Adjustable Pressure Limiting Valve on:
[Wikipedia]
[Google]
[Amazon]
An adjustable pressure-limiting valve (commonly abbreviated to APL valve, and also referred to as an expiratory valve, relief valve or spill valve) is a type of
An adjustable pressure-limiting valve (commonly abbreviated to APL valve, and also referred to as an expiratory valve, relief valve or spill valve) is a type of flow control valve
A flow control valve regulates the flow or pressure of a fluid. Control valves normally respond to signals generated by independent devices such as flow meters or temperature gauges.
Operation
Control valves are normally fitted with actuators a ...
used in anaesthesiology
Anesthesiology, anaesthesiology, or anaesthesia is the medical specialty concerned with the total perioperative care of patients before, during and after surgery. It encompasses anesthesia, intensive care medicine, critical emergency medicine ...
as part of a breathing system. It allows excess fresh gas flow
Fresh gas flow refers to the mixture of medical gases and volatile anaesthetic agents which is produced by an anaesthetic machine. The flow rate and composition of the fresh gas flow is determined by the anaesthetist.
Typically the fresh gas flow ...
and exhaled gases to leave the system while preventing ambient air from entering.
Mechanism
Such valves were first described by the American dentist Jay Heidbrink, who used a thin disc that was held in place by a spring. The valve is adjustable and spring-loaded, allowing the opening pressure of the valve to be controlled by screwing the valve top which modifies thepressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
on the spring. A very light spring is used, so that at its minimum setting the valve can be opened by the patient's breathing alone using low pressures. In contemporary APL valves, three orifices or "ports" are present: one for intake of gas, one for return of gas to the patient, and an exhaust port for waste gas which can be connected to a scavenging system. Wednesday, April 22, 2020
References
{{Mechanical ventilation Anesthetic equipment History of medical and surgical specialties Mechanical ventilation Safety valves Valves