#american medical journal

[biomedres]

A Brief Overview on the Methods of Impact Evaluation of Public Policies

A Brief Overview on the Methods of Impact Evaluation of Public Policies in Biomedical Journal of Scientific & Technical Research

https://biomedres.us/fulltexts/BJSTR.MS.ID.006047.php

Impact assessment is an important tool for the formulation and implementation of evidence-informed public policies. The primary objective of this article is to present a brief review of the methods most commonly used in evaluating the impact of public policies, and the secondary objective is to present examples of the application of these methods in the evaluation of programs to promote physical activity. Quasi-experimental methods are configured as an important alternative for the construction of causal inferences about the impact of policies and programs, especially when it is not possible to participate in these interventions and do not happen randomly. In this sense, we highlight the propensity score matching method and the difference-in-differences estimator, which can be used alone, combined with each other or with other methods to generate valid and robust estimates of the causal effect. At the end of the article, the application of these methods in evaluating the impact of physical activity programs in Brazil and the United States is presented, emphasizing the versatility of these methods to assess the impact by comparing groups of aggregated units (such as municipalities), either to verify the effect of an intervention on groups of individuals.

For more articles in Journals on Biomedical Sciences click here bjstr 

Follow on Twitter : https://twitter.com/Biomedres01 Follow on Blogger :https://biomedres01.blogspot.com/ Like Our Pins On : https://www.pinterest.com/biomedres/

[athenaeumscientificpublishers]

What are the benefits of an American medical journal? - Athenaeum Scientific Publisher

Researchers, academics, and professionals publishing their work is a crucial part of sharing knowledge and advancing their fields. Recently, an American medical journal from Athenaeum Scientific Publisher.

have emerged as a popular alternative to traditional publishing models.

The advantages of using Open access journals

These types of journals are online publications that make research articles available to readers for free, without any barriers or restrictions. Unlike traditional journals, which require readers to pay subscription fees or purchase articles on a pay-per-view basis, Open Access Journals make their articles freely available to anyone who wants to read them. This model has been made possible by advances in digital technology, which have lowered the cost of publishing and distribution. In the American medical journal, original articles are published that emphasize on the new research findings.

Benefits of Open Access Journals

Open Access Journals offer a range of benefits to both authors and readers. For authors, these Journals provide a wider audience for their work, which can lead to greater visibility, citations, and impact. Because these journals remain freely available, authors can also reach readers who might not have access to traditional journals due to financial or institutional constraints.

For readers, these Journals provide immediate access to the latest research in their fields, without the need for costly subscriptions. This can be particularly valuable for researchers in developing countries or those without access to well-funded libraries.

Open Access Journals also promote transparency and accountability in scientific research. Because articles are freely available and can be downloaded and shared by anyone, there is a greater potential for replication and scrutiny of research findings. This can help to improve the quality and reliability of scientific research.

Global Impact of Open-Access Journals

The impact of these innovative journals has been felt globally, with researchers and readers around the world benefiting from their open and accessible model. In many developing countries, these journals have been crucial in enabling researchers to access the latest scientific research and share their work with a wider audience.

Open Access Journals have also played a role in promoting scientific collaboration and knowledge-sharing across borders. Because articles are freely available, researchers from different countries and institutions can easily access each other's work and build on each other's findings. This can lead to new discoveries, breakthroughs, and collaborations that might not have been possible under traditional publishing models.

Bottom Line

There are now thousands of Open Access Journals in a wide range of disciplines, from science and technology to humanities and social sciences. These types of journals offer a range of benefits to both authors and readers and have had a global impact on scientific research and knowledge-sharing. As an author or reader, you can join the Open Access movement by supporting these Journals, publishing your work in these types of Journals, and sharing the latest research with your colleagues and peers. By doing so, you can help to create a more open, transparent, and collaborative scientific community. If you want to get additional information about these journals, please visit our website, Athenaeum Scientific Publisher now!

[biomedgrid]

