How does elevated intra-abdominal pressure affect ventilation?

• A. Increases diaphragmatic movement and improves lung compliance.
• B. Decreases diaphragmatic movement and lung compliance; may worsen ventilation; consider positioning and abdominal decompression if needed.
• C. Has no effect on ventilation.
• D. Directly increases tidal volume.

Answer: (B)

Elevated intra-abdominal pressure hampers ventilation by pushing the diaphragm upward, which limits how far the diaphragm can move during breaths. This reduces chest wall and lung compliance, lowers functional residual capacity, and makes the lungs stiffer. With less ability for the lungs to expand for a given pressure, tidal volumes can drop and the work of breathing or the required ventilator pressures increase. In practice, this can worsen ventilation and oxygenation, especially if the abdomen remains distended or becomes more distended.

Because of this, the situation is managed by strategies that relieve diaphragmatic compression and abdominal distension. Positioning the patient to optimize diaphragmatic excursion (for example, moving to a position that reduces abdominal pressure on the diaphragm) and abdominal decompression (such as drainage to reduce distension or surgical decompression if necessary) are considered to improve ventilation.

This explains why the correct choice emphasizes decreased diaphragmatic movement and decreased lung compliance, with potential ventilation worsening and the need for positioning and decompression. The idea that ventilation would improve or that tidal volume would increase is not consistent with the effect of high intra-abdominal pressure.