Ch. 12 Test, Improving Ventilation Flashcards
During mechanical ventilation of a patient with COPD, the PaCO2 = 58 mm Hg and the = 5.5 L/min. The desired PaCO2 for this patient is 45 mm Hg. To what should the be changed?
a. 4.3 L/min
b. 4.8 L/min
c. 6.6 L/min
d. 7.1 L/min
ANS: D
DIF: 2 REF: p. 224
A patient with CHF is being mechanically ventilated. The patient’s current PaCO2 = 28 mm Hg, and the ventilator set rate is 16/minute. The desired PaCO2 for this patient is 40 mm Hg. To what should the set rate be changed?
a. 7/min
b. 11/min
c. 14/min
d. 18/min
ANS: B
DIF: 2 REF: p. 225
A patient with pneumonia and underlying COPD is being mechanically ventilated in the VC-CMV mode with VT 650 mL. The resulting PaCO2 is 62 mm Hg. What change should be made to the VT to obtain a desired PaCO2 of 50 mm Hg for this patient?
a. 400 mL
b. 800 mL
c. 1000 mL
d. 1200 mL
ANS: B
DIF: 2 REF: p. 223
The average tidal volume range in an individual with no pulmonary problems is which of the following?
a. 4 to 5 mL/kg IBW
b. 5 to 8 mL/kg IBW
c. 8 to 10 mL/kg IBW
d. 12 to 15 mL/kg IBW
ANS: B
Recommended guidelines are to target the VT to 5 to 8 mL/kg ideal body weight (IBW) while ensuring that the plateau pressure (Pplateau) is maintained at less than 30 cm H2O.
DIF: 1 REF: p. 223
A male patient (76-kg IBW) with no history of pulmonary disease is brought to the emergency department for treatment of a drug overdose. He is intubated and placed on mechanical ventilation with VC-CMV, f = 12/min, VT = 450 mL. The resulting arterial blood gas values are: pH 7.32, PaCO2 53 mm Hg, and HCO3- 25 mEq/L. The most appropriate action to correct the acid-base disturbance is which of the following?
a. Increase VT to 595 mL
b. Increase VT to 760 mL
c. Increase frequency to 16/min
d. Decrease frequency to 10/min
ANS: A
The desired target for VT for this patient is 5 to 8 mL/kg IBW. Because the set VT of 450 mL is at 5.9 mL/kg, there is room to increase the VT. After calculating the desired VT using the formula, the new volume is at 7.8 mL/kg. A VT of 760 mL would be at 10 mL/kg IBW.
DIF: 3 REF: p. 225
A female patient (59-kg IBW) with no history of pulmonary disease is being invasively ventilated with VC-CMV, f = 12/min, VT = 470 mL, PEEP = 5 cm H2O, FIO2 = 0.5. ABG results with these settings are: pH 7.31, PaCO2 54 mm Hg, PaO2 92 mm Hg, SaO2 90%, HCO3- 24 mEq/L. The most appropriate action for the respiratory therapist to take is which of the following?
a. Increase f to 16/min
b. Increase VT to 635 mL
c. Decrease VT to 400 mL
d. Decrease PEEP to 3 cm H2O
ANS: A
The target VT for an individual without pulmonary disease is 5 to 8 mL/kg IBW. This patient’s VT range is 295 mL to 472 mL, meaning that the upper limit of this range has been reached. The f should be changed to increase this patient’s minute ventilation.
A 28-year-old female (55-kg IBW) is being mechanically ventilated with VC-CMV, f = 14/min, VT = 700 mL. The patient has no history of pulmonary disease. The resulting ABG values are: pH 7.55, PaCO2 27 mm Hg, HCO3- 23 mEq/L. The most appropriate action to take is which of the following?
a. Decrease VT to 600 mL
b. Decrease VT to 450 mL
c. Decrease f to 12/min
d. Decrease f to 10/min
ANS: B
The original volume setting exceeded the maximum VT for this patient. The VT should be set between 275 mL and 440 mL to achieve 5 to 8 mL/kg IBW. Therefore, the VT must be reduced to avoid overdistention.
Desired VT = 473 mL
The VT of 450 mL is closest to the desired VT and is more in line with the acceptable range.
