Ventilatory muscle endurance training in normal subjects and patients with cystic fibrosis.

Ventilatory muscles can become fatigued, and this can contribute to respiratory failure. 
Patients with chronic obstructive lung disease may benefit from improving their 
ventilatory muscle endurance to improve resistance to fatigue. Ventilatory muscle endurance 
was measured in 30 normal subjects and 55 patients with cystic 
fibrosis by finding the highest level of normocapnic hyperpnea that could 
be sustained for 15 min. Subjects with cystic fibrosis had 36 
per cent higher ventilatory muscle endurance than normal subjects, reflecting the 
chronic training stress of breathing against increased respiratory loads. Four normal 
subjects and 4 subjects with cystic fibrosis participated in a specific 
ventilatory muscle endurance training program consisting of 25 min per day 
of maximal normocapnic hyperpnea 5 days per week for 4 weeks. 
The cystic fibrosis patients who trained improved their ventilatory muscle endurance 
by 51.6 per cent, whereas the normal subjects who trained showed 
a 22.1 per cent increase in ventilatory muscle endurance. Seven subjects 
with cystic fibrosis participated in a 4-week physical activity training program 
consisting of at least 1.5 hours per day of intensive swimming 
and canoeing at summer camp. They increased their ventilatory muscle endurance 
by 56.7 per cent. There were no other pulmonary function changes. 
Ventilatory muscle endurance can be readily improved in cystic fibrosis equally 
well by specific ventilatory muscle endurance exercise. 