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In my book there is a plot of the arterial pressure against time.
From the plot, during heart contraction, there is greater pressure on the artery and during heart relaxation, there is lower amount of pressure on the arteries.
This makes sense because P = F/A, the surface area of the heart is smaller when it is contracted versus when it is relaxed, hence greater pressure.
But why is there a small bump while the pressure is decreasing from systolic pressure to diastolic pressure?
This bump is related to the closure of the aortic valve as a reaction to the retrograde blood flow which in turn gives small change in blood pressure.
Blood pump designers are able to vary the following parameters: rotor diameter, number of blades, inlet and outlet angles, blade height, volute or diffuser diameter, and operating speed. These values can be derived based on the mathematical relationships explained below.
From a known rotational speed, a linear velocity tangential to the impeller (U) can be found at any given radius by Eq. (10.6) :
Thus, the theoretical power and pump head, assuming no losses, given by Euler's relation can be derived as Eq. (10.7) :
where U1 and U2 are linear velocities of the impeller inlet and outlet, respectively, and Vθ1 and Vθ2 are the tangential velocities of the fluid at the impeller inlet and outlet, respectively, as defined in Fig. 10.2 .
Fig. 10.2 . Velocity diagram for axial-flow pump, as viewed on the cross section of a blade. Vx1/Vx2 are the axial velocities, Vθ2 is the tangential component of the fluid velocity, U1/U2 are the tangential blade velocities, W1/W2 are the relative velocities, β1/β2 are the inlet and outlet relative angles, α2 is the inlet angle of the diffuser vane, and Cl is the chord length.
In a pump that has an impeller with a constant diameter along the flow path, the tangential velocity of the impeller blades also remains constant in other words, U1 = U2. This would not be the case in a mixed-flow or centrifugal-flow pump. By continuity of mass, in a pump with a constant cross-sectional area for flow, the axial velocity at the inlet (Vx1) and outlet (Vx2) of the pump is uniform as described in Eq. (10.8) :
where A is the cross-sectional area for flow.
Now that both the tangential and axial velocities are known, applying basic trigonometry rules to the velocity diagrams for the blade cascade notation in Fig. 10.2 yields Eqs. (10.9) and (10.10) , which can be used to calculate the tangential component of the fluid velocity:
where Vx1 and Vx2 are the normal components of the fluid velocity and the impeller inlet and outlet, respectively α1 is the angle between the tangential velocity component and the fluid velocity β2 is the outlet angle of the impeller, measured from the axial direction and U is the mean-line linear velocity of the rotor blades.
Thus, the pump head in Eq. (10.7) can be written as Eq. (10.11) :
When designing the impeller, the flow vector is assumed to be parallel to the axis of rotation of the impeller at the pump inlet thus, it becomes more convenient to use Eq. (10.12) for head estimation:
where Vx is the axial component of the fluid velocity, β1 is the inlet angle of the impeller, and β2 is the outlet angle of the impeller.
The arterial pulse waveform
The arterial pulse waveform can be separated into three distinct components
- The systolic phase, characterised by a rapid increase in pressure to a peak, followed by a rapid decline. This phase begins with the opening of the aortic valve and corresponds to the left ventricular ejection
- The dicrotic notch, which represents the closure of the aortic valve
- The diastolic phase, which represents the run-off of blood into the peripheral circulation.
The waveform can be separated into an anacrotic (upstroke) and dicrotic (downstroke) limbs. The origin of the term is from Greek dikrotos, which means "beating twice" (krotos meaning "stroke") anacrotic having been abbreviated from anadicrotic.
The peak correlates with the systolic blood pressure as measured by a normal non-invasive cuff. The trough (i.e. the lowest reading before the next pressure wave) is the diastolic pressure. The mean arterial pressure (MAP) is calculated from the area under the pressure curve, which is a more accurate way of doing it than the old "diastolic plus one-third times the pulse pressure" method. That method can get you into trouble. Consider the arterial pressure waveforms below. Though with identical systolic and diastolic pressures, the area under the curve for one waveform is substantially smaller, leading to a lower MAP.
The pulse pressure waveform has several components, each invested with some sort of meaning. These components are:
- Systolic upstroke
- Systolic peak pressure
- Systolic decline
- Dicrotic notch
- Diastolic runoff
- End-diastolic pressure
The significance of these features is discussed in detail below.
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What Drives CV Inflammation?
The most common driver of CV inflammation (as well as heart attack and stroke) is prediabetes (also called insulin resistance or metabolic syndrome) .
It’s associated with aging or unhealthy fat stores. It dramatically increases the growth rate of plaque within the artery walls.
In 2017, the CDC said there were over 84 million adults in the US with prediabetes . However, 90% of these people don’t know they are prediabetic (CDC, 2017).
