Critical Care Medicine-Pulmonary Disorders>>>>>Thromboembolic Disease and Hemoptysis
Question 5#

A 67-year-old female with a history of DVT/PE, hypertension, diabetes mellitus, and coronary artery disease undergoes a hemicolectomy with end ileostomy for colorectal carcinoma. On postoperative day 4, she aspirates following an episode of emesis. She is intubated and transferred to the ICU for further management. Ventilator settings are as follows:

Her HR is 105 bpm; BP is 127/64 mm Hg, saturation 85%. Her most recent ABG reveals:

Which of the following interventions is MOST likely to improve the oxygen delivery in this patient?

A. Change the mode of ventilation to pressure control
B. Decrease the I:E ratio
C. Transfuse 1 unit of PRBC
D. Start norepinephrine infusion

Correct Answer is C


Correct Answer: C

Increase in dead space ventilation contributes to the V/Q mismatch in patients with pulmonary embolism. Oxygen attached to hemoglobin contributes a great extent to the overall oxygen content in the arterial system. The other factors that contribute to the arterial oxygen content include the oxygen saturation and partial pressure of oxygen in the blood or the dissolved oxygen.

This is depicted by the equation, CaO2 = (1.34 × Hgb × SaO2 ) + (0.0031 × PaO2 ).

The role of the dissolved component of oxygen is negligible as it is multiplied by a factor of 0.0031. The saturation of oxygen has an upper limit of 100% which limits its ability to improve the content above a certain limit. Consequently, PRBC transfusion is most effective in increasing the oxygen content of arterial blood, especially in an anemic patient. Oxygen delivery is a product of oxygen content and cardiac output. Although inotropes could increase cardiac output, this patient has appropriate hemodynamics at this time which would not warrant inotropic support.


  1. Hess D, Kacmarek R. Blood gases. Chapter 28. Essential of Mechanical Ventilation. 4th ed. 2014.
  2. Lumb A. Oxygen. Nunn’s Applied Respiratory Physiology, Chapter 10. 8th ed. 2017:169-202, E3.