Respiratory and Thoracic Anesthesia Flashcards

During one-lung ventilation (OLV), which mechanism is primarily responsible for hypoxic pulmonary vasoconstriction (HPV) in the non-ventilated lung?

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.

A patient undergoing right pneumonectomy develops sudden hypotension and elevated CVP immediately after lung removal. The most likely cause is:

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.

Which inhalational agent has the LEAST inhibitory effect on hypoxic pulmonary vasoconstriction at clinically used concentrations?

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.

The recommended tidal volume during one-lung ventilation to minimize ventilator-induced lung injury is:

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.

When positioning a double-lumen tube (DLT) for left-sided surgery, which side should the bronchial lumen be inserted into?

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.

Carbon dioxide retention during one-lung ventilation is best managed by:

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.

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:

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.