Выражение встречается в следующем контексте:
A device used in a respiratory or anaesthesia breathing circuit or system to maintain a degree of positive pressure in a patient's airway at the end of expiration. It is typically constructed of plastic/metal materials, and has a valve that is actuated by a spring to provide expiratory airway resistance, and an adjustable knob (usually not graduated) that is typically set between 0 and 20 cmH20 pressure, but may be fully closed (locked) when controlled/assisted ventilation is applied. It is normally used with anaesthetic breathing systems, pulmonary resuscitators, or ventilators. It is commonly known as a pop-off valve, relief valve, or spill valve. This is a reusable device.

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