Indication of BOLD-specific venous flow-volume changes from precisely controlled hyperoxic vs. hypercapnic calibration.
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ABSTRACT:
SUBMITTER: Mark CI
PROVIDER: S-EPMC3318148 | biostudies-other | 2012 Apr
REPOSITORIES: biostudies-other
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Project description:Resting-state brain activity has been widely investigated using blood oxygenation level dependent (BOLD) contrast techniques. However, BOLD signal changes reflect a combination of the effects of cerebral blood flow (CBF), cerebral blood volume (CBV), as well as the cerebral metabolic rate of oxygen (CMRO2). In this study, resting-state brain activation was detected and compared using the following techniques: (a) BOLD, using a gradient-echo echo planar imaging (GE-EPI) sequence; (b) CBV-weighted signal, acquired using gradient and spin echo (GRASE) based vascular space occupancy (VASO); and (c) CBF, using pseudo-continuous arterial spin labeling (pCASL). Reliable brain networks were detected using VASO and ASL, including sensorimotor, auditory, primary visual, higher visual, default mode, salience and left/right executive control networks. Differences between the resting-state activation detected with ASL, VASO and BOLD could potentially be due to the different temporal signal-to-noise ratio (tSNR) and the short post-labeling delay (PLD) in ASL, along with differences in the spin-echo readout of VASO. It is also possible that the dynamics of spontaneous fluctuations in BOLD, CBV and CBF could differ due to biological reasons, according to their location within the brain.
| S-EPMC6235966 | biostudies-literature
Project description:High-flow oxygen through nasal cannula (HFNC) provides adequate oxygenation and can be an alternative to noninvasive ventilation (NIV) for patients with hypoxemic respiratory failure. The aim of the present study was to assess the efficacy of HFNC versus NIV in hypercapnic respiratory failure. Patients (n = 40) who were admitted to the Emergency Department of Alexandra Hospital due to hypercapnic respiratory failure (PaCO2 ? 45 mmHg) were randomized assigned into two groups, i.e., an intervention group (use of HFNC, n = 20) and a control group (use of NIV, n = 20). During their hospitalization in the Intensive Care Unit, vital signs (respiratory and heart rate, arterial blood pressure) and arterial blood gases (ABG) were closely monitored on admission, after 24 h and at discharge. No difference between the two groups regarding the duration of hospitalization and the use of HFNC or NIV was observed (p > 0.05). On admission, the two groups did not differ in terms of gender, age, body mass index, APACHE score, predicted death rate, heart rate, arterial blood pressure and arterial blood gases (p > 0.05). Respiratory rate in the HFNC group was lower than in the NIV group (p = 0.023). At discharge, partial carbon dioxide arterial pressure (PaCO2) in the HFNC group was lower than in the NIV group (50.8 ± 9.4 mmHg versus 59.6 ± 13.9 mmHg, p = 0.024). The lowerPaCO2 in the HFNC group than in the NIV group indicated that HFNC was superior to NIV in the management of hypercapnic respiratory failure.
| S-EPMC7459687 | biostudies-literature
Project description:IntroductionLow-flow veno-venous extracorporeal CO2 removal (ECCO2R) is an adjunctive therapy to support lung protective ventilation or maintain spontaneous breathing in hypercapnic respiratory failure. Low-flow ECCO2R is less invasive compared to higher flow systems, while potentially compromising efficiency and membrane lifetime. To counteract this shortcoming, a high-longevity system has recently been developed. Our hypotheses were that the novel membrane system provides runtimes up to 120 h, and CO2 removal remains constant throughout membrane system lifetime.MethodsSeventy patients with pH ≤ 7.25 and/or PaCO2 ≥9 kPa exceeding lung protective ventilation limits, or experiencing respiratory exhaustion during spontaneous breathing, were treated with the high-longevity ProLUNG system or in a control group using the original gas exchanger. Treatment parameters, gas exchanger runtime, and sweep-gas VCO2 were recorded across 9,806 treatment-hours and retrospectively analyzed.Results25/33 and 23/37 patients were mechanically ventilated as opposed to awake spontaneously breathing in both groups. The high-longevity system increased gas exchanger runtime from 29 ± 16 to 48 ± 36 h in ventilated and from 22 ± 14 to 31 ± 31 h in awake patients (p < 0.0001), with longer runtime in the former (p < 0.01). VCO2 remained constant at 86 ± 34 mL/min (p = 0.11). Overall, PaCO2 decreased from 9.1 ± 2.0 to 7.9 ± 1.9 kPa within 1 h (p < 0.001). Tidal volume could be maintained at 5.4 ± 1.8 versus 5.7 ± 2.2 mL/kg at 120 h (p = 0.60), and peak airway pressure could be reduced from 31.1 ± 5.1 to 27.5 ± 6.8 mbar (p < 0.01).ConclusionUsing a high-longevity gas exchanger system, membrane lifetime in low-flow ECCO2R could be extended in comparison to previous systems but remained below 120 h, especially in spontaneously breathing patients. Extracorporeal VCO2 remained constant throughout gas exchanger system runtime and was consistent with removal of approximately 50% of expected CO2 production, enabling lung protective ventilation despite hypercapnic respiratory failure.
