Cerebral Oxygenation During Exercise in Cardiac Patients

Heart-brain interaction in cardiogenic dementia: pathophysiology and therapeutic potential

Diagnosis and treatment of patients with cardiovascular and neurologic diseases primarily focus on the heart and brain, respectively. An increasing number of preclinical and clinical studies have confirmed a causal relationship between heart and brain diseases. Cardiogenic dementia is a cognitive impairment caused by heart dysfunction and has received increasing research attention. The prevention and treatment of cardiogenic dementia are essential to improve the quality of life, particularly in the elderly and aging population. This study describes the changes in cognitive function associated with coronary artery disease, myocardial infarction, heart failure, atrial fibrillation and heart valve disease. An updated understanding of the two known pathogenic mechanisms of cardiogenic dementia is presented and discussed. One is a cascade of events caused by cerebral hypoperfusion due to long-term reduction of cardiac output after heart disease, and the other is cognitive impairment regardless of the changes in cerebral blood flow after cardiac injury. Furthermore, potential medications for the prevention and treatment of cardiogenic dementia are reviewed, with particular attention to multicomponent herbal medicines.

Effect of Acute Cardiovascular Exercise on Cerebral Blood Flow: A Systematic Review

A single bout of cardiovascular exercise can have a cascade of physiological effects, including increased blood flow to the brain. This effect has been documented across multiple modalities, yet studies have reported mixed findings. Here, we systematically review evidence for the acute effect of cardiovascular exercise on cerebral blood flow across a range of neuroimaging techniques and exercise characteristics. Based on 52 studies and a combined sample size of 1,174 individuals, our results indicate that the acute effect of cardiovascular exercise on cerebral blood flow generally follows an inverted U-shaped relationship, whereby blood flow increases early on but eventually decreases as exercise continues. However, we also find that this effect is not uniform across studies, instead varying across a number of key variables including exercise characteristics, brain regions, and neuroimaging modalities. As the most comprehensive synthesis on the topic to date, this systematic review sheds light on the determinants of exercise-induced change in cerebral blood flow, a necessary step toward personalized interventions targeting brain health across a range of populations.

Changes in transcranial near-infrared spectroscopy values reflect changes in cardiac index during cardiac surgery

To determine whether changes in transcranial near-infrared spectroscopy (NIRS) values reflect changes in cardiac index (CI) in adult cardiac surgical patients. Single-center prospective post hoc analysis. University hospital. One hundred and twenty-four adult patients undergoing cardiac surgery. In each patient, several CI measurements were taken, and NIRS values were collected simultaneously. We used a hierarchical linear regression model to assess the association between NIRS values and CI. We calculated a crude model with NIRS as the only factor included, and an adjusted model, where mean arterial pressure, end-tidal CO₂ , and oxygen saturation were used as confounding factors. A total of 1301 pairs of NIRS and CI values were collected. The analysis of separate NIRS and CI pairs revealed a poor association, which was not statistically significant when adjusted with the chosen confounders. However, when the changes in NIRS from baseline or from the previous measurement were compared to those of CI, a clinically and statistically significant association between NIRS and CI was observed also in the adjusted model. Compared to the baseline and to the previous measurement, respectively, the regression coefficients with 95% confidence intervals were 0.048 (0.041-0.056) and 0.064 (0.055-0.073) in off-pump coronary artery bypass patients and 0.022 (0.016-0.029) and 0.026 (0.020-0.033) in patients who underwent cardiopulmonary bypass. In an unselected cardiac surgical population, the changes in NIRS values reflect those in CI, especially in off-pump coronary artery bypass patients. In this single-center post hoc analysis of data from a prospectively collected database of cardiac surgery patients, paired measurements of cardiac output and NIRS revealed that while there was a no correlation between individual paired measurements, a small correlation was found in changes in the two measurements from baseline values. This highlights a potential to utilize changes in NIRS from baseline to suggest changes in cardiac output in cardiac surgical populations.

Cerebral oxygenation during cardiopulmonary exercise testing in cardiorespiratory diseases: A systematic review

BACKGROUND

Cardiopulmonary exercise testing (CPET) is the gold standard for analyzing cardiorespiratory fitness and integrating physiological responses. However, the presence of chronic diseases may compromise cerebral hemodynamic responses during CPET. In addition, the acute response of cerebral oxygenation during incremental CPET may identify abnormal behavior and ensure greater safety for patients with cardiovascular, respiratory, and metabolic diseases.

OBJECTIVE

To summarize the cerebral oxygenation acute response during CPET of patients with cardiovascular, metabolic, or respiratory diseases.

METHODS

From inception to 23rd September 2022, five databases (PubMed, SCOPUS, Web of Science, Embase and CINAHAL) were searched for cross-sectional studies performing incremental CPET and measuring the cerebral oxygenation acute response in cardiovascular, metabolic, or respiratory diseases compared with healthy individuals. The Downs and Black tool assessed the risk of bias of the studies.

RESULTS

We included seven studies with 428 participants (305 men and 123 women), aged 43 to 70 years. Of these, 101 had heart failure NYHA II and III; 77 idiopathic dilated cardiomyopathy; 33 valvular disease; 25 coronary heart disease; 22 pulmonary arterial hypertension; 15 had severe obstructive sleep apnea (OSA) and 166 were apparently healthy. There was no eligible article with metabolic disease. There was a lower magnitude increase in cerebral oxygenation of cardiovascular patients compared with the healthy individuals during the CPET. Furthermore, pulmonary arterial hypertension patients presented increased cerebral oxygen extraction, differently to those with severe OSA.

CONCLUSION

Considering the heterogeneity of the included studies, patients with cardiovascular disease may suffer from reduced cerebral oxygen supply, and individuals with OSA presented lower brain oxygen extraction during the CPET. Future studies should aim for strategies to improve cerebral oxygenation to ensure greater safety at CPET of cardiovascular and OSA patients. An acute response pattern for metabolic and other respiratory diseases was not established.

The Exercising Brain: An Overlooked Factor Limiting the Tolerance to Physical Exertion in Major Cardiorespiratory Diseases?

“Exercise starts and ends in the brain”: this was the title of a review article authored by Dr. Bengt Kayser back in 2003. In this piece of work, the author highlights that pioneer studies have primarily focused on the cardiorespiratory-muscle axis to set the human limits to whole-body exercise tolerance. In some circumstances, however, exercise cessation may not be solely attributable to these players: the central nervous system is thought to hold a relevant role as the ultimate site of exercise termination. In fact, there has been a growing interest relative to the “brain” response to exercise in chronic cardiorespiratory diseases, and its potential implication in limiting the tolerance to physical exertion in patients. To reach these overarching goals, non-invasive techniques, such as near-infrared spectroscopy and transcranial magnetic stimulation, have been successfully applied to get insights into the underlying mechanisms of exercise limitation in clinical populations. This review provides an up-to-date outline of the rationale for the “brain” as the organ limiting the tolerance to physical exertion in patients with cardiorespiratory diseases. We first outline some key methodological aspects of neuromuscular function and cerebral hemodynamics assessment in response to different exercise paradigms. We then review the most prominent studies, which explored the influence of major cardiorespiratory diseases on these outcomes. After a balanced summary of existing evidence, we finalize by detailing the rationale for investigating the “brain” contribution to exercise limitation in hitherto unexplored cardiorespiratory diseases, an endeavor that might lead to innovative lines of applied physiological research.

