Final answer:
Increasing the frequency of suctioning to clear secretions in the endotracheal tube is the most direct intervention to treat thick mucus obstructing a patient's airway on mechanical ventilation.
Step-by-step explanation:
When a nurse observes thick, white secretions in the endotracheal tube (ET) of a patient who is receiving mechanical ventilation, the most direct intervention is to increase suctioning frequency to every hour. This action will help to clear the secretions and ensure that the airway remains open to support proper breathing.
Accumulation of thick mucus can occur when CFTR channels are absent, leading to inadequate chloride ion transport and the lack of a water concentration gradient. Without osmotic pressure pulling water into the mucus, it can become thick and sticky, hindering removal by ciliated epithelia and potentially leading to blocked airways and bacterial infections.
Other relevant interventions may also be necessary for overall patient care but would not directly address the issue of secretions in the ET tube.