EDAIC Respiratory and Thoracic Anesthesia 2 — Questions and Answers
Question 1: During one-lung ventilation (OLV), which mechanism is primarily responsible for hypoxic pulmonary vasoconstriction (HPV) in the non-ventilated lung?
- Increased alveolar CO2 tension
- Decreased alveolar O2 tension (Correct answer)
- Elevated pulmonary arterial pressure
- Activation of beta-2 adrenoreceptors
Correct answer: Decreased alveolar O2 tension
HPV is triggered by low alveolar PO2 in the non-ventilated lung, causing vasoconstriction that diverts blood toward the ventilated lung and reduces intrapulmonary shunt.
Question 2: A patient undergoing right pneumonectomy develops sudden hypotension and elevated CVP immediately after lung removal. The most likely cause is:
- Tension pneumothorax on the left side
- Acute right ventricular failure due to increased pulmonary vascular resistance (Correct answer)
- Hemorrhage from the bronchial stump
- Paradoxical air embolism through a patent foramen ovale
Correct answer: Acute right ventricular failure due to increased pulmonary vascular resistance
After pneumonectomy, the entire cardiac output passes through the remaining lung, dramatically increasing PVR and precipitating acute RV failure.
Question 3: Which inhalational agent has the LEAST inhibitory effect on hypoxic pulmonary vasoconstriction at clinically used concentrations?
- Isoflurane
- Sevoflurane
- Desflurane
- Nitrous oxide (Correct answer)
Correct answer: Nitrous oxide
Nitrous oxide has minimal direct effect on HPV compared to the volatile halogenated agents, though it is rarely used alone in thoracic surgery.
Question 4: The recommended tidal volume during one-lung ventilation to minimize ventilator-induced lung injury is:
- 10-12 mL/kg IBW
- 8-10 mL/kg IBW
- 5-6 mL/kg IBW (Correct answer)
- 3-4 mL/kg IBW
Correct answer: 5-6 mL/kg IBW
Current lung-protective OLV strategy uses tidal volumes of 5-6 mL/kg ideal body weight to prevent overdistension of the ventilated lung.
Question 5: When positioning a double-lumen tube (DLT) for left-sided surgery, which side should the bronchial lumen be inserted into?
- Left bronchus always (Correct answer)
- Right bronchus always
- Left bronchus for left-sided surgery
- Right bronchus for left-sided surgery
Correct answer: Left bronchus always
A left-sided DLT is preferred for most thoracic cases because the right upper lobe bronchus is easily blocked; for left pneumonectomy a right-sided DLT or bronchial blocker is used instead.
Question 6: Carbon dioxide retention during one-lung ventilation is best managed by:
- Increasing respiratory rate rather than tidal volume (Correct answer)
- Switching to volume-controlled ventilation exclusively
- Administering sodium bicarbonate
- Applying CPAP to the operative lung
Correct answer: Increasing respiratory rate rather than tidal volume
Increasing respiratory rate raises minute ventilation while keeping tidal volumes low, minimizing barotrauma and volutrauma during OLV.
Question 7: A 58-year-old male with FEV1 40% predicted requires right lower lobectomy. His predicted postoperative FEV1 is calculated to be 28% predicted. This finding suggests:
- Surgery is absolutely contraindicated
- The patient has a high risk and requires cardiopulmonary exercise testing (Correct answer)
- No additional workup is needed if DLCO is normal
- Intraoperative HFJV should be planned
Correct answer: The patient has a high risk and requires cardiopulmonary exercise testing
Predicted postoperative FEV1 <40% predicted places the patient in a high-risk category requiring further evaluation such as cardiopulmonary exercise testing to assess VO2max.
EDAIC Respiratory and Thoracic Anesthesia 2
During one-lung ventilation (OLV), which mechanism is primarily responsible for hypoxic pulmonary vasoconstriction (HPV) in the non-ventilated lung?