To or some years now, resistive inhalational loads have been used to evaluate the endurance capacity of the inspiratory musculature under exertion. The capacity to sustain the muscular exertion required to inhale depends on the force and duration of the inhalational muscle contraction, which is determined by the pressure-time ratio. It is known that healthy subjects and patients with COPD become fatigued with diaphragmatic pressure-time ratios over 0.15.This technique is also used as a rehabilitative measure for the respiratory muscle function, as well as in the evaluation of the effectiveness of certain drugs such as caffeine. In patients with COPD, it is observed that the maximum inspiratory pressures (MIPs) and the exertion capacity are diminished owing probably to pulmonary hyperinflation, to changes in the exchange of gases, and to concomitant nutritional deficiencies.
Nevertheless, the effects of application of resistive inhalational loads on the maximum inspiratory and expiratory pressures in such patients are not known.
The purpose of this study was to evaluate the possible variation of the maximum inspiratory and expiratory pressures after the application of inspiratory loads generating 65 percent of MIP in patients with stable COPD.