Biomed Grid | Antihypertensive Peptides in Dairy Products

Introduction

Milk and dairy products are rich in protein content, and main proteins in milk casein and whey proteins are the principle bioactive peptide precursors [1]. Although there are numerous studies on bioactive peptides, the first discoveries of bioactive peptides from foods are dairy products. These bioactive peptides have different functions such as antihypertensive, opioid, immune-modulatory, antimicrobial, and antioxidant [2, 3, 4, 5]. Hypertension is a condition in which the blood vessels have persistently raised pressure [6]. It affects approximately 30% of the adult population worldwide [7]. It is a prominent risk factor for cardiovascular diseases such as coronary heart disease, peripheral artery disease, and stroke. Even though it is a controllable disease high prevalence, and serious consequences make hypertension an important comprehensive health threat [7]. ACE (peptidyldipeptide hydrolase, EC 3.4.15.1) is an exopeptidase which splits various peptides from C-terminal and forms dipeptides. ACE performs a critical role in regulating the blood pressure by the renin-angiotensin and bradykinin pathways. Angiotensin I is a decapeptide and inactive in its intact form. ACE catalyzes hydrolyzation of angiotensin I to the potent vasoconstrictor octapeptide angiotensin II[8]. Bradykinin, a vasodilator, is involved in the blood pressure system. ACE also controls the blood pressure by degrading bradykinin. Thus, inhibition of ACE results in an antihypertensive effect. Consequently, synthetic ACE inhibitors such as captopril and enalapril, are used in the treatment of hypertension and other related heart diseases [9]. However, they can cause adverse effects such as hypotension, cough, altered taste, rash and angioedema [10]. Bioactive peptides are natural and healthier alternatives to synthetic ACE inhibitors without side effects [11]. Although there are many different protein sources of ACE inhibitor peptides, milk proteins are accepted as the primary sources [12]. Chemical structures of peptides are important for binding to the catalytic sites of ACE [13, 14]. The presence of aromatic or branched hydrophobic structures in the tripeptide structure at the carbon end of the peptide is necessary for binding [13, 15]. Several functional dairy products are present in the market comprising antihypertensive peptides. Calpis sour milk in Japan (Calpis Co Ltd, Tokyo, Japan) cultured via Saccharomyces cerevisiae and Lactobacillus helveticus poses two potent ACE inhibitory peptides, Val-Pro-Pro and Ile-Pro-Pro [15]. These two peptides are also present in calcium-enriched fermented milk drink in Finland [16]. In short- and long-term human studies have shown that IPP and VPP peptides decrease blood pressure [4]. BioZate contains β-lactoglobulin fragments as functional bioactive peptides [16]. This paper will review studies on antihypertensive especially, ACE inhibitor peptides and their production in dairy products.

Factors Affecting Occurrence of Bioactive Peptides in Dairy Products

The bioactive peptide profile of a dairy product is tightly dependent on processes used such as thermal processes, homogenization, pressure applications, coagulation of milk, fermentation, and ripening [17]. Thermal processes are essential in the production of almost all dairy products. Reactions that occurred during thermal processes can affect the structure of proteins and the bioactive peptide content of the product [17, 18]. Thermal processes affect activities of natural enzymes found in milk, thus affect the peptide profile of the last product. Caseins are hydrolyzed through the action of enzymes from different sources such as casein residue coagulants, natural milk enzymes, starter culture enzymes, enzymes of seconder cultures and non-starter lactic acid bacteria [5].

ACE Inhibitor Peptides Naturally Found in Milk and Dairy Products

In general, dairy products, in particular, fermented dairy products, are the most popular foods for the intake of bioactive peptides with their sensory properties and high levels of consumption favored by consumers [1]. Some of these studies summarized in (Table 1). Among the dairy products, ripened cheeses contain numerous peptides, affecting the properties of the final product such as taste, odor, and texture due to the variety and complexity of the production methods. ACE inhibitor peptides in Spanish cheeses (Cabrales, Idiazábal, Roncal, Manchego, Mahón and goat’s milk) are identified [14]. In this study, researchers confirmed ACE inhibition effect of 8 synthetic peptides (VRGP, PFP, QP, DKIHP, PKHP, FP, PP, and DKIHPF). Since proteolysis and peptide formation continue during cheese ripening, the ACE inhibitor effect may alter during the cheese maturation period. Further proteolysis during ripening may cause hydrolyzation of bioactive peptides and inactivation of them. Gomez-Ruiz et al. [19] determined the ACE-inhibitor peptides in Manchego cheese. The antihypertensive activity reached the maximum level after eight months of maturation and decreased again after twelve months of maturation. Likewise, Gouda ripened for 8 months decreased more strongly the blood pressure of spontaneously hypertensive rats than 24-month-old Gouda, although they have a similar ACE inhibitor activity in vitro [3]. In view of composition rich in proteins, cheese whey can be considered as a valuable source of bioactive proteins [20]. Alongside studies on bioactivities of cheese varieties some researchers identified ACE inhibitor peptides (FVAPFPE, NLHLPLPLLQ, FVAPFPEVFG, NLHLPLPLQ originated from αs1-casein, β-casein, αs1-casein, β-casein, respectively) in a liquid waste deriving from Ricotta cheese production [21]. Probiotic fermented milk beverage from milk of different species also have antihypertensive activity [22, 23]. Caseins are the best precursors for the production of angiotensin I am converting enzyme (ACE) [de Gobba et al. 2014].

Table 1: Antihypertensive peptides found in dairy products.

Production of ACE Inhibitor Peptides from Milk Proteins

Basically, there are two approaches to generate ACE-inhibitor peptides from milk proteins. One approach is to utilize the proteolytic enzymes of lactic acid bacteria in fermented dairy products. The other approach is to hydrolyze milk proteins in vitro by one protease or a combination of various proteases or peptidases.

Production of ACE Inhibitor Peptides with Enzymes

Most of the researches about the production of bioactive peptides with enzymes have utilized digestive enzymes, and commercial dry cheese whey, purified whey proteins or microfiltration permeates as a substrate [27]. Besides, other digestive enzymes from different sources and various milk protein preparations have been studied to generate antihypertensive peptides (Table 2). Different bioactive peptides are produced from caseins of milk from different species, which implicates the sequence and conformation of the caseins affect the bioactive peptide yield [28]. Minervini et al. [29] used a proteinase from Lactobacillus helveticus PR4 to obtain ACE inhibitor and antimicrobial peptides from casein of milk from six different species (bovine, sheep, goat, pig, buffalo, and human). Abdel-Hamid et al. [29] identified new peptide sequences (FPGPIPK, IPPK, QPPQ) showing ACE inhibitor activity generated from buffalos’ skim milk hydrolyzed with papain.

