Ventilator exhalation valve
This is the exhalation valve on disposable ventilator tubing, in use in a patient (my wife). It's presently on a PLV-100 model ventilator (the only model we've found that works for us, but the manufacturer has informed us that they're phasing it out. She has no other way to breath currently).
NEVERTHELESS... The small clear tubing pushes on a rubber diaphragm, sealing the large corrugated tube during breath delivery. To allow exhalation, the small white tubing is lowered in pressure and the air can rush out (of the patient).
The blue tubing is used by the ventilator to sense air pressure for other purposes: 1. In the right mode, a patient can trigger a breath with a settable pressure (usually negative), 2. A safety, maximum airway pressure limit which, when hit, triggers automatic release of all pressure and an alarm.
If the ventilator doesn't sense a settable minimum pressure, DURING BREATHS, for more than 15 seconds, it also alarms.