| S-EPMC10129028 | biostudies-literature
Project description:Determination of compartment-specific cerebral blood volume (CBV) changes is important for understanding neurovascular physiology and quantifying blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI). In isoflurane-anesthetized cats, we measured the spatiotemporal responses of arterial CBV (CBV(a)) and total CBV (CBV(t)) induced by a 40-second visual stimulation, using magnetization transfer (MT)-varied BOLD and contrast-agent fMRI techniques at 9.4?T. To determine the venous CBV (CBV(v)) change, we calculated the difference between CBV(t) and CBV(a) changes. The dynamic response of CBV(a) was an order of magnitude faster than that of CBV(v), while the magnitude of change under steady-state conditions was similar between the two. Following stimulation offset, ?CBV(a) showed small poststimulus undershoots, while ?CBV(v) slowly returned to baseline. The largest CBV(a) and CBV(t) response occurred after 10 seconds of simulation in cortical layer 4, which we identified as the stripe of Gennari by T(1)-weighted MRI. The CBV(v) response, however, was not specific across the cortical layers during the entire stimulation period. Our data indicate that rapid, more-specific arterial vasodilation is followed by slow, less-specific venous dilation. Our finding implies that the contribution of CBV(v) changes to BOLD signals is significant for long, but not short, stimulation periods.
| S-EPMC3099637 | biostudies-literature
Project description:Introduction: Currently, there is a lack of evidence on the utilization of high-flow nasal cannula (HFNC) in patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD) accompanied by hypercapnic respiratory failure. We aimed to explore the efficacy and safety of HFNC compared with conventional oxygen therapy (COT) in such patients.Methods: This was a prospective, randomized, controlled trial. Patients with AECOPD with a baseline arterial blood gas pH ?7.35, PaO2 <60 mmHg, and PaCO2 >45 mmHg were enrolled. The primary endpoint was treatment failure, which needs mechanical ventilation.Results: A total of 320 patients were randomized to either the HFNC group (n = 160) or the COT group (n = 160). Sixteen (10.0%) patients in the HFNC group had treatment failure during hospitalization, which was significantly lower than the COT group figure of 31 (19.4%) patients (p = 0.026). Twenty-four hours after recruitment, the PaCO2 of the HFNC group was lower than that of the COT group (54.1 ± 9.79 mmHg vs 56.9 ± 10.1 mmHg, p = 0.030). PaCO2 higher than 59 mmHg after HFNC for 24 h was identified as an independent risk factor for treatment failure [OR 1.078, 95% CI 1.006-1.154, p = 0.032].Conclusion: In AECOPD patients with acute compensated hypercapnic respiratory failure, HFNC improved the prognosis compared with COT. Therefore, HFNC might be considered for first-line oxygen therapy in select patients.Trial registration number: ClinicalTrials.Gov: NCT02439333.
