Although Meakins and Christie identified dyspnea as the main limiting factor for patients with chronic airflow limitation, defining this symptom as “the consciousness of the need for increased respiratory effort” and identifying its multifactorial origins, the main concept underlying limitation was until very recently that of the attainment of a ventilatory or gas exchange limit. This concept was formally put forward by Baldwin, Coumand and Richards in 1949, and elaborated during the next-50 years; patients were unable to exercise beyond the point at which ventilation reached the maximal voluntary ventilation (MW) or a fall in arterial POl impaired oxygen delivery to exercising muscle.
These authors put forward the concept of breathing reserve, the ratio of maximal exercise ventilation to MW, later elaborated into the ‘dyspnea index’ by Hugh-Jones and Lambert and into a method to predict exercise capacity in patients with chronic obstructive lung disease (COLD) by Armstrong et al.
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Figure 1) Ronald Christie (1902-1986)
Figure 2) Jonathan Meakins (1882-1859)