Which parameters primarily influence the PaO2 in patients receiving ventilatory support?

The primary parameters that influence the partial pressure of oxygen in arterial blood (PaO2) for patients receiving ventilatory support include the fraction of inspired oxygen (FIO2), mean airway pressure, and positive end-expiratory pressure (PEEP).

FIO2 determines the concentration of oxygen that the patient is breathing, meaning a higher FIO2 directly increases the amount of oxygen available for diffusion into the bloodstream, thus raising the PaO2.

Mean airway pressure relates to the overall pressure in the airways throughout the entire respiratory cycle, which influences the distribution of ventilation and perfusion in the lungs. Optimal mean airway pressure can facilitate better recruitment of collapsed or poorly ventilated alveoli, enhancing gas exchange and improving PaO2 levels.

PEEP helps to maintain alveolar inflation at the end of expiration, preventing atelectasis and ensuring that more surface area in the lungs is available for gas exchange. By keeping the alveoli open, PEEP improves oxygenation by allowing for a greater exchange of oxygen and carbon dioxide.

These parameters work synergistically to improve oxygen delivery to the patient, making them the primary influences on PaO2 during ventilatory support.