Table 2: Using proteases to generate ACE inhibitor peptides from milk proteins.

ACE inhibitor and antioxidant capacity of 6 synthetic peptides (WY, WYS, WYSL, WYSLA, WYSLAM, WYSLAMA) deriving from β-lactoglobulin were evaluated [30]. Dipeptide WY β-lactoglobulin fragment f (19-20) showed potent ACE inhibitor activity. ACE inhibitor activity depends on the amino acid sequence in the C-terminus of the peptide, and the amino acid Ser at the C –terminus showed a potential decreasing effect on ACE inhibitor activity. Sheep cheese whey hydrolyzed using proteinase from Bacillus sp. P7 to generate ACE inhibitor peptides [20]. ACE inhibitor activity was dependent on hydrolysis time. In a recent work, trypsin from bovine pancreas employed to hydrolyze whey from the production of panela cheese to generate bioactive peptides [27]. The researchers found a significant correlation between antioxidant and ACE inhibitor activity.

Production of ACE Inhibitor Peptides through Fermentation

In the dairy industry mainly highly proteolytic starter cultures are preferred. Bioactive peptides can be generated by the starter culture or non-starter bacteria added as an adjunct culture (Table 3).

Table 3: Obtaining ACE inhibitor peptides by using adjunct culture and fermentation.

Ahtesh et al. [1] produced a new fermented functional dairy product with combination of L. helveticus and Flavourzyme® using a bioreactor. They have achieved to obtain an acceptable product with high ACE inhibitor activity. L. helveticus is a highly proteolytic bacterium, thus, there are many studies on both fermentation with this bacterium and hydrolysis with proteinases of this bacterium [22, 28].

Similarly, researchers utilized L. helveticus LH-B02 strain in order to improve the ACE inhibitor activity in Prato cheese [5]. They observed that levels of ACE inhibitor peptides β-casein (f193-206) and β-casein (f194-209) increased while relative intensity of αS1- casein (f1-9) reduced. Gonzalez Gonzalez et al. [25] isolated highly proteolytic lactic acid bacteria from Chiapas cheese and evaluated tendency of releasing bioactive peptides of selected strains. They employed four selected strains for fermentation of milk and observed that most proteolytic strain has lowest ACE inhibitor activity, presumably according to further breakdown peptides to inactive amino acids. Solieri et al. [31], fermented bovine milk with non-starter lactic acid bacteria (Lactobacillus casei, Lactobacillus paracasei and Lactobacillus rhamnosus strains) to evaluate their potential to produce fermented milk with enhanced ACE inhibitor activity [32, 34, 35]. They concluded that the strains used in the study especially L.casei PRA205 can produce high amounts of VPP and IPP peptides.

Conclusion

In recent years, the tendency to consume functional health-promoting foods has increased the interest in bioactive peptides. There are numerous studies on bioactive peptides in foods in the literature. Dairy products, which are an indispensable part of a healthy and balanced diet, are considered as ideal sources for bioactive peptides and natural alternatives to therapeutic drugs due to their high protein content and technological processes in production. However, the mechanism of action of bioactive peptides is not fully described. Molecular studies employing new technologic enhancements and peptidomics approach are necessary to understand the mechanisms of antihypertensive peptides as well as to design functional products.

Read More About this Article: https://biomedgrid.com/fulltext/volume7/antihypertensive-peptides-in-dairy-products.001139.php

For more about: Journals on Biomedical Science :Biomed Grid | Current Issue

[dontmeantobepoliticalbut]

Florida Gov. Ron DeSantis (R) has signed the “Protections of Medical Conscience Act,” a law that allows healthcare providers or payors to deny service on the basis of “a conscience-based objection,” including any ethical, moral, or religious beliefs. The bill provides no definition for what constitutes a “moral” or “ethical” belief.

The law seeks to protect health care providers and payers from the “threat of discrimination for providing conscience-based health care.” However, advocates worry it’ll be used to deny LGBTQ+ people gender-affirming care, HIV-prevention medication, and other essential and life-saving care.

The law allows any medical provider — including doctors, nurses, ambulance drivers, pharmacists, mental health professionals, lab technicians, nursing home workers, and hospital administrators — as well as insurance companies and payment entities, the right to deny care on the basis of any conscientious objection. This care can include refusing to conduct research and recordkeeping or denying medical tests, diagnoses, referrals, medications, and therapy, the American Civil Liberties Union (ACLU) notes.

The newly signed law says denial of care can’t be based on a patient’s race, color, religion, sex, or national origin, but it provides no protections on the basis of sexual orientation or gender identity. Additionally, the law also allows healthcare employers to discriminate in hiring and bars medical boards from disciplining doctors for spreading misinformation, essentially forcing employers to keep workers who refuse to do their jobs, the Human Rights Campaign (HRC) noted.

