If a patient on a ventilator desaturates to 82% with all connections secure and suctioning ineffective, which change should be attempted first?

• A. Increase FiO2
• B. Increase PEEP
• C. Decrease tidal volume
• D. Increase respiratory rate

Answer: (A)

Raising the fraction of inspired oxygen is the quickest way to improve oxygenation when a ventilated patient desaturates. If the airway and circuits are secure and suctioning hasn’t helped, the problem is the amount of oxygen reaching the lungs. Increasing FiO2 directly raises the oxygen available for diffusion into the blood, which can rapidly lift the SpO2 from desaturated levels toward normal.

Other adjustments affect ventilation and CO2 removal more than oxygenation. Increasing tidal volume can alter pressures and risk lung injury if not careful, and increasing the respiratory rate mainly changes CO2 clearance rather than the immediate oxygen content. PEEP helps recruit collapsed alveoli and improve oxygenation, but it’s typically considered after confirming FiO2 isn’t at an adequate level or when there’s persistent hypoxemia despite adequate FiO2. So, the first step is to increase FiO2 to address the low oxygenation directly.