Introduction

After heart failure, we pass to the other common causes of breathlessness and weakness, namely bronchial and lung conditions. There is a popular image of the tragic composer coughing his last in an impoverished attic. Although it is almost a cliché, there have been examples, with some raising the question of how composition occurred at all.

Respiratory disease affects either the airways to the lungs or the lungs themselves. The airways convey inspired air through the larynx (voicebox) to the trachea (windpipe) and thence to the bronchi and their smaller multiple divisions, the bronchioles. The action of the chest is to expand, thereby creating a negative pressure in the pleural cavity, which is the membranous sack surrounding a lung. That in turn causes the sponge-like lung to expand, sucking the fresh air in during inspiration. The basic lung mechanism is an exchange membrane, wherewith oxygen in the inspired air is transferred to the blood. Then, as the chest pressures reverse, the lung shrinks as we expire and exhale carbon dioxide.

There are several broad groups of lung disease: