Why is a water bottle attached to the oxygen tubing for a mouth-breathing client receiving oxygen?

Using a water bottle attached to the oxygen tubing for a mouth-breathing client receiving oxygen serves the purpose of humidifying the oxygen that is bypassing the client's nose. When oxygen is delivered directly via tubing, particularly in higher concentrations, it can dry out the mucous membranes in the airways, leading to discomfort and potential complications like nasal irritation or bleeding.

Humidification helps to maintain moisture levels in the respiratory tract, making the delivery of oxygen more comfortable for the client, especially when they are breathing through their mouth, which does not provide the natural humidification typically offered by nasal breathing. This is particularly critical for patients who need extended oxygen therapy, as prolonged exposure to dry oxygen can cause significant discomfort and increase the risk of respiratory issues.

The other options do not address the immediate physiological needs of the client as effectively as humidification does. Preventing oxygen toxicity, while important in certain situations, is not directly related to the humidification process. Cost and comfort are relevant, but the primary function of the water bottle in this context is to provide necessary moisture to the airflow.