Oxygen Difference Research Articles

Oxygen pulse during cardiopulmonary exercise testing in cardiac patients as a surrogate of stroke volume: fact or fiction?

Abstract Background According to the Fick equation, oxygen uptake (VO2) equals the product of cardiac output (CO) and arteriovenous oxygen difference (a-vO2Diff). Cardiopulmonary exercise testing (CPET) provides the oxygen pulse (O2pulse) as the ratio of VO2 and heart rate. The O2pulse is often considered a surrogate for stroke volume (SV) during effort, ignoring the AVO2Diff, to assess the hemodynamic response during exercise. Purpose To compare O2pulse and SV measured independently by simultaneous CPET and exercise echocardiography (CPETecho). Methods Observation study of CPETecho exams performed between July 2015 and May 2024. The O2pulse was obtained by CPET at rest, intermediate and peak loads, while the SV was calculated by the ultrasound velocity time integral of the left ventricular outflow tract and the estimated a-vO2Diff by the Fick equation. Variables were compared by one-way ANOVA and Tukey test. Differences in O2pulse and SV between intermediate and peak (ΔO2pulse and ΔSV) were used to analyze the agreement of effort patterns: ‘ascending’ with values increasing from intermediate to peak, or ‘descending’ with the opposite response. The pattern agreement was evaluated by Cohen kappa. A p < 0.05 was considered significant. Results A total of 1,866 exams were included in the study (54.1% males, age: 65.4 ± 13.9 y). The indications for the exams were heart failure with preserved ejection fraction (39.7%), valvular heart diseases (35.5%), investigation of myocardial ischemia (6.3%) and others (18.5%). The VO2 at intermediate level was 66±16% of the peak values. The O2pulse significantly raised from rest to intermediate and peak (4.0±1.9, 9.0±3.3 and 10.9±3.9 mL/beat; p < 0.0001; Figure 1). The SV during rest, intermediate and peak were 70.2±18.1, 84.5±20.9 and 85.1±21.3 mL/beat, respectively, without significant difference between intermediate and peak (p = 0.074). In contrast, the a-vO2Diff progressively increased from rest, intermediate and peak (p < 0.001). Notably, the ΔO2pulse and ΔSV exhibited a very weak correlation (r = 0.11, Figure 2). An ascending pattern was identified in 86.4% when considering ΔO2pulse and in 48% for ΔSV, with specific agreement of 43.4%. Conversely, a descending pattern was identified in 13.6% for ΔO2pulse and in 52.0% for ΔSV, with a specific agreement of 8.9%. The overall agreement was 52.3% (Cohen's kappa: 0.07), indicating almost no agreement between the patterns. Conclusion This study reveals a very low agreement between changes in O2pulse and SV during exercise in cardiac patients. The rise in O2pulse from intermediate to peak exercise was more closely related to the increase in a-vO2Diff whereas SV remained constant. Consequently, in cardiac patients, O2pulse changes cannot be assumed to be a reliable surrogate for SV changes, but rather reflect the combined effects of SV and muscle oxygen extraction, underscoring the importance of CPETecho for assessing exercise hemodynamic trends accurately.

Sex differences in myocardial oxygenation and energetics in patients with severe aortic stenosis without obstructive coronary artery disease before and after aortic valve replacement

Sex differences in myocardial oxygenation and energetics in patients with severe aortic stenosis without obstructive coronary artery disease before and after aortic valve replacement

Cortical hemodynamics of electrographic status epilepticus in the critically ill.

The pathophysiological mechanisms of status epilepticus (SE) underlying potential brain injury remain largely unclear. This study aims to employ functional near-infrared spectroscopy (fNIRS) combined with video-electroencephalography (vEEG) to monitor brain hemodynamics continuously and non-invasively in critically ill adult patients experiencing electrographic SE. Our primary focus is to investigate neurovascular coupling and cerebrovascular changes associated with seizures, particularly during recurring and/or prolonged episodes. Eleven critically ill adult patients underwent simultaneous vEEG-fNIRS with large cortical coverage. Data from seven patients with identified electrographic SE were analyzed. The timing of recorded seizures was marked using standardized critical care EEG terminology. A general linear model was employed to extract the hemodynamic response to seizures from the fNIRS recordings. Linear mixed-effects models were utilized to correlate hemodynamic responses with seizure characteristics. A total of >200 h of monitoring and >1000 seizures were recorded. In most patients, an increase in oxyhemoglobin (HbO) and a decrease in deoxyhemoglobin (HbR) were observed during shorter-duration seizures. Although a similar response could also be seen initially for longer-duration seizures, this hemodynamic change was often followed by a progressive decline in HbO concentration and an increase in HbR. At the systemic level, no significant difference in peripheral oxygenation occurred during seizures, and only small changes in mean arterial blood pressure and heart rate occurred in four and two patients, respectively. We demonstrate the feasibility of using multichannel vEEG-fNIRS to measure the hemodynamic changes associated with electrographic seizures in critically ill adult patients. Our findings suggest that disrupted neurovascular coupling is more prevalent during prolonged seizures compared to recurrent short-duration seizures. This research provides valuable insights into the dynamic interplay between neuronal activity and hemodynamics during critical care seizures.

