What situation could cause a patient using home O2 therapy to feel no oxygen from the cannula?

The situation where a patient using home oxygen therapy feels no oxygen from the cannula can indeed be affected by the water level in the humidifier. If the water level is low, the humidifier may not function properly, leading to inadequate delivery of humidified oxygen. Humidification is important in oxygen therapy to prevent drying of the airway and potential discomfort for the patient. When the water level drops too low, the flow of oxygen might be impeded or the oxygen delivered may not adequately meet the patient's needs.

While a power interruption can affect the entire system, especially for electrically powered devices like a concentrator, it may not apply in all cases, particularly if the patient uses a portable tank or if the home setup still has some functioning backup. Connected tubing generally indicates a properly set up system, and an incorrect flow setting would still typically deliver some level of oxygen, albeit potentially insufficient for the patient’s needs. None of these options directly address the immediate issue of humidification and its role in effective oxygen delivery.