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The decibel is a relative unit of measurement corresponding to one tenth of bel. It is used to express the ratio of one value of a power or field quantity to another, on a logarithmic scale, the logarithmic quantity being called the power level or field level, respectively.
The amplitude of a periodic variable is a measure of its change over a single period. There are various definitions of amplitude, which are all functions of the magnitude of the differences between the variable's extreme values. In older texts the phase is sometimes called the amplitude.
Blood pressure (BP) is the pressure of circulating blood on the walls of blood vessels. Most of this pressure is due to work done by the heart by pumping blood through the circulatory system. Used without further specification, "blood pressure" usually refers to the pressure in large arteries of the systemic circulation. Blood pressure is usually expressed in terms of the systolic pressure over diastolic pressure and is measured in millimeters of mercury (mmHg), above the surrounding atmospheric pressure.
Heart rate is the speed of the heartbeat measured by the number of contractions (beats) of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide. It is usually equal or close to the pulse measured at any peripheral point. Activities that can provoke change include physical exercise, sleep, anxiety, stress, illness, and ingestion of drugs.
A uterine contraction is a muscle contraction of the uterine smooth muscle.
Cardiotocography (CTG) is a technical means of recording the fetal heartbeat and the uterine contractions during pregnancy. The machine used to perform the monitoring is called a cardiotocograph, more commonly known as an electronic fetal monitor (EFM).
Vascular resistance is the resistance that must be overcome to push blood through the circulatory system and create flow. The resistance offered by the systemic circulation is known as the systemic vascular resistance (SVR) or may sometimes be called by the older term total peripheral resistance (TPR), while the resistance offered by the pulmonary circulation is known as the pulmonary vascular resistance (PVR). Systemic vascular resistance is used in calculations of blood pressure, blood flow, and cardiac function. Vasoconstriction increases SVR, whereas vasodilation decreases SVR.
The acoustic reflex is an involuntary muscle contraction that occurs in the middle ear in response to loud sound stimuli or when the person starts to vocalize.
Uterine rupture is when the muscular wall of the uterus tears during pregnancy or childbirth. Symptoms while classically including increased pain, vaginal bleeding, or a change in contractions are not always present. Disability or death of the mother or baby may result.
The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions.
Cervical weakness, also called cervical incompetence or cervical insufficiency, is a medical condition of pregnancy in which the cervix begins to dilate (widen) and efface (thin) before the pregnancy has reached term. Definitions of cervical weakness vary, but one that is frequently used is the inability of the uterine cervix to retain a pregnancy in the absence of the signs and symptoms of clinical contractions, or labor, or both in the second trimester. Cervical weakness may cause miscarriage or preterm birth during the second and third trimesters. Another sign of cervical weakness is funneling at the internal orifice of the uterus, which is a dilation of the cervical canal at this location.
Nutcracker esophagus, or hypertensive peristalsis, is a disorder of the movement of the esophagus characterized by contractions in the smooth muscle of the esophagus in a normal sequence but at an excessive amplitude or duration. Nutcracker esophagus is one of several motility disorders of the esophagus, including achalasia and diffuse esophageal spasm. It causes difficulty swallowing, or dysphagia, to both solid and liquid foods, and can cause significant chest pain; it may also be asymptomatic. Nutcracker esophagus can affect people of any age, but is more common in the sixth and seventh decades of life.
The myogenic mechanism is how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow within the blood vessel constant. Myogenic response refers to a contraction initiated by the myocyte itself instead of an outside occurrence or stimulus such as nerve innervation. Most often observed in smaller resistance arteries, this 'basal' tone may be useful in the regulation of organ blood flow and peripheral resistance, as it positions a vessel in a preconstricted state that allows other factors to induce additional constriction or dilation to increase or decrease blood flow.
Aortic valve area calculation is an indirect method of determining the area of the aortic valve. The calculated aortic valve orifice area is currently one of the measures for evaluating the severity of aortic stenosis. A valve area of less than 1.0 cm2 is considered to be severe aortic stenosis.
The factors that determine the values for alveolar pO2 and pCO2 are:
The Alveolar–arterial gradient (A-aO2, or A–a gradient), is a measure of the difference between the alveolar concentration (A) of oxygen and the arterial (a) concentration of oxygen. It is used in diagnosing the source of hypoxemia.
Roberto Caldeyro-Barcia was a Uruguayan doctor who pioneered the field of maternal-fetal medicine, or perinatology. His research with Dr. Hermógenes Alvarez created Montevideo units, a measure of uterine performance during labor. He was a founding editor of the Journal of Perinatal Medicine, a widely published author, a lecturer, and as of 2010 the only Uruguayan to be nominated for a Nobel Prize.
Stochastic resonance is a phenomenon that occurs in a threshold measurement system when an appropriate measure of information transfer is maximized in the presence of a non-zero level of stochastic input noise thereby lowering the response threshold; the system resonates at a particular noise level.
Increased intracranial pressure (ICP) is one of the major causes of secondary brain ischemia that accompanies a variety of pathological conditions, most notably traumatic brain injury (TBI), strokes, and intracranial hemorrhages. It can cause complications such as vision impairment due to intracranial pressure (VIIP), permanent neurological problems, reversible neurological problems, seizures, stroke, and death. However, aside from a few Level I trauma centers, ICP monitoring is rarely a part of the clinical management of patients with these conditions. The infrequency of ICP can be attributed to the invasive nature of the standard monitoring methods. Additional risks presented to patients can include high costs associated with an ICP sensor's implantation procedure, and the limited access to trained personnel, e.g. a neurosurgeon. Alternative, non-invasive measurement of intracranial pressure, non-invasive methods for estimating ICP have, as a result, been sought.
References
- ↑ "MATERNITY GUIDE - Labor & Delivery". Archived from the original on 2018-05-20. Retrieved 2010-03-28.
- ↑ Ball, RH; Espinoza, MI; Parer, JT (1994). "Regional blood flow in asphyxiated fetuses with seizures". Am J Obstet Gynecol. 170 (1): 156–261.