Cerebral oximetry: a developing tool for monitoring cerebral oxygenation during cardiopulmonary resuscitation

Despite improvements in cardiopulmonary resuscitation (CPR), survival and neurologic recovery after cardiac arrest remain very poor because of the impact of severe ischemia and subsequent reperfusion injury. As the likelihood of survival and favorable neurologic outcome decreases with increasing severity of ischemia during CPR, developing methods to measure the magnitude of ischemia during resuscitation, particularly cerebral ischemia, is critical for improving overall outcomes. Cerebral oximetry, which measures regional cerebral oxygen saturation (rSO₂ ) by near-infrared spectroscopy, has emerged as a potentially beneficial marker of cerebral ischemia during CPR. In numerous preclinical and clinical studies, higher rSO₂ during CPR has been associated with improved cardiac arrest survival and neurologic outcome. In this narrative review, we summarize the scientific rationale and validation of cerebral oximetry across populations and pathophysiologic states, discuss the evidence surrounding its use to predict return of spontaneous circulation, rearrest, and neurologic outcome, and provide suggestions for incorporation of cerebral oximetry into CPR practice.

Exercise intolerance in pulmonary arterial hypertension: insight into central and peripheral pathophysiological mechanisms

Exercise intolerance is a cardinal symptom of pulmonary arterial hypertension (PAH) and strongly impacts patients' quality of life (QoL). Although central cardiopulmonary impairments limit peak oxygen consumption (V' O2peak ) in patients with PAH, several peripheral abnormalities have been described over the recent decade as key determinants in exercise intolerance, including impaired skeletal muscle (SKM) morphology, convective O2 transport, capillarity and metabolism indicating that peripheral abnormalities play a greater role in limiting exercise capacity than previously thought. More recently, cerebrovascular alterations potentially contributing to exercise intolerance in patients with PAH were also documented. Currently, only cardiopulmonary rehabilitation has been shown to efficiently improve the peripheral components of exercise intolerance in patients with PAH. However, more extensive studies are needed to identify targeted interventions that would ultimately improve patients' exercise tolerance and QoL. The present review offers a broad and comprehensive analysis of the present literature about the complex mechanisms and their interactions limiting exercise in patients and suggests several gaps in knowledge that need to be addressed in the future for a better understanding of exercise intolerance in patients with PAH.

Muscle and cerebral oxygenation during cycling in chronic obstructive pulmonary disease: A scoping review

To synthesize evidence for prefrontal cortex (PFC), quadriceps, and respiratory muscle oxygenation using near-infrared spectroscopy (NIRS) during cycling in individuals with chronic obstructive pulmonary disease (COPD). A scoping review was performed searching databases (inception-August 2020): Ovid MEDLINE, EMBASE, Cochrane Systematic Reviews, Cochrane Central Register of Controlled Clinical Trials, CINAHL, SPORTDiscus and Pedro. The search focused on COPD, cycling, and NIRS outcomes. 29 studies (541 COPD participants) were included. Compared to healthy individuals (8 studies), COPD patients at lower cycling workloads had more rapid increases in vastus lateralis (VL) deoxygenated hemoglobin (HHb); lower increases in VL total hemoglobin (tHb) and blood flow; and lower muscle tissue saturation (StO₂). Heliox and bronchodilators were associated with smaller and slower increases in VL HHb. Heliox increased VL and intercostal blood flow compared to room air and supplemental oxygen in COPD patients (1 study). PFC oxygenated hemoglobin (O₂Hb) increased in COPD individuals during cycling in 5 of 8 studies. Individuals with COPD and heart failure demonstrated worse VL and PFC NIRS outcomes compared to patients with only COPD-higher or more rapid increase in VL HHb and no change or decrease in PFC O₂Hb. Individuals with COPD present with a mismatch between muscle oxygen delivery and utilization, characterized by more rapid increase in VL HHb, lower muscle O₂Hb and lower muscle StO₂. PFC O₂Hb increases or tends to increase in individuals with COPD during exercise, but this relationship warrants further investigation. NIRS can be used to identify key deoxygenation thresholds during exercise to inform PFC and muscle oxygenation.

The Effects of Fast and Slow Yoga Breathing on Cerebral and Central Hemodynamics

Background:

Yoga breathing has shown to impose significant cardiovascular and psychological health benefits.

Objective:

The mechanism (s) responsible for these health benefits remain unclear. The aim of the present study was to assess the differences in cerebral and central hemodynamic responses following fast breathing (FB) and slow breathing (SB) protocols compared to breathing awareness (BA) as a control.

Methods:

Twenty healthy participants (10 males and 10 females) volunteered to take part in the study. Participants were between ages 18–55 years (group mean: 24 ± 5 years), with a height of 168.7 ± 9.8 cm and a weight of 70.16 ± 10.9 kg. A familiarization trial including FB and SB protocols were performed by each participant at least 24 h before the testing day. The breathing protocols were designed to achieve 6 breath/min for SB and ~ 120 breaths/min for FB.

Results:

FB resulted in an increase in both right prefrontal cortex (RPFC) and left prefrontal cortex (LPFC) hemoglobin difference (Hbdiff) (brain oxygenation) compared to BA (P < 0.05). FB resulted in an increased Hbdiff in LPFC compared to RPFC SB (P < 0.05). FB resulted in an increased Hbdiff in LPFC compared to SB (P < 0.05).

Conclusion:

FB may be an effective yoga breathing technique for eliciting cerebral brain oxygenation indicated by increased Hbdiff. These results may be applicable to both healthy and clinical populations.

New Directions in Exercise Prescription: Is There a Role for Brain-Derived Parameters Obtained by Functional Near-Infrared Spectroscopy?

In the literature, it is well established that regular physical exercise is a powerful strategy to promote brain health and to improve cognitive performance. However, exact knowledge about which exercise prescription would be optimal in the setting of exercise–cognition science is lacking. While there is a strong theoretical rationale for using indicators of internal load (e.g., heart rate) in exercise prescription, the most suitable parameters have yet to be determined. In this perspective article, we discuss the role of brain-derived parameters (e.g., brain activity) as valuable indicators of internal load which can be beneficial for individualizing the exercise prescription in exercise–cognition research. Therefore, we focus on the application of functional near-infrared spectroscopy (fNIRS), since this neuroimaging modality provides specific advantages, making it well suited for monitoring cortical hemodynamics as a proxy of brain activity during physical exercise.

The response of a standardized fluid challenge during cardiac surgery on cerebral oxygen saturation measured with near-infrared spectroscopy

Near infrared spectroscopy (NIRS) has been used to evaluate regional cerebral tissue oxygen saturation (ScO₂) during the last decades. Perioperative management algorithms advocate to maintain ScO₂, by maintaining or increasing cardiac output (CO), e.g. with fluid infusion. We hypothesized that ScO₂ would increase in responders to a standardized fluid challenge (FC) and that the relative changes in CO and ScO₂ would correlate. This study is a retrospective substudy of the FLuid Responsiveness Prediction Using Extra Systoles (FLEX) trial. In the FLEX trial, patients were administered two standardized FCs (5 mL/kg ideal body weight each) during cardiac surgery. NIRS monitoring was used during the intraoperative period and CO was monitored continuously. Patients were considered responders if stroke volume increased more than 10% following FC. Datasets from 29 non-responders and 27 responders to FC were available for analysis. Relative changes of ScO₂ did not change significantly in non-responders (mean difference - 0.3% ± 2.3%, p = 0.534) or in fluid responders (mean difference 1.6% ± 4.6%, p = 0.088). Relative changes in CO and ScO₂ correlated significantly, p = 0.027. Increasing CO by fluid did not change cerebral oxygenation. Despite this, relative changes in CO correlated to relative changes in ScO₂. However, the clinical impact of the present observations is unclear, and the results must be interpreted with caution.Trial registration:http://ClinicalTrial.gov identifier for main study (FLuid Responsiveness Prediction Using Extra Systoles-FLEX): NCT03002129.