| S-EPMC7699989 | biostudies-literature
Project description:BackgroundDespite the encouraging results of noninvasive ventilation (NIV) in chronic hypercapnic COPD patients, it is also evident that some patients do not tolerate NIV or do not benefit from it. We conducted a study in which COPD patients with stable, chronic hypercapnia were treated with NIV and nasal high-flow (NHF) to compare effectiveness.MethodsIn a multi-centered, randomized, controlled, cross-over design, patients received 6 weeks of NHF ventilation followed by 6 weeks of NIV ventilation or vice-versa (TIBICO) between 2011 and 2016. COPD patients with stable daytime hypercapnia (pCO2≥50 mmHg) were recruited from 13 German centers. The primary endpoint was pCO2 changes from baseline blood gas, lung function, quality of life (QoL), the 6 min walking test, and duration of device use were secondary endpoints.ResultsA total of 102 patients (mean±SD) age 65.3±9.3 years, 61% females, body mass index 23.1±4.8 kg/m2, 90% GOLD D, pCO2 56.5±5.4 mmHg were randomized. PCO2 levels decreased by 4.7% (n=94; full analysis set; 95% CI 1.8-7.5, P=0.002) using NHF and 7.1% (95% CI 4.1-10.1, P<0.001) from baseline using NIV (indistinguishable to intention-to-treat analysis). The difference of pCO2 changes between the two devices was -1.4 mmHg (95% CI -3.1-0.4, P=0.12). Both devices had positive impact on blood gases and respiratory scores (St. George's Respiratory Questionnaire, Severe Respiratory Insufficiency Questionnaire).ConclusionsNHF may constitute an alternative to NIV in COPD patients with stable chronic hypercapnia, eg, those not tolerating or rejecting NIV with respect to pCO2 reduction and improvement in QoL.
| S-EPMC6615713 | biostudies-literature
Project description:IntroductionAcute respiratory failure is a common clinical condition accounting for nearly 116?000 admissions in the UK hospitals. Acute type 2 respiratory failure is also called acute hypercapnic respiratory failure (AHRF) and characterised by an elevated arterial CO2 level of >6?kPa due to pump failure. Acute exacerbation of chronic obstructive pulmonary disease is the most common cause of AHRF. High-flow nasal therapy (HFNT) is a new oxygen delivery system that uses an oxygen-air blender to deliver flow rates of up to 60?L/min. The gas is delivered humidified and heated to the patient via wide-bore nasal cannula.Methods and analysisWe hypothesised that HFNC as the initial oxygen administration method will reduce the number of patients with AHRF requiring non-invasive ventilation in patients at 6?hours post intervention when compared with low-flow nasal oxygen (LFO). A randomised single-centre unblinded controlled trial is designed to test our hypothesis. The trial will compare two oxygen administration methods, HFNT versus LFO. Patients will be randomised to one of the two arms if they fulfil the eligibility criteria. The sample size is 82 adult patients (41 HFNT and 41 LFO) presenting to the emergency department.Ethics and disseminationEthical approval was obtained from the Office for Research Ethics Committees Northern Ireland (REC reference: 20/NI/0049). Dissemination will be achieved in several ways: (1) the findings will be presented at national and international meetings with open-access abstracts online and (2) in accordance with the open-access policies proposed by the leading research funding bodies we aim to publish the findings in high-quality peer-reviewed open-access journals.Trial registration numberThe trial was prospectively registered at the clinicaltrials.gov registry (NCT04640948) on 20 November 2020.
| S-EPMC7798411 | biostudies-literature
Project description:BACKGROUND:Nasal Highflow (NHF) delivers a humidified and heated airflow via nasal prongs. Current data provide evidence for efficacy of NHF in patients with hypoxemic respiratory failure. Preliminary data suggest that NHF may decrease hypercapnia in hypercapnic respiratory failure. The aim of this study was to evaluate the mechanism of NHF mediated PCO2 reduction in patients with chronic obstructive pulmonary disease (COPD). METHODS:In 36 hypercapnic COPD patients (PCO2 >?45 mmHg), hypercapnia was evaluated by capillary gas sampling 1 h after NHF breathing under four conditions A to D with different flow rates and different degrees of leakage (A?=?20 L/min, low leakage, two prongs, both inside; B?=?40 L/min, low leakage, two prongs, both inside; C?=?40 L/min, high leakage, two prongs, one outside and open; D?=?40 L/min, high leakage, two prongs, one outside and closed). Under identical conditions, mean airway pressure was measured in the hypopharynx of 10 COPD patients. RESULTS:Hypercapnia significantly decreased in all patients. In patients with capillary PCO2 >?55 mmHg (n =?26), PCO2 additionally decreased significantly by increased leakage and/or flow rate in comparison to lower leakage/ flow rate conditions (A?=?94.2?±?8.2%; B?=?93.5?±?4.4%; C?=?90.5?±?7.2%; D?=?86.8?±?3.8%). The highest mean airway pressure was observed in patients breathing under condition B (2.3?±?1.6 mbar; p <?0.05). CONCLUSIONS:This study demonstrates effective PCO2 reduction with NHF therapy in stable hypercapnic COPD patients. This effect does not correlate with an increase in mean airway pressure but with increased leakage and airflow, indicating airway wash out and reduction of functional dead space as important mechanisms of NHF therapy. These results may be useful when considering NHF treatment in hypercapnic COPD patients. TRIAL REGISTRATION:Clinical Trials: NCT02504814; First posted July 22, 2015.
