What setting in HFOV affects the values for primary control of PaO2?

The correct choice relates to the mean airway pressure (Paw) because it plays a critical role in determining the oxygenation status of a patient being treated with high-frequency oscillatory ventilation (HFOV). Mean airway pressure is the average pressure in the airways during one complete respiratory cycle, and it directly influences the recruitment of collapsed alveoli, consequently impacting gas exchange and the partial pressure of oxygen in arterial blood (PaO2).

Increasing the mean airway pressure can improve oxygenation by expanding the lung volume, thus enhancing the surface area available for gas exchange. This can help increase the amount of oxygen that diffuses into the bloodstream and improve overall oxygenation. Additionally, Paw can also influence the shunting and V/Q (ventilation/perfusion) mismatch in the lungs, further affecting the levels of oxygen in the blood.

The other settings, while significant in their own contexts, do not primarily control PaO2 values in the same direct manner. For instance, amplitude mainly affects the tidal volume delivered to the patient, frequency influences the rate of oscillations but not directly the mean pressure, and tidal volume is more associated with carbon dioxide elimination than primary control of oxygen levels.