Pre-frontal Cortex Oxygenation Changes During Aerobic Exercise in Elite Athletes Experiencing Sport-Related Concussion

Aims: Recent research suggests that aerobic exercise can be performed safely within the first week following a concussion injury and that early initiation of exercise may speed recovery. To better understand the physiological changes during a concussion, we tested the hypothesis that mild-to-intense exercise testing can be performed within days immediately following injury, and can be used to discern differences between the concussed and normal healthy state. Thus, the purpose was to observe the cerebral hemodynamic responses to incremental exercise testing performed acutely post-concussion in high-performance athletes. Methods: This study was a within- and between-experimental design, with seven male university ice hockey teams participating. A subgroup of five players acted as control subjects (CON) and was tested at the same time as the 14 concussed (mTBI) players on Day 2, 4, and 7 post-concussion. A 5-min resting baseline and 5-min exercise bouts of mild (EX1), moderate (EX2), and high (EX3) intensity exercise were performed on a cycle ergometer. Near-infrared spectroscopy was used to monitor pre-frontal cortex oxy-haemoglobin (HbO2), deoxy-haemoglobin (HHb), and total blood volume (tHb) changes. Results: ANOVA compared differences between testing days and groups, and although large percentage changes in HbO2 (20-30%), HHb (30-40%), and tHb (30-40%) were recorded, no significant (p ≤ 0.05) differences in cerebral hemodynamics occurred between mTBI vs. CON during aerobic exercise testing on any day post-injury. Furthermore, there was a linear relationship between exercise intensity vs. cerebral hemodynamics during testing for each day (r 2 = 0.83-0.99). Conclusion: These results demonstrate two novel findings: (1) mild-to-intense aerobic exercise testing can be performed safely as early as Day 2 post-concussion injury in a controlled laboratory environment; and (2) evidence-based objective measures such as cerebral hemodynamics can easily be collected using near-infrared spectroscopy (NIRS) to monitor physiological changes during the first-week post-injury. This research has important implications for monitoring physiological recovery post-injury and establishing new rehabilitation guidelines.

Aerobic Training and Mobilization Early Post-stroke: Cautions and Considerations

Knowledge gaps exist in how we implement aerobic exercise programs during the early phases post-stroke. Therefore, the objective of this review was to provide evidence-based guidelines for pre-participation screening, mobilization, and aerobic exercise training in the hyper-acute and acute phases post-stroke. In reviewing the literature to determine safe timelines of when to initiate exercise and mobilization we considered the following factors: arterial blood pressure dysregulation, cardiac complications, blood-brain barrier disruption, hemorrhagic stroke transformation, and ischemic penumbra viability. These stroke-related impairments could intensify with inappropriate mobilization/aerobic exercise, hence we deemed the integrity of cerebral autoregulation to be an essential physiological consideration to protect the brain when progressing exercise intensity. Pre-participation screening criteria are proposed and countermeasures to protect the brain from potentially adverse circulatory effects before, during, and following mobilization/exercise sessions are introduced. For example, prolonged periods of standing and static postures before and after mobilization/aerobic exercise may elicit blood pooling and/or trigger coagulation cascades and/or cerebral hypoperfusion. Countermeasures such as avoiding prolonged standing or incorporating periodic lower limb movement to activate the venous muscle pump could counteract blood pooling after an exercise session, minimize activation of the coagulation cascade, and mitigate potential cerebral hypoperfusion. We discuss patient safety in light of the complex nature of stroke presentations (i.e., type, severity, and etiology), medical history, comorbidities such as diabetes, cardiac manifestations, medications, and complications such as anemia and dehydration. The guidelines are easily incorporated into the care model, are low-risk, and use minimal resources. These and other strategies represent opportunities for improving the safety of the activity regimen offered to those in the early phases post-stroke. The timeline for initiating and progressing exercise/mobilization parameters are contingent on recovery stages both from neurobiological and cardiovascular perspectives, which to this point have not been specifically considered in practice. This review includes tailored exercise and mobilization prescription strategies and precautions that are not resource intensive and prioritize safety in stroke recovery.

Cardiovascular and cerebral hemodynamics during exercise and recovery in obese individuals as a function of their fitness status

The aim of this study was to compare cardiovascular hemodynamics and cerebral oxygenation/perfusion (COP) during and after maximal incremental exercise in obese individuals according to their aerobic fitness versus age‐matched healthy controls (AMHC). Fifty‐four middle–aged obese (OB) and 16 AMHC were recruited. Maximal cardiopulmonary function (gas exchange analysis), cardiac hemodynamics (impedance cardiography), and left frontal COP (near‐infrared spectroscopy: NIRS) were measured continuously during a maximal incremental ergocycle test. During recovery, reoxygenation/perfusion rate (ROPR: oxyhemoglobin: ΔO₂Hb, deoxyhemoglobin: ΔHHb and total hemoglobin: ΔtHb; with NIRS) was also measured. Obese participants (OB, n = 54) were divided into two groups according to the median V˙O2 peak: the low‐fit obese (LF‐OB, n = 27) and the high‐fit obese (HF‐OB, n = 27). During exercise, end tidal pressure of CO₂ (PETCO₂), and COP (ΔO₂Hb, ΔHHb and ΔtHb) did not differ between groups (OB, LF‐OB, HF‐OB, AMHC). During recovery, PETCO₂ and ROPR (ΔO₂Hb, ΔHHb and ΔtHb) were similar between the groups (OB, LF‐OB, HF‐OB, AMHC). During exercise and recovery, cardiac index was lower (P < 0.05) in LF‐OB versus the other two groups (HF‐OB, AMHC). As well, systolic blood pressure was higher during exercise in the OB, LF‐OB and HF‐OB groups versus AMHC (P < 0.05). When compared to AMHC, obese individuals (OB, LF‐OB, HF‐OB) have a similar cerebral vasoreactivity by CO₂ and cerebral hemodynamics during exercise and recovery, but a higher systolic blood pressure during exercise. Higher fitness in obese subjects (HF‐OB) seems to preserve their cardiopulmonary and cardiac function during exercise and recovery.

Revisiting the physiological effects of exercise training on autonomic regulation and chemoreflex control in heart failure: does ejection fraction matter?

Heart failure (HF) is a global public health problem that, independent of its etiology [reduced (HFrEF) or preserved ejection fraction (HFpEF)], is characterized by functional impairments of cardiac function, chemoreflex hypersensitivity, baroreflex sensitivity (BRS) impairment, and abnormal autonomic regulation, all of which contribute to increased morbidity and mortality. Exercise training (ExT) has been identified as a nonpharmacological therapy capable of restoring normal autonomic function and improving survival in patients with HFrEF. Improvements in autonomic function after ExT are correlated with restoration of normal peripheral chemoreflex sensitivity and BRS in HFrEF. To date, few studies have addressed the effects of ExT on chemoreflex control, BRS, and cardiac autonomic control in HFpEF; however, there are some studies that have suggested that ExT has a beneficial effect on cardiac autonomic control. The beneficial effects of ExT on cardiac function and autonomic control in HF may have important implications for functional capacity in addition to their obvious importance to survival. Recent studies have suggested that the peripheral chemoreflex may also play an important role in attenuating exercise intolerance in HFrEF patients. The role of the central/peripheral chemoreflex, if any, in mediating exercise intolerance in HFpEF has not been investigated. The present review focuses on recent studies that address primary pathophysiological mechanisms of HF (HFrEF and HFpEF) and the potential avenues by which ExT exerts its beneficial effects.

