Improved Pulmonary Function and Exercise Tolerance With Inspiratory Muscle Conditioning in Children With Cystic Fibrosis
Elspeth H. Sawyer and Thomas L. Clanton: Chest 1993; 104:1490-97

This study documented the effect of inspiratory muscle conditioning in children with cystic fibrosis. Subjects, ages 7 to 14 years, were divided into two groups. The experimental group (n=10) trained at a high pressure load (>29 cmH20) and the control group (n=10) trained at a minimal pressure load (<15 cmH20), using a threshold loading device. Subjects trained 30 minutes a day for 10 weeks. Pulmonary function, inspiratory muscle strength, and exercise tolerance were measured at the beginning and end of the training period. Pulmonary function was measured by body plethysmography. Inspiratory muscle strength was determined by standard measures of maximal inspiratory pressure (PImax) against an occluded airway. Exercise tolerance was measured by the length of time subjects could walk on a treadmill. Findings indicated that the experimental group showed significant increases in inspiratory muscle strength, vital capacity, total lung capacity, and exercise tolerance in comparison to the control group.

Points of Interest: Respiratory dysfunction in patients with CF is associated with hyperinflation, increases in airway resistance, and elevated work of breathing.1 However, much of what is currently known about the effects of hyperinflation and increased work of breathing on the respiratory muscles has come from studies on adults with COPD;2 Less is known about patients with CF.
Considering the fact that many patients with CF appear to have a relatively high functional status of their respiratory muscles compared with normal individuals, is there any reason to believe that they would benefit from respiratory muscle training? Gaultier et al2 have suggested that the work of breathing is greatly elevated at rest in some patients with CF, approaching a level that would induce fatigue and/or failure of the respiratory pump. Furthermore, Asher et al3 demonstrated indirect evidence of fatigue in 8 of 11 patients at two thirds of maximum work capacity. Changes at this level could be consistent with impending respiratory muscle fatigue. It is possible that the apparently high functional status of the respiratory muscles in some patients with CF may be needed to overcome the elevated impedance of their respiratory system and that additional respiratory muscle training may be beneficial.
Because of the rapid progression of the disease over the second and third decades of life, improvement in inspiratory muscle capacity to normal or supernormal levels early in the time course of the disease may be potentially useful in attenuating the decline in functional status later in time.
It is also possible that the high-intensity training resulted in a reduction in the sensation of dyspnea. Recent studies suggest that improvements in maximum inspiratory pressures following IMT procedures result in a reduction in the sensation of the intensity of loading in response to artificially aplied resistive or elastic loads.4

Medical Comment: By simply attaching a manometer to the monitoring adaptor of the Breather, you can coach your patient to reach a chosen inspiratory pressure target. Once the patient recognizes the force that must be achieved to reach the pressure target, the manometer may be removed if desired. Note: See Patient Training Protocol for further instructions.

1. Doershuk, C., Boat, T. Cystic fibrosis. In: Behrman R.E., Vaughan V.C., eds. Nelson textbook of pediatrics. 13th ed. Philadelphia: WB Saunders Co, 1987; 926-35.
2. Sharp, J.T. The chest wall and respiratory muscles in airflow limitation. In: Roussos C, Macklem P, eds. The thorax. New York: Marcel Dekker Inc, 1985; 1155-1201.
3. Asher, M., Pardy, R. The effect of inspiratory muscle training in patients with cystic fibrosis. AM. Rev. Respir. Dis. 1982; 126:855-59.
4. Redline, S. Gittfruedm S. Effects of changes in inspiratory muscle strength on the sensation of respiratory force. J. Appl. Physiol. 1991; 70:240-45.