Glossary of SCUBA Diving - P

P

panic

A sudden sensation of fear which is so strong as to dominate or prevent reason and logical thinking, replacing it with overwhelming feelings of anxiety and frantic agitation consistent with an animalistic fight-or-flight reaction

parallel compartments

Further information: Decompression (diving)#Perfusion limited tissues and parallel tissue models

A decompression model comprising a group of tissues with varied rates of perfusion, but supplied by blood of approximately equivalent gas concentration. It is assumed that there is no gas transfer between tissue compartments by diffusion. This results in a parallel set of independent tissues, each with its own rate of ingassing and outgassing dependent on the rate of blood flowing through the tissue

partial pressure

The pressure that a component gas of a gas mixture would exert if it alone was present in the volume occupied by the gas mixture.

pendulum rebreather

Rebreather with a single breathing hose from the mouthpiece to the counterlung. Gas passes through it in both directions, unlike the one-way loop configuration.

perfusion limited

Further information: Decompression (diving)#Deterministic models

The assumption in a decompression model that perfusion has the dominant influence on gas uptake and release.

personal locator beacon

also PLB

Radio beacons for personal use which are intended to indicate a person in distress who is away from normal emergency services.

personal safety equipment

Equipment worn by personnel to reduce risk of injury at sites where it is not practicable to eliminate the hazard, including ear protectors, safety glasses, hard hats, gloves, overalls, respirators etc.

PFO

patent foramen ovale: A form of congenital heart defect that enables blood flow between the left and right atria through a gap in the interatrial septum.

pig

Further information: Pigging#Pipeline Inspection Gauge

Pipeline inspection gauge: A tool that is sent through a pipeline and propelled by the pressure of the product in the pipeline itself.

pigtail

Coiled section of pipe to provide greater flexibility.

pillar valve

see cylinder valve

pin index connection

Standard connection type for portable medical oxygen cylinder valves and regulators.

PLB

see personal locator beacon

PLEM

Pipeline end manifold:. Point where flexible underwater hose string is attached to connect seabed pipeline with Single point mooring.

pneumo breathing

Use of the pneumofathometer hose to supply breathing gas to a surface supplied diver in an emergency. Supply can be from the diver's own pneumo hose or from a standby diver's pneumo hose.

pneumofathometer

also pneumo

Instrument to measure depth of a diver using a gauge calibrated in msw, fsw, or often both, to measure the ambient pressure at the diver by measuring the pressure in a hose filled with air with an open end at the diver.

pneumothorax

Air or other breathing gas in the chest cavity, often resulting in a collapsed lung.

positive displacement

(of compressor) Compresses gas by reducing volume of compression chamber (cylinder) by mechanical means (piston) to produce higher pressure of the contents.

pony cylinder

Relatively small scuba set carried as an independent alternative breathing gas source by a scuba diver.

P-port

A large bore quick connector fitting designed and used by Draeger on diving and firefighting breathing apparatus, which has been used in rebreathers, particularly modifications.

pre-fill external inspection

Examination of the external condition of a pressure vessel and fittings to ensure that it complies with requirements before accepting for filling.

professional diving

Diving which is done as part of the diver's employment or professional occupation.

PTT

Push to talk: Voice communication systems which require the user to press a button to transmit. Used with through water systems to conserve battery power.

public safety diving

pull

A relatively long pull on a lifeline when used for rope signals. (see "bell" for comparison).

P-valve

also Pee-valve Further information: Dry suit#The P-valve

A valved catheter fitted to a dry suit, which enables a diver to urinate at any time without having to get out of the water.

Pyle stops

Further information: Decompression (diving)#Pyle stops

Named after Richard Pyle, an early advocate of deep stops. An additional brief deep decompression stop, typically 2 minutes long and half way between the maximum depth and the first conventional decompression stop.