Cerebral and Limb Tissue Oxygenation During Peripheral Venoarterial Extracorporeal Life Support

Femoral access in extracorporeal life support (ECLS) has been associated with regional variations in arterial oxygen saturation, potentially predisposing the patient to ischemic tissue damage. Current monitoring techniques, however, are limited to intermittent bedside evaluation of capillary refill among other factors. The aim of this study was to assess whether cerebral and limb regional tissue oxygen saturation (rSO₂) values reflect changes in various patient-related parameters during venoarterial ECLS (VA-ECLS). This retrospective observational study included adults assisted by femorofemoral VA-ECLS. Bifrontal cerebral and bilateral limb tissue oximetry was performed for the entire duration of support. Hemodynamic data were analyzed parallel to cerebral and limb rSO₂. A total of 23 patients were included with a median ECLS duration of 5 [1-20] days. Cardiac arrhythmias were observed in 12 patients, which was associated with a decreased mean rSO₂ from 61%±11% to 51%±10% during atrial fibrillation and 67%±9% to 58%±10% during ventricular fibrillation (P<0.001 for both). A presumably sudden increase in cardiac output due to myocardial recovery (n=8) resulted in a significant decrease in mean cerebral rSO₂ from 73%±7% to 54%±6% and from 69%±9% to 53%±8% for the left and right cerebral hemisphere, respectively (P=0.012 for both hemispheres). Also, right radial artery partial gas pressure for oxygen decreased from 15.6±2.8 to 8.3±1.9 kPa (P=0.028). No differences were found in cerebral desaturation episodes between patients with and without neurologic complications. In six patients, limb rSO₂ increased from on average 29.3±2.7 to 64.0±5.1 following insertion of a distal cannula in the femoral artery (P=0.027). Likewise, restoration of flow in a clotted distal cannula inserted in the femoral artery was necessary in four cases and resulted in increased limb rSO₂ from 31.3±0.8 to 79.5±9.0; P=0.068. Non-invasive tissue oximetry adequately reflects events influencing cerebral and limb perfusion and can aid in monitoring tissue perfusion in patients assisted by ECLS.

Cognitive function in patients with stable coronary heart disease: Related cerebrovascular and cardiovascular responses

Chronic exercise has been shown to prevent or slow age-related decline in cognitive functions in otherwise healthy, asymptomatic individuals. We sought to assess cognitive function in a stable coronary heart disease (CHD) sample and its relationship to cerebral oxygenation-perfusion, cardiac hemodynamic responses, and V˙O2 peak compared to age-matched and young healthy control subjects. Twenty-two young healthy controls (YHC), 20 age-matched old healthy controls (OHC) and 25 patients with stable CHD were recruited. Cognitive function assessment included short term—working memory, perceptual abilities, processing speed, cognitive inhibition and flexibility and long-term verbal memory. Maximal cardiopulmonary function (gas exchange analysis), cardiac hemodynamic (impedance cardiography) and left frontal cerebral oxygenation-perfusion (near-infra red spectroscopy) were measured during and after a maximal incremental ergocycle test. Compared to OHC and CHD, YHC had higher V˙O2 peak, maximal cardiac index (CI max), cerebral oxygenation-perfusion (ΔO₂ Hb, ΔtHb: exercise and recovery) and cognitive function (for all items) (P<0.05). Compared to OHC, CHD patients had lower V˙O2 peak, CI max, cerebral oxygenation-perfusion (during recovery) and short term—working memory, processing speed, cognitive inhibition and flexibility and long-term verbal memory (P<0.05). V˙O2 peak and CI max were related to exercise cerebral oxygenation-perfusion and cognitive function (P<0.005). Cerebral oxygenation-perfusion (exercise) was related to cognitive function (P<0.005). Stable CHD patients have a worse cognitive function, a similar cerebral oxygenation/perfusion during exercise but reduced one during recovery vs. their aged-matched healthy counterparts. In the all sample, cognitive functions correlated with V˙O2 peak, CI max and cerebral oxygenation-perfusion.

A Pilot Study Using Preoperative Cerebral Tissue Oxygen Saturation to Stratify Cardiovascular Risk in Major Non-Cardiac Surgery

This prospective pilot study evaluated whether low preoperative cerebral tissue oxygen saturation is associated with unfavourable outcomes after major elective non-cardiac surgery. Eighty-one patients over 60 years of age, American Society of Anesthesiologists physical status 3 or 4, were recruited. Resting cerebral tissue oxygen saturation was recorded on room air, and after oxygen supplementation, using cerebral oximetry. The primary outcome was 30-day major adverse event of combined mortality or severe morbidity, and the secondary outcome was 30-day new disability. Eleven patients (13.6%) suffered a major adverse event, and 28 patients (34.6%) experienced new disability. Room air cerebral tissue oxygen saturation was significantly different between patients who had a major adverse event, 67% (95% confidence interval [CI] 65–70) versus unaffected, 71% (95% CI 70–72; P=0.04). No statistical difference was found between patients for new disability (range 70%– 74%; P=0.73). Room air cerebral tissue oxygen saturation was significantly associated with major adverse events (odds ratio 1.36 (95% CI 1.03–1.79), P=0.03). Saturation levels ≤68% carried a positive likelihood ratio of 2.2 for death or severe morbidity, P=0.04. A definitive trial is required to confirm if cerebral oximetry can be used to stratify the cardiovascular risk of patients presenting for non-cardiac surgery.

Cerebral microvascular blood flow and CO2 reactivity in pulmonary arterial hypertension

Hypocapnia and endothelial dysfunction might impair microvascular cerebral blood flow (CBF_micr) and cerebrovascular reactivity to CO₂ (CVR_CO2). Pulmonary arterial hypertension (PAH) is characteristically associated with chronic alveolar hyperventilation and microvascular endothelial dysfunction. We therefore determined CBF_micr (pre-frontal blood flow index (BFI) by the indocyanine green-near infrared spectroscopy methodology) during hypocapnia and hypercapnia in 25 PAH patients and 10 gender- and age-matched controls. Cerebral BFI was lower in patients than controls at similar transcutaneous PCO₂ (PtcCO₂) levels in both testing conditions. In fact, while BFI increased from hypocapnia to hypercapnia in all controls, it failed to increase in 17/25 (68%) patients. Thus, BFI increased to a lesser extent from hypo to hypercapnia ("Δ") in patients, i.e., they showed lower Δ BFI/Δ PtcCO₂ ratios than controls. In conclusion, CBF_micr and CVR_CO2 are lessened in clinically stable, mildly-impaired patients with PAH. These abnormalities might be associated with relevant clinical outcomes (hyperventilation and dyspnea, cognition, cerebrovascular disease) being potentially amenable to pharmacological treatment.

Near-infrared spectroscopy for medical applications: Current status and future perspectives

The near-infrared radiation (NIR) window, also known as the "optical window" or "therapeutic window", is the range of wavelengths that has the maximum depth of penetration in tissue. Indeed, because NIR is minimally absorbed by water and hemoglobin, spectra readings can be easily collected from the body surface. Recent reports have shown the potential of NIR spectroscopy in various medical applications, including functional analysis of the brain and other tissues, as well as an analytical tool for diagnosing diseases. The broad applicability of NIR spectroscopy facilitates the diagnosis and therapy of diseases as well as elucidating their pathophysiology. This review introduces recent advances and describes new studies in NIR to demonstrate potential clinical applications of NIR spectroscopy.

