognitive impairment is more frequent in those with chronic lung disease than those without. Chronic obstructive pulmonary disease affects 210 million people, with cognitive impairment present in 60% of certain populations. Co-morbid cognitive dysfunction also appears to impact on important outcomes such as quality of life, hospitalisation and survival. This review summarises the evidence of an association between cognition, impaired lung function and obstructive lung disease. It goes on to examine the contribution of neuro-imaging to our understanding of the underlying pathophysiology. While the mechanisms of brain pathology and cognitive impairment are likely to be complex and multi-factorial, there is evidence to suggest a key role for occult cerebrovascular damage independent of traditional vascular risk factors, including smoking.

Evaluation of symptomatic drug effects in Alzheimer's disease: strategies for prediction of efficacy in humans

In chronic diseases such as Alzheimer's disease (AD), the arsenal of biomarkers available to determine the effectiveness of symptomatic treatment is very limited. Interpretation of the results provided in literature is cumbersome and it becomes difficult to predict their standardization to a larger patient population. Indeed, cognitive assessment alone does not appear to have sufficient predictive value of drug efficacy in early clinical development of AD treatment. In recent years, research has contributed to the emergence of new tools to assess brain activity relying on innovative technologies of imaging and electrophysiology. However, the relevance of the use of these newer markers in treatment response assessment is waiting for validation. This review shows how the early clinical assessment of symptomatic drugs could benefit from the inclusion of suitable pharmacodynamic markers. This review also emphasizes the importance of re-evaluating a step-by-step strategy in drug development.

Intersaccadic drift velocity is sensitive to short-term hypobaric hypoxia

Hypoxia, defined as decreased availability of oxygen in the body's tissues, can lead to dyspnea, rapid pulse, syncope, visual dysfunction, mental disturbances such as delirium or euphoria, and even death. It is considered to be one of the most serious hazards during flight. Thus, early and objective detection of the physiological effects of hypoxia is critical to prevent catastrophes in civil and military aviation. The few studies that have addressed the effects of hypoxia on objective oculomotor metrics have had inconsistent results, however. Thus, the question of whether hypoxia modulates eye movement behavior remains open. Here we examined the effects of short-term hypobaric hypoxia on the velocity of saccadic eye movements and intersaccadic drift of Spanish Air Force pilots and flight engineers, compared with a control group that did not experience hypoxia. Saccadic velocity decreased with time-on-duty in both groups, in correlation with subjective fatigue. Intersaccadic drift velocity increased in the hypoxia group only, suggesting that acute hypoxia diminishes eye stability, independently of fatigue. Our results suggest that intersaccadic drift velocity could serve as a biomarker of acute hypoxia. These findings may also contribute to our understanding of the relationship between hypoxia episodes and central nervous system impairments.

Deficient cardiovascular stress reactivity predicts poor executive functions in adults with attention-deficit/hyperactivity disorder

Associations between cardiovascular stress markers, subjective stress reactivity, and executive functions were studied in 60 adults (30 with attention-deficit/hyperactivity disorder, ADHD, and 30 controls) using the Paced Auditory Serial Addition Test (PASAT, a test of executive functions) as a cognitive stressor. Despite higher self-perceived stress, the adults with ADHD showed lower or atypical cardiovascular stress reactivity, which was associated with poorer performance on PASAT. Using cardiovascular stress markers, subjective stress, and results on PASAT as predictors in a logistic regression, 83.3% of the ADHD group and 86.9% of the controls could be classified correctly.

Cognition and chronic hypoxia in pulmonary diseases

Lung disease with chronic hypoxia has been associated with cognitive impairment of the subcortical type.

The cognitive consequences of critical illness: practical recommendations for screening and assessment

Critically ill patients are at risk for several secondary complications, including delirium and long-term cognitive impairment. The exact mechanisms of delirium and ICU-related cognitive decline are not fully understood; however, the authors review several recent investigations that have proposed plausible explanations. This article also includes several practical guidelines for the identification and management of delirium to aid in the development and implementation of clinical procedures that will lower the risk for ICU delirium and cognitive decline.

Compromised arterial oxygen saturation in elderly asthma sufferers results in selective cognitive impairment

Forty elderly patients with asthma or chronic obstructive pulmonary disorder (COPD) were compared to a comparison group of forty age-matched healthy volunteers on a range of measures of cognitive performance, and levels of arterial haemoglobin oxygen saturation recorded. Members of the patient group were found to have significantly lower oxygen saturation compared to the comparison group, and performed significantly poorer on tests of delayed word recall and serial subtractions, but not on other tasks. Correlational analysis between participants' oxygen saturation levels and test scores across the whole sample indicated significant positive relationships existed for the digit symbol substitution and serial subtractions tasks. The results are discussed in terms of cerebral oxygen delivery, glucose metabolism, age related cognitive decline, and relative task demands.

Functional neurotoxic effects in rats elicited by 3-nitropropionic acid in acute and subacute administration

Changes possibly induced by 3-NP in electrophysiological functional characteristics of the central nervous system are, in contrast to biochemical and morphological alterations, less well known. In this study, the usability of a standard neurophysiological investigation system to detect functional changes caused by 3-NP administration in rats was studied. In subacute treatment, 10 or 15mg/kg 3-NP was given i.p. on five consecutive days to groups of 10 rats and the effects were checked 4 weeks later. Acutely treated rats received 20mg/kg i.p. after several control records. For recording, the animals' left hemisphere was exposed in urethane anesthesia. Silver electrodes were placed on the cortical sensory foci and tungsten needles in the subcortical (caudatum, globus pallidus) recording sites. Spontaneous electrical activity, as well as somatosensory, visual and auditory evoked potentials, were recorded. Following subacute treatment, the slowest (theta) and fastest (beta2 and gamma) frequencies of the spontaneous activity were changed, differently in the cortical versus subcortical sites. In the sensory evoked potentials after subacute treatment, an increase of the latency was seen in all sensory areas. In the acutely treated animals, the amplitude of the somatosensory evoked potential decreased after giving 3-NP. With double stimuli, the relation of the two responses was treatment- and interval-dependent. Understanding the mechanism of these effects may widen the knowledge base for using 3-NP in disease models.

Clinical identification of cognitive impairment in ICU survivors: insights for intensivists

BACKGROUND

A growing body of research has demonstrated the presence of ongoing cognitive impairment in large numbers of ICU survivors.

OBJECTIVE

This review offers a practical framework for practicing intensivists and those following patients after their ICU stay for the identification of cognitive impairment in ICU survivors.

CONCLUSIONS

Early detection of cognitive impairment in critically ill patients is an important and achievable goal, but overt cognitive impairment remains unrecognized in most cases. However, it can be identified by objective (test scores) or subjective evidence (clinical judgment, patient observation, family interaction).