why does exterional dyspnea occur in conjestive heart failure?

IN CHF the heart is flabby and doesn't pump well. Fluids back up into the lungs and cause difficulty breathing. In severe episodes the patient can have a pink frothy foam at the mouth. The treatment is to get some of that fluid off the system and for emergency situations Lasix is the drug of choice.

EMT Paramedic

Dyspnea, or shortness of breath, resulting from

increased pressure, fluid, or both in the lungs, is a

common symptom of congestive heart failure. http://www.med.yale.edu/library/heartbk/14.pdf