Regional cerebral hemodynamic response to incremental exercise is blunted in poorly controlled patients with uncomplicated type 1 diabetes

OBJECTIVE

Cerebral vasoreactivity to pharmacologically induced hypercapnia is impaired in poorly controlled patients with type 1 diabetes but otherwise free from microangiopathy. However, whether this response is also compromised during exercise, a daily-life physiological condition challenging regional cerebral hemodynamics, is unknown. We aimed to investigate prefrontal cortex hemodynamics during incremental maximal exercise in patients with uncomplicated type 1 diabetes, taking into account long-term glycemic control as well as exercise- and diabetes-influenced vasoactive stimuli.

RESEARCH DESIGN AND METHODS

Two groups of patients (type 1 diabetes with adequate glycemic control [T1D-A], n = 8, HbA1c 6.8 ± 0.7% [51 ± 7.7 mmol/mol]; type 1 diabetes with inadequate glycemic control [T1D-I], n = 10, HbA1c 9.0 ± 0.7% [75 ± 7.7 mmol/mol]) were compared with 18 healthy control subjects (CON-A and CON-I) matched for physical activity and body composition. Throughout exercise, near-infrared spectroscopy allowed investigation of changes in oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), and total hemoglobin (THb) in the prefrontal cortex. Venous and arterialized capillary blood was sampled during exercise to assess for factors that may alter prefrontal cortex hemodynamics and oxygenation.

RESULTS

No differences were observed between T1D-A and CON-A, but VO2max was impaired (P < 0.05) and cerebral blood volume (THb) increase blunted (P < 0.05) in T1D-I compared with CON-I. Nonetheless, O2Hb appeared unaltered in T1D-I probably partly due to blunting of simultaneous neuronal oxygen extraction (i.e., a lower HHb increase; P < 0.05). There were no intergroup differences in arterial oxygen content, Paco2, pH, [K(+)], and free insulin levels.

CONCLUSIONS

Maximal exercise highlights subtle disorders of both hemodynamics and neuronal oxygenation in the prefrontal cortex of poorly controlled patients with type 1 diabetes. These findings may warn clinicians of brain endothelial dysfunction occurring even before overt microangiopathy during exercise.

Innovative approaches in the perioperative care of the cardiac surgical patient in the operating room and intensive care unit

Perioperative care for cardiac surgery is undergoing rapid evolution. Many of the changes involve the application of novel technologies to tackle common challenges in optimizing perioperative management. Herein, we illustrate recent advances in perioperative management by focusing on a number of novel components that we judge to be particularly important. These include: the introduction of brain and somatic oximetry; transesophageal echocardiographic hemodynamic monitoring and bedside focused ultrasound; ultrasound-guided vascular access; point-of-care coagulation surveillance; right ventricular pressure monitoring; novel inhaled treatment for right ventricular failure; new approaches for postoperative pain management; novel approaches in specialized care procedures to ensure quality control; and specific approaches to optimize the management for postoperative cardiac arrest. Herein, we discuss the reasons that each of these components are particularly important in improving perioperative care, describe how they can be addressed, and their impact in the care of patients who undergo cardiac surgery.

The Effect of Parkinson Drug Timing on Cardiovascular Response during Treadmill Exercise in a Person with Parkinson Disease and Freezing of Gait

PURPOSE

To examine the response of cerebral oxygenation during treadmill walking in a person with Parkinson disease (PD) who experiences freezing of gait (FOG) and to determine whether the oxygen response was related to the timing of his PD medication. Client Description: A 61-year-old man with PD performed two bouts of treadmill testing on the same day, during the on- and off-phases of his PD medication. Measures and Outcome: The client experienced two FOG episodes during the first testing session (on-phase with hypokinetic movement session). Cerebral oxygen response (measured by near-infrared spectroscopy) was stable until the FOG episodes occurred, at which point it decreased until the FOG episode was over. No electrocardiogram (ECG) changes or lightheadedness were noted; blood pressure (BP) remained stable. During the second exercise testing session (off-phase with dyskinetic movement session), the client did not experience any FOG episodes, and his cerebral oxygen response remained stable. Toward the end of the second testing session, he experienced lightheadedness and a drop in BP of approximately 30 mmHg, along with significant ST segment depression on his ECG.

IMPLICATIONS

Haemodynamic and cerebral oxygen changes occurred that were specific to the timing of the client's PD medication and to his FOG episodes. This case study shows a person with PD demonstrating decreased cerebral oxygenation during FOG, which may be based on his variable response to levodopa medication or may be attributable to as yet unidentified physiologic mechanisms.

Factors affecting intraoperative changes in regional cerebral oxygen saturation in patients undergoing liver transplantation

BACKGROUND

Regional oxygen saturation (rSO(2)) is a sensitive marker of cerebral hypoperfusion during liver transplantation. However, bilirubin absorbs near-infrared light, resulting in falsely low rSO(2) values. We sought to determine whether rSO(2) values vary in response to bilirubin concentrations during liver transplantation and to assess whether rSO(2) changes were associated with factors reflecting cerebral oxygen delivery in patients with hyperbilirubinemia.

METHODS

Measurements of rSO(2) values continuous cardiac output (CO), mean arterial pressure, central venous pressure, body temperature, arterial blood gas analysis, and laboratory parameters were simultaneously performed at 1 hour after the surgical incision (baseline) and at 3 predetermined times during the anhepatic and neohepatic phases in 95 end-stage liver disease patients including 67 males of Child A/B/C/29/29/37 categories respectively. Relationships between changes in parameters were evaluated by correlation and multivariate regression analyses.

RESULTS

The 273 measurements revealed changes in rSO(2) (range, -18% to 40%) to correlate significantly with alterations in hemoglobin (Hb), serum glucose, lactate, prothrombin time, pH, partial arterial CO(2) pressure (PaCO(2)), and CO, but not with serum total bilirubin (TB). Multivariate linear regression analysis revealed that changes in Hb, CO, PaCO(2), and pH were independent of rSO(2) changes during liver transplantation.

CONCLUSIONS

Our findings showed that rSO(2) changes were independently associated with factors reflecting cerebral oxygen delivery, such as Hb, CO, PaCO(2), and pH, whereas rSO(2) values did not correlate with changes in bilirubin concentrations, indicating that rSO(2) changes reveal cerebral oxygen balance regardless of TB levels among patients undergoing liver transplantation.

The effects of exercise under hypoxia on cognitive function

Increasing evidence suggests that cognitive function improves during a single bout of moderate exercise. In contrast, exercise under hypoxia may compromise the availability of oxygen. Given that brain function and tissue integrity are dependent on a continuous and sufficient oxygen supply, exercise under hypoxia may impair cognitive function. However, it remains unclear how exercise under hypoxia affects cognitive function. The purpose of this study was to examine the effects of exercise under different levels of hypoxia on cognitive function. Twelve participants performed a cognitive task at rest and during exercise at various fractions of inspired oxygen (FIO₂: 0.209, 0.18, and 0.15). Exercise intensity corresponded to 60% of peak oxygen uptake under normoxia. The participants performed a Go/No-Go task requiring executive control. Cognitive function was evaluated using the speed of response (reaction time) and response accuracy. We monitored pulse oximetric saturation (SpO₂) and cerebral oxygenation to assess oxygen availability. SpO₂ and cerebral oxygenation progressively decreased during exercise as the FIO₂ level decreased. Nevertheless, the reaction time in the Go-trial significantly decreased during moderate exercise. Hypoxia did not affect reaction time. Neither exercise nor difference in FIO₂ level affected response accuracy. An additional experiment indicated that cognitive function was not altered without exercise. These results suggest that the improvement in cognitive function is attributable to exercise, and that hypoxia has no effects on cognitive function at least under the present experimental condition. Exercise-cognition interaction should be further investigated under various environmental and exercise conditions.

