A client with acute bronchitis is admitted to the health care facility and is receiving supplemental oxygen via nasal cannula. When monitoring this client, the nurse suddenly hears a high-pitched whistling sound. What is the most likely cause of this sound?

a) The water level in the humidifier reservoir is too low.
b) The oxygen tubing is pinched.
c) The client has a nasal obstruction.
d) The oxygen concentration is above 44%.

Answer: b) The oxygen tubing is pinched.