Question

A patient with severe COPD and baseline PaCO2 of 55 mmHg is intubated for hypercapnic respiratory failure.  Initial ventilator settings include AC mode, rate 20/min, tidal volume 500 ml, PEEP 5 cm H2O, FIO2 0.4.  An ABG after 30 minutes on these settings is as follows: pH 7.48, PaCO2 40 mmHg, PaO2 120 mmHg.  The patient is “riding” the vent with an observed respiratory rate of 20 /min.  Which of the following would you recommend for managing the patient’s ventilator?

a)

Maintain current ventilator settings

b)

Switch to high frequency oscillatory ventilation

c)

Decrease respiratory rate to 12/min

d)

Decrease tidal volume to 200 ml

Answer 1

A patient with severe COPD and baseline PaCO2 of 55 mmHg is intubated for hypercapnic respiratory failure.

Initial ventilator settings include AC mode, rate 20/min, tidal volume 500 ml, PEEP 5 cm H2O, FIO2 0.4. In this case, the RR is 20/min, the reason behind this hyperventilation is carbon dioxide washout. (The main aim is the compensation of hypercapnia)

An ABG after 30 minutes on these settings is as follows: pH 7.48, PaCO2 40 mmHg, PaO2 120 mmHg.

This ABG shows pH in the alkaline range, The CO2 wash out successful because PaCO2 is 40 mmHg, The reason for the excess alkaline condition may be body also producing HCO3(Bicarbonate ions) to compensate, so now, we don't need of hyperventilation and we can reduce the respiratory rate.

Answer - C. Decrease respiratory rate to 12/min