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β
Published in James F. Pankow, Aquatic Chemistry Concepts, 2019
If any amount of strong base is added to any aqueous solution, the pH will go up. Conversely, if any amount of strong acid is added, the pH will go down. Chemists are often interested in knowing how pH-sensitive a system is to incremental addition of strong base or acid; the parameter that quantifies this concept is the buffer intensity β. In the environment, many aquatic organisms depend on the pH of the water to be in some particular range, and deviations from that range cause stress, or in extreme cases, mass die-offs. In the human body, a great many important biochemical reactions are very pH sensitive, so buffering is again extremely important. For humans, nothing makes this point more clearly than noting that human blood needs to be in a very narrow pH range so that pHdependent reactions can proceed at needed rates. For arterial blood, the normal range is 7.35 to 7.45; for venous blood, 7.32 to 7.42. Having recently passed through the lungs, arterial blood is slightly more alkaline because of loss of some metabolically generated CO2 to exhaled air. “Acidosis” is the condition when blood pH is too low, and “alkalosis” is the condition when blood pH is too high. (Acidosis in humans often leads to tachypnea/hyperventilation as a means to off-gas CO2 and raise blood pH.) Most natural water organisms benefit when their aquatic environment is characterized by an adequately large β so as to prevent significant swings in pH due to acid/base additions or losses.
Chapter 17 Respiratory Function
Published in B H Brown, R H Smallwood, D C Barber, P V Lawford, D R Hose, Medical Physics and Biomedical Engineering, 2017
Arterial blood appears red and venous blood more blue because haemoglobin and oxyhaemoglobin have different optical absorption spectra. The attenuation of electromagnetic radiation by a sample can be described by the Beer-Lambert law in the form
Effect of rheological models on pulsatile hemodynamics in a multiply afflicted descending human aortic network
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Sumit Kumar, B.V. Rathish Kumar, S.K. Rai, Om Shankar
Previously, most of the researchers have studied ascending abdominal arteries. The authors suggest the downward abdominal arterial network in this article, compounded by multiple diseased conditions like AAA and RIIAS and outlets, including bifurcations with realistically tapering lumens and investigate the flow dynamics corresponding to five rheological models. This study is further extension of our previous work (Kumar et al. 2022) in which geometry is generated by considering the D/La of AAA and D/Ls of RIIAS an vital role in deciding the diseased region and its failure predictions. In this work, while the AAA is at moderate level (i.e. at 47% of fusiform blowup) the RIIAS is at the severity of 91% constriction. However, altering the amount of dilatation and shrinkage in the same artery may influence the mechanical properties of the wall. RIIAS can cause a decrease in arterial blood in the iliac artery. This decreased blood supply to the human body’s lower extremities might induce tingling of the organs in that region.
Hearables, in-ear sensing devices for bio-signal acquisition: a narrative review
Published in Expert Review of Medical Devices, 2021
Colver Ken Howe Ne, Jameel Muzaffar, Aakash Amlani, Manohar Bance
SpO2 is a percentage estimate of arterial blood oxygen saturation. The gold standard measurement for this parameter is the arterial blood gas analysis, which is both invasive and painful for the subject. In most clinical settings it is measured through pulse oximetry, which utilizes PPG techniques for measurement [36]. In this case, 2 wavelengths are used simultaneously (red light 660 nm and infrared light, 880–940 nm) and the ratio of absorbance of both wavelengths enables an estimation of blood oxygen saturation due to differential absorption of infrared light by oxygenated and deoxygenated hemoglobin [37]. There are two methods to detect this – transmittance and reflectance oximetry. The transmittance method directly measures light transmitted through tissue and is typically used peripherally such as the finger. The reflectance method detects the backscatter of light using a sensor placed adjacent to the emitter [38]. The main advantage of the reflectance method is that unlike transmittance, it is not restricted to peripheral sites where tissue is thin. This is important because such peripheral body sites are affected by hypothermia and vasoconstriction that can impair accuracy of SpO2 readings [38]. In terms of hearables, this also enables recording from sites like the ear canal which as mentioned above has the advantage of greater stability.
The FlowOx device for the treatment of peripheral artery disease: current status and future prospects
Published in Expert Review of Medical Devices, 2021
In peripheral artery disease (PAD), arterial blood flow to the extremities is impeded. Clinically, the severity of PAD ranges from asymptomatic disease to intermittent claudication or atypical extremity pain during exercise, and to critical limb ischemia characterized by rest-pain, tissue loss, and gangrene. Patients with PAD have an increased risk of cardiovascular morbidity and mortality, and the treatment strategy consists of cardiovascular risk modifying treatments, and treatment of leg symptoms. Exposure of the affected leg to cyclic pressure changes increases the macro- and microcirculatory blood flow and may be used for the treatment of PAD [1,2]. The principles of this treatment have been described since he early 20th century, however, has more recently become a treatment option for selected patients, as a new treatment device has been developed [3–5].