RRT RRT Clinical Concepts 3 — Questions and Answers
Question 1: A patient with status asthmaticus is intubated. Dynamic hyperinflation is suspected. Which intervention directly addresses auto-PEEP?
- Increase inspiratory flow rate to allow longer expiratory time (Correct answer)
- Increase tidal volume
- Add extrinsic PEEP equal to auto-PEEP
- Administer IV bicarbonate
Correct answer: Increase inspiratory flow rate to allow longer expiratory time
Increasing inspiratory flow rate shortens inspiratory time, thereby lengthening expiratory time and reducing air trapping and auto-PEEP.
Question 2: Which condition is characterized by a diffusion defect rather than a V/Q mismatch as the primary mechanism of hypoxemia?
- Pneumonia
- Pulmonary embolism
- Pulmonary fibrosis (Correct answer)
- Atelectasis
Correct answer: Pulmonary fibrosis
Pulmonary fibrosis thickens the alveolar-capillary membrane, impairing oxygen diffusion across it.
Question 3: A COPD patient has chronic hypercapnia with pH 7.38, PaCO2 58 mmHg, HCO3 33 mEq/L. Administering high-flow oxygen may cause hypoventilation because:
- Oxygen is toxic to the respiratory center
- The hypoxic drive is abolished (Correct answer)
- Oxygen increases airway resistance
- Bicarbonate excretion is stimulated
Correct answer: The hypoxic drive is abolished
In some COPD patients chronically reliant on hypoxic drive, supplemental oxygen can blunt the stimulus to breathe, causing hypoventilation.
Question 4: Which hemodynamic finding is most consistent with cor pulmonale?
- Elevated pulmonary artery wedge pressure
- Elevated right ventricular pressure with normal PAWP (Correct answer)
- Decreased central venous pressure
- Decreased pulmonary vascular resistance
Correct answer: Elevated right ventricular pressure with normal PAWP
Cor pulmonale causes right heart strain from pulmonary hypertension, elevating RV pressure while the left heart and PAWP remain normal.
Question 5: A patient post-lobectomy develops subcutaneous emphysema and a persistent air leak from the chest tube. The most likely cause is:
- Pulmonary embolism
- Bronchopleural fistula (Correct answer)
- Pleural effusion
- Atelectasis
Correct answer: Bronchopleural fistula
A bronchopleural fistula is an abnormal communication between the bronchial tree and the pleural space, causing persistent air leak.
Question 6: Which parameter should be monitored to assess adequacy of alveolar ventilation in a mechanically ventilated patient?
- SpO2
- PaO2
- PaCO2 (Correct answer)
- P(A-a)O2 gradient
Correct answer: PaCO2
PaCO2 is the direct measure of alveolar ventilation; rising PaCO2 indicates hypoventilation.
Question 7: The Hering-Breuer reflex limits tidal volume by:
- Chemoreceptor stimulation from CO2
- Stretch receptor activation in the lung (Correct answer)
- Peripheral oxygen sensing
- Baroreceptor response to blood pressure
Correct answer: Stretch receptor activation in the lung
Pulmonary stretch receptors activated by lung inflation send signals via the vagus nerve to terminate inspiration, preventing overdistension.
RRT RRT Clinical Concepts 3
A patient with status asthmaticus is intubated.
Dynamic hyperinflation is suspected.
Which intervention directly addresses auto-PEEP?