| expiratory dyspnea | Difficulty with the expiratory phase of breathing, often due to obstruction in the larynx or large bronchi, such as by a foreign body. (05 Mar 2000) |
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| expiratory reserve volume | The extra volume of air that can be expired with maximum effort beyond the level reached at the end of a normal, quiet expiration. Common abbreviation is erv. (12 Dec 1998) |
| expiratory resistance | Resistance to flow of gas out of the lungs or the total resistance to flow of gas during the expiratory phase of the respiratory cycle. (05 Mar 2000) |
| expiratory stridor | A singing sound due to the semi-approximated vocal folds offering resistance to the escape of air. (05 Mar 2000) |
| zero end-expiratory pressure | Airway pressure which, at the end of expiration, equals atmospheric pressure. (05 Mar 2000) |
| forced expiratory flow | Expiratory flow during measurement of forced vital capacity; subscripts specify the exact parameter measured, e.g., peak instantaneous flow, the instantaneous flow at some specified point on the curve of volume expired versus time, or on the flow-volume curve, the mean flow between two expired volumes. (05 Mar 2000) |
| forced expiratory flow rates | Measurements of rates of airflow during a forced vital capacity determination. (12 Dec 1998) |
| forced expiratory time | The time taken to expire a given volume or a given fraction of vital capacity during measurement of forced vital capacity; subscripts specify the exact parameters measured. (05 Mar 2000) |
| forced expiratory volume | Measure of the maximum amount of air during a forced vital capacity determination that can be expelled in a given number of seconds. It is usually given as fev followed by a subscript indicating the number of seconds over which the measurement is made, although it is sometimes given as a percentage of forced vital capacity. (12 Dec 1998) |
| ACE level | <investigation> This is a blood test which measures the concentration of angiotensin-converting enzyme (ACE) in the bloodstream. Elevations in angiotensin-converting enzyme are seen sarcoidosis, histoplasmosis, alcoholic cirrhosis, asbestosis, berylliosis, diabetes, Hodgkin's disease, hyperthyroidism, amyloidosis, primary biliary cirrhosis, idiopathic pulmonary fibrosis, pulmonary embolism, scleroderma, silicosis, tuberculosis, Gaucher's disease and leprosy. The normal values are 18 to 67 U/ml over 20 years of age (people under 20 have higher levels). (15 Jan 1998) |
| acoustic reference level | The biological reference level for sound measurements. When the term decibel is used to indicate the noise level, a reference quantity is implied; this reference value is usually expressed as a sound pressure of 20 micronewtons per square meter. The reference level is referred to as 0 decibels, the baseline of the scale of noise level's; this baseline is considered the weakest sound that can be heard by a person with very good hearing in an extremely quiet location. Other equivalent reference level's still being used include 0.0002 microbar and 0.0002 dyne per square centimeter. (05 Mar 2000) |
| background level | The average amount of a substance present in the environment. Originally referring to naturally occurring phenomena. Used in toxic substance monitoring. (05 Dec 1998) |
| blood porphyrin level | A test which is used to measure red blood cell porphyrin levels. Porphyrins are pigments found in both animal and plant life. This test is useful in evaluating any number of porphyrin disorders (involving the various porphyrins) of red blood cells. Increased levels of coproporphyrins can indicate congenital erythropoietic porphyria or sideroblastic anaemia. Increased protoporphyrins may be seen in infection, thalassaemia, sideroblastic anaemia, iron deficient anaemia, increased erythropoiesis and lead poisoning. Increased uroporphyrins may indicate congenital erythropoietic porphyria or erythropoietic protoporphyria. (27 Sep 1997) |
| carbon dioxide blood level | A measure of the bicarbonate level in the blood based on a venipuncture specimen. The serum carbon dioxide is one of the normally reported values in the electrolytes profile. Lower levels of carbon dioxide indicate an acidosis. The normal level is 20 to 29 mEq/L. Lower than normal levels can indicate diabetic ketoacidosis, lactic acidosis, alcoholic ketoacidosis, kidney disease, renal failure, diarrhoea, Addison's disease, ethylene glycol poisoning or methanol poisoning. Greater than normal levels can be seen with excessive vomiting, hyperaldosteronism and Cushing's syndrome. (27 Sep 1997) |
| vasopressin level | This test measures the amount of ADH in the serum. It is used to detect disorders that may affect the level of ADH in the serum. Normal values are: 0 to 4.7 pg/ml. Elevated ADH levels can indicate a CNS infection, fluid imbalance, CNS tumour, SIADH or acute porphyria. Low levels can indicate: diabetes insipidus or damage to the pituitary gland. (27 Sep 1997) |