ABSTRACT
The authors review the literature concerning the possibilities of modifying the mechanical characteristics of the respiratory system with breathing retraining and other chest physiotherapy intervention. Breathing retraining techniques with prolonged and active expiration induce increased work of breathing and do not help diaphragmatic function. Only pursed lips breathing seems to produce some mechanical advantages. The seated and forward position with fixed arms may reduce dyspnea but this does not appear to be caused by a decrease in operating lung volumes. By contrast, the dorsal decubitus position may reduce hyperinflation, giving some mechanical advantage to the diaphragm but does not reduce dyspnea and is not a position spontaneously adopted by patients. General muscular training may reduce ventilatory demand, and by reducing respiratory frequency lead to a decrease in the end expiratory lung volume; therefore inducing improvement in exercise tolerance.
