In a bubble humidifier, which condition would NOT cause the pop-off alarm to sound?

• A. Kinked connecting tubing
• B. Leak in the water reservoir
• C. Clogged nasal cannula
• D. Flowmeter set too high

Answer: (B)

In a bubble humidifier, the pop-off alarm is tied to protecting the airway from too much pressure in the breathing circuit. It sounds when the circuit pressure climbs to a relief threshold, venting gas to prevent barotrauma. So anything that creates higher resistance or pushes more flow through the circuit tends to raise pressure and trigger the pop-off—such as a kinked connecting tube, a clogged nasal cannula, or setting the flowmeter too high, all of which increase back pressure or overall flow in the line.

A leak in the water reservoir, on the other hand, doesn’t increase circuit pressure. It simply reduces the amount of water available for humidification and can affect humidity, but it doesn’t cause a pressure rise in the patient's circuit. Therefore it would not cause the pop-off alarm to sound.