Cerebral hemodynamics: concepts of clinical importance

Cerebral hemodynamics and metabolism are frequently impaired in a wide range of neurological diseases, including traumatic brain injury and stroke, with several pathophysiological mechanisms of injury. The resultant uncoupling of cerebral blood flow and metabolism can trigger secondary brain lesions, particularly in early phases, consequently worsening the patient's outcome. Cerebral blood flow regulation is influenced by blood gas content, blood viscosity, body temperature, cardiac output, altitude, cerebrovascular autoregulation, and neurovascular coupling, mediated by chemical agents such as nitric oxide (NO), carbon monoxide (CO), eicosanoid products, oxygen-derived free radicals, endothelins, K+, H+, and adenosine. A better understanding of these factors is valuable for the management of neurocritical care patients. The assessment of both cerebral hemodynamics and metabolism in the acute phase of neurocritical care conditions may contribute to a more effective planning of therapeutic strategies for reducing secondary brain lesions. In this review, the authors have discussed concepts of cerebral hemodynamics, considering aspects of clinical importance.

Alveolar gas exchange and tissue deoxygenation during exercise in type 1 diabetes patients and healthy controls

We used near-infrared spectroscopy to investigate whether leg and arm skeletal muscle and cerebral deoxygenation differ during incremental cycling exercise in men with type 1 diabetes (T1D, n=10, mean±SD age 33±7 years) and healthy control men (matched by age, anthrometry, and self-reported physical activity, CON, n=10, 32±7 years) to seek an explanation for lower aerobic capacity (˙VO2peak) often reported in T1D. T1D had lower ˙VO2peak (35±4mlkg(-1)min(-1) vs. 43±8mlkg(-1)min(-1), P<0.01) and peak work rate (219±33W vs. 290±44W, P<0.001) than CON. Leg muscle deoxygenation (↑ [deoxyhemoglobin]; ↓ tissue saturation index) was greater in T1D than CON at a given absolute submaximal work rate, but not at peak exercise, while arm muscle and cerebral deoxygenation were similar. Thus, in T1D compared with CON, faster leg muscle deoxygenation suggests limited circulatory ability to increase O(2) delivery as a plausible explanation for lower ˙VO2peak and earlier fatigue in T1D.

Aerobic interval training improves oxygen uptake efficiency by enhancing cerebral and muscular hemodynamics in patients with heart failure

BACKGROUND

Abnormal ventilatory/hemodynamic responses to exercise contribute to functional impairment in patients with heart failure (HF). This study investigates how interval and continuous exercise regimens influence functional capacity by modulating ventilatory efficiency and hemodynamic function in HF patients.

METHODS

Forty-five HF patients were randomized to perform either aerobic interval training (AIT; 3-minute intervals at 40% and 80% VO(2peak)) or moderate continuous training (MCT; sustained 60% VO()for 30 min/day, 3 days/week for 12 weeks, or to a control group that received general healthcare (GHC). A noninvasive bio-reactance device was adopted to measure cardiac hemodynamics, whereas a near-infrared spectroscopy was employed to assess perfusion/O2 extraction in frontal cerebral lobe (∆[THb]FC/∆[HHb]FC) and vastus lateralis (∆[THb]VL/∆[HHb]VL), respectively.

RESULTS

Following the 12-week intervention, the AIT group exhibited higher oxygen uptake efficiency slope (OUES) and lower VE-VCO2 slope than the MCT and GHC groups. Furthermore, AIT, but not MCT, boosted cardiac output (CO) and increased ∆[THb]FC, ∆[THb]VL, and ∆[HHb]VL during exercise. In multivariate analyses, CO was the dominant predictor of VO(2peak). ∆[THb]FC and ∆[THb]VL, which modulated the correlation between CO and OUES, were significantly correlated with OUES. Simultaneously, ∆[THb]VL was the only factor significantly associated with VE-VCO2 slope. Additionally, AIT reduced plasma brain natriuretic peptide, myeloperoxidase, and interleukin-6 levels and increased the Short Form-36 physical/mental component scores and decreased the Minnesota Living with Heart Failure questionnaire score.

CONCLUSIONS

AIT effectively improves oxygen uptake efficiency by enhancing cerebral/muscular hemodynamics and suppresses oxidative stress/inflammation associated with cardiac dysfunction, and also promotes generic/disease-specific qualities of life in patients with HF.

Abnormal end-tidal PO(2) and PCO(2) at the anaerobic threshold correlate well with impaired exercise gas exchange in patients with left ventricular dysfunction

BACKGROUND

The aim of the present study was to compare the end-tidal O(2) pressure (PETO(2)) to end-tidal CO(2) pressure (PETCO(2)) in cardiac patients during rest and during 2 states of exercise: at anaerobic threshold (AT) and at peak. The purpose was to see which metabolic state, PETO(2) or PETCO(2), best correlated with exercise limitation.

METHODS AND RESULTS

Thirty-eight patients with left ventricular (LV) ejection fraction <40% underwent cardiopulmonary exercise testing (CPX). PETO(2) and PETCO(2) were measured during CPX, along with peak O(2) uptake (VO(2)), AT, slope of the increase in ventilation (VE) relative to the increase in CO(2) output (VCO(2)) (VE vs. VCO(2) slope), and the ratio of the increase in VO(2) to the increase in work rate (ΔVO(2)/ΔWR). Both PETO(2) and PETCO(2) measured at AT were best correlated with peakVO(2), AT, ΔVO(2)/ΔWR and VE vs. VCO(2) slope. PETO(2) at AT correlated with reduced peak VO(2) (r=-0.60), reduced AT (r=-0.52), reduced ΔVO(2)/ΔWR (r=-0.55) and increased VE vs. VCO(2) slope (r=0.74). PETCO(2) at AT correlated with reduced peak VO(2) (r=0.67), reduced AT (r=0.61), reduced ΔVO(2)/ΔWR (r=0.58) and increased VE vs. VCO(2) slope (r=-0.80).

CONCLUSIONS

PETCO(2) and PETO(2) at AT correlated with peak VO(2), AT and ΔVO(2)/ΔWR, but best correlated with increased VE vs. VCO(2) slope. PETO(2) and PETCO(2) at AT can be used as a prime index of impaired cardiopulmonary function during exercise in patients with LV failure.

Frontal cerebral cortex blood flow, oxygen delivery and oxygenation during normoxic and hypoxic exercise in athletes

During maximal hypoxic exercise, a reduction in cerebral oxygen delivery may constitute a signal to the central nervous system to terminate exercise. We investigated whether the rate of increase in frontal cerebral cortex oxygen delivery is limited in hypoxic compared to normoxic exercise. We assessed frontal cerebral cortex blood flow using near-infrared spectroscopy and the light-absorbing tracer indocyanine green dye, as well as frontal cortex oxygen saturation (S(tO2)%) in 11 trained cyclists during graded incremental exercise to the limit of tolerance (maximal work rate, WRmax) in normoxia and acute hypoxia (inspired O2 fraction (F(IO2)), 0.12). In normoxia, frontal cortex blood flow and oxygen delivery increased (P < 0.05) from baseline to sub-maximal exercise, reaching peak values at near-maximal exercise (80% WRmax: 287 ± 9 W; 81 ± 23% and 75 ± 22% increase relative to baseline, respectively), both leveling off thereafter up to WRmax (382 ± 10 W). Frontal cortex S(tO2)% did not change from baseline (66 ± 3%) throughout graded exercise. During hypoxic exercise, frontal cortex blood flow increased (P = 0.016) from baseline to sub-maximal exercise, peaking at 80% WRmax (213 ± 6 W; 60 ± 15% relative increase) before declining towards baseline at WRmax (289 ± 5 W). Despite this, frontal cortex oxygen delivery remained unchanged from baseline throughout graded exercise, being at WRmax lower than at comparable loads (287 ± 9 W) in normoxia (by 58 ± 12%; P = 0.01). Frontal cortex S(tO2)% fell from baseline (58 ± 2%) on light and moderate exercise in parallel with arterial oxygen saturation, but then remained unchanged to exhaustion (47 ± 1%). Thus, during maximal, but not light to moderate, exercise frontal cortex oxygen delivery is limited in hypoxia compared to normoxia. This limitation could potentially constitute the signal to limit maximal exercise capacity in hypoxia.

