The practical nurse (PN) learns in report that a client has a prescription for continuous humidified oxygen at 4 L/minute via a nasal cannula. Upon entering the client's room, the PN observes that the oxygen flow rate is set at 1 L/minute, there is no water in the humidifier, and there are reddened areas on the client's ears under the cannula tubing. The client has a respiratory rate of 22 breaths/minute and has dry and cracked mucous membranes. Which action should the PN take first?