How does the PaO2/FiO2 ratio influence mobilization decisions in ARDS or hypoxemic patients?

• A. A better ratio (>150–200) supports mobilization; a markedly low ratio suggests caution or postponement.
• B. Ratio dictates intensity of exercise in all cases.
• C. Ratio is irrelevant to mobilization decisions.
• D. A higher ratio means immediate extubation.

Answer: (A)

PaO2/FiO2 measures how effectively the lungs transfer oxygen into the blood and is a practical gauge of oxygenation reserve during activity. In ARDS or hypoxemic patients, this ratio helps determine how safely you can mobilize someone, since exercise increases oxygen demand and the risk of desaturation.

A higher ratio, roughly above 150–200, indicates enough oxygenation to support mobilization with appropriate monitoring. It suggests you can proceed with cautious activity and progressive rehabilitation, provided ventilation settings, oxygen delivery, and hemodynamics are stable. If the ratio is markedly low, the patient is at greater risk for desaturation and cardiovascular stress during movement, so you’d be more cautious or postpone mobilization until oxygenation improves or is optimized (adjust FiO2, PEEP, ventilator support) and stability is ensured.

The ratio informs safety but doesn’t rigidly set exercise intensity in every case, and it doesn’t alone decide extubation—that requires broader readiness criteria.