In a statement, the HRC said the newly signed law “creates a license to discriminate by allowing healthcare employers to discriminate in hiring, and it bars medical boards from disciplining doctors for spreading misinformation.”

Kara Gross, legislative director and senior policy counsel of the ACLU of Florida, wrote, “This bill is shocking in its breadth, vagueness, and government overreach into the private sector and regulated businesses. It goes far beyond any alleged claims of religious freedom.”

Gross notes that anyone in the medical field — including at public and private schools, colleges, and universities — could choose to deny service to someone they personally dislike. Medical workers could refuse to assist in an active medical emergency, such as helping an unwed mother to give birth. Medical office clerks could refuse to return patient calls, and pharmacists could refuse to dispense contraceptives or medications to heal sexually transmitted infections, citing their “ethical” or “moral” beliefs.

Brandon Wolf, press secretary for the LGBTQ+ organization Equality Florida, told the Pensacola News Journal, “This puts patients in harm’s way, is antithetical to the job of health care providers, and puts the most vulnerable Floridians in danger.”

“Our state should be in the business of increasing access to medical care, not giving providers and companies a sweeping carve out of nondiscrimination laws,” Wolf added. “Shame on the Governor for putting Floridians’ health at risk to score cheap, political points.”

DeSantis was joined at the signing ceremony for the new law by State Surgeon General and Department of Health Secretary Joseph Ladapo. He has spoken out against science-based federal guidelines that support gender-affirming care for transgender teens, citing debunked studies about transgender people.

In July 2020, Ladapo appeared in a viral video as part of a group called America’s Frontline Doctors. The video was organized by the Tea Party Patriots, a right-wing group backed by wealthy Republican donors.

The group in the video, which had no epidemiologists or immunologists, promoted the anti-malaria medication hydroxychloroquine as a “cure” for COVID-19, said that face masks don’t slow the virus’s spread, and that COVID-19 is less deadly than the flu — all three claims are untrue. Lapado has written numerous op-eds repeating the video’s false claims.

The video also featured Dr. Stella Immanuel, a pediatrician and religious minister who has said that “demonic seed” inserted into sleeping individuals causes endometriosis and ovarian cysts.

[jeraliey]

"As the health world has recognized with the development of the concept of planetary health, the natural world is made up of one overall interdependent system. Damage to one subsystem can create feedback that damages another—for example, drought, wildfires, floods, and the other effects of rising global temperatures destroy plant life and lead to soil erosion and so inhibit carbon storage, which means more global warming.2 Climate change is set to overtake deforestation and other land-use change as the primary driver of nature loss.3"

"Human health is damaged directly by both the climate crisis, as the journals have described in previous editorials,8,9 and by the nature crisis.10 This indivisible planetary crisis will have major effects on health as a result of the disruption of social and economic systems—shortages of land, shelter, food, and water, exacerbating poverty, which in turn will lead to mass migration and conflict. Rising temperatures, extreme weather events, air pollution, and the spread of infectious diseases are some of the major health threats exacerbated by climate change.11"

[6ebe]

no one in my family reps my humanities degree 😞

[fauvester]

these are my star trek doctor ocs emtala jcaho (pronounced jay-ko) and ama n'jem

[pastdaily]

The Healthcare Debate Of 1956 - Past Daily After Hours Reference Room

A few good subscribers: Become a Patron! https://pastdaily.com/wp-content/uploads/2012/08/healthcare-debate-1956.mp3 At the risk of sounding like a broken record and belaboring a point over and over, the argument over Universal Healthcare, Affordable Healthcare, proposed legislation for some subsidized Healthcare are all old issues. Issues that have been at forefront of the American…

[cannabisbusinessexecutive]

Online Marijuana Shops Make It Easy for Minors to Buy, Study Finds

Many online marijuana dispensaries do not enforce age limits on purchases, and they have other lax policies that enable minors to buy cannabis on the internet, according to a new study published on Monday in The Journal of the American Medical Association Pediatrics. The Numbers The research examined the age-verification policies and other practices of 80 online dispensaries, based in 32 states,…

[fiercynn]

poetry outlets that support a free palestine

after finding out that the poetry foundation/POETRY magazine pulled a piece that discussed anti-zionism because they "don't want to pick a side" during the current genocide, i decided to put together a list of online outlets who are explicitly in solidarity with palestine where you can read (english-language) poetry, including, except where otherwise stated, by palestinian poets!

my criteria for this is not simply that they have published palestinian poets or pro-palestine statements in the past; i only chose outlets that, since october 7, 2023, have done one of the following:

published a solidarity statement against israeli occupation & genocide

signed onto the open letter for writers against the war on gaza and/or the open letter boycotting the poetry foundation

published content that is explicitly pro-palestine or anti-zionist, including poetry that explicitly deals with israeli occupation & genocide

shared posts that are pro-palestine on their social media accounts

fyi this is undoubtedly a very small sample. also some of these sites primarily feature nonfiction or short stories, but they do all publish poetry.

