Lung Hyperinflation: A Complication of Breathing Disorders

Lungs function to bring fresh air in and remove waste gases from the body. Inhaled oxygen travels through the mouth or nose, down the windpipe, through the bronchial tubes, and into the lungs. From there, oxygen is transferred to the bloodstream, where it is carried throughout the body, supporting vital functions in the organs. The bloodstream is also responsible for carrying carbon dioxide (CO2) back to the lungs. CO2 is a waste product of oxygen use in the body. Incoming oxygen and outgoing CO2 are exchanged in the alveoli, tiny air sacs in the lungs. CO2 is expelled through exhalation. In healthy lung function, this exchange is kept in careful balance, allowing for comfortable and efficient breathing.

Lung hyperinflation or pulmonary hyperinflation occurs when air is, essentially, trapped in the lungs, resulting in overinflation and extension of the organ. The disorders that cause the symptom are characterized by inadequate exhalation; in other words, the body's inability to remove air from the lungs efficiently.

Hyperinflation of the lungs results in uncomfortable and frightening symptoms, including shortness of breath, tightness in the chest, and heavy, rapid, or shallow breathing. People with hyperinflated lungs describe an acute yet unsatisfied need to inhale and exhale, often referred to as "air hunger." Physical symptoms of hyperinflation may lead to emotional or psychological fear, anxiety, or panic. Respiratory distress can result, which intensifies the physical symptoms. Observable signs of chronic hyperinflation include changes in the walls of the chest, the shape of the diaphragm, and the muscle fibers in the lungs.

Breathing disorders that can cause lung hyperinflation result in physical and functional changes to the windpipe, bronchial tubes, and lungs. Airway tissue, muscle, and blood vessel damage is common, giving rise to impaired lung emptying. Permanent changes to the shape of the airway due to inflammation and swelling can also obstruct the flow of air. Factors that increase the risk of hyperinflation include chronic overproduction of mucus in people with cystic fibrosis and frequent asthmatic bronchoconstriction. Most commonly associated with the complication, however, is chronic obstructive pulmonary disease or COPD.

COPD is a group of breathing disorders that includes emphysema and chronic bronchitis. Cigarette smoking is the primary cause of COPD, though air pollution and infections also contribute to the disease. Lung hyperinflation is a common complication because, like other risk factors, COPD causes progressive damage to the airway.

Lung hyperinflation may be static or dynamic. In the former, lung volume permanently increases, and the lungs are chronically overinflated. The amount of time necessary to expel air from the lungs is also affected, and this interrupts the balance between inhalation and exhalation. Dynamic hyperinflation is transient and occurs as a result of increased ventilatory demand. Exercise, anxiety, or exacerbation of impaired breathing symptoms may temporarily interrupt the ability of the lungs to properly empty.

A complication in itself, chronic lung hyperinflation can also lead to other issues. The uncomfortable symptoms it causes can prompt an individual to avoid activity, resulting in an overall decline in physical condition. Impaired lung emptying and inadequate inhalation can also cause respiratory muscle fatigue and failure. Hyperinflation is also associated with stress to and dysfunction of the left ventricle of the heart and the subsequent development of cardiovascular disease.

Lung hyperinflation is diagnosed by measuring the lungs' functional residual capacity (FRC) and residual volume (RV). FRC is the volume of air remaining the lungs during normal expiration, and RV is the volume remaining following maximum exhalation. Lung hyperinflation is most accurately diagnosed using body plethysmography, though doctors generally measure FRC and RV with a spirometer, a device into which a person breathes. They may also use alternative respiratory function tests, but the results are not as reliable.

Lung hyperinflation may be treated using various methods, and doctors often address the patient's symptoms with a combination of treatments. Bronchodilators relax and widen the airways, allowing for more efficient respiration. Portable oxygen tanks and invasive ventilation are examples of breathing assistance. Pulmonary rehabilitation is a form of exercise training focused on conditioning the body and lungs to require less ventilation. Surgery is less common but may be necessary to reduce lung volume capacity.

Breath-hold divers sometimes practice intentional, temporary hyperinflation. The sport requires the athlete to dive beneath the water without the assistance of scuba diving equipment. Breath-hold divers have learned to hyperinflate their lungs through glossopharyngeal insufflation (GI), which involves gulping air into the lungs, increasing oxygen storage beyond that which can be achieved by breathing naturally. Studies suggest intentional hyperinflation is reversible and has no lasting consequences.