Exercise-disordered breathing in chronic heart failure.

Patients with heart failure develop various ventilatory abnormalities, including reduced ventilatory reserves, increased ventilatory demands, and high work and cost of breathing. They tend to breathe with a rapid-shallow pattern, have low end-expiratory lung volumes, and may develop rhythmic oscillations in ventilation and tidal volume. These abnormalities likely contribute to exercise limitations and are associated with a worsening prognosis.