| PLA | peripheral laser angioplasty; phenyl lactate; phospholipase A; phospholipid antibody; placebo therap... |
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| DBPCFC | Double-blind placebo-controlled food challenge |
| CPTP | culture-positive toxin-positive |
| PPV | pneumococcal polysaccharide vaccine; porcine parvovirus; positive predictive value; positive pressur... |
| PEEP | Positive End-Expiratory Pressure ? Ix 1. PaO2 < 60 mmHg, ... |
| positive, false | A result that is erroneously positive when a situation is normal. An example of a false positive: a particular test designed to detect cancer of the toenail is positive but the person does not have toenail cancer. (12 Dec 1998) |
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| positive feedback | <physiology> The return of some of the output of a system as input so as to exert some control in the process. (18 Nov 1997) |
| positive focal length | <microscopy> Any lens which converges parallel rays to a focus at the back of the lens is a positive lens and has a positive focal length. The focal length is measured from the second principal point of the lens to the point on the lens axis where the rays from an infinitely distant point are brought to focus. See: negative focal length. (05 Aug 1998) |
| positive G | Gravity or acceleration in the usual head-to-foot direction in flying or in standing upright; the reverse of negative G. (05 Mar 2000) |
| positive image | <microscopy> A developed image in which dark areas correspond to dark areas of the original subject. (05 Aug 1998) |
| positive lens | <physics> Any lens with a positive focal length. Such lenses are thicker in the centre than around the circumference. There are three types of positive lenses, double convex or biconvex, planoconvex, converging concavoconvex or converging meniscus. (05 Aug 1998) |
| positive meniscus | A convexoconcave lens in which the power of the convexity exceeds that of the concavity. Synonym: positive meniscus. (05 Mar 2000) |
| positive-negative pressure breathing | Inflation of the lungs with positive pressure and deflation with negative pressure by an automatic ventilator. (05 Mar 2000) |
| positive ocular | <microscopy> A Ramsden ocular or any modification of it. The diaphragm is below the field lens. (05 Aug 1998) |
| positive phase | The period following the negative phase, during which the opsonic index rises. (05 Mar 2000) |
| positive-pressure respiration | A method of mechanical ventilation in which pressure is maintained to increase the volume of gas remaining in the lungs at the end of expiration, thus reducing the shunting of blood through the lungs and improving gas exchange. (12 Dec 1998) |
| positive-pressure respiration, intrinsic | Non-therapeutic positive end-expiratory pressure occurring frequently in patients with severe airway obstruction. It can appear with or without the administration of external positive end-expiratory pressure (positive-pressure respiration). It presents an important load on the inspiratory muscles which are operating at a mechanical disadvantage due to hyperinflation. Auto-peep may cause profound hypotension that should be treated by intravascular volume expansion, increasing the time for expiration, and/or changing from assist mode to intermittent mandatory ventilation mode. (12 Dec 1998) |
| positive rays | Those originating in a gas discharge tube and moving in a direction opposite to that of cathode ray's; made up of positively charged ions. Synonym: positive rays. (05 Mar 2000) |
| positive scotoma | A scotoma that is perceived as a black spot within the field of vision. (05 Mar 2000) |
| positive stain | <technique> Direct binding of a dye with a tissue component to produce contrast; in electron microscopy, heavy metals like uranyl and lead salts are used to bind to selective cell constituents to produce increased density to the electron beam, i.e., contrast. (05 Mar 2000) |