Question

  • Why is it important to make note of the counts for the perfusion and ventilation studies? What do you think the ratio of counts should be,

 and why?

  • When doing a perfusion and ventilation with DTPA what one should be done first, and why?

  • If a patient has know pulmonary hypertension what special consideration do you need to do.

  • What is a right to left cardiac shunt?

Answer 1

Perfusion:Perfusion is measured as the rate at which blood is delivered to tissue,or volume of blood per unit time (blood flow) per unit tissue mass.

Ventilation;Ventilation: The exchange of air between the lungs and the atmosphere so that oxygen can be exchanged for carbon dioxide in the alveoli (the tiny air sacs in the lungs).

According to the current guidelines the count rate of the second study should be at least 3 times that of the first study. It is not always easy to meet this requirement, particularly since the deposed quantity of ventilation activity is not well known. The aim was therefore to analyse data from a multicentre survey to determine whether this essential precondition was strictly met.

METHODS: In a multicentre survey 48 tertiary hospitals were asked to submit projections of all V/P-SPECT studies performed in January 2014. In total, 286 complete data sets from 16 institutions could be evaluated. First, the count rates of the first projections from the V-studies were subtracted from those of the P-studies. The resulting count rates in the first SPECT projections were then divided to calculate the activity ratios between the pure perfusion and ventilation scans (P/V-ratio at least 3 according to the guidelines).

RESULTS: The range of the P/V ratio was 0.57-78.71, the mean P/V ratio was 6.94 ± 9.56. For 71 of the 286 external V/P studies (about 25%) the P/V ratio was < 3, in 23 studies (about 8%) the ratio failed to even reach the factor 2.

CONCLUSIONS: An activity ratio of 3 between the perfusion and ventilation scan was not reached in about 25% of the 286 V/P studies (in around 8% the P/V ratio was <2), so that V/P studies were performed inadequately in a considerable number of procedures. Controlling the count rate increase during the perfusion tracer application (e. g. by handheld monitor) is therefore essential to avoid insufficient data.

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Yes, perfusion be done first,becauze

Perfusion is the passage of fluid through the circulatory system or lymphatic system to an organ or a tissue,usually referring to the delivery of blood to a capillary bed in tissue. Perfusion is measured as the rate at which blood is delivered to tissue,or volume of blood per unit time (blood flow) per unit tissue mass. The SI unit is m³/(s·kg), although for human organs perfusion is typically reported in ml/min/g.The word is derived from the French verb "perfuser" meaning to "pour over or through".All animal tissues require an adequate blood supply for health and life. Poor perfusion (malperfusion), that is, ischemia, causes health problems, as seen in cardiovascular disease, including coronary artery disease, cerebrovascular disease, peripheral artery disease, and many other conditions.

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Ventilation: The exchange of air between the lungs and the atmosphere so that oxygen can be exchanged for carbon dioxide in the alveoli (the tiny air sacs in the lungs).

The use of lung scintigraphy in evaluating suspected pulmonary embolism (PE) is controversial. Several diagnostic methods have been described for lung scans, of which the most widely applied uses 99mTc-MAA for perfusion, 133Xe for ventilation and PIOPED diagnostic criteria. This study evaluates the accuracy of lung scintigraphy using an alternative ventilation agent, 99mTc-diethylenetriamine pentacetic acid (DTPA) aerosol, and specific criteria.

METHODS: Diagnostic criteria for DTPA aerosol ventilation were prospectively applied to 5017 patients over a 9-yr period. Lung scan interpretations were analyzed for frequency of occurrence, and results were compared to those of angiography in 455 patients.

RESULTS: Scans were interpreted as normal, low or high probability in 79% of patients and as either indeterminate or medium probability in 21% of patients. Three patients had normal scans and negative angiography. In patients with low-probability scans, 111 angiograms were performed: 103 (93%) were negative, and 8 (7%) were positive. In patients with indeterminate scans, 114 angiograms were performed: 85 (75%) were negative, and 29 (25%) were positive. In patients with medium-probability scans, 149 angiograms were performed: 86 (58%) were negative, and 63 (42%) were positive. In patients with high-probability scans, 78 angiograms were performed: 6 (8%) were negative, and 72 (92%) were positive.

CONCLUSION: These results indicate that lung scintigraphy using DTPA aerosol and our criteria is accurate in diagnosing and stratifying risk of pulmonary embolic disease.

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Pulmonary hypertension is a type of high blood pressure that affects the arteries in your lungs and the right side of your heart.

In one form of pulmonary hypertension, tiny arteries in your lungs, called pulmonary arterioles, and capillaries become narrowed, blocked or destroyed. This makes it harder for blood to flow through your lungs, and raises pressure within your lungs' arteries. As the pressure builds, your heart's lower right chamber (right ventricle) must work harder to pump blood through your lungs, eventually causing your heart muscle to weaken and fail.

