RRT RRT Knowledge 3 — Questions and Answers
Question 1: A patient with cystic fibrosis is ordered high-frequency chest wall oscillation (HFCWO). The primary mechanism of mucus clearance with this therapy is:
- Increasing mucociliary transport by ciliary stimulation
- Creating oscillating airflow that alters mucus rheology and facilitates clearance (Correct answer)
- Generating negative intrathoracic pressure to mobilize secretions
- Delivering aerosolized DNase directly to airways
Correct answer: Creating oscillating airflow that alters mucus rheology and facilitates clearance
HFCWO generates rapid chest wall compressions that create oscillating airflow, thinning mucus and moving it toward central airways.
Question 2: Which hemodynamic parameter is MOST directly measured by a pulmonary artery catheter (Swan-Ganz)?
- Cardiac output via thermodilution (Correct answer)
- Systemic vascular resistance
- Ejection fraction
- Coronary perfusion pressure
Correct answer: Cardiac output via thermodilution
The pulmonary artery catheter directly measures cardiac output using thermodilution; SVR and other derived values are calculated.
Question 3: A patient on volume-controlled ventilation develops a sudden increase in peak airway pressure with unchanged plateau pressure. The MOST likely cause is:
- Decreased lung compliance
- Increased airway resistance (Correct answer)
- Tension pneumothorax
- Ventilator circuit disconnect
Correct answer: Increased airway resistance
A rise in peak pressure with an unchanged plateau pressure indicates increased airway resistance (e.g., bronchospasm, secretions, kinked tube) since plateau reflects compliance.
Question 4: The normal P50 for adult hemoglobin (the PaO2 at which Hgb is 50% saturated) is approximately:
- 17 mmHg
- 27 mmHg (Correct answer)
- 37 mmHg
- 47 mmHg
Correct answer: 27 mmHg
The normal P50 for adult hemoglobin is approximately 27 mmHg, representing the midpoint of the oxyhemoglobin dissociation curve.
Question 5: Which condition causes a LEFT shift of the oxyhemoglobin dissociation curve?
- Fever
- Hypercapnia
- Alkalosis (Correct answer)
- 2,3-DPG elevation
Correct answer: Alkalosis
Alkalosis decreases 2,3-DPG effect and increases hemoglobin's affinity for oxygen, shifting the curve left (Hgb holds O2 more tightly).
Question 6: In a patient receiving pressure-controlled ventilation (PCV), an increase in lung compliance will result in:
- Increased tidal volume at the same set pressure (Correct answer)
- Decreased tidal volume at the same set pressure
- No change in tidal volume
- Increased respiratory rate
Correct answer: Increased tidal volume at the same set pressure
In PCV, the driving pressure is fixed; improved compliance allows more volume delivery per breath, so tidal volume increases.
Question 7: A respiratory therapist is setting up a large-volume nebulizer (LVN) for oxygen delivery. To achieve an FiO2 of 0.40, the air-to-oxygen entrainment ratio should be set to approximately:
- 1:1
- 3:1 (Correct answer)
- 5:1
- 10:1
Correct answer: 3:1
A 3:1 air-to-oxygen entrainment ratio with a 100% oxygen source produces an approximate FiO2 of 0.40.
RRT RRT Knowledge 3
A patient with cystic fibrosis is ordered high-frequency chest wall oscillation (HFCWO).
The primary mechanism of mucus clearance with this therapy is: