A 59-kg IBW female patient is being mechanically ventilated in ...

[BRWH]

A 59-kg IBW female patient is being mechanically ventilated in the CMV mode, f = 12/min, VT = 400 mL, PEEP = 5 cm H2O, FIO2 = 0.5. The ABG results on these settings show a respiratory acidosis and severe hypoxemia.
 
  The respiratory therapist increases the set VT and increases the PEEP to 12 cm H2O. The resulting ABGs show improved oxygenation, but the patient still has a respiratory acidosis. The respiratory acidosis may be due to which of the following?
  a. Tissue hypoxia
  b. Increased dead space
  c. Increased cardiac output
  d. Continued hypoventilation

Question 2

A patient diagnosed with sepsis who is being mechanically ventilated has a combined minute ventilation of 25 L/min with a PaCO2 of 38 mm Hg. The reason for these findings is most likely which of the following?
 
  1. Increased CO2
  2. Decreased CO2
  3. Increased VD/VT
  4. Decreased VD/VT
  a. 1 and 3 only
  b. 1 and 4 only
  c. 2 and 3 only
  d. 2 and 4 only

[AmberC1996]

Answer to Question 1

ANS: B
If an increase in alveolar ventilation does not correct a respiratory acidosis, the condition is usu-ally caused by pulmonary embolism, low pulmonary perfusion, or increased dead space. The re-duction in pulmonary blood flow caused by high alveolar pressures can increase dead space. In this patient's case, the increase in PEEP is most likely the reason for the continued respiratory acidosis.

Answer to Question 2

ANS: A
Metabolic rate and CO2 are elevated in patients who have fever, burns, multiple trauma, sepsis, hyperthyroidism, muscle tremors or seizures, agitation, and in those patients who have undergone multiple surgical procedures. Regardless of the cause, it is clear that E will be increased and WOB will be elevated. Increasing the ventilator rate will decrease the patient's WOB, but auto-PEEP may occur. If auto-PEEP is a factor, it may be beneficial to add enough pressure support (PS) for the spontaneous breaths to reduce WOB through the ET and circuit. Other options might include switching to PC-CMV and using sedation to reduce the patient's work.

[BRWH]

Excellent

[nguyenhoanhat]

Gracias!