Which factor specifically reduces functional residual capacity during pneumoperitoneum?

Which factor specifically reduces functional residual capacity during pneumoperitoneum?

• A. Increased intraabdominal pressure
• B. Decreased heart rate
• C. Increased hemoglobin
• D. Decreased body temperature

Answer: (A)

Functional residual capacity is the lung volume at the end of a passive exhale and depends on the balance between lung recoil and chest wall expansion. When the abdomen is insufflated during pneumoperitoneum, intra-abdominal pressure rises and pushes the diaphragm upward into the thoracic cavity. This diaphragmatic elevation reduces the vertical dimension of the chest, decreases thoracic volume, and especially diminishes the dependent lung volumes, leading to a lower end-expiratory volume. In short, increased intra-abdominal pressure directly compresses the lungs and reduces functional residual capacity, making it the factor that reduces FRC during pneumoperitoneum. The other choices don’t directly affect FRC in this context: heart rate changes don’t change the lung’s resting volume; higher hemoglobin alters oxygen transport but not lung volume; and body temperature variations don’t acutely alter FRC during pneumoperitoneum.

Functional residual capacity is the lung volume at the end of a passive exhale and depends on the balance between lung recoil and chest wall expansion. When the abdomen is insufflated during pneumoperitoneum, intra-abdominal pressure rises and pushes the diaphragm upward into the thoracic cavity. This diaphragmatic elevation reduces the vertical dimension of the chest, decreases thoracic volume, and especially diminishes the dependent lung volumes, leading to a lower end-expiratory volume. In short, increased intra-abdominal pressure directly compresses the lungs and reduces functional residual capacity, making it the factor that reduces FRC during pneumoperitoneum.

The other choices don’t directly affect FRC in this context: heart rate changes don’t change the lung’s resting volume; higher hemoglobin alters oxygen transport but not lung volume; and body temperature variations don’t acutely alter FRC during pneumoperitoneum.