Sex Differences in Cardiovascular Adaptations Following Aerobic Exercise Training Programs: A Systematic Review and Meta-analysis.

The influence of aerobic exercise training on cardiovascular adaptations in healthy males vs females is unclear. This systematic review and meta-analysis summarized sex-based differences in cardiac adaptations following aerobic exercise training interventions in healthy adults. Five electronic databases were searched from inception to June 2024. Cardiac adaptation data included peak oxygen uptake, heart rate, arteriovenous oxygen difference, systolic and diastolic blood pressure, stroke volume, cardiac output, left ventricular (LV) mass, LV end diastolic volume (LVEDV), LV end systolic volume (LVESV), and LV ejection fraction (LVEF). Meta-analyses were conducted in RevMan 5.4. Meta-analyses were conducted on 4 outcomes: LV mass, LVEDV, LVESV, and LVEF. The meta-analysis revealed no sex differences in LV mass (standardized mean difference= -0.01, 95% confidence interval [CI]: -0.29, 0.27, P= 0.97), LVESV (mean difference [MD]= 1.85, 95% CI: -3.45, 7.10, P= 0.5), or LVEF (MD= -0.9, 95% CI: -3.26, 1.46, P= 0.45) following aerobic exercise interventions. Meta-analyses revealed a sex difference in LVEDV: males show a greater improvement in LVEDV (MD= 7.67, 95% CI: 2.75, 12.59, P= 0.002) than females after aerobic exercise training. No other sex differences were observed in any of the other outcomes. The overall risk of bias was low, and the quality of evidence was moderate. Aerobic exercise interventions were associated with a larger increase in LVEDV in men relative to women, yet no sex differences were found in cardiac morphology (LV mass) or functional indices (LVEF).

Boys vs men differences in muscular fatigue, muscle and cerebral oxygenation during maximal effort isometric contractions: the effect of muscle blood flow restriction.

To examine whether the children's superiority, over adults, to resist fatigue during repeated maximal-efforts depends on their often-cited oxidative advantage, attributed to greater muscle blood flow and O2-delivery. We also investigated the mechanisms underlying child-adult differences in muscle-oxygenation (due to O2-supply or O2-utilization) and examined if there are age-differences in cerebral-oxygenation response (a brain-activation index). Eleven men (23.3 ± 1.8yrs) and eleven boys (11.6 ± 1.1yrs) performed 15 maximal-effort handgrips (3-s contraction/3-s rest) under two conditions: free-flow circulation (FF) and arterial-occlusion (OCC). Force, muscle-oxygenation (TSImuscle) and cerebral-oxygenation (oxyhemoglobin-O2Hbcerebral; total hemoglobin-tHbcerebral; deoxyhemoglobin-HHbcerebral) were assessed. In boys, force declined less (-26.3 ± 2.6 vs. -34.4 ± 2.4%) and at slower rate (-1.56 ± 0.16 vs. -2.24 ± 0.17%·rep-1) vs. men in FF (p < 0.01-0.05; d = 0.60-1.24). However, in OCC there were no age-differences in the magnitude (-38.3 ± 3.0 vs. -37.8 ± 3.0%) and rate (-2.44 ± 0.26 vs. -2.54 ± 0.26%·rep-1) of force decline. Boys compared to men, exhibited less TSImuscle decline in both protocols, and lower muscle VO2 (p < 0.05). Boys, also, presented a smaller O2Hbcerebral and tHbcerebral rise than men in FF; exercising with OCC increased the O2Hbcerebral and tHbcerebral response in boys. Using MVIC as a covariate in FF condition, abolished boys-men differences in force and TSImuscle decline and O2Hbcerebral rise. During repeated maximal-efforts: (i) blood flow is a significant contributor to children's superiority over adults to resist fatigue; (ii) age-difference in muscle hypoxia/deoxygenation is rather attributed to men's greater metabolic demand than to lower muscle-perfusion; and (iii) cerebral oxygenation/blood volume increase more in men than boys under free circulation, implying greater brain activation.