outlets that focus entirely on palestinian or SWANA (southwest asia and north africa) literature

we are not numbers, a palestinian youth-led project to write about palestinian lives

arab lit, a magazine for arabic literature in translation that is run by a crowd-funded collective

sumuo, an arab magazine, platform, and community (they appear to have a forthcoming palestine special print issue edited by leena aboutaleb and zaina alsous)

mizna, a platform for contemporary SWANA (southwest asian & north africa) lit, film, and art

the markaz review, a literary arts publication and cultural institution that curates content and programs on the greater middle east and communities in diaspora

online magazines who have published special issues of all palestinian writers (and all of them publish palestinian poets in their regular issues too)

fiyah literary magazine in december 2021, edited by nadia shammas and summer farah (if you have $6 usd to spare, proceeds from the e-book go to medical aid for palestinians)

strange horizons in march 2021, edited by rasha abdulhadi

the baffler in june 2021, curated by poet/translators fady joudah & lena khalaf tuffaha

the markaz review has two palestine-specific issues, on gaza and on palestinians in israel, currently free to download

literary hub featured palestinian poets in 2018 for the anniversary of the 1948 nakba

adi magazine, who have shifted their current (october 2023) issue to be all palestinian writers

outlets that generally seem to be pro-palestine/publish pro-palestine pieces and palestinian poetry

protean magazine (here's their solidarity statement)

poetry online (offering no-fee submissions to palestinian writers)

sundog lit (offering no-fee submissions to palestinian writers through december 1, 2023)

guernica magazine (here's a twitter thread of palestinian poetry they've published) guernica ended up publishing a zionist piece so fuck them too

split this rock (here's their solidarity statement)

the margins by the asian-american writers' workshop

the offing magazine

rusted radishes

voicemail poems

jewish currents

the drift magazine

asymptote

the poetry project

ctrl + v journal

the funambulist magazine

n+1 magazine (signed onto the open letter and they have many pro-palestine articles, but i'm not sure if they have published palestinian poets specifically)

hammer & hope (signed onto the letter but they are a new magazine only on their second issue and don't appear to have published any palestinian poets yet)

if you know others, please add them on!

[biomedres]

Intraoperative Cone Beam CT in Hybrid Operating Room Set-Up as An Alternative to Postoperative CT for Pedicle Screw Breach Detection

Intraoperative Cone Beam CT in Hybrid Operating Room Set-Up as An Alternative to Postoperative CT for Pedicle Screw Breach Detection in Biomedical Journal of Scientific & Technical Research

https://biomedres.us/fulltexts/BJSTR.MS.ID.006022.php

Background: CT is considered the gold standard for detecting pedicle breach. However, CBCT may be a viable and low radiation dose alternative, to provide intraoperative feedback to surgeons to permit in-room revisions of misplaced screws. Methods: To assess the ability and reliability of intraoperative cone-beam CT (CBCT) from a robotic C-arm in a hybrid operating room (OR) two hundred forty-one pedicle screws were inserted in cervical, thoracic and lumbar spine of 7 cadavers, followed by CBCT and CT imaging. The CT images served as the standard of reference. Agreement on screw placement between both imaging systems was assessed using Cohen’s Kappa coefficient (κ). Sensitivity, specificity, receiver operating characteristic (ROC), area under the empirical and fitted ROC curves (AUC) were computed to assess CBCT as a diagnostic tool compared to CT. The patient effective radiation dose (ED) was calculated for comparison. A systematic literature review was performed to provide perspective to the obtained results. Results: Almost perfect agreement in assessing pedicle screw grading between CBCT and CT was observed (κ=0.84). The sensitivity and specificity of CBCT were 0.84 and 0.98, respectively. The AUC derived from the empirical and fitted ROC curves were 0.95 and 0.96, respectively. Conclusion: Intraoperative CBCT by C-arm in a hybrid OR is highly reliable in identification of screw placement at significant dose reduction.

For more articles in Journals on Biomedical Sciences click here bjstr

Follow on Twitter : https://twitter.com/Biomedres01 Follow on Blogger :https://biomedres01.blogspot.com/ Like Our Pins On : https://www.pinterest.com/biomedres/

[allthecanadianpolitics]

A study conducted by the B.C. Centre for Disease Control has found that prescribing medical-grade opioids dramatically reduced the rates of deaths and overdoses for drug users living in B.C. The study, published in the British Medical Journal, is described as "the first known instance of a North American province or state providing clinical guidance to physicians and nurse practitioners for prescribing pharmaceutical alternatives to patients at risk of death from the toxic drug supply." Researchers looked at anonymized health-care data of 5,882 people between March 2020 and August 2021, all of whom had opioid or stimulant use disorder. Those individuals filled a prescription under the B.C. Risk Mitigation Guide — clinical guidance developed in March 2020 to allow for physical distancing during the COVID-19 pandemic, and to reduce deaths through harm reduction.