The year before, UCLA reported that over half of all adult Californians have prediabetes (Babey, 2016). This makes the above CDC’s estimates conservative. That could be largely because CDC based its findings only on fasting glucose and hemoglobin A1c. Both tests have high false-negative rates, even when used together (Kraft, 2008).
Oxidation is another significant driver of the inflammatory process.
The oxidation process gives humans significant advantages in terms of energy. We can extract 36 units of energy from a glucose molecule. That compares to only 6 energy units derived by more primitive species such as yeast.
This human ability to transport and use oxygen does give us extra power. However, in return, this oxygen metabolism exacts a toll of increased oxidation as we age. As a matter of fact, oxidation is the essential force described in one of the most popular theories of aging—the mitochondrial theory.
In the mitochondrial theory of aging, the furnaces of the cell (the mitochondria) slowly decline because of chronic oxidation damage. This oxidation’s role in aging is what drove the decades-long focus on supplements and antioxidants.
Fourier analysis is based on the hypothesis of segmental stationary random oscillation, the principle of linear superposition of sine waves, and global average of waveform convolution over each time segment. The HHT is based on the hypothesis of nonstationary process, the principle of linear superposition of nonlinear IMFs, and local determinations of amplitude and frequency (through differentiation rather than convolution) of each IMF. In terms of the IMF, the first k modes can be added together to represent the oscillations about the mean trend Mkʱ(t). The Fourier series cannot represent time variation in the nonstationary signal, and it does not have such a property to separate a signal into two parts, one part representing a mean trend while the other part represents oscillations about the mean. The number of the intrinsic modes, n, is finite. In general, the n < log2N, where N is the total number of data points. The number of harmonics in Fourier analysis is N˲. Comparison of the Hilbert and Fourier spectra shown in Fig. Fig.4 4 E and F shows that both spectra display a major frequency at 𢒅 Hz where the energy is concentrated. This is close to the heart rate of the rat. This rate decreases when the oxygen concentration decreased. These two spectra are in different vertical scales. The Hilbert spectrum contains no energy with frequency 㸐 Hz, and it also has fewer yet more diffused frequency bands than the Fourier spectrum. This is because the Hilbert spectrum presents the transient variation of the frequency from one instant to the next whereas the Fourier spectrum gives only the global mean. The mean values certainly will show less variations. The Fourier spectrum contains more frequency bands because any deviation of waveform from the basic harmonic will result in strong higher harmonics whereas the Hilbert spectrum allows variation of instantaneous frequencies, hence the fuzzy spread in frequencies, calling attention to the fact that the heart rate is also a stochastic variable, which could be studied by the same intrinsic mode method. The strong higher harmonic band with frequency 㸐 Hz in the Fourier spectrum is probably spurious. The clarity of the set of mean trends and the corresponding set of the oscillations is a unique contribution of the IMF method.
Interpretation of Arterial Blood Gases (ABGs)
David A. Kaufman, MD
Chief, Section of Pulmonary, Critical Care & Sleep Medicine
Bridgeport Hospital-Yale New Haven Health
Assistant Clinical Professor, Yale University School of Medicine
(Section of Pulmonary & Critical Care Medicine)
Interpreting an arterial blood gas (ABG) is a crucial skill for physicians, nurses, respiratory therapists, and other health care personnel. ABG interpretation is especially important in critically ill patients.
The following six-step process helps ensure a complete interpretation of every ABG. In addition, you will find tables that list commonly encountered acid-base disorders.
Many methods exist to guide the interpretation of the ABG. This discussion does not include some methods, such as analysis of base excess or Stewart’s strong ion difference. A summary of these techniques can be found in some of the suggested articles. It is unclear whether these alternate methods offer clinically important advantages over the presented approach, which is based on the “anion gap.”
Step 1: Assess the internal consistency of the values using the Henderseon-Hasselbach equation:
Management and Treatment
How is PAD treated?
Lifestyle changes, medications and interventional procedures are the treatments available for PAD.
Lifestyle Changes. Initial treatment of PAD includes making lifestyle changes to reduce your risk factors. Changes you can make to manage your condition include:
- Quit smoking. Ask your doctor about smoking cessation programs available in your community.
- Eat a balanced diet that is high in fiber and low in cholesterol, fat and sodium. Limit fat to 30 percent of your total daily calories. Saturated fat should account for no more than 7 percent of your total calories. Avoid trans fats including products made with partially-hydrogenated and hydrogenated vegetable oils. If you are overweight, losing weight will help you lower your total cholesterol and raise your HDL (good) cholesterol. A registered dietitian can help you make the right dietary changes.
