What is an endotracheal tube primarily used for?

An endotracheal tube is primarily used for helping a patient breathe by providing a clear airway and ensuring adequate ventilation. This tube is inserted into the trachea through the mouth or nose and allows for mechanical ventilation in cases where a patient is unable to breathe on their own or requires assistance due to respiratory distress, general anesthesia, or critical illness.

This intervention is crucial during surgeries and emergency situations, as it enables the delivery of oxygen directly into the lungs and helps to remove carbon dioxide, thereby maintaining effective gas exchange. The design of the endotracheal tube also allows for suctioning of secretions and the administration of medications such as surfactants in pediatrics.

The other options listed refer to procedures or devices that serve different purposes. While administering anesthesia can occur during intubation, it is not the primary function of the endotracheal tube itself. Draining fluid from the lungs falls under thoracostomy procedures or chest tubes, and measuring lung capacity is typically done with spirometry, which does not involve the endotracheal tube. Thus, the correct answer highlights the vital role of the tube in providing respiratory support.