Oxygenation Effects of Antihypertensive Agents in Intensive Care: A Prospective Comparative Study of Nicardipine and Urapidil.

Acute arterial hypertension within the critical care context may necessitate the administration of intravenous antihypertensive agents. Nicardipine and urapidil are notable for their application in intensive care units. Nonetheless, dihydropyridine calcium channel inhibitors (DCCIs) such as nicardipine are implicated in the impairment of hypoxic pulmonary vasoconstriction, potentially disrupting oxygenation. This study aimed to assess the differences in patient oxygenation when these antihypertensive agents are administered intravenously. This bicentric, prospective, observational investigation spanning five intensive care units evaluated patients requiring intravenous nicardipine or urapidil. Oxygenation data were recorded from the start of therapy until the 12th hour. Comparative analysis was performed between patient groups based on the antihypertensive agent administered, along with subgroup investigations to identify populations with an elevated risk of hypoxemia. From November 2021 to November 2023, 197 patients were included: 98 (50%) were treated with nicardipine, and 99 (50%) were treated with urapidil. Hypoxemia occurred in 97 (49%) patients and was more prevalent in the nicardipine cohort, affecting 65 (66%) patients, as opposed to 32 (32%) patients in the urapidil cohort (RR 2.05, 95% CI [1.48-2.82], P < 0.001). Subgroup analysis revealed a significant association between patients with pulmonary atelectasis (RR 2.30, 95% CI [1.4-3.7], P < 0.001) and obesity (RR 2.7, 95% CI [1.5-4.6], P < 0.001). Considering these findings, cautious consideration of the patient's respiratory status should be exercised when initiating intravenous DCCI treatment. However, given the limitations of this study, a controlled trial on hypertension management in the ICU is needed.

Effect of low-frequency neuromuscular electrical stimulation combined with passive cycle ergometry on hemodynamics in healthy adults.

There have been few studies that have examined hemodynamic responses to low-frequency neuromuscular electrical stimulation (LF-NMES), and the effects of combining passive cycle ergometry are still unclear. The purpose of this study was to examine the effects of a combination of LF-NMES and passive cycle ergometry on hemodynamic responses with a primary focus on the Fick principle in healthy adults. A randomized, crossover trial was conducted to evaluate the responses to three types of supine exercises (LF-NMES alone, LF-NMES with passive cycle ergometry, and voluntary cycle ergometry) adjusted to the same exercise intensity as the oxygen consumption of 14 mL/kg/min in 13 healthy adult men. Blood pressure, heart rate, blood lactate concentration, stroke volume (SV), cardiac output (CO), and left ventricular end-diastolic volume (LVEDV) were measured during each exercise in all subjects. The arterial-venous oxygenation difference (A-V̇o2 difference) was calculated based on Fick's equation. LVEDV, SV, and CO were lower, and the A-V̇o2 difference and blood lactate concentration were higher in LF-NMES alone than those in voluntary cycle ergometry and LF-NMES with passive cycle ergometry (P < 0.05). The blood lactate concentration was lower in LF-NMES with passive cycle ergometry than that in LF-NMES alone, but slightly higher than that in voluntary cycle ergometry (P < 0.05). Hemodynamic and metabolic responses of exercise with LF-NMES alone seemed consistent with insufficient peripheral perfusion based on the elevation of A-V̇o2 difference and blood lactate concentration. The findings suggest that combining passive cycle ergometry with LF-NMES improves the insufficient peripheral perfusion induced by LF-NMES alone.NEW & NOTEWORTHY This is the first study to evaluate cardiac output, oxygen consumption, and A-V̇o2 difference during LF-NMES of endurance exercise modality. LF-NMES alone may not demonstrate hemodynamic responses induced by voluntary endurance exercise, however, demonstrates those when combined with passive cycle ergometry. LF-NMES with passive cycle ergometry may be a more effective approach in cardiac rehabilitation for patients without the ability of voluntary exercise because it may increase cardiac output and venous return as represented by the LVEDV.

Retraction Note: Early or delayed cord clamping during transition of term newborns: does it make any difference in cerebral tissue oxygenation?

