A patient is receiving 100% oxygen in the emergency room. Which of the following parameters indicates the patient may require ventilatory assistance?

  1. VD/VT = 40%
  2. Static compliance = 45 cm H2O
  3. A-a gradient = 360 mm Hg
  4. MIP = -30 cm H2O



An A-a gradient greater than 350 mm Hg on 100% oxygen indicates the patient may need ventilatory support to reduce their work of breathing and increase oxygenation. Therefore, the correct answer is 3. A-a gradient.