med 610 clinical respiratory diseases & critcare med

Mechanical Ventilation

Case 2

A 45 year-old. 6-foot tall man presented to the emergency room with a two day history of fever and cough productive of brown sputum. He was hemodynamically stable at the time with a blood pressure of 130/87. His chest x-ray showed a right middle lobe infiltrate and his room air ABG showed: pH 7.32, PCO2 32, PO2 78, HCO3- 18. He was started on antibiotics and admitted to the floor. Four hours later, the nurse calls because she is concerned that he is doing worse. On your arrival in the room, his blood pressure is 85/60, his pulse is120 and his oxygen saturation, which had been 97% on 2L oxygen by nasal cannula is now 78% on a non-rebreather mask. The patient is obviously laboring to breathe with use of accessory muscles and is less responsive than he was on admission. He is diaphoretic and cannot talk in full sentences. On lung exam, he has crackles throughout the bilateral lung fields. You obtain a chest x-ray which shows increasing bilateral, diffuse lung opacities. An ABG is done while he is on the non-rebreather mask and shows: pH 7.17, PCO2 45, PO2 58, HCO3- 14.

What should you do now? Is there a role for CPAP or bi-level positive airway pressure in managing his hypoxemia?


A decision is made to intubate the patient and initiate mechanical ventilation for worsening respiratory failure. The intubation proceeds without difficulty. The tube position is confirmed and the anesthesiologist leaves the room. The respiratory therapist has secured the breathing tube. She turns to you and asks what settings you would like to use for the ventilator?

What information do you need to provide to the respiratory therapist?


The respiratory therapist suggests you use the volume targeted assist Control (AC) mode of mechanical ventilation. How does this work? How does it differ from Synchronized Intermittent Mandatory Ventilation (SIMV) or Pressure Control (PC)?

Which mode is better for your patient?


Suppose you put the patient on a volume-targeted Assist Control mode of mechanical ventilation. How do you choose the tidal volume?


What respiratory rate should you choose for the patient?


What should the FIO2 and PEEP be set at?


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