Retraction Note: Early or delayed cord clamping during transition of term newborns: does it make any difference in cerebral tissue oxygenation?

A Ramped Treadmlll Protocol Exercise Test Identifies Higher Ambulatory Oxygen Needs in IPF and COPD.

In the United States (U.S.), ambulatory oxygen is recommended for patients with idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD) who experience symptomatic exertional hypoxemia. Ambulatory oxygen need is often determined by submaximal hall walk testing; however, this may fail to accurately characterize exertional hypoxemia in some patients. Assess for differences in ambulatory oxygen needs between IPF and COPD patients who completed a ramped treadmill protocol exercise test (RTPET) and correlate oxygen flow rates determined at highest level exertion with lung function and exercise parameters. Oxygen "need" is defined as flow rate needed to maintain oxygen saturation >90% in patients who desaturate to <88%. We conducted a retrospective review of RTPET results for IPF and COPD patients who also recently completed spirometry. The RTPET has three phases: rest, submaximal usual pace walking at 0% treadmill grade for 3 minutes, and highest level walking at the UP walk speed with increasing treadmill grade by 2% every 2 minutes. IPF patients were part of a clinical registry while COPD patients were identified based on diagnosis coding and spirometry (FEV1/FVC <0.70). The RTPET for both groups was completed based on a pulmonologist's referral. We included 329 IPF and 2,343 COPD patients. A greater proportion of IPF patients required ambulatory oxygen to maintain saturation >90%. After adjusting for demographic covariates and exercise parameters, IPF patients required higher ambulatory oxygen flow rates compared to COPD subjects with similar DLCO values. Of patients who did not require oxygen with submaximal usual pace testing, 49% with IPF and 24% with COPD required oxygen at highest level exertion. The RTPET identified higher oxygen flow needs at highest level exertion in IPF versus COPD patients; however, in both diseases, there was a significant proportion of patients who were only found to have exertional desaturation at highest level exertion. Current oxygen policies and reliance on submaximal testing may fail to meet the needs of patients with IPF and COPD. Further studies are needed to determine if oxygen prescriptions targeting highest level desaturation improve clinical outcomes, symptoms, or quality-of-life.

Abstract 4139170: Relationship between hemodynamics and oxygen consumption in hypertrophic cardiomyopathy during maximal stress testing

Background: Hypertrophic cardiomyopathy (HCM) is a global heart disease with great variability in disease severity, which can lead to significant impairment of exercise capacity. In healthy populations, oxygen consumption is related to cardiac output and arteriovenous oxygen difference. We sought to determine the relationship between hemodynamics (cardiac output and stroke volume) and oxygen consumption in HCM compared to healthy controls during maximal stress testing. Aims: To evaluate associations between the trajectories of hemodynamic function and oxygen consumption in HCM compared to healthy controls. Methods: Twenty individuals with HCM (51±15 years old, body mass index (BMI): 28±3 kg/m 2 , females, n=4) and 16 healthy controls (66±7 years old, 27±6 kg/m 2 , females, n=6) were included in the present study. Participants completed a maximal-graded stress test coupled with non-invasive hemodynamic bioreactance (cardiac output, stroke volume) and gas exchange (oxygen consumption, VO 2 ) measurements. Data were analyzed in quartiles (exercise only) and phases (rest, pre-pedalling, exercise and recovery) of the maximal-graded stress test. Results: In HCM, cardiac output declined in the fourth quartile of the exercise phase of the stress test (-0.39 L/min, p &lt;0.001) whilst VO 2 increased (3.86 ml/kg/min, p &lt;0.001). There was a significant difference in the gradient of cardiac output between HCM and controls in the final quartile of the test (-1.6 vs. 18.1 L/min, p&lt;0.001). In coherence, stroke volume declined in the fourth quartile of the test (-18.4 ml, p &lt;0.01) in response to increasing VO 2 in HCM. The rates of recovery were faster in HCM compared to the control group for VO 2 (-4.3 vs -2.6 mL/second, p&lt;0.001), cardiac output (-0.03 vs -0.02 L/second, p&lt;0.001), heart rate (-0.17 vs -0.10 beats/second, p&lt;0.001), and stroke volume (-0.18 vs -0.07 L/second, p&lt;0.001). Conclusions: In HCM, cardiac output declined during the later stages of maximal stress testing whereas in controls it continued to rise, indicating impaired maximal cardiac output responses to exercise. These findings have implications for exercise prescription and training regimens in HCM suggesting avoidance of maximal exercise levels.

