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Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently, if there is any leak from the positively pressured system, it will egress into the surrounding environment. This is in contrast to a negative pressure room, where air is sucked in. [1] [2]
This article uses the physics sign convention for work, where positive work is work done by the system. Using this convention, by the first law of thermodynamics, The yellow area represents the work done = + where W is work, U is internal energy, and Q is heat. [1] Pressure-volume work by the closed system is defined as:
Positive airway pressure (PAP) is a mode of respiratory ventilation used in the treatment of sleep apnea.PAP ventilation is also commonly used for those who are critically ill in hospital with respiratory failure, in newborn infants (), and for the prevention and treatment of atelectasis in patients with difficulty taking deep breaths.
The application of positive pressure may be intended to prevent upper airway collapse, as occurs in obstructive sleep apnea, or to reduce the work of breathing in conditions such as acute decompensated heart failure. CPAP therapy is highly effective for managing obstructive sleep apnea.
The volume of the system is classified as a "deformation variable", and is properly measured externally to the system, in the surroundings. Pressure–volume work can have either positive or negative sign. Pressure–volume work, performed slowly enough, can be made to approach the fictive reversible quasi-static ideal.
Bubble CPAP is a non-invasive ventilation strategy for newborns with infant respiratory distress syndrome (IRDS). It is one of the methods by which continuous positive airway pressure (CPAP) is delivered to a spontaneously breathing newborn to maintain lung volumes during expiration.
A second function of the PCV valve is to act as a flame arrester and to prevent positive pressure from the intake system from entering the crankcase. This can happen on turbocharged engines or when a backfire takes place, and the positive pressure could damage the crankcase seals and gaskets, or even cause a crankcase explosion. The PCV valve ...
The process does no pressure-volume work, since such work is defined by =, where P is pressure. The sign convention is such that positive work is performed by the system on the environment. If the process is not quasi-static, the work can perhaps be done in a volume constant thermodynamic process. [1]