- Exercise. Begin a regular exercise program, such as walking. Walking is very important and can aid the treatment of PAD. Patients who walk regularly can expect a marked improvement in the distance they are able to walk before experiencing leg pain. (See Walking Program Box)
- Manage other health conditions, such as high blood pressure, diabetes or high cholesterol.
- Practice good foot and skin care to prevent infection and reduce the risk of complications. (See Foot Care Guidelines Box)
Medications may be recommended to treat conditions such as high blood pressure (anti- hypertensive medications) or high cholesterol (statin medications).
An antiplatelet medication such as aspirin or clopidogrel (Plavix) may be prescribed to reduce the risk of heart attack and stroke.
Vascular Medicine and Preventive Cardiology and Rehabilitation offer a structured supervised walking program to help you succeed and maximize your exercise efforts. Please call 216.444.4420 or 800.223.2273 ext. 4420 to make an appointment.
Cilostazol (Pletal) may be prescribed to improve walking distance. This medication has been shown to help people with intermittent claudication exercise longer before they develop leg pain and to walk longer before they must stop because of the pain. However, not all patients are eligible to take this medication. Your doctor will tell you if you are eligible.
Interventional procedures. More advanced PAD can be treated with interventional procedures such as angioplasty (to widen or clear the blocked vessel), angioplasty with stent placement (to support the cleared vessel and keep it open), or atherectomy (to remove the blockage).
In some cases, surgical procedures such as peripheral artery bypass surgery may be performed to reroute blood flow around the blood vessel blockage.
New therapies are currently being researched. Please ask your doctor if any other treatment options are available for you.
If any of these procedures are recommended, your health care team will give you more information about the procedures so you will know what to expect.
Can PAD be cured?
There is no cure for PAD. Quitting smoking, exercising regularly, limiting fat and following a healthy diet, and managing your risk factors — such as diabetes, high cholesterol and high blood pressure — can help to reduce the progression of the disease.
Foot Care Guidelines
Every day, examine your legs as well as the tops and bottoms of your feet and the areas between your toes. Look for any blisters, cuts, cracks, scratches or other sores. Also check for redness, increased warmth, ingrown toenails, corns and calluses. Use a mirror to view the leg or foot if necessary, or have a family member look at the area for you.
Once or twice a day, apply a moisturizing cream or lotion to your legs and soles and top of your feet to prevent dry skin and cracking. Do not apply lotion between your toes or on areas where there is an open sore or cut. If the skin is extremely dry, use the moisturizing cream more often. Care for your toenails regularly. Cut your toenails after bathing, when they are soft. Cut toenails straight across and smooth with a nail file.
If you have diabetes, it is important to see a podiatrist.
Do not self-treat corns, calluses or other foot problems. Go to a podiatrist to treat these conditions.
Don't wait to treat a minor foot or skin problem. Follow your doctor's guidelines.
Other tests may include angiography, CT scan or MRI.
During angiography (also called arteriography), contrast material (dye) is injected into the blood vessels being examined, and X-ray pictures of the inside of the blood vessels are produced to evaluate blood flow and detect possible blockages.
A CT scan is a technique in which multiple X-rays are taken from different angles in a very short period of time. The images are collected by a computer and cross-sectional “slices” of the blood vessel are shown on the monitor.
MRI uses powerful magnets to create images of internal organs and blood vessels.
Taking Control of Peripheral Arterial Disease
Despite the prevalence of PAD, it is surprisingly underdiagnosed and undertreated (3). The good news is that, although PAD is a serious condition with potentially serious consequences, it is treatable. Like most health conditions, PAD is more treatable when it is detected early.Being aware that you have risk factors for PAD may motivate you to take action to prevent PAD from developing. The same advice for maintaining a healthy heart applies to maintaining healthy circulation overall:
- Manage your weight
- Eat a low fat, low sugar diet that includes at least five servings of fresh fruits and vegetables every day
- Don’t smoke.
- With your doctor’s approval, exercise, doing an activity you enjoy, for at least 30 minutes a day on most days of the week.
If you have heart disease, you should discuss your risk factors for PAD with your doctor and report any symptoms you are having such as pain, weakness or numbness in the legs. Your doctor may order a simple test, known as the ankle-brachial index (ABI), to diagnose PAD The ABI test involves measuring the blood pressures in the arms and the legs using a hand-held Doppler device.
If you already have mild PAD, your doctor may prescribe exercise therapy, dietary changes, smoking cessation and medication. Common medications prescribed for atherosclerosis and PAD include anti-platelet agents (such as aspirin or clopidogrel) and cholesterol lowering medications (“statins”). The best things that you can do for yourself in this situation are to quit smoking, control your high blood pressure, take your medications, and manage your diabetes.