Abstract 4143256: Non-invasive, Radiation-free, Non-contrast Myocardial Volume Oxygen Consumption Quantification Using Free-breathing MR Blood Oximetry

Background: Myocardial oxygen consumption (MVO 2 ) is a central marker in measuring cardiac energetics. Current methods to quantify MVO 2 are inaccessible due to the requirement of invasive procedures or PET agents that require onsite cyclotrons. Hypothesis A free-breathing, non-ECG-gated, motion-resolved Cardiac MR blood oximetry technique can noninvasively quantify MVO 2 in standard clinical MRI scanners without using ionizing radiation and contrast agents. Method: The developed free-breathing CMR imaging technique was prescribed in a 3T clinical scanner to the mid left ventricle (LV) and the cross-section of the coronary sinus(CS) slices of the heart to obtain the corresponding blood oxygenation (SbO 2 ) and the hematocrit (Hct) in heart chambers. 2D phase contrast CMR was performed in the CS to quantify the myocardial blood flow (MBF). The MVO 2 was quantified with Fick’s law (MVO 2 =arterio-venous oxygen difference x MBF). We examined the developed method in healthy pigs (N=7) under rest and adenosine stress and validated it against invasive blood sampling. In addition, we tested the method’s clinical feasibility in healthy human volunteers (N=4). Results: Comparable blood oxygenation levels (SbO 2 ) and MVO 2 were measured and compared between the non-invasive CMR and invasive ground truth (Fig. 1). Significantly increased coronary sinus SbO 2 is observed in both methods during adenosine infusion. It is accompanied by decreased MVO 2 and rate pressure product (RPP) (Rest: CMR=10.2±2.7ml/min, Inv.=10.8±6.9 ml/min, RPP=7956.9±620.9 mmHg/min; Stress: CMR=5.3±1.9 ml/min, Inv=6.3±3.6 ml/min, RPP=5338.2±618.3 mmHg/min). In Fig. 2, the healthy human volunteers' MVO 2 estimations(14.1±6.7ml/min) shows no statistical difference compared to the previous invasive measurements(16.5±4.8 ml/min, Ganz, et al. circulation 1971). Conclusions: The proposed noninvasive CMR technique can quantify MVO 2 in standard MRI scanners without using a needle. It has the potential to provide an accessible, risk-free assessment of myocardial metabolism for patients with potential metabolism impairments.

The Effect of Expressive Touch and Music on Pain, Vital Signs, and Brain Oxygenation: Mixed-Method Study with Clinical Trial

PurposeSubjective methods should be used to evaluate pain. It is important to know how pain affects vital signs and brain oxygenation. This study aimed to determine the effects of expressive touch and music applied after lumbar disc herniation surgery on pain, vital signs, and brain oxygenation. DesignThis was a convergent, parallel, mixed-methods study utilizing randomized controlled trials and semi-structured qualitative interviews. MethodsWith power analysis, 132 (44: expressive touch, 44: music, 44: control) patients were included in the study. Thirty-two patients were included in the qualitative research sample. Expressive touch and music interventions were repeated 3 times. Pain, vital signs, and brain oxygenation values were recorded before and after the interventions. Qualitative data were collected after the interventions. ResultsIt was determined that expressive touch and music significantly decreased the patients’ pain levels compared to the control group (X2: 67.118), (p < .001). It was found that expressive touch and music created a significant difference in respiration (X2: 15.289), blood pressure (X2: 8.754-8.706), saturation (X2: 47.953), and brain oxygenation (X2: 31.473-37.110), (p < .001). Music was found to be more effective than expressive touch on pain and brain oxygenation. The interventions relaxed and distracted the patients. ConclusionsIt was found that expressive touch and music were effective in reducing pain level, keeping vital signs within physiological limits, and increasing brain oxygenation. Further studies are needed to examine the effects of other methods used in postoperative pain management on brain oxygenation.

