Which statement best describes the pulmonary response to CO2 pneumoperitoneum?

Which statement best describes the pulmonary response to CO2 pneumoperitoneum?

• A. Decreased tidal volume
• B. Increased functional residual capacity
• C. Decreased respiratory rate
• D. Increased minute ventilation to eliminate absorbed CO2

Answer: (D)

CO2 from the pneumoperitoneum is absorbed into the bloodstream, raising PaCO2 and stimulating the body's ventilatory drive. The lungs respond by increasing alveolar ventilation to blow off the excess CO2. This results in a higher minute ventilation, which is achieved by increasing tidal volume and/or respiratory rate. That is why the statement describing an increase in minute ventilation to eliminate absorbed CO2 is the best choice. In more detail, minute ventilation equals tidal volume times respiratory rate, and hypercapnia from CO2 absorption prompts the respiratory centers to boost ventilation. Under anesthesia this is often achieved by increasing tidal volume and/or rate on the ventilator to maintain normocapnia. Why the other options don’t fit: lowering tidal volume would hamper CO2 clearance, whereas the typical response is to increase ventilation. Functional residual capacity tends to decrease rather than increase with CO2 pneumoperitoneum due to diaphragmatic elevation and decreased chest wall compliance. Respiratory rate generally rises in response to hypercapnia, not falls.

CO2 from the pneumoperitoneum is absorbed into the bloodstream, raising PaCO2 and stimulating the body's ventilatory drive. The lungs respond by increasing alveolar ventilation to blow off the excess CO2. This results in a higher minute ventilation, which is achieved by increasing tidal volume and/or respiratory rate. That is why the statement describing an increase in minute ventilation to eliminate absorbed CO2 is the best choice.

In more detail, minute ventilation equals tidal volume times respiratory rate, and hypercapnia from CO2 absorption prompts the respiratory centers to boost ventilation. Under anesthesia this is often achieved by increasing tidal volume and/or rate on the ventilator to maintain normocapnia.

Why the other options don’t fit: lowering tidal volume would hamper CO2 clearance, whereas the typical response is to increase ventilation. Functional residual capacity tends to decrease rather than increase with CO2 pneumoperitoneum due to diaphragmatic elevation and decreased chest wall compliance. Respiratory rate generally rises in response to hypercapnia, not falls.