Dyspnoea is an awareness of breathlessness. It can be due to cardiac or respiratory causes. It is also a symptom during exercise in healthy people. Breathlessness may occur only on exercise or may be present at rest. The New York Heart Association has replaced by a very similar grading known as ‘cardiac status’
replaced by a very similar grading known as ‘cardiac status’. It is also clinically valuable to grade dyspnoea by the amount of physical exertion possible before breathlessness occurs, e.g. climbing 14 stairs or walking 200 yards on the flat. Left ventricular failure causes dyspnoea because of a rise in left atrial pressure and pulmonary capillary pressure leading to interstitial and alveolar oedema. This makes the lung stiff (less compliant) and this increases the amount of respiratory effort necessary to breathe. Usually a fast breathing rate (tachypnoea) is also present due to stimulation of the pulmonary stretch receptors.
This is a form of breathlessness that occurs when the patient lies flat. Orthopnoea occurs because lying flat results in the redistribution of blood, leading to an increased central and pulmonary blood volume. Recumbency also causes the abdominal contents to press up against the diaphragm. Both factors increase the difficulty of breathing. Patients usually cope with orthopnoea by
propping themselves up with pillows.