An underrecognized phenotype of pulmonary emphysema with marked pulmonary gas exchange but with mild or moderate airway obstruction

In patients with pulmonary emphysema and mild to moderate airflow limitation, one does not expect the features marked exertional dyspnea and hypoxemia as well as a profound decrease in diffusing capacity of the lung for carbon monoxide (DLCO). Here we describe this phenotype and its prognosis. From our database, we retrospectively selected cases associating emphysema, exertional breathlessness, O2 requirement at least upon exercise, forced expiratory volume in 1 sec (FEV1) ≥ 50% predicted, and DLCO ≤ 50% predicted, without associated combined pulmonary fibrosis and emphysema, right-to-left shunt, or severe pulmonary hypertension. Over a 12-year period, we identified 16 patients with emphysema and the above presentation. At the initial evaluation, the median age was 62 years (interquartile range 53.8–68.9). The median FEV1 and DLCO% predicted and mean pulmonary artery pressure were 86 (65–95)%, 38 (31–41)%, and 20 (17–25) mm Hg, respectively. On room air, the median arterial partial pressure of oxygen and partial pressure of carbon dioxide in arterial blood were 63.5 (55.8–69) mm Hg and 34.5 (31–36) mm Hg with increased median alveolar-arterial oxygen difference (46 [39–51] mm Hg). After the initial evaluation, the respiratory condition worsened in 13 of 14 (92.8%) patients with one or more re-evaluations (median follow-up 2.6 [0.9–5.8] years). In 12, lung transplantation was considered. Four patients died after 5.8, 5.7, 7.1, and 0.8 years of follow-up, respectively. We describe an underrecognized phenotype of pulmonary emphysema featuring a particular profile characterized by marked exertional dyspnea, impaired pulmonary gas exchange with low DLCO and marked oxygen desaturation at least on exercise but with mild or moderate airway obstruction.

The impact of exercise training in Fontan procedure patients: a systematic review and meta-analysis

Abstract Background Patients undergoing the Fontan procedure experience long-term complications related to decreased exercise capacity. Exercise training(ET) has emerged as a non-pharmacological solution for increasing cardiorespiratory fitness. However, the effect and safety of exercise training in patients following the Fontan procedure are still unclear. Objectives We aimed to perform a meta-analysis comparing ET versus no exercise intervention for patients following Fontan operation in efficacy and safety outcomes. Methods We systematically searched PubMed, Embase, and Cochrane databases on November 23, 2023, for randomized controlled trials (RCTs) comparing ET, including aerobic, endurance, or inspiratory muscle training, versus no exercise intervention in patients following Fontan operation. We computed mean differences (MD) with a 95% confidence interval (CI) for continuous endpoints. The primary endpoint was (1) peak O2 consumption. Our study also included the secondary endpoints of: (2) maximum workload; (3) peak heart rate(HR); and (4) peak saturation of O2. We performed a subgroup analysis between different exercise therapies. Results This meta-analysis included five RCTs and 154 patients. Follow-up ranged from 3 to 6 months. Regarding ET, two studies used aerobics, one used endurance, and three used inspiratory muscle therapy as exercise therapy for patients with Fontan operations. Our findings on the maximum workload endpoint were more significant for exercise therapy (MD 20.98W; 95% CI 5.32 to 36.65; p&amp;lt;0.01; Fig. 1A) compared to no intervention group. However, there was no significant difference in peak oxygen (MD 2.03 ml/kg/min; 95% CI -0.29 to 4.35; p=0.095; Fig. 1B), peak HR (MD 1.10 bpm; 95% CI -4.07 to 6.27; p=0.68); and peak saturation of O2 (MD 0.39%; 95% CI -1.93 to 2.72; p=0.74). A subgroup analysis between different ET types (aerobic vs. endurance vs. inspiratory muscle training) showed no significant subgroup interaction(p=0.91; Fig. 1B). Conclusion In this meta-analysis, ET is associated with a slight increase in maximum workload in patients following the Fontan procedure. Further multicenter RCTs are warranted to assess the efficacy of comparing different types of ET and their impact on peak oxygen consumption.

Trajectories and sex differences of brain structure, oxygenation and perfusion functions in normal aging