Special consideration for the patient of pulmonary hypertension;

Lifestyle and home remedies

Although medical treatment can't cure pulmonary hypertension. Lifestyle changes also can help improve your condition. Consider these tips:

• Get plenty of rest. Resting can reduce the fatigue that might come from having pulmonary hypertension.

• Stay as active as possible. Even the mildest forms of activity might be too exhausting for some people who have pulmonary hypertension. For others, moderate exercise such as walking might be beneficial — especially when done with oxygen. But first, talk to your doctor about specific exercise restrictions.

  In most cases, it's recommended that you not lift heavy weights. Your doctor can help you plan an appropriate exercise program.

• Don't smoke. If you smoke, the most important thing you can do for your heart and lungs is to stop. If you can't stop smoking by yourself, ask your doctor to prescribe a treatment plan to help you quit. Also, avoid secondhand smoke if possible.
• Avoid pregnancy and birth control pills. If you're a woman of childbearing age, avoid pregnancy. Pregnancy can be life-threatening for both you and your baby. Also avoid using birth control pills, which can increase your risk of blood clots. Talk to your doctor about alternative forms of birth control. If you do become pregnant, it's important to consult with your doctor as pulmonary hypertension can cause serious complications to both you and the fetus.
• Avoid traveling to or living at high altitudes. High altitudes can worsen the symptoms of pulmonary hypertension. If you live at an altitude of 8,000 feet (2,438 meters) or higher, your doctor might recommend that you move to a lower altitude.
• Avoid situations that can excessively lower blood pressure. These include sitting in a hot tub or sauna or taking long hot baths or showers. These activities lower your blood pressure and can cause fainting or even death. Also avoid activities that cause prolonged straining, such as lifting heavy objects or weights.
• Follow a nutritious diet and stay at a healthy weight. Aim to eat a healthy diet of whole grains, a variety of fruits and vegetables, lean meats and low-fat dairy products. Avoid saturated fat, trans fat and cholesterol. It's likely your doctor will recommend limiting the amount of salt in your diet. Aim to maintain a healthy weight.
• Ask your doctor about medications. Take all your medications as prescribed. Ask your doctor about any other medications before taking them, as some can interfere with your medication or worsen your condition.
• See your doctor at follow-up appointments. Your doctor may recommend regular follow-up appointments. Let your doctor know if you have any questions about your condition or medications you're taking, or if you have any symptoms or side effects from your medications. If pulmonary hypertension is affecting your quality of life, ask your doctor about options that could improve your quality of life.
• Get vaccines. Your doctor may recommend getting an influenza and pneumonia vaccine, as these conditions can cause serious issues for people with pulmonary hypertension.
• Get support. If you're feeling stressed or worried due to your condition, get support from family or friends. Or, consider joining a support group with others who have pulmonary hypertension.

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Right to left cardiac shunt;

A right-to-left shunt is a cardiac shunt which allows blood to flow from the right heart to the left heart. This terminology is used both for the abnormal state in humans and for normal physiological shunts in reptiles.

Causes;

Congenital defects can lead to right-to-left shunting immediately after birth:

• Persistent truncus arteriosus (minimal cyanosis)
• Transposition of great vessels
• Tricuspid atresia
• Tetralogy of Fallot
• Total anomalous pulmonary venous return

A mnemonic to remember the conditions associated with right-to-left shunting involves the numbers 1-5, as follows:

• 1 Combination Vessel: Persistent truncus arteriosus (minimal cyanosis)
• 2 Vessels involved: Transposition of great vessels
• 3 Leaflets: Tricuspid atresia
• 4 Tetra- prefix: Tetralogy of Fallot
• 5 Words: Total anomalous pulmonary venous return

• Symptoms;

  Early cyanosis is a symptom of a right-to-left shunt.^[2] A right-to-left shunt results in decreased blood flow through the pulmonary system, leading to decreased blood oxygen levels (hypoxemia). Hypoxemia manifests as cyanosis, or "blue babies."

  Diagnosis;

  Differentiation between a right-to-left shunt and pulmonary disease is often aided clinically by the results of a hyperoxia test.^{[citation needed]} Using high levels of inspired oxygen should have little effect on the dissolved O2 in the blood because highly oxygenated blood is diluted by shunted (low oxygenation) blood.

  Shunt equation;

• { Q_{s}/Q_{t}=(CcO_{2}-CaO_{2})/(CcO_{2}-CvO_{2})}

• Qs/Qt is the shunt fraction
• CcO2 is the end-capillary oxygen content
• CaO2 is the arterial oxygen content
• CvO2 is the mixed venous oxygen content