Complex sentence: This can cause drowning, by filling the lungs with fluid, if there has been enough material in the stomach, or, with less material, can cause stomach acids to damage the lungs and create a condition known as "aspiration pneumonia".
Split into simpler sentences: This can cause drowning, by filling the lungs with fluid, if there has been enough material in the stomach. With lesser material, gastric distention can cause stomach acids to damage the lungs and create a condition known as "aspiration pneumonia".