Final answer:
An increase in Paco2 from 48 to 55 mm Hg in a patient with severe chronic lung disease would suggest rapid decompensation.
Step-by-step explanation:
A patient with severe chronic lung disease who develops rapid decompensation may show certain signs and symptoms. In this scenario, the finding that would suggest rapid decompensation is a Paco2 increase from 48 to 55 mm Hg. Paco2 represents the partial pressure of carbon dioxide in the blood. An increase in Paco2 indicates an accumulation of carbon dioxide, which can be a sign of worsening respiratory distress in a patient with chronic lung disease.