The effects on cognitive functions of a movement-based intervention in patients with Alzheimer's type dementia: a pilot study

OBJECTIVE

To explore the effect of a non-aerobic movement based activity on cognition in people with Alzheimer's type dementia (AD).

METHODS

The sample consisted of 27 patients fulfilling the AD ICD-10 diagnostic criteria. The patient sample was randomly divided into two groups: The Exercise Group received 6 weeks movement training and comprised 15 participants with a mean age of 70.5 years (SD: 8). Control Group participated in a standard care group, which served as a control intervention, and consisted of 12 patients with an average age of 75.7 years (SD: 6.90). Cognitive functions were assessed using six computerised tests from the CANTAB, pre and post training. Data were analysed using t-tests. The false discovery rate (FDR) for multiple comparisons as well as Cohen's d effect size was used to assess the significant effects.

RESULTS

Significant improvements in sustained attention, visual memory and a trend in working memory were found in the Exercise Group compared to Control Group after the 6 weeks training. In addition, after 6 weeks the Control Group deteriorated significantly in attention, while the AD patients who undertook the physical exercise showed a discrete improvement.

CONCLUSIONS

The present study shows that a short course of non-aerobic movement based exercise is already effective at least in some aspects of cognitive functioning in patients with AD. Although the present study is a pilot study with small samples, nevertheless, the results are promising for the further investigation and development of non-aerobic movement programmes.

Suppression of cerebral hemodynamics is associated with reduced functional capacity in patients with heart failure

This investigation elucidated the underlying mechanisms of functional impairments in patients with heart failure (HF) by simultaneously comparing cardiac-cerebral-muscle hemodynamic and ventilatory responses to exercise among HF patients with various functional capacities. One hundred one patients with HF [New York Heart Association HF functional class II (HF-II, n = 53) and functional class III (HF-III, n = 48) patients] and 71 normal subjects [older control (O-C, n = 39) and younger control (Y-C, n = 32) adults] performed an incremental exercise test using a bicycle ergometer. A recently developed noninvasive bioreactance device was adopted to measure cardiac hemodynamics, and near-infrared spectroscopy was employed to assess perfusions in the frontal cerebral lobe (Δ[THb](FC)) and vastus lateralis muscle (Δ[THb](VL)). The results demonstrated that the Y-C group had higher levels of cardiac output, Δ[THb](FC), and Δ[THb](VL) during exercise than the O-C group. Moreover, these cardiac/peripheral hemodynamic responses to exercise in HF-III group were smaller than those in both HF-II and O-C groups. Although the change of cardiac output caused by exercise was normalized, the amounts of blood distributed to frontal cerebral lobe and vastus lateralis muscle in the HF-III group significantly declined during exercise. The HF-III patients had lower oxygen-uptake efficiency slopes (OUES) and greater Ve-Vo(2) slopes than the HF-II patients and age-matched controls. However, neither hemodynamic nor ventilatory response to exercise differed significantly between the HF-II and O-C groups. Cardiac output, Δ[THb](FC), and Δ[THb](VL) during exercise were directly related to the OUES and Vo(2peak) and inversely related to the Ve-Vco(2) slope. Moreover, cardiac output or Δ[THb](FC) was an effect modifier, which modulated the correlation status between Δ[THb](VL) and Ve-Vco(2) slope. We concluded that the suppression of cerebral/muscle hemodynamics during exercise is associated with ventilatory abnormality, which reduces functional capacity in patients with HF.

Does cerebral oxygenation affect cognitive function during exercise?

This study tested whether cerebral oxygenation affects cognitive function during exercise. We measured reaction times (RT) of 12 participants while they performed a modified version of the Eriksen flanker task, at rest and while cycling. In the exercise condition, participants performed the cognitive task at rest and while cycling at three workloads [40, 60, and 80% of peak oxygen uptake ([Formula: see text])]. In the control condition, the workload was fixed at 20 W. RT was divided into premotor and motor components based on surface electromyographic recordings. The premotor component of RT (premotor time) was used to evaluate the effects of acute exercise on cognitive function. Cerebral oxygenation was monitored during the cognitive task over the right frontal cortex using near-infrared spectroscopy. In the exercise condition, we found that premotor time significantly decreased during exercise at 60% peak [Formula: see text] relative to rest. However, this improvement was not observed during exercise at 80% peak [Formula: see text]. In the control condition, premotor time did not change during exercise. Cerebral oxygenation during exercise at 60% peak [Formula: see text] was not significantly different from that at rest, while cerebral oxygenation substantially decreased during exercise at 80% peak [Formula: see text]. The present results suggest that an improvement in cognitive function occurs during moderate exercise, independent of cerebral oxygenation.

Reaction time to peripheral visual stimuli during exercise under hypoxia

The purpose of this study was to test the hypothesis that decrease in cerebral oxygenation compromises an individual's ability to respond to peripheral visual stimuli during exercise. We measured the simple reaction time (RT) to peripheral visual stimuli at rest and during and after cycling at three different workloads [40%, 60%, and 80% peak oxygen uptake (VO2)] under either normoxia [inspired fraction of oxygen (FIO2)=0.21] or normobaric hypoxia (FIO2=0.16). Peripheral visual stimuli were presented at 10 degrees to either the right or the left of the midpoint of the eyes. Cerebral oxygenation was monitored during the RT measurement over the right frontal cortex with near-infrared spectroscopy. We used the premotor component of RT (premotor time) to assess effects of exercise on the central process. The premotor time was significantly longer during exercise at 80% peak VO2 (normoxia: 214.2+/-33.0 ms, hypoxia: 221.5+/-30.1 ms) relative to that at rest (normoxia: 201.0+/-27.2 ms, hypoxia: 202.9+/-29.7 ms) (P<0.01). Under normoxia, cerebral oxygenation gradually increased up to 60% peak VO2 and then decreased to the resting level at 80% peak VO2. Under hypoxia, cerebral oxygenation progressively decreased as exercise workload increased. We found a strong correlation between increase in premotor time and decrease in cerebral oxygenation (r2=0.89, P<0.01), suggesting that increase in premotor time during exercise is associated with decrease in cerebral oxygenation. Accordingly, exercise at high altitude may compromise visual perceptual performance.

Cerebral desaturation during cardiac arrest: its relation to arrest duration and left ventricular pump function

OBJECTIVE

To determine the impact of brief periods of cardiac arrest (CA) on regional cerebral oxygen saturation (rSO2) in patients with low left ventricular ejection fraction (LVEF <30%).

DESIGN

Prospective observational study.

SETTING

Cardiac surgery room at a university hospital.

