DETERMINING THE ROLE OF EXERCISE IN PATIENTS WITH CHRONIC PULMONARY-DISEASE

Chronic pulmonary diseases are common in the community and their patho physiology is complex. The principal symptoms are dyspnea and limited exercise capacity. Some, but not all, patients have true ventilatory l imitation where the maximal exercise ventilation (V-Emax) equals the m easured maximal ventilatory volume (MVV). Those with obstructive disea se have impeded expiration requiring an obligatory expiratory time for adequate lung emptying (i.e., a timing constraint). In these patients , increased breathing frequency during exercise tends to lead to hyper inflation and smaller tidal volumes, circumstances that predictably wo rsen breathing efficiency (i.e., result in high VD/VT). Those with res trictive disease characteristically have limited inspiratory capacity but unimpeded or even accelerated expiration (i.e. tidal volume constr aint). These patients characteristically exhibit rapid respiratory rat es (e.g., >50.min(-1)) at end exercise.