Continue Reading

Tagging @politicsofcanada

[biomedgrid]

Biomed Grid | Relation of a Pulse Transit Time to the Blood Pressure in Bifurcated Cardiovascular Networks

Introduction

Pulse Arrival Time (PAT) is the generally established empirical marker for continuous non-intrusive blood pressure monitoring, which is defined as a time required for a pulse wave to travel from the heart to a peripheral site. A popular estimate of PAT is the timebased delay between R wave peak of Electrocardiogram (ECG) and a characteristic point of a Photoplethysmogram (PPG). PAT consists of two components: the non-constant Pre-Ejection Period (PEP), which is a duration of the ventricle contraction up to aortic valve opening, and the Pulse Transit Time (PTT), which defines the period for the arterial pulse wave to travel from the aortic valve to the peripheral site.

A simple measurement setup consisting of arm Electrocardiogram (ECG) and Peripheral Site Photoplethysmogram (PPG) allows to assess PAT as the time delay between ECG R peak and one of the optional points in the PPG waveform: peak, foot, maximum values of the slope, or the second derivative of PPG waveform. PEP can be derived noninvasively using for instance thoracic Impedance Plethysmogram (IPG) as described in [1, 2, 3]. Estimation of a systolic and diastolic BP is based on equivalence of the measured and model- based prediction of PTT. In general, prediction methods can be categorized into data-driven, physics-based and hybrid approaches. Data-driven approaches investigate relationship between BP and PTT through the linear or nonlinear regression analysis, employing a simple set of basic functions, or using artificial intelligence (neural network). Physics-based approaches assume that a reliable physical model describing connection of a PTT to BP is available. Hybrid approaches combines the methods to calibrate the personalized bio-physical properties, improving prediction.

As follows from the physical modelling, PTT and PWV are mainly affected by four factors: arterial compliance, cardiac output, peripheral resistance, and a blood pressure. Most data driven approaches select the only single parameter as an independent variable, which is a PTT or the averaged PWV, to predict systolic and diastolic blood pressures. The physics-based approach automatically accounts for the full set of factors affected BP according to the physical model, i.e. cardiac output, stroke volume, vascular compliance, peripheral resistance. The following sections describe PTT based blood pressure estimation according to the classification. Since many of the papers using data driven regression analysis are listed in several reviews, we will not cite relating individual papers, focusing mainly on a physical modeling as a foundation for linking PTT to systolic and diastolic BP.

Data-Driven BP Estimation

Multiple linear and nonlinear regressions have been explored by different authors using combinations of exponential, power, logarithm, polynomial and logistics functions to fit the experimental dataset of PTT (or PWV) vs BP [3, 4, 5]. In [6] the heart rate as a second independent variable in addition to PTT is introduced in a linear regression, which according to the authors improves the accuracy of BP prediction. In the monograph [7] the Young’s modulus is presented as an exponential function of pressure, where E0- is the Yong modulus at zero pressure, and α -empirical coefficient. As a result, the formal substitute of the modified elastic modulus E into the Moens-Korteweg expression for the PWV results in a pulse wave velocity dependent on a blood pressure, is the Moens-Korteweg speed of propagation at zero pressure, α-is a calibrating constant.

The mentioned approach is completely empirical, since it does not fit the paradigm of classical mechanics, which specifies physical nonlinearity by appropriate constitutive equations in terms of stress – strain components. The described expression cannot be derived from the fluid-structure interaction model using any constitutive equations. It could be converted to the linear regression (in a log scale) by application of logarithm to the expression for PWV, which results in

where is the distance of a pulse propagation, a, b-are determined from the best fit procedure. Equation (2) remains nowadays a one of the most widely used technique for noninvasive continuous BP monitoring. The modified logarithm-based regression was successfully applied in [8] to monitor BP as a function of PTT under the effect of hydrostatic pressure due to hand elevations. The effect of including PEP in BP estimation is under investigation in different papers based on empirical regression analysis over different cohorts of human subjects [4, 9, 10]. The simplest approach is an attempt to estimate PEP as a percentage of the RR interval, with the following subtraction from PAT to obtain PTT [11]. There is still a controversial evidence from different authors regarding effect of PEP on BP. The impact of PEP on the overall PAT decreases with distance from the heart, so that for the short PATs, like ones extracted from the ear-worn device, correction with PEP is required.

Neural Network (NN) modeling has recently been in place predicting BP as a function of a set of measured parameters. In [12] a total of 17 parameters were selected as the set of independent variables being chosen as characteristic feature points from ESG and PPG signals. Two different neural networks have been used to predict separately brachial systolic and diastolic blood pressures as functions of ECG and PPG measurements. The maximum error range in the brachial BP prediction is reported in terms of a root mean square error RMSE=±5.2mmHg. In [13] the SVR (Support Vector Machine Regression) algorithm is applied to establish relationship between human physiological data and systolic and diastolic BPs. The different number of main physiological indexes, obtained from ECG and PPG, include PTT, HR, SPO2 and others, are explored in application of NN modeling. The maximum error range of a brachial BP prediction is reported as ±10mmHg.

Few studies managed to compare different noninvasive BP estimations in a wide physiological BP range. None of data driven approaches proved to be ubiquitous, being able to monitor with a reasonable accuracy the only single feature of a BP, either systolic, or diastolic or a mean [3, 4, 5].

