Fick principle

OBJECTIVES: Chronic Mesenteric Ischaemia (CMI) is an underdiagnosed but severe condition. Access to functional testing is often limited and the diagnosis is usually based primarily on symptoms and imaging. One of the functional tests available is measurement of the Splanchnic Blood Flow (SBF). The purpose of the present investigation was to evaluate if changes in the splanchnic perfusion after revascularisation can be detected by measuring the SBF and hepatic vein oxygenation. MATERIALS AND METHODS: The SBF was measured in ten patients before and after revascularisation of the mesenteric arteries by either percutaneous transluminal angioplasty (n=9) or open revascularisation (n=1)...

Measuring regional cerebral blood flow (rCBF) after revascularization for moyamoya disease, as a type of ischemic cerebrovascular disease, is crucial. This study aims to validate our novel technology that combines near-infrared spectroscopy (NIRS) with a frequency filter to extract the arterial component. We measured rCBF before and after revascularization for moyamoya disease and at the end of the surgery using NIRO-200NX (Hamamatsu Photonics, Japan) and indocyanine green (ICG). rCBF was calculated using Fick's principle, change in arterial ICG concentrations, and maximum arterial ICG concentration...

Cardiorespiratory fitness (CRF) has been proposed as a vital sign for the past several years, supported by a wealth of evidence demonstrating its significance as a predictor of health trajectory, exercise/functional capacity, and quality of life. According to the Fick equation, oxygen consumption (VO2 ) is the product of cardiac output (CO) and arterial-venous oxygen difference, with the former being a primary driver of one's aerobic capacity. In terms of the dependence of aerobic capacity on a robust augmentation of CO from rest to maximal exercise, left ventricular (LV) CO has been the historic focal point...

The skin is not only the site of drug application, but also the site of exposure to various chemical substances. Prediction of skin permeability, body absorption, and local skin concentration of chemicals are very important to assure efficacy and safety. Most in silico models for skin permeation of chemical are based on the prediction of its permeability coefficient (P, unit cm/s), and a certain level of prediction accuracy has been obtained. On the other hand, the amount absorbed in the body of a chemical is calculated from the sum of the amount of skin permeation and the amount under the stratum corneum (viable epidermis and dermis)...

OBJECTIVES: The objectives of this study were to 1) in patients without pulmonary function, determine resting energy expenditure (REE) in venovenous extracorporeal membrane oxygenation (ECMO) acute respiratory distress syndrome (ARDS) patients by paralysis status and 2) determine the threshold tidal volume (TV) associated with meaningful gas exchange as determined by measurable end-tidal carbon dioxide elimination (etV̇co2 ). DESIGN: Retrospective observational study...

The placenta facilitates the transport of nutrients to the fetus, removal of waste products from the fetus, immune protection of the fetus and functions as an endocrine organ, thereby determining the environment for fetal growth and development. Additionally, the placenta is a highly metabolic organ in itself, utilizing a majority of the oxygen and glucose derived from maternal circulation. Consequently, optimal placental function is required for the offspring to reach its genetic potential in utero. Among ruminants, pregnant sheep have been used extensively for investigating pregnancy physiology, in part due to the ability to place indwelling catheters within both maternal and fetal vessels, allowing for steady-state investigation of blood flow, nutrient uptakes and utilization, and hormone secretion, under non-stressed and non-anesthetized conditions...

BACKGROUND: Inefficiency of lung gas exchange during general anesthesia is reflected in alveolar (end-tidal) to arterial (end-tidal-arterial) partial pressure gradients for inhaled gases, resulting in an increase in alveolar deadspace. Ventilation-perfusion mismatch is the main contributor to this, but it is unclear what contribution arises from diffusion limitation in the gas phase down the respiratory tree (longitudinal stratification) or at the alveolar-capillary barrier, especially for gases of high molecular weight such as volatile anesthetics...

One promising approach for mapping CMRO2 is dual-calibrated functional MRI (dc-fMRI). This method exploits the Fick Principle to combine estimates of CBF from ASL, and OEF derived from BOLD-ASL measurements during arterial O2 and CO2 modulations. Multiple gas modulations are required to decouple OEF and deoxyhemoglobin-sensitive blood volume. We propose an alternative single gas calibrated fMRI framework, integrating a model of oxygen transport, that links blood volume and CBF to OEF and creates a mapping between the maximum BOLD signal, CBF and OEF (and CMRO2 )...

In response to the coronavirus disease 2019 (COVID-19) pandemic, the State of Maryland established a 250-bed emergency response field hospital at the Baltimore Convention Center to support the existing healthcare infrastructure. To operationalize this hospital with 65 full-time equivalent (FTE) clinicians in less than four weeks, more than 300 applications were reviewed, 186 candidates were interviewed, and 159 clinicians were credentialed and onboarded. The key steps to achieve this undertaking involved employing multidisciplinary teams with experienced personnel, mass outreach, streamlined candidate tracking, pre-interview screening, utilizing all available expertise, expedited credentialing, and focused onboarding...

OBJECTIVES: Cardiac output (CO) measurements employing the direct Fick principle represent the gold standard in right-sided heart catheterization (RHC). The current widespread approach in hemodynamic workup however uses the indirect Fick principle with assumed values for oxygen uptake (VO2 ) leading to incorrect CO values in up to 25% of patients. We have tested a contemporary breath-by-breath gas analyzer that allows precise real-time measurements of VO2 with appropriate time and effort to serve the direct Fick principle...

