Numerical analysis of stress distribution in the upper arm tissues under an inflatable cuff：Implications for noninvasive blood pressure measurement

An inflatable cuff wrapped around the upper arm is widely used in noninvasive blood pressure measurement.However, the mechanical interaction between cuff and arm tissues, a factor that potentially affects the accuracy of noninvasive blood pressure measurement, remains rarely addressed. In the present study, finite element（FE） models were constructed to quantify intra-arm stresses generated by cuff compression, aiming to provide some theoretical evidence for identifying factors of importance for blood pressure measurement or explaining clinical observations. Obtained results showed that the simulated tissue stresses were highly sensitive to the distribution of cuff pressure on the arm surface and the contact condition between muscle and bone. In contrast, the magnitude of cuff pressure and small variations in elastic properties of arm soft tissues had little influence on the efficiency of pressure transmission in arm tissues. In particular, it was found that a thickened subcutaneous fat layer in obese subjects significantly reduced the effective pressure transmitted to the brachial artery, which may explain why blood pressure overestimation occurs more frequently in obese subjects in noninvasive blood pressure measurement.

Phantom of Human Adipose Tissue and Studies of Light Propagation and Light Absorption for Parameterization and Evaluation of Noninvasive Optical Fat Measuring Devices

A method for noninvasive determination of fat and water content in the human body is examined. A spatially resolved spectroscopy method is used which can record low intensity near infrared spectra. This novel approach is compared to other methods for the determination of fat and water content. Monte Carlo simulations of light propagation in tissue are shown and the production and characterization of optical phantoms of adipose tissue are investigated.

EFFICIENT FITTING RANGE FOR GLUCOSE MEASUREMENT WITH OPTICAL COHERENCE TOMOGRAPHY

Studies of non-invasive glucose measurement with optical coherence tomography(OCT)in tissue-simulating phantoms and biological tissues show that glucose has an effect on the OCT signal slope.Choosing an efficient fitting range to calculate the OCT signal slope is important because it helps to improve the precision of glucose measurement.In this paper,we study the problem in two ways:(1)scattering-induced change of OCT signal slope versus depth in intralipid suspensions with different concentrations based on Monte Carlo(MC)simulations and experiments and(2)efficient fitting range for glucose measurement in 3%and 10%intralipid.The results show that the OCT signal slope expresses a contrary change with scattering coefficient below a certain depth in high intralipid concentrations,so that there is an effective fitting depth.With an efficient fitting range from 100μm to the effective fitting depth,the precision of glucose measurement can be 4.4mM for 10%intralipid and 2.2mM for 3%intralipid.

OPTICAL MEASUREMENT OF PHOTOSENSITIZER CONCENTRATION IN VIVO

Most techniques for measuring tissue concentrations of drugs are invasive,time-consuming,and often require the removal of tissue or bodyfluids.Optical pharmacokinetics(OP)is a minimally invasive alternative giving an immediate result.Pulses of white light are directed at the tissue of interest using afiber optic probe.Scattered light is detected by a secondfiber immediately adjacent to thefirst in the same probe(separation 1.7 mm).Using the photosensitizer disulfonated aluminium phthalocyanine(AlS_(2)Pc),OP measurements were made in phantoms and on the mouth,stomach,colon,skin,and liver of normal rats 1 and 24 h after intravenous AlS_(2)Pc administration.AlS_(2)Pc concentration was determined by calculating the area under the curve(AUC)in the spectral region around the peak drug absorption or measuring the height of the peak.Spectral baseline interpolation removed the need for pre-drug,control optical measurements.OP measurements correlated well with values from alkali chemical extraction(CE)of the corresponding tissues,(R^(2)0.87=0.97).OP measurements in the mouth also correlated with CE of less accessible internal organs(R^(2)0.77-0.88).In phantoms,the lowest detectable concentration was 0.1μg/g.In vivo,results were limited by the lower accuracy in the CE measurements but were almost certainly comparable.An incidentalfinding was a 12-15nm red shifted component in the spectra observed 1 h after drug administration,suggesting partitioning of the drug in different microenvironment compartments,which could prove to be of considerable interest in future studies.In conclusion,OP shows promise for real-time measurement of concentrations of drugs with suitable absorption peaks.

Metabolic Disorders Combined with Noninvasive Tests to Screen Advanced Fibrosis in Nonalcoholic Fatty Liver Disease

Background and Aims:Nonalcoholic fatty liver disease(NAFLD)is associated with metabolic disorders.This study aimed to explore the role of metabolic disorders in screening advanced fibrosis in NAFLD patients.Methods:A total of 246 histologically-proven NAFLD patients were enrolled across 14 centers.We compared the severity of fibrosis in patients with different components of metabolic disorders.Based on standard noninvasive tests and metabolic disorders,we developed new algorithms to identify advanced fibrosis.Results:Metabolic syndrome(MetS)was frequent in NAFLD patients(133/246,54%).Patients with MetS had a higher proportion of significant fibrosis(p=0.014)and higher LSM values(9.2 kPa,vs.7.4 kPa,p=0.002)than those without MetS.Patients with more metabolic disorders had higher fibrosis stages(p=0.017).Reduced highdensity lipoprotein cholesterol(odds ratio[OR]:2.241,95%confidence interval[CI]:1.004–5.002,p=0.049)and raised fasting glucose(OR:4.500,95%CI:2.083–9.725,p<0.001)were significantly associated with advanced fibrosis.Using these two metabolic disorders as a screening tool,a sensitivity,specificity and accuracy of 92%,81%and 83%was achieved,respectively.With the new algorithms combining metabolic disorders with noninvasive measurements,the number of patients requiring liver biopsy was reduced,especially in combination with the Fibrosis-4 score and metabolic disorders(36%to 17%,p<0.001).In addition,this stepwise algorithm could achieve a high accuracy(85%)and high negative predictive value(93%).Conclusions:Metabolic disorders should be taken into consideration in the diagnosis of advanced fibrosis.With further validation and investigation,new algorithms could be recommended in primary care units to spare patients from unnecessary referral and liver biopsies.

Portal hypertension in nonalcoholic fatty liver disease: Challenges and perspectives

Nonalcoholic fatty liver disease(NAFLD)has become the most common chronic liver disease worldwide.NAFLD‐related cirrhosis is often complicated by portal hypertension(PHT).Recent evidence showed that portal venous pressure(PVP)starts to rise in the early stages of NAFLD,even in absence of advanced fibrosis or cirrhosis.However,the precise pathological mechanisms of this process are still poorly understood.Lipid accumulation,hepatocellular ballooning,sinusoidal endothelial cell dysfunction,capillarization,microthrombosis,increased angiogenesis,and pericellular fibrosis may all be involved in the early development of increased PVP in NAFLD.Direct measurement of PHT is invasive and impractical in noncirrhotic NAFLD individuals and may also underestimate its severity.Thus,the development and validation of noninvasive and more accurate measurements,including new serum biomarkers,scoring models,and imaging techniques(such as ultrasonography,elastography,and magnetic resonance imaging),are urgently needed.Owing to the increasing morbidity,challenges in the prevention and management of PHT in NAFLD are unprecedented.This review article aims to briefly discuss these challenges and summarizes the mechanisms,diagnosis,and emerging therapies for PHT in people with NAFLD.