Asthma.

'Asthma' is derived from the Greek root ασθμαινω, meaning 'gasp for breath'. The term originally did not define a disease, but was employed to describe respiratory symptoms of a variety of pulmonary conditions. Over the centuries, several models have been proposed to understand the pathophysiologic abnormalities of asthma. By the beginning of the 20th century, asthma was seen to be a unique illness characterized by 'spasmodic afflictions of the bronchial tubes'. Consistent with the nature of asthma as a complex disease, the models for asthma pathogenesis have become increasingly complex. Research has moved from antiquated ideas to a descriptive functional approach to one that relies on pathophysiology in cellular and molecular biology, immunology, microbiology and genetics/genomics. As more advanced technologies for measuring lung function were developed, the features of asthma were steadily unraveled and its pathophysiology clarified. Asthma was shown to be associated with transient increases in airway resistance, reductions in forced expiratory volumes and flows, hyperinflation of the lungs and increased work of breathing, as well as abnormalities in the distribution of ventilation, perfusion and arterial blood gases. Today, asthma is seen as a chronic inflammatory disease which is not yet fully understood in its pathophysiology; therefore, therapy is still on the path to becoming optimal.