Physical Modeling BP Estimation

In this section, we assess physics-based models’ capabilities to predict systolic and diastolic BP as a function of model required independent parameters. Considering an arbitrary pressure-area connection, P = P(A) ,we present system of conservation laws in the following non-conservative quasi-linear form

where fluid density. This system could be transformed to the decoupled system of equations for the characteristic variables (Riemann variables), which read

Relating characteristic directions (eigenvalues) read

and forward and backward running characteristics can be found accordingly

Since the slope of a forward running characteristic line is determined by PWV =

Equation (7) serves to calculate the PTT required for the pulse wave to propagate through the Nv vessels, each of the length along the flow pathway from the left ventricle to the peripheral site.

Nonlinear Vs Linear Models

In this section three type of nonlinear models are reviewed following the papers [14, 15]: the infinitesimally Small Deformation Linear Elasticity Model (SDL), Small Deformation Hyperplastic Model (SDH) and Finite Deformation hyper elastic Model (FDH). The Fung’s exponential descriptor for passive behavior of arteries [16] presents strain energy density function for the pseudo elastic wall deformation in a form

Here are material constants, are the circumferential and axial strain components. In a 1D problem strain energy of the wall can be simplified by setting Equilibrium condition results in a generalized tube law for the hyperelastic wall the Moens-Korteweg speed at

Equations (10) and (6) present the instantaneous PWV for the SDH model in a compliant hyperelastic artery as the following

Model SDL is achieved by setting hyperelastic material coefficient to zero so that the expressions for PWV in model 2 follows from (10) at

Model FDH, which considers finite deformation, is derived based on the same expression for strain energy (8), where and is interpreted as the Green-Lagrange strain components in circumferential and axial directions accordingly. Relating Cauchy stress components.

are governed by equilibrium conditions

Here: are the stretch ratios in circumferential, radial and axial directions accordingly; r, h-are the luminal radius and thickness in a deformed state,

All three models have been tested against Histand and Anliker results on a PWV measurements presented in [17, 18] and reproduced in (Figure 1) by square markers. The experimental curve notably exhibits curvature starting from elevated level of pressure exceeding 140mmHg. Material parameters have been identified for each model independently, based on a best fit procedure. The Finite Deformation Hyper Elasticity (FDH) model and Small Deformation Hyper Elasticity (SDH) model have the highest quality of fitting process, creating practically the same regression line in (Figure 1) within the physiological range of BP. The Small Deformation Model with Linear Elasticity (SDL) was not able to fit the experimental curve at the quality of FDH or SDH models.

Figure 1: The nonlinear model FDH produced the best fit of the PWV vs. transmural pressure function.

Figure 2: Simulation results show that within a physiological longitudinal pre-stress load effects PWV by ~ 3%. Tz denotes the axial physiological Lagrangian stress.

Dash lines indicate theoretical prediction. Square markers illustrate the total set of experimental points. Using the properties extracted from the nonlinear model the lower (solid) line shows the effect on PWV using the partially nonlinear model SDH, combining hyper elasticity with small deformation. To illustrate the effect of a longitudinal force on PWV the variation of PWV due to the variability of a longitudinal pre-stress force is presented in (Figure 2). According to simulation within the realistic physiological range of a longitudinal stress, the relative deviation in PWV does not exceed 3%.

Several PWV estimations presented in literature is based on its correlation with the BP and an arterial wall compliance. The study in [19]examined the impact of a systolic flow correction of a measured PWV on blood pressure prediction accuracy using data from two published in vivo studies. Both studies examined the relationship between PWV and blood pressure under pharmacological manipulation, one in mongrel dogs and the other in healthy adult males. Systolic flow correction of the measured PWV improves the R2 correlation to blood pressure from 0.51 to 0.75 for the mongrel dog study, and 0.05 to 0.70 for the human subjects’ study. The results support the hypothesis that systolic flow correction is an essential element of non-invasive, cuff-less blood pressure estimation based on PWV measures.

Thick Wall Vessels

A novel mathematical model predicting PWV propagation with rigorous account of, blood vessel elasticity, and finite deformation of multi-layer thick wall arterial segments was studied in [20]. It was found that the account for the multilayer model affects distribution of local parameters in the proximity of the external layer (adventitia) and does not affect stiffness related to the internal layer. The latter means that the single thick layer model is enough to predict PWV of an arterial segment. (Figure 3) depicts the dependence of PWV on pressure for the Systole Phase (marked as “SBP”) and a Diastole Phase (marked as “DBP”) for three vessels of different thicknesses of a human aorta. All results have been compared with the simplified thin walled model of a membrane shell interacting with an incompressible fluid.

Figure 3: Simulation results show that within a physiological longitudinal pre-stress load effects PWV by ~ 3%. Tz denotes the axial physiological Lagrangian stress.

To explore inaccuracies induced by use of the less complex thin wall model, error in both PWV and blood pressure were calculated for a blood pressure of SBP/DBP = 150/95mmHg representing the median of stage 1 hypertension. The single layer thick wall model improves PWV accuracy by (4.0-8.4%) corresponding to the relative wall thickness (H/R1) range of 0.07-0.38. One of the goals for the model is PWV based blood pressure prediction, where the thick wall model offers an improvement of (3.3-19.4%).