DIF: 3 REF: p. 223
A male patient (83 kg IBW) is intubated and ventilated with PC-CMV, f = 12/min, set PIP = 28 cm H2O, resulting in a VT of 430 mL. The ABG results on this setting are: pH 7.35, PaCO2 45 mm Hg, and HCO3- 23 mEq/L. Forty-eight hours later on the same settings, the ABG results are: pH 7.54, PaCO2 27 mm Hg, and HCO3- 21 mEq/L with an exhaled VT of 800 mL. The most appropriate action at this time is which of the following?
a. Decrease PIP to 25 cm H2O
b. Decrease PIP to 19 cm H2O
c. Decrease f to 10/min
d. Decrease f to 8/min
ANS: B
At first the patient responded appropriately to the PC-CMV settings. At that point the Cs was 15 mL/cm H2O. After 48 hours, the patient’s lungs improved and the same pressure, 28 cm H2O, resulted in a VT of 800 mL. The patient’s Cs now is 28.5 mL/cm H2O, and the combination of Cs and PIP is resulting in respiratory alkalosis. The acceptable VT range for this patient is 415 to 664 mL (5 to 8 mL/kg IBW). Because the exhaled tidal volume now exceeds this range, the volume needs to be reduced. This is accomplished by reducing the set PIP using the following formulas:
DIF: 3 REF: p. 223, 225
A patient with an IBW of 68 kg is intubated and being mechanically ventilated with VC-CMV, f = 12/min, and VT = 470 mL. The patient has a combined respiratory rate of 25/min. The ABG results are: pH 7.56, PaCO2 26 mm Hg, and HCO3- 22 mEq/L. The most appropriate action is to do which of the following?
a. Decrease the set f to 8/min
b. Decrease the set VT to 300 mL
c. Sedate and paralyze the patient
d. Change the mode to VC-IMV
ANS: D
The patient has ventilator-induced respiratory alkalosis, because the patient is triggering the machine breaths each time there is a spontaneous effort. Decreasing the set f will not alter the rate at which the patient is assisting. Decreasing the set VT to 300 mL will most likely result in the patient breathing at a faster rate because of the low volume. The patient could be sedated and paralyzed. However, the patient is not demonstrating a need for this option (i.e., extreme agitation, increased WOB, and patient-ventilator asynchrony). Changing to the VC-SIMV mode will allow the patient to breathe spontaneously and not trigger a machine breath each time.
DIF: 3 REF: p. 226
Metabolic acidosis may be caused by which of the following?
a. Overdose with salicylate
b. Diuretic administration
c. Nasogastric suctioning
d. Lactate administration
ANS: A
Ingestion of salicylate causes the production of acid, resulting in metabolic acidosis.
DIF: 1 REF: p. 226
Metabolic alkalosis can be caused by which of the following?
a. Renal failure
b. Potassium deficiency
c. Carbonic anhydrase inhibitors
d. Ethylene glycol
ANS: B
Potassium deficiency causes acid to shift into the cells, reducing the amount of acid in the blood.
DIF: 1 REF: p. 226
If respiratory acidosis persists after alveolar ventilation of a patient has been increased, which of the following could be the cause?
a. Chronic obstructive pulmonary disease
b. Pulmonary embolism
c. Pulmonary edema
d. Low PEEP levels
ANS: B
If pure respiratory acidosis persists even after alveolar ventilation has been increased, the patient may have a problem with increased dead space. One cause of increased dead space is a pulmonary embolism or low cardiac output, resulting in low pulmonary perfusion.
DIF: 1 REF: p. 228
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
ANS: B
If an increase in alveolar ventilation does not correct a respiratory acidosis, the condition usually is caused by pulmonary embolism, low pulmonary perfusion, or increased dead space. The reduction 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.
DIF: 2 REF: p. 228
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?
- Increased
- Decreased
- Increased VD/VT
- Decreased VD/VT
a. 1 and 3 only
b. 1 and 4 only
c. 2 and 3 only
d. 2 and 4 only
ANS: A
Sepsis increases the metabolic rate and . However, given the level, the PaCO2 should be lower. The reason it is not lower is the increased and VD/VT.
DIF: 1 REF: p. 228
In which of the following situations should iatrogenic hyperventilation be considered?
a. Severe traumatic brain injury
b. Initial treatment for increased intracranial pressure
c. Acute head injuries with increased intracranial pressure
d. Acute neurological deterioration with increased intracranial pressure
ANS: D
Hyperventilation may be needed for brief periods when acute neurological deterioration is present and the ICP is elevated. Current therapeutic guidelines for head injuries with increased ICP do not recommend prophylactic hyperventilation (PaCO2
