Effusion

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Related to Pericardial effusion: pericarditis

effusion

1. the flow of a gas through a small aperture under pressure, esp when the density is such that the mean distance between molecules is large compared to the diameter of the aperture
2. Med
a. the escape of blood or other fluid into a body cavity or tissue
b. the fluid that has escaped

Effusion

 

the slow leakage of gas through a small aperture. Two cases of effusion are distinguished. In the first case, the diameter of the opening is small compared with the mean free path of the molecules (the pressure in the vessel is very low). In such a case, molecular effusion occurs in which collisions between molecules play no part, and the overall volume of gas escaping per unit time is Effusion, where S is the area of the aperture, μ is the molecular mass of the gas, R is the universal gas constant, T is the absolute temperature of the gas, and p1 and p2 are the gas pressures on the two sides of the aperture. The effusion method of measuring very low pressures (about 10–3–10–4 mm Hg) is based on this case.

In the second case, where the gas pressure is so high that the mean free path is smaller than the diameter of the aperture, the leakage of gas obeys the laws of hydrodynamics. The molecules escape from the aperture in the form of a jet, and the volume of gas discharged per unit time is inversely proportional to the square root of the density of the gas. This law underlies a method of determining the density of gases from the time of their discharge through small apertures (0.10–0.01 mm). However, if the pressure within the vessel is considerably greater than the external pressure, the amount of gas escaping is proportional to the pressure in the vessel.


Effusion

 

the process of lava (magma) pouring out onto the earth’s surface. When the lava cools, effusive rocks are formed, bedded in the form of lava flows and lava sheets. Effusion, one of the manifestations of volcanic activity, is usually accompanied by an explosion, with discharges of small fragments (volcanic ash, sand, or tuff) or large chunks (volcanic bombs and slags). Viscous acidic lava sometimes will not flow, but rather is extended, forming volcanic domes.

effusion

[e′fyü·zhən]
(medicine)
A pouring out of any fluid into a body cavity or tissue.
(physical chemistry)
The movement of a gas through an opening which is small as compared with the average distance which the gas molecules travel between collisions.
(science and technology)
The act or process of leaking or pouring out.
Any material that is effused.
References in periodicals archive ?
Patients with large pericardial effusions or cardiac tamponade undergo pericardiocentesis and may require drain placement or pericardial window to prevent recurrence.
Endoscopic pericardiectomy was offered to the owner as the treatment of choice for recurrent idiopathic pericardial effusion or neoplastic pericardial effusion.
Uremic pericarditis is one of the common complications of uremia and the life threatening complications like pericardial effusion with acute cardiac tamponade can occasionally develop.
Both pericardial effusion and left pleural effusion were clear yellow, and cytodiagnosis from both fluids demonstrated atypical cells similar to the cells present in urine from the left renal pelvis.
Management of tuberculous pericarditis and tuberculous pericardial effusion in Transkei: results at 10 year follow-up.
A pericardial effusion is a notable finding that is seen uncommonly in hypothyroidism but more frequently in patients with more severe thyroid hormone deficiency, such as in myxedema (4).
Based on the patient's history, examination and advanced imaging studies revealing pericardial effusion and tamponade, this patient was determined to be in cardiovascular distress secondary to the pericardial effusion.
Pericardial tamponade (fluid accumulation resulting from pericardial effusion which compresses the heart and impairs its ability to function)
Transthoracic echocardiography; massive pericardial effusion and cardiac tamponade
The postmortem specimens consisted of cerebrospinal, pericardial effusion, and pleural effusion fluids; lung, liver, spleen, and kidney tissues; skin; and bone marrow aspirate.
Therefore, computed tomography (CT) of the abdomen and thorax was ordered for further evaluation and pericardial effusion and periaortitis was detected beginning from the arcus and lasting to the abdominal aorta (Figures 1 and 2).
The CT findings were a moderate to severe pericardial effusion, with a fluid rim of approximately 2 cm, around the whole pericardium (as shown in Fig.