What is it, the common treatments, effects on the exercise response, effects of exercise and exercise recommendations.
Cystic fibrosis (CF) is a disorder of the cystic fibrosis transmembrane conductance regulator (CFTCR) gene, which is a gene that provides instructions to make the CFTCR protein. Impaired function to this protein can result in secretion of thickened mucus in the lungs and digestive tract, causing damage. This thickened mucus instigates chronic inflammation, infection, and finally, tissue destruction in the airways of the lungs, ultimately resulting in a deterioration in lung function.
An irregular function of the CFTCR protein can also affect pancreatic digestive enzymes and damage to islets of Langerhans (pancreatic cells that secreting insulin and glucagon). This can result in insulin deficiency and the development of diabetes. The diminished secretion of pancreatic digestive enzymes can result in impaired absorption of fats and protein, and thus, result in protein-calorie malnutrition.
Common management practices involve improving poor nutritional status, with particular attention to reducing fat mass; supplementing with pancreatic enzyme supplements to aid with digestion of dietary fats and proteins; improving physical fitness; mucus removal techniques to clear the airways, and antibiotic therapy to treat pulmonary infection and inflammation. Insulin therapy is also necessary for those who have developed CF-related diabetes. Supplemental oxygen may also be necessary, particularly during exertion or physical activity.
The main effects CF has on the exercise response include impairment to ventilation and central blood flow circulation, decreases in muscle mass (due to nutritional deficiencies), and decline in aerobic capacity after childhood. CF may also lead to the development of hyperinflation (decrease in lung tissue elasticity), which may increase the risk of lung injury and, due to mechanical disadvantages, increase the energy and oxygen costs of breathing. In addition, chronic mucus secretion may cause progressive airflow obstruction, which may compromise oxyhemoglobin saturation levels (SpO2, the blood’s capacity to carry oxygen) and increase carbon dioxide retention during exercise.
Although research into this area is severely limited, according to the American College of Sports and Medicine (ACSM, 2016), the best available evidence to date suggests that aerobic exercise can improve:
- Exercise capacity
- Pulmonary function
- Muscular endurance and strength
- Mucus clearance
- Bone mineral density
- Chest wall mobility
For adults with CF the Basic CDD4 Recommendations for exercise can be used (see link below):
However, these guidelines may not be adequate for children, teenagers or young adults. Instead, exercise must be fun – play – and not boring. Both exercise and habitual exercise should be individualised to the client’s needs and severity of disease (determined by spirometry or pulmonary function testing), with an overall goal to maintain physical function, vitality and a near normal function. For those that suffer from mild-moderate CF, exercise capacity is generally impaired due to non-pulmonary factors. Hence, exercise programs should aim to prevent lung function deterioration; and improve/maintain chest mobility and peripheral muscle strength, mass, and power. For those with severe disease, pulmonary factors limit exercise capacity, and hence, additional inspiratory muscle training (to improve ventilatory efficacy and work of breathing) and high-intensity interval training (to train muscles with low ventilatory burden) should be included.
Special considerations for people with CF include the use of oxygen supplementation and/or bronchodilator premedication before exercise (if needed), constant monitoring of SpO2 (for those with abnormally low concentration of oxygen in the blood), monitoring side effects of oral corticosteroid therapy (e.g. muscular pain, obesity, increased blood glucose and pressure), bone pain with severe diseases (e.g. hypertrophic pulmonary osteoarthropathy), and severely limited exercise capacity at end-stage lung disease. Other considerations include monitoring physical activity levels, muscle atrophy, and osteoporosis side effects from medication. Some contraindications to exercise for children include fever, scuba diving, SpO2 <90%, heart problems, and contact sports (for those with enlarged spleens or liver disease).