Patients with obstructive sleep apnea (OSA) are at elevated risk of developing systemic vascular disease and cognitive dysfunction. Here, cerebral oxygen metabolism was assessed in patients with OSA by means of a magnetic resonance-based method involving simultaneous measurements of cerebral blood flow rate and venous oxygen saturation in the superior sagittal sinus for a period of 10 minutes at an effective temporal resolution of 1.3 seconds before, during, and after repeated 24-second breath-holds mimicking spontaneous apneas, yielding, along with pulse oximetry-derived arterial saturation, whole-brain CMRO2 via Fick's Principle...

BACKGROUND: Transthoracic echocardiography (TTE) is the diagnostic routine standard for assessing aortic stenosis (AS). However, its inaccuracies in determining stroke volume (SV) and aortic valve area (AVA) call for a more precise and dependable method. Phase-contrast cardiovascular magnetic resonance imaging (PC-CMR) is a promising tool to push these boundaries. Thus, the aim of this study was to validate a novel approach based on PC-CMR against the gold-standard of invasive determination of AVA in AS compared to TTE...

Assessment of microcirculatory functional capacity is considered to be of prime importance for therapy guidance and outcome prediction in critically ill intensive care patients. Here, we show determination of skin microcirculatory oxygen delivery and consumption rates to be a feasible approach at the patient's bedside. Real time laser-doppler flowmetry (LDF) and white light spectrophotometry (WLS) were used for assessment of thenar skin microperfusion, regional Hb and postcapillary venous oxygen saturation before and after forearm ischemia...

Extracorporeal membrane oxygenation (ECMO) can be delivered in veno-arterial (VA) and veno-venous (VV) configurations based on the cannulation strategy. VA and VV ECMO are delivered primarily for haemodynamic and respiratory support in patients with severe heart and lung failure, respectively. The Fick principle describes the relationship between blood flow and oxygen consumption - key parameters in the physiological management of extracorporeal support. This review will discuss the application of the Fick principle in: (i) recirculation in VV ECMO; (ii) the quantification of oxygen delivery (DO2) in VV ECMO and (iii) the quantification of transpulmonary blood flow and systemic arterial oxygen saturation in VA ECMO...

BACKGROUND: Chronic mesenteric ischaemia (CMI) is a vastly underdiagnosed condition that typically leads to postprandial abdominal pain and weight loss. The aim of the study was to explore the involvement of various mesenteric vessels in total splanchnic blood flow (SBF) and hepatic vein oxygenation. METHODS: Single-blinded comparative trial of 476 patients clinically suspected of CMI. Routine investigation included measurement of hepatic vein oxygen saturation, indirect measurement of the total splanchnic blood flow (SBF), using Fick's principle and the tracer [99m Tc]Mebrofenin, before and after a meal, and digital subtraction angiography...

BACKGROUND & AIMS: The aim was to measure fractional hepatic blood volume (HBV) and hepatic blood flow (HBF) before and after a meal in patients with cirrhosis ( n  = 7) and healthy persons ( n  = 6). METHODS: Catheters were placed in a radial artery and a hepatic vein for blood sampling and a peripheral vein for indocyanine green (ICG) infusion. A 6-min positron emission tomography (PET) liver scan was performed after inhalation of 1000 MBq 15 O-CO and repeated after ingestion of a standard meal...

BACKGROUND: Cardiac catheterization and cardiovascular magnetic resonance (CMR) imaging have distinct diagnostic roles in the congenital heart disease (CHD) population. Invasive CMR (iCMR) allows for a more thorough assessment of cardiac hemodynamics at the same time under the same conditions. It is assumed but not proven that iCMR gives an incremental value by providing more accurate flow quantification. METHODS: Subjects with CHD underwent real-time 1.5 T iCMR using a passive catheter tracking technique with partial saturation pulse of 40° to visualize the gadolinium-filled balloon, CMR-conditional guidewire, and cardiac structures simultaneously to aid in completion of right (RHC) and left heart catheterization (LHC)...

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) therapy is a rescue strategy for severe cardiopulmonary failure. The estimation of cardiac output during VA-ECMO is challenging. A lung circuit ([Formula: see text]Lung ) and an ECMO circuit ([Formula: see text]ECMO ) with oxygenators for CO2 removal ([Formula: see text]CO2 ) and O2 uptake ([Formula: see text]O2 ) simulated the setting of VA-ECMO with varying ventilation/perfusion ([Formula: see text]/[Formula: see text]) ratios and shunt. A metabolic chamber with a CO2 /N2 blend simulated [Formula: see text]CO2 and [Formula: see text]O2 ...

INTRODUCTION: Sprint interval training (SIT), characterized by brief bouts of 'supramaximal' exercise interspersed with recovery periods, increases peak oxygen uptake ([Formula: see text]) despite a low total exercise volume. Per the Fick principle, increased [Formula: see text] is attributable to increased peak cardiac output ([Formula: see text]) and/or peak arterio-venous oxygen difference (a-vO2diff ). There are limited and equivocal data regarding the physiological basis for SIT-induced increases in [Formula: see text], with most studies lasting ≤ 6 weeks...

Hemodynamic optimization is vital in high risk surgical patients or in high risk surgical procedures. The main objective of hemodynamic management is to maintain tissue perfusion and preserve aerobic metabolism through a cardiac output coupled with the metabolic demand. The technologies used for cardiac output monitoring use special techniques (e.g. lithium dilution or transpulmonary thermodilution) or implementation of dedicated devices with considerable rates of potential complications (pulmonary artery catheter)...