A patient is receiving 100% oxygen in the emergency room. Which of the following parameters indicates the patient may require ventilatory assistance?
- VD/VT = 40%
- Static compliance = 45 cm H2O
- A-a gradient = 360 mm Hg
- 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.