asthma vs dyspnea

asthma

noun
  • A long-term respiratory condition, in which the airways may unexpectedly and suddenly narrow, often in response to an allergen, cold air, exercise, or emotional stress. Symptoms include wheezing, shortness of breath, chest tightness, and coughing. 

dyspnea

noun
  • Difficult or labored respiration; shortness of breath. 

How often have the words asthma and dyspnea occurred in a corpus of books? (source: Google Ngram Viewer )