Chapter 17

This chapter will address Practice Pattern 6C of the Guide to Physical Therapist Practice: Impaired Ventilation, Respiration/Gas Exchange and Aerobic Capacity/Endurance Associated with Airway Clearance Dysfunction. As you may recall from the oxygen transport pathway (see Chapter 5, Physiology of the Cardiovascular and Pulmonary Systems), the ability to exchange oxygen and carbon dioxide is dependent on an unobstructed path from the upper airways to the lungs. Normally, pulmonary secretions are easily removed from the airways by the mucociliary escalator, clearing the way for gas exchange to occur. When a dysfunction exists in the airway clearance mechanism, the inability to remove pulmonary secretions may result in decreased oxygen carried to the circulatory system, resulting in impaired muscle performance and aerobic endurance.

This chapter provides a review of the anatomy and physiology of the pulmonary system and describes the pathophysiology of cystic fibrosis (CF), an obstructive lung disease. The components of physical therapy (PT) management via Practice Pattern 6C will be illustrated, using a case study of a patient with CF. The management of airway clearance dysfunction is integral to this patient population and will demonstrate the effects of this dysfunction on impairments in physical function. Threshold levels or factors that affect ventilation, airway clearance, activity, and musculoskeletal function will be described and matched to appropriate interventions. The International Classification of Functioning, Disability and Health (ICF) will be used to demonstrate the body functions and structures evident in CF and their relation to activity and participation. Finally, though research efforts in this area are ongoing, there are limits to our knowledge about the disease of CF and the PT management that is currently used. Future directions for discovery in the realm of CF are discussed.

### Anatomy

The pulmonary system can be divided into two distinct categories: the musculoskeletal pump and a gas-exchanging organ.13 These components act in synchrony to achieve both ventilation and respiration. Whereas the pump is made up of the thorax and attaching muscles, gas exchange is carried out by the upper and lower divisions of the airways and associated components.

There are 23 generations or divisions of airways.2 The primary lobule or acinus consists of a transitional zone of bronchioles, alveolar ducts, and alveoli.2,4 Capillaries surround the alveoli for ease of gas exchange. The lungs are supplied with blood from the bronchial circulation (airways) and the pulmonary artery (alveoli).2,4 Gas exchange occurs by diffusion across the blood–gas barrier and follows the principles of Fick's law. Basically, the rate of gas transferred depends on the area of exchange, thickness of the area, and the partial pressure between the two sides.2 If the lung tissue was spread out over the ground, the total size of the area would be similar to that of a tennis court.2 The properties of the “gas” and tissue where the gas is being exchanged also ...

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