PATIENTS

Seventy-seven consecutive patients undergoing elective implantation of a cardioverter/defibrillator in monitored anesthesia care. According to preoperative assessments, left ventricular function was classified as normal (LVEF >50%), moderately impaired (LVEF 30%-50%), or severely reduced (LVEF <30%).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

rSO2 was determined during threshold testing with concomitant induction of CA. In patients with LVEF <30%, mean baseline rSO2 (59%) was already below the lower range of normal despite normal arterial blood pressure, heart rate, and arterial oxygen saturation. rSO2 increased by 6% after 6 L/min oxygen insufflation (p < 0.05) and dropped again in each group after CA, reaching a nadir after successful defibrillation. Patients with LVEF <30% and baseline rSO2 <63% exhibited the lowest values. They also showed the highest incidence (11%) of critical cerebral desaturations (i.e., >20% drop from baseline or rSO2 value <50%). rSO2 in patients with LVEF <30% was always below that determined in patients with LVEF >30% (p < 0.05). There was a strong correlation between rSO2 values before CA and rSO2 nadir (p < 0.05). The drop in rSO2 was only moderately related to the brief CAs (p < 0.05).

CONCLUSION

These findings demonstrate that severely compromised left ventricular pump function is associated with diminished rSO2. As these patients seem to be more susceptible to critical desaturations, they may be prone to severe tissue hypoxemia unless adequate oxygen delivery is reestablished rapidly. This may contribute to the poor neurologic outcome after successful resuscitation in patients with LVEF <30%.

Prognostic value of end-tidal CO2 pressure during exercise in patients with left ventricular dysfunction

We compared the prognostic power of end-tidal CO(2) pressure (PETCO(2)) during exercise, an index of arterial CO(2) pressure, with those of established respiratory gas indexes during exercise testing in patients with left ventricular dysfunction. Seventy-eight consecutive patients with a left ventricular ejection fraction (LVEF) Collapse

Key Words

• end-tidal co₂ pressure
• peak \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \dot{\rm{v}} $$\end{document}o₂
• exercise testing

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MESH Headings

• Aged
• Carbon Dioxide/metabolism
• Exercise/physiology
• Exercise Test/methods
• Female
• Follow-Up Studies
• Humans
• Kaplan-Meier Estimate
• Male
• Middle Aged
• Oxygen Consumption/physiology
• Predictive Value of Tests
• Prognosis
• Prospective Studies
• ROC Curve
• Respiratory Function Tests/methods
• Risk Factors
• Stroke Volume/physiology
• Ventricular Dysfunction, Left/diagnosis
• Ventricular Dysfunction, Left/mortality
• Ventricular Dysfunction, Left/physiopathology

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Grants Collapse

Affiliation(s)

Masayo Hoshimoto-Iwamoto The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan School of Health and Sports Science, Juntendo University, Chiba, Japan
Akira Koike The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Osamu Nagayama The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Akihiko Tajima The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Takeya Suzuki Department of Cardiovascular Medicine, Toho University Omori Medical Center, Tokyo, Japan
Tokuhisa Uejima The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Hitoshi Sawada The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan
Tadanori Aizawa The Cardiovascular Institute, 3-10 Roppongi 7-chome, Minato-ku, Tokyo, 106-0032 Japan

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Clinical significance of cerebral oxygenation during exercise in patients with coronary artery disease

BACKGROUND

Recent investigations have demonstrated that cerebral oxyhemoglobin (O(2)Hb) decreases during exercise in patients with left ventricular dysfunction, reflecting a cerebral hypoxia. We sought to establish a prognostic value of decreased cerebral O(2)Hb during exercise in cardiac patients, and to compare it with those of indexes obtained from cardiopulmonary exercise testing (CPX).

METHODS AND RESULTS

A total of 344 consecutive patients with coronary artery disease were enrolled in the study. All the patients performed CPX, during which cerebral O(2)Hb was continuously monitored using near-infrared spectroscopy. There were 13 cardiac deaths and 78 cardiovascular events during the prospective follow-up period of 1,231+/-538 days. The change of O(2)Hb measured at the forehead from rest to peak exercise (DeltaO(2)Hb) was significantly lower in non-survivors than in survivors (-1.5+/-3.3 vs 1.7+/-3.2 micromol/L, p=0.0004). By multivariate Cox proportional hazards analysis, DeltaO(2)Hb and left ventricular ejection fraction (LVEF) were found to be independent prognostic markers for cardiac deaths. The DeltaO(2)Hb, LVEF and peak oxygen uptake were found to be significant prognostic markers for cardiovascular events, mainly for heart failure worsening and sudden cardiac death.

CONCLUSION

The present findings suggest that a decrease in cerebral O(2)Hb during exercise predicts future cardiovascular events in patients with coronary artery disease.

Baseline regional cerebral oxygen saturation correlates with left ventricular systolic and diastolic function

OBJECTIVE

To evaluate the correlation between baseline cerebral oxygen saturation (ScO(2)) and cardiac function as assessed by pulmonary artery catheterization and transesophageal echocardiography (TEE).

DESIGN

A retrospective study.

SETTING

A tertiary care university hospital.

PARTICIPANTS

Cardiac surgery patients.

MEASUREMENTS AND RESULTS

Patients undergoing cardiac surgery with bilateral recording of their baseline ScO(2) using the INVOS 4100 (Somanetics, Troy, MI) were selected. A pulmonary artery catheter was used to obtain their hemodynamic profile. Left ventricular (LV) systolic and diastolic function was evaluated by TEE, after the induction of anesthesia, using standard criteria. A model was developed to predict ScO(2). A total of 99 patients met the inclusion criteria. There were significant correlations between mean ScO(2) values and central venous pressure (CVP) (r = -0.31, p = 0.0022), pulmonary capillary wedge pressure (r = -0.25, p = 0.0129), mean pulmonary artery pressure (MPAP) (r = -0.24, p = 0.0186), mean arterial pressure/MPAP ratio (r = 0.33, p = 0.0011), LV fractional area change (<35, 35-50, and >or=50, p = 0.0002), regional wall motion score index (r = -0.27, p = 0.0062), and diastolic function (p = 0.0060). The mean ScO(2) had the highest area under the receiver operating characteristic curve (0.74; confidence interval, 0.64-0.84) to identify LV systolic dysfunction. A model predicting baseline ScO(2) was created based on LV systolic echocardiographic variables, CVP, sex, mitral valve surgery, and the use of beta-blocker (r(2) = 0.42, p < 0.001).

CONCLUSION

Baseline ScO(2) values are related to cardiac function and are superior to hemodynamic parameters at predicting LV dysfunction.

Enhancing effect of cerebral blood volume by mild exercise in healthy young men: a near-infrared spectroscopy study

A mechanism by which exercise improves brain function may be attributed to increase in cerebral blood volume (CBV) with physical activity. However, the exact exercise intensity that influences CBV is still uncertain. To clarify this issue, 10 healthy young male participants were asked to perform a graded cycling exercise to the point of exhaustion while their prefrontal cortex CBVs are being monitored using near-infrared spectroscopy. Overall responsive cerebral oxygenation showed a non-linear pattern with three distinct phases. The CBV-threshold (CBVT), an event where rapid oxygenation takes place, occurred at approximately 42% of the V O2max. The CBVT preceded the lactate threshold (LT), which was at approximately 55% of the V O2max. The V O2max was not predictive of the CBVT in among the subjects. Our results indicate that oxygenation of the prefrontal cortex increases during graded cycling even at exercise intensities below the LT, suggesting the potential role of mild exercise in enhancing CBV.