It is also very important that patients with PAD take especially good care of the feet to prevent non-healing sores. Important components of foot care for patients with PAD include: wearing comfortable, appropriately fitting shoes inspecting the feet regularly for sores keeping the feet clean and well moisturized and, taking regular care of the toe nails. In some cases, a patient with PAD is referred to a podiatrist for specialized foot care.
Other Treatments for Peripheral Arterial Disease
More advanced PAD that is causing severe pain and limited mobility may require endovascular (i.e., minimally invasive) or surgical treatment. Some of the same treatments that are used for heart disease are also used for treating PAD.
In this procedure, a miniature balloon is passed through a catheter into the arteries. As the balloon is expanded inside the artery, it pushes against the plaque and opens up the artery.
These are tiny metal support coils that are inserted into the arteries. Once they are in place, stents expand against the inner blood vessel wall to support it and hold it open. Stents can be placed through a small opening using catheters (long, thin tubes) without major surgery.
Similar to heart bypass, a surgeon uses a section of the patient's healthy vein or a synthetic replacement to create a bypass around the blocked area in the leg artery. This is usually reserved for the most severe PAD.
With early diagnosis, lifestyle changes and treatment, you can stop PAD from getting worse. In fact, some studies have shown that symptoms due to PAD can be reversed with exercise combined with careful control of cholesterol and blood pressure. If you think you are at risk for PAD or may already have the disease, talk to your primary care doctor or cardiologist so that you can get started on a prevention or treatment program as soon as possible. With proper diagnosis and treatment, you can still enjoy the good things in life - like shopping, sightseeing and golf!
For questions or more information about PAD, call the Miller Family Heart, Vascular & Thoracic Institute Resource and Information Center Nurse at 216.445.9288 or toll-free 866.289.6911. For an appointment with a Cleveland Clinic women’s heart or vascular specialist, call toll-free 800.223.1696 or locally, 216.444.9343.
The following list includes the most common signs and symptoms in people with dermatomyositis. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition.
- A reddish-purple rash around the eyelids
- Red or violet bumps that form on the outside joints of the hand (Gottron papules)
- Red or violet bumps on the knees and elbows
- Discolored skin on shoulders, neck, upper back (shawl sign)
- Muscle weakness starting in the arms and/or legs
- Joint pain
This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.
The Perfusion Index and Other Correlates of Hemodynamic State
The new Masimo SET pulse oximeter (Masimo Corporation, Irvine, CA) reports a perfusion index, the ratio of the pulsatile amplitude of a photoplethysmogram to its DC component. Early reports suggest that the perfusion index is sensitive to proximal sympathectomy,58proximal arterial clamping,59and neonatal left heart obstruction.60Other metrics from a photoplethysmogram that have been recently investigated are related to beat-to-beat waveform variability of either peak levels or amplitude, which are nonspecific metrics analogous to ABP pulsus paradoxus. Changes in waveform variability metrics have been significantly associated with hypotension (for systolic variation and δ-down: r = 0.6 correlation with ΔSBP61), respiratory volume (for a novel oscillation metric: r = 0.89 correlation with breath volume30), wedge pressure (for δ-down: r =−0.6 correlation with wedge pressure62), and hypovolemia (systolic variation of 17 ± 12 SD % at baseline vs. systolic variation of 32 ± 12 SD % after loss of 10% blood volume63). The Masimo SET pulse oximeter reports perfusion index variability, which will presumably show similar correlations.
There are a number of other waveform features that correlate with central hemodynamic parameters. In the operating room, a measure of the photoplethysmogram's systolic width correlated with mean arterial pressure (r = 0.80).64In a cardiac catheterization suite, the “maximum decreasing systolic slope” correlated with changes in peripheral vascular resistance (r = 0.66).65Features from the second derivative of the photoplethysmogram have been correlated with vascular compliance.66–68
Back to the present…RELAX
High blood pressure, especially, can stretch and damage the walls of the arteries, making the heart pump even harder and in turn, be a major risk factor for serious complications like heart disease and stroke.
It’s why Dr. Ferdinand and others place so much attention on getting that measurement right.
“It’s one of the most important maneuvers done in clinical medicine,” he says.
Yet, because so many factors can affect a person’s blood pressure at any given time, Becker doesn’t hedge all her bets on any one reading in isolation.
“We kind of look at blood pressure over time as an average,” she says.
Ferdinand advises for those who are feeling anxious, not to get it measured right away.
“It’s going to be a little high,” he cautions.
Ferdinand says instead, wait a few minutes. Some even recommend, when appropriate, that a patient measure it again at home. Becker’s technique: asking patients about his or her week to provide some benign distraction.
So perhaps as anxiety and stress might build, in those moments or minutes before a doctor or nurse enters that exam room, one could maybe find some solace flipping through that six-month-old Time magazine that’s probably on the table.