A manometer is being used to monitor a continuous-flow mask CPAP device set at 10 cm H2O. What is the most likely cause if the pressure decreases to 2 cm H2O upon inhalation?

The scenario describes a manometer that is being used to monitor the CPAP pressure in a patient. When the CPAP device is functioning properly, it should maintain the set pressure of 10 cm H2O. If the pressure decreases significantly to 2 cm H2O during inhalation, it suggests a failure to maintain the necessary pressure, which is critical for effective continuous positive airway pressure therapy.

The most plausible cause of the pressure drop upon inhalation relates to the insufficiency of gas flow to the patient system. If the flow of gas is inadequate or there is an obstruction in the system, the CPAP device cannot compensate for the negative pressure created by the patient's inhalation, leading to a pronounced drop in recorded pressure. This drop signifies that the device is unable to provide adequate oxygenation or ventilation support during inhalation, which undermines the therapeutic effectiveness of the CPAP system.

Understanding why this is the correct answer involves considering how CPAP devices function. They work to maintain a constant airway pressure during both inhalation and exhalation. Proper gas flow is crucial; without it, the system cannot sustain the necessary pressure against the negative pressure created by the patient's effort to breathe in.