Which of the following is a type of spontaneous breathing option?

Continuous positive airway pressure (CPAP) is indeed classified as a spontaneous breathing option because it encourages spontaneous respiration by maintaining a constant level of pressure in the airways throughout the breathing cycle. This setup allows the patient to inhale and exhale naturally while preventing airway collapse, which is particularly beneficial for patients with obstructive sleep apnea or respiratory failure.

In a CPAP setup, the patient must initiate their breaths, and the machine provides a constant baseline pressure, ensuring that the airways remain open, thus facilitating the spontaneous breathing process. This characteristic distinguishes CPAP from other mechanical ventilation modes that may involve controlled or assisted breaths provided by the ventilator.

Other choices, while they're methods of ventilation, do not primarily facilitate spontaneous breathing. For example, inverse ratio ventilation and pressure control ventilation can involve ventilator-triggered breaths, and direct mechanical ventilation typically refers to controlled breaths delivered by the ventilator, which do not rely on the patient's spontaneous effort.