Calibration Free Approaches

Willemet et al. [21, 22] proposed approach to use cardiovascular simulator for generation of a database of “virtual subjects” with sizes limited only by computational resources. In their study, the databases were generated using one-dimensional model of wave propagation in an artery network comprising of 55 largest human arteries. A linear elastic model was employed to describe deformation of arterial walls. The database is created by running the cardiovascular model repeatedly. The seven model parameters were varied: elastic artery PWV, muscular artery PWV, the diameter of elastic arteries, the diameter of muscular arteries, Heart Rate (HR), SV and peripheral vascular resistance. 3325 healthy virtual subjects presented a diversity of hemodynamic, structural and geometric characteristics. For each virtual subject, all characteristics are known at every point of the systemic arterial tree, i.e. anatomical and structural properties, as well as pressure, flow, pulse wave velocity and area waves at the larger arteries, therefore allowing the computation of the exact value of the diagnostic tool.

Huttunen et al. [23] used cardiovascular modelling of the entire adult circulation to create a database of “virtual subjects”, which is applied with machine learning to construct predictors for health indices. They carry out theoretical assessment of estimating aortic pulse wave velocity, diastolic and systolic blood pressure and stroke volume using pulse transit/arrival timings derived from photoplethysmography signals. The generated database was then used as training data for Gaussian process regressors applied finally to simulation. Simulated results provide theoretical assessment of accuracy for predictions of the health indices. For instance, aortic pulse wave velocity was estimated with a high accuracy (r>0.9. Similar accuracy has been reached for diastolic blood pressure, but predictions of systolic blood pressure proved to be less accurate (r > 0.75).

Conclusion

Developed technologies in general allow to implement a PTT/ PAT-based system to predict continuously cardiovascular health markers such as arterial blood pressure, cardiac output, arterial stiffness. However, none of approaches is able so far to monitor accurately all cardiac markers for the wide range of physiological conditions. The limitations to be addressed in future are the following. First, each model must be investigated for its limitations. We believe that a calibration stage is required to build a reliable simulator within the range of investigated conditions. Also, most of the research addresses healthy population, which is characterized by different behavior of a vascular system rather than group with medical conditions. In the current review we only consider pulse transit and arrival type of time information as the input to the predictor. It would be beneficial to develop approaches that do not need reference measurement for the aortic valve opening/R-peak.

Read More About this Article: https://biomedgrid.com/fulltext/volume7/relation-of-a-pulse-transit-time-to-the-blood-pressure-in-bifurcated-cardiovascular-networks.001135.php

For more about: Journals on Biomedical Science :Biomed Grid | Current Issue

[theladyvanya]

X

[benjaminzmillerinvestorquestions]

Will www.feedban.com read the Journal of the American Medical Association (JAMA)?

Will www.feedban.com read the Journal of the American Medical Association (JAMA)?

The Journal of the American Medical Association is a peer-reviewed medical journal published by the American Medical Association.    Yes, you can read The Journal of the American Medical Association with  www.feedban.com  The Journal of the American Medical Association  has an RSS feed.  Feedban.com is an RSS aggregator and can pull in this news source to read. With regards to the absolute…

[lifewithchronicpain]

Physicians are using excuses to intentionally dissuade people with disabilities from their practices, researchers say in a new study exposing just how pervasive discrimination against this population is in health care.

In focus groups, doctors described making strategic choices to turn away individuals with disabilities. They reported telling patients with disabilities that they would require specialized care and that “I am not the doctor for you.” In other cases, physicians said they simply indicate that “I am not taking new patients” or “I do not take your insurance.”

The findings come from a study published this month in the journal Health Affairs. It is based on focus groups conducted in late 2018 by researchers at the Northwestern University Feinberg School of Medicine, the University of Massachusetts and Harvard Medical School with 22 primary care and specialist doctors who were selected from a national database.

Many of the participants described accommodating people with disabilities as burdensome and some used outdated language like “mentally retarded.” Doctors frequently indicated that individuals with disabilities account for a small number of patients, making it hard to justify having accessible equipment. They also had little knowledge of their obligations under the Americans with Disabilities Act, with one suggesting that the law works “against physicians.”

The latest study builds on findings published earlier this year from a survey of 714 doctors that was done by some of the same researchers. Just 56% of physicians who participated in the survey said they welcome people with disabilities at their practices and only 41% indicated that they could provide such patients with a similar quality of care to others. Meanwhile, more than a third of doctors queried said they had little or no knowledge of their legal obligations under the ADA.

“Taken together, the focus groups and survey responses provide a substantive and deeply concerning picture of physicians’ attitudes and behaviors relating to care for people with disabilities,” the study authors note.

The findings suggest that bias continues to greatly influence health care more than 30 years after passage of the ADA, which prohibits discrimination against people with disabilities, including in medical services.

Tara Lagu, a professor of hospital medicine and medical social sciences at Northwestern University and an author of the study, described the doctors’ attitudes toward the ADA in particular as “upsetting and disappointing.”

“Our body of work suggests that physician bias and discriminatory attitudes may contribute to the health disparities that people with disabilities experience,” Lagu said. “We need to address the attitudes and behavior that perpetuate the unequal access experienced by our most vulnerable patients.”