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1. position; posterior; postpartum; pressure; pulse; pupil. 2. Symbol for the element phosphorus. 3. Symbol for partial pressure, preferably italicized. 4. Probability.


page; probability (in statistics); pupil.


Symbol for the isotope of phosphorus with mass number 15; radioactive; atomic mass (weight) 15.


pulmonic second sound.


In chemistry, an abbreviation of para-.

after- or post-.


SEE: under gene.


0.1 The inspiratory mouth occlusion pressure measured 0.1 seconds after a breath initiates. Higher pressures are found in those mechanically ventilated patients who are more difficult to wean from ventilatory support. A more negative pressure implies a patient with an increased ventilatory demand (shortness of breath) and a less negative pressure means a patient is obtunded or has weak respiratory muscles.


physician assistant; posteroanterior; pulmonary artery.

P & A

percussion and auscultation.


1. Symbol for the element protactinium. 2. Abbreviation of pascal.


physician assistant.


(pon) [Hindi pān] The leaf of the betel tree (Piper betle). Chewing paan is common in the Indian subcontinent, Southeast Asia, and Indonesia. Betel leaf is a stimulant and is associated with the development of oral cancers.


The oxygen pressure gradient between the alveoli and the arterial blood.


(pab′yŭ-lŭm) [L. pabulum, food, nourishment] Food or nourishment; esp. in an absorbable solution.


premature atrial contraction.


(pās) Patient Advise and Consent Encounter.


(pās′māk″ĕr) 1. Anything that influences the rate and rhythm of occurrence of an activity or process. 2. In cardiology, a specialized cell or group of cells that automatically generates impulses that spread to other regions of the heart. The normal cardiac pacemaker is the sinoatrial node, a group of cells in the right atrium near the entrance of the superior vena cava. SYN: pacer. 3. A generally accepted shorthand term for an artificial cardiac pacemaker. SEE: artificial cardiac p.

artificial cardiac p. A device that can trigger mechanical contractions of the heart by emitting periodic electrical discharges. Pacemakers are used most often to treat patients with symptomatic slow heart rates or long pauses between heart beats (such as patients with third-degree ...

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