Background: Brain structure, oxygenation and perfusion are important factors in aging. Coupling between regional cerebral oxygen consumption and perfusion also reflects functions of neurovascular unit (NVU). Their trajectories and sex differences during normal aging important for clinical interpretation are still not well defined. In this study, we aim to investigate the relationship between brain structure, functions and age, and exam the sex disparities.Method: A total of 137 healthy subjects between 20∼69 years old were enrolled with conventional MRI, structural three-dimensional T1-weighted imaging (3D-T1WI), 3D multi-echo gradient echo sequence (3D-mGRE), and 3D pseudo-continuous arterial spin labeling (3D-pCASL). Oxygen extraction fraction (OEF) and cerebral blood flow (CBF) were respectively reconstructed from 3D-mGRE and 3D-pCASL images. Cerebral metabolic rate of oxygen (CMRO2) were calculated as follows: CMRO2=CBF·OEF·[H]a, [H]a=7.377 μmol/mL. Brains were segmented into global gray matter (GM), global white matter (WM), and 148 cortical subregions. OEF, CBF, CMRO2, and volumes of GM/WM relative to intracranial volumes (rel_GM/rel_WM) were compared between males and females. Generalized additive models were used to evaluate the aging trajectories of brain structure and functions. The coupling between OEF and CBF was analyzed by correlation analysis. P or PFDR < 0.05 was considered statistically significant.Results: Females had larger rel_GM, higher CMRO2 and CBF of GM/WM than males (P < 0.05). With control of sex, CBF of GM significantly declined between 20 and 32 years, CMRO2 of GM declined subsequently from 33 to 41 years and rel_GM decreased significantly at all ages (R2 = 0.27, P < 0.001; R2 = 0.17, P < 0.001; R2 = 0.52, P < 0.001). In subregion analysis, CBF declined dispersedly while CMRO2 declined widely across most subregions of the cortex during aging. Robust negative coupling between OEF and CBF was found in most of the subregions (r range = -0.12∼-0.48, PFDR < 0.05).Conclusion: The sex disparities, age trajectories of brain structure and functions as well as the coupling of NVU in healthy individuals provide insights into normal aging which are potential targets for study of pathological conditions.

Oxygen Delivery and Consumption in Patients Who Are Comatose After Out-of-Hospital Cardiac Arrest Are Affected by Blood Pressure Target.

In the management of patients resuscitated from out-of-hospital cardiac arrest, a primary goal is to restore sufficient oxygen delivery (DO2) to meet demands in oxygen consumption (VO2). This post hoc analysis of the BOX (Blood Pressure and Oxygen Targets) study included adult patients who were comatose and experienced out-of-hospital cardiac arrest from a presumed cardiac cause, who were randomized to a mean arterial blood pressure (MAP) target of 63 mm Hg (MAP63) or 77 mm Hg (MAP77) and a Restrictive PaO2 target of 9 to 10 kPa versus a Liberal target of 13 to 14 kPa in a 2×2 factorial design. A pulmonary artery catheter was inserted following randomization. DO2 and VO2 were calculated as: DO2=cardiac output × arterial oxygen content, and VO2= cardiac output × arteriovenous oxygen difference. Of 789 patients, 730 (92.5%) were included in this substudy. A total of 362 patients were randomized to MAP77, and 368 to MAP63, 368 to a liberal Pao2 target, and 362 to a restrictive target. At all prespecified time points, DO2 in MAP77 was higher compared with MAP63, with a cumulative treatment effect of 203 L (95% CI, 132-274) O2 after 36 hours. VO2 was higher in MAP77 after 36 hours, with a cumulative treatment effect of 21.9 L (95% CI, 5.8-38) O2, compared with the MAP63 group. Targeting a MAP of 77 mm Hg resulted in an overall increase in DO2 and a smaller increase in VO2 compared with a MAP target of 63 mm Hg. A higher Pao2 target did not result in any difference in DO2 or VO2.

Mechanisms of adaptations in cardiorespiratory fitness with exercise prescriptions differing in volume and intensity in middle-age men

Background: To examine the mechanisms of adaptations in cardiorespiratory fitness with different dose of amount and intensity exercise training in middle-aged men. Methods: A total of 67 sedentary subjects aged 40-49 yr were assigned to participate for 12 weeks in a control group or in one of three exercise groups: 1) low volume/moderate intensity 2) low volume/vigorous intensity and 3) high volume/vigorous intensity. They were tested for VO2max, cardiac output (Q) and stroke volume (SV) before and after training and maximal arterial-venous oxygen difference (a-vO2diff) calculated by the Fick Equation. Results: Contrasted to control group, VO2max increased similar in both LVVI and HVVI groups after 12 weeks; It indicated that the intensity of exercise appears to make a greater benefit than the amount of exercise on VO2max. However, Maximal cardiac output (Qmax) and a-vO2diff contributed to increase VO2max were differences in both of vigorous intensity groups. In LVVI group, Qmax together with maximal a-vO2diff contributed to the greater VO2max; in HVVI group, the majority of the increment in VO2max was relied on larger Qmax whereas a widened a-vO2diff. Conclusion: It is appropriate to recommend vigorous intensity exercise to improve cardiorespiratory fitness and encourage higher amount to confer additional benefit for Qmax.

