Critical Care Medicine-Pulmonary Disorders>>>>>Respiratory Diagnostic Modalities and Monitoring
Question 4#

An 88-year-old woman with an acute GI bleed undergoes endoscopic evaluation and subsequently remains intubated in the ICU in anticipation of further intervention the following day. She is 5′6″ and has her ideal body weight of 60 kg throughout her life. Her arterial blood gas (ABG) shows:

She is hemodynamically stable, and her airway pressures are low.

Which of the following is the MOST appropriate next step in her management?

A. Increase FiO2
B. Increase tidal volume
C. Increase PEEP
D. Decrease FiO2

Correct Answer is B


Correct Answer: B

This patient has a minute ventilation of ∼4.5 L, which is inadequate, as the ABG indicates a respiratory acidosis. Since physiologic and anatomic dead space both increase with age, this is not entirely surprising. The patient has an additional issue—her oxygenation is adequate but suboptimal. A PaO2 of 68 on 50% FiO2 indicates a large A-a gradient. The patient’s relatively low Tv (5.3 mL/kg) should raise suspicion of atelectasis from hypoventilation. This could be combated with frequent recruitment maneuvers and increasing PEEP (answers C and D).

However, increasing the tidal volume would increase the minute ventilation and improve atelectasis and is a reasonable first step in management of this patient (answer B). For instance, increasing tidal volume to 400 mL (7 mL/kg ideal body weight) would still be well within the lung protective paradigm while increasing the patient’s minute ventilation by 25%.


  1. Determann RM, Royakkers A, Wolthuis EK, et al. Ventilation with lower tidal volumes as compared with conventional tidal volumes for patients without acute lung injury: a preventive randomized controlled trial. Crit Care. 2010;14(1):R1. doi:10.1186/cc8230.
  2. Wrigge H, Pelosi P. Tidal volume in patients with normal lungs during general anesthesia: lower the better? Anesthesiology. 2011;114(5):1011- 1013.