Predictive Value Positive | Health Dictionary

The probability that a person with a reactive test has the disease and is not a false reaction.


Predictive Value Positive | Health Dictionary

Keywords of this word: Predictive Value Positive


CONTINUOUS POSITIVE AIRWAYS PRESSURE

Medical Dictionary

A method for treating babies who su?er from alveolar collapse in the lung as a result of HYALINE MEMBRANE DISEASE (see also RESPIRATORY DISTRESS SYNDROME).... Medical Dictionary

FALSE POSITIVE

Dictionary of Tropical Medicine

A positive test result for a condition that is not, in fact, present.... Dictionary of Tropical Medicine

GRAM-POSITIVE/NEGATIVE

Herbal Medical

Gram’s Method is a staining procedure that separates bacteria into those that stain (positive) and those that don’t (negative). Gram-positive bugs cause such lovely things as scarlet fever, tetanus, and anthrax, while some of the gram negs can give you cholera, plague, and the clap. This is significant to the microbiologist and the pathologist; otherwise I wouldn’t worry. Still, knowing the specifics (toss in anaerobes and aerobes as well), you can impress real medical professionals with your knowledge of the secret, arcane language of medicine.... Herbal Medical

GRAM-POSITIVE/NEGATIVE

Medical Dictionary

See GRAM’S STAIN.... Medical Dictionary

INTERMITTENT POSITIVE PRESSURE (IPP)

Medical Dictionary

The simplest form of intermittent positive-pressure ventilation is mouth-to-mouth resuscitation (see APPENDIX 1: BASIC FIRST AID) where an individual blows his or her own expired gases into the lungs of a non-breathing person via the mouth or nose. Similarly gas may be blown into the lungs via a face mask (or down an endotracheal tube) and a self-in?ating bag or an anaesthetic circuit containing a bag which is in?ated by the ?ow of fresh gas from an anaesthetic machine, gas cylinder, or piped supply. In all these examples expiration is passive.

For more prolonged arti?cial ventilation it is usual to use a specially designed machine or ventilator to perform the task. The ventilators used in operating theatres when patients are anaesthetised and paralysed are relatively simple devices.They often consist of bellows which ?ll with fresh gas and which are then mechanically emptied (by means of a weight, piston, or compressed gas) via a circuit or tubes attached to an endotracheal tube into the patient’s lungs. Adjustments can be made to the volume of fresh gas given with each breath and to the length of inspiration and expiration. Expiration is usually passive back to the atmosphere of the room via a scavenging system to avoid pollution.

In intensive-care units, where patients are not usually paralysed, the ventilators are more complex. They have electronic controls which allow the user to programme a variety of pressure waveforms for inspiration and expiration. There are also programmes that allow the patient to breathe between ventilated breaths or to trigger ventilated breaths, or inhibit ventilation when the patient is breathing.

Indications for arti?cial ventilation are when patients are unable to achieve adequate respiratory function even if they can still breathe on their own. This may be due to injury or disease of the central nervous, cardiovascular, or respiratory systems, or to drug overdose. Arti?cial ventilation is performed to allow time for healing and recovery. Sometimes the patient is able to breathe but it is considered advisable to control ventilation – for example, in severe head injury. Some operations require the patient to be paralysed for better or safer surgical access and this may require ventilation. With lung operations or very unwell patients, ventilation is also indicated.

Arti?cial ventilation usually bypasses the physiological mechanisms for humidi?cation of inspired air, so care must be taken to humidify inspired gases. It is important to monitor the e?cacy of ventilation – for example, by using blood gas measurement, pulse oximetry, and tidal carbon dioxide, and airways pressures.

Arti?cial ventilation is not without its hazards. The use of positive pressure raises the mean intrathoracic pressure. This can decrease venous return to the heart and cause a fall in CARDIAC OUTPUT and blood pressure. Positive-pressure ventilation may also cause PNEUMOTHORAX, but this is rare. While patients are ventilated, they are unable to breathe and so accidental disconnection from the ventilator may cause HYPOXIA and death.

Negative-pressure ventilation is seldom used nowadays. The chest or whole body, apart from the head, is placed inside an airtight box. A vacuum lowers the pressure within the box, causing the chest to expand. Air is drawn into the lungs through the mouth and nose. At the end of inspiration the vacuum is stopped, the pressure in the box returns to atmospheric, and the patient exhales passively. This is the principle of the ‘iron lung’ which saved many lives during the polio epidemics of the 1950s. These machines are cumbersome and make access to the patient di?cult. In addition, complex manipulation of ventilation is impossible.

Jet ventilation is a relatively modern form of ventilation which utilises very small tidal volumes (see LUNGS) from a high-pressure source at high frequencies (20–200/min). First developed by physiologists to produce low stable intrathoracic pressures whilst studying CAROTID BODY re?exes, it is sometimes now used in intensive-therapy units for patients who do not achieve adequate gas exchange with conventional ventilation. Its advantages are lower intrathoracic pressures (and therefore less risk of pneumothorax and impaired venous return) and better gas mixing within the lungs.... Medical Dictionary

P VALUE

Community Health

See “probability”.... Community Health

POSITIVE AGEING

Community Health

See “healthy ageing”.... Community Health

POSITIVE HEALTH

Community Health

A state of health beyond an asymptomatic state. It usually includes the quality of life and the potential of the human condition. It may also include self-fulfilment, vitality for living and creativity. It is concerned with thriving rather than merely coping. See also “health”.... Community Health

PREDICTIVE VALUE

Community Health

1 The statistic generated by dividing the number of true positives by the sum of the true positives and false positives. For example, the number of cases with truly good care divided by the sum of the cases with truly good care plus those cases classified with good care who did not receive it i.e. the likelihood that a person classified as the recipient of good care actually received good care. 2 In screening and diagnostic tests, the probability that a person with a positive test result is a true positive (i.e. does have the disease) is referred to as the “predictive value of a positive test”. The predictive value of a negative test is the probability that a person with a negative test does not have the condition or disease. The predictive value of a screening test is determined by the sensitivity and specificity of the test, and by the prevalence of the condition for which the test is used.... Community Health

PREDICTIVE VALUE NEGATIVE

Dictionary of Tropical Medicine

The probability that a person with a negative test is free of the disease and is not a false negative.... Dictionary of Tropical Medicine

PREDICTIVE VALUE POSITIVE

Dictionary of Tropical Medicine

The probability that a person with a reactive test has the disease and is not a false reaction.... Dictionary of Tropical Medicine

PROBABILITY (P VALUE)

Community Health

The likelihood that an event will occur. When looking at differences between data samples, statistical techniques are used to determine if the differences are likely to reflect real differences in the whole group from which the sample is drawn, or if they are simply the result of random variation in the samples. It is the probability that a test statistic would be as extreme as, or more extreme than that observed if the null hypothesis were true. The letter P, followed by the abbreviation n.s. (not significant) or by the symbol < (less than) and a decimal notation such as 0.01, 0.05, is a statement of the probability that the difference observed could have occurred by chance, if the groups are really alike, i.e. under the null hypothesis. Although investigators may choose their own significance levels in most studies, a result whose probability value is less than 5% (P<0.05) or 1% (P<0.01) is considered sufficiently unlikely to have occurred by chance to justify the designation “statistically significant”. For example, a probability (or P value) of 1% indicates that the differences observed would have occurred by chance in one out of a hundred samples drawn from the same data.... Community Health