| S-EPMC5784698 | biostudies-literature
Project description:Background and Objectives: Laparoscopic surgery, which results in less bleeding, less postoperative pain, and better cosmetic results, may affect the lung dynamics via the pneumoperitoneum. After laparoscopic surgery, atelectasis develops. The primary aim of the present study is to demonstrate the effects of two different ventilation modes on the development of atelectasis using lung ultrasound, and the secondary outcomes include the plateau pressure, peak inspiratory pressure, and compliance differences between the groups. Materials and Methods: In this study, 62 participants aged 18-75 years undergoing laparoscopic cholecystectomy were enrolled. The patients were randomly assigned into two groups: the volume-controlled ventilation (VCV) group (group V) or the pressure-controlled-volume guaranteed ventilation (PCV-VG) group (group PV). The lung ultrasound score (LUS) was obtained thrice: prior to induction (T1), upon the patient's initial arrival in the recovery room (T2), and just before departing the recovery unit (T3). The hemodynamic data and mechanical ventilation parameters were recorded at different times intraoperatively. Results: The LUS score was similar between the groups at all the times. The change in the LUS score of the right lower anterior chest was statistically higher in the VCV group than the PCV group. The peak inspiratory pressure (PIP) was found to be statistically higher in the V group than the PV group five minutes after induction (T5) (20.84 ± 4.32 p = 0.021). The plateau pressure was found to be higher in the V group than the PV group at all times (after induction (Tind) 17.29 ± 5.53 p = 0.004, (T5) 17.77 ± 4.89 p = 0.001, after pneumoperitoneum (TPP) 19.71 ± 4.28 p = 0.002). Compliance was found to be statistically higher in the PV group than the V group at all times ((Tind) 48.87 ± 15.37 p = 0.011, (T5) 47.94 ± 13.71 p = 0.043, (TPP) 35.65 ± 6.90 p = 0.004). Before and after the pneumoperitoneum, the compliance was determined to be lower in the V group than the PV group, respectively (40.68 ± 13.91 p = 0.043, 30.77 ± 5.73 p = 0.004). Conclusions: LUS score was similar between groups at all times. The PCV-VG mode was superior to the VCV mode in providing optimal ventilatory pressures and maintaining high dynamic compliance in patients undergoing laparoscopic abdominal surgery.
| S-EPMC10607930 | biostudies-literature
Project description:Objective: Vascular malformations affect 3% of neonates. Venous malformations (VMs) are the largest group representing more than 50 % of cases. In hereditary forms of VMs gene mutations have been identified, but for the large group of spontaneous forms the primary cause and downstream dysregulated genes are unknown. Methods and Results: We have performed a global comparison of gene; expression in slow-flow VMs and normal saphenous veins using human whole genome micro-arrays. Genes of interest were validated with qRT-PCR. Gene expression in the tunica media was studied after laser micro-dissection of small pieces of tissue. Protein expression in endothelial cells (ECs) was studied with antibodies. We detected 511 genes more than 4-fold down- and 112 genes more than 4-fold up-regulated. Notably, chemokines, growth factors, transcription factors and regulators of extra-cellular matrix (ECM) turnover were regulated. We observed activation and arterialization of ECs of the VM proper, whereas ECs of vasa vasorum exhibited up-regulation of inflammation markers. In the tunica media, an altered ECM turnover and composition was found. Conclusions: Our studies demonstrate dysregulated gene expression in tunica interna, media and externa of VMs, and show that each of the three layers represents a reactive compartment. The dysregulated genes may serve as therapeutic targets. Experiment Overall Design: - 4 samples Experiment Overall Design: - samples are replicates with dye swap
2008-06-15 | E-GEOD-7190 | biostudies-arrayexpress