Differences In Skeletal Muscle Oxygenation Of Vastus Laterals And Gastrocnemius During Exhaustive Exercise

Differences In Skeletal Muscle Oxygenation Of Vastus Laterals And Gastrocnemius During Exhaustive Exercise

Impact of staged goal-directed fluid therapy on postoperative pulmonary complications in patients undergoing McKeown esophagectomy: a randomized controlled trial

BackgroundOur aim was to evaluate the influence of staged goal directed therapy (GDT) on postoperative pulmonary complications (PPCs), intraoperative hemodynamics and oxygenation in patients undergoing Mckeown esophagectomy.MethodsPatients were randomly divided into three groups, staged GDT group (group A, n = 56): stroke volume variation (SVV) was set at 8–10% during the one lung ventilation (OLV) stage and 8–12% during the two lung ventilation (TLV) stage, GDT group (group B, n = 56): received GDT with a target SVV of 8–12% During the entire surgical procedure, and control group (group C, n = 56): conventional fluid therapy was administered by mean arterial pressure (MAP), central venous pressure (CVP), and urine volume. The primary outcome was the incidence of postoperative pulmonary complications within Postoperative days (POD) 7. The secondary outcomes were postoperative lung ultrasound (LUS) B-lines artefacts (BLA) scoring, incidence of other complications, the length of hospital stay, intraoperative hemodynamic and oxygenation indicators included mean arterial pressure (MAP), heart rate (HR), cardiac index (CI), cardiac output (CO), oxygenation index (OI), respiratory indices (RI), alveolar-arterial oxygen difference (Aa-DO2).ResultsPatients in group A and group B had a lower incidence of PPCs (7/56 vs. 17/56 and 9/56 vs. 17/56, p < 0.05), and a fewer B-lines score on postoperative ultrasound (4.61 ± 0.51 vs. 6.15 ± 0.74 and 4.75 ± 0.62 vs. 6.15 ± 0.74, p < 0.05) compared to group C. The CI, CO, MAP, and OI were higher in group A compared to group B and group C in the stage of thoracic operation. During the abdominal operation stage, patients in group A and group B had a better hemodynamic and oxygenation indicators than group C.ConclusionsIn comparison to conventional fluid therapy, intraoperative staged GDT can significantly reduce the incidence of postoperative pulmonary complications in patients undergoing McKeown esophagectomy, facilitating patient recovery. Compared to GDT, it can improve intraoperative oxygenation and stabilize intraoperative hemodynamics in patients.Trial registrationThis study was registered in the Chinese Clinical Trial Registry on 24/11/2021 (ChiCTR2100053598).

Gender Differences in Prefrontal Cortex Response to Negative Emotional Stimuli in Drivers.

Road safety improvement is a governmental priority due to driver-caused accidents. Driving style variation affects safety, with emotional regulation being pivotal. However, functional near-infrared spectroscopy (fNIRS) studies show inconsistent prefrontal cortex activity during emotion processing. This study examines prefrontal cortex response to negative emotional stimuli, particularly traffic accident images, across drivers diverse in age and gender. The study involved 118 healthy males (44.38 ± 12.98 years) and 84 females (38.89 ± 10.60 years). The Multidimensional Driving Style Inventory (MDSI) was used to assess driving behavior alongside fNIRS recordings. Participants viewed traffic accident and neutral images while prefrontal oxygenation was monitored. Women rated traffic accidents (t-test = 2.43; p < 0.016) and neutral images (t-test = 2.19; p < 0.030) lower in valence than men. Arousal differences were significant for traffic accident images (t-test = -3.06; p < 0.002). correlational analysis found an inverse relationship between Dissociative scale scores and oxygenation (all p-values ≤ 0.013). Greater prefrontal oxygenation occurred with neutral images compared to traffic accidents. Left hemisphere differences (t-test = 3.23; p < 0.001) exceeded right hemisphere differences (t-test = 2.46; p < 0.015). Subgroup analysis showed male participants to be driving these disparities. Among adaptive drivers, significant oxygenation differences between neutral and accident images were evident in both hemispheres (left: t-test = 2.72, p < 0.009; right: t-test = 2.22, p < 0.030). Male drivers with maladaptive driving styles, particularly dissociative ones, exhibit reduced prefrontal oxygenation when exposed to neutral and traffic accident images. This response was absent in female drivers, with no notable age-related differences.