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Resources: Glossary

The Glossary contains terms commonly associated with ventilators, the community, and respiratory physiology. Click on a hyperlinked letter to view the entries that begin with that letter, then scroll down in the window to find the word you are looking for.

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Pa Pascals - Unit of pressure; 1 cm H2O = 98.06 Pa.
Palv Alveolar Pressure - Representative pressure in the alveoli of the lungs.
Panting Spontaneous, high frequency (in the range of 3 breaths/second) low tidal volume breathing.
Pao Pressure at the airway opening, e.g., at the interface between the patient's airways and the end of the patient circuit, or the atmosphere.
Partial Pressure In a gas mixture: the pressure that a component, X, of a gas mixture would exhibit if X alone occupied the volume that is occupied by the entire mixture at the temperature of the mixture. Symbol: PX. For example: the partial pressure of oxygen is PO2, and the partial pressure of carbon dioxide is PCO2.
Partial Volume The volume that the amount of a component gas in a gas mixture would occupy if that amount of the component gas existed at the pressure of the total mixture.
Patient Circuit (also Breathing Circuit) The tubing that carries the gas between the ventilator and the patient. It can include a humidifier, water traps, nebulizer, sensors, and various connectors and valves.
Patient System Those parts of the ventilator and patient circuit (including attachments) through which gas moves at physiologic pressures during ventilation of the patient.
Patient System Compliance The effective compliance of the patient system; reflects the distensibility of the patient circuit and the other structures comprising the system as well as the compressibility of the gas within all of these structures.
Patient Wye The connector that joins the inspiratory and expiratory limbs of a two-limb patient circuit to the patient airway.
Patm Atmospheric Pressure - Usually the same as ambient, or local, pressure in the vicinity of the patient.

Pressure-Controlled Ventilation (See Pressure Control Mode.)

PEEP Positive End-Expiratory Pressure - Airway pressure is maintained above ambient during a machine-generated breath.
PF Peak Flow, Peak Inspiratory Flow
pH Electrode Electrochemical device sensitive to the concentration of H+ ions in solution.
Phase (of a breath) Various portions of the breathing cycle defined by the direction and sequence of flow; e.g., in the inspiratory phase, flow is either into the lungs or has stopped after the lungs have expanded; during the expiratory phase, flow is either out of the lungs or has stopped after the lungs have deflated.
PIP Peak Inspiratory Pressure - The maximum value achieved by the pressure in the patient circuit during a machine inspiration.
Plateau Pressure A pressure value that is maintained constant during a portion of the inspiratory phase of the breath.
Pneumatic System A system in which gas pressure differences and their rates of change are related to gas flows, their integrals and their rates of change.
Pneumotachometer A device that measures the flow of gas through it under local conditions of temperature and pressure.
Poisseuille's Law An expression of the linear relationship between the pressure gradient (difference) along a straight tube and the velocity of a viscous gas undergoing laminar flow through the tube.
Power The rate of change of energy or, equivalently, the rate of change of work; expressed in units of watts, BTU's or joules.
PPS (See Proportional Pressure Support).
PPV Positive Pressure Ventilation - Mechanical ventilation that applies a pressure above ambient to the airways to produce or assist inspiration.
Pressure Force per unit area; expressed in units such as cm H2O, pascals, kilopascals, or pounds per square inch (psi).
Pressure Augmentation A combination of pressure control and volume control to provide the fast flow response to patient demand of pressure control. along with the assured volume delivery of volume control. Also called VAPS (Volume-Assured Pressure Support).
Pressure Limited Ventilation A preset peak pressure is reached and maintained before the end of inspiration. When used in the volume control mode, the delivered volume is limited also since excess flow is vented to the atmosphere.
Pressure-Control Mode A mode of ventilator operation in which the ventilator attempts to deliver a preset pressure waveform during inspiration. Typically, sufficient flow is provided to achieve and maintain a set pressure in the patient circuit during the inspiratory phase of the breath.
Prioritized Alarms Alarms that have audible and visible signals that differ according to the severity of the conditions causing the alarm.
Proportional Pressure Support PPS™ Proportional Pressure Support PPS™ compensates for the additional workload due to pathological increased resistance and decreased compliance of the patient. Proportional Pressure Support PPS™ has its origins in Proportional Assist Ventilation PAV which was introduced by Prof. Magdy Younes in the early 90s. The principle is now used under license by Dräger (Source: Dräger Medizintechnik GmbH). The distinctive feature of this mode in comparison to other support modes is that positive pressure delivered at the airway is directly proportional to patient effort.
PSV Pressure Support Ventilation - A mode supplement that augments the patient's spontaneous inspiratory effort by providing flow sufficient to establish and maintain a preset pressure in the patient circuit throughout inspiration. Expiration begins when the required flow drops below a preset level. PSV may be applied to spontaneous breaths during ventilatory modes such SIMV.
Pulmonary Pertaining to the lungs.
Pulse Oximeter A device that measured the pulse rate of the heart and the oxygen saturation of the blood using differential reflectance colorimeter technology.
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