What do “secret behavior” and “secret management” mean?
ALS leads to reduced respiratory function (hypoventilation) due to weakness (paresis) or stiffness (spasticity) of the respiratory muscles. A well-known consequence of hypoventilation is reduced ventilation of the lung tissue and impaired gas exchange (the release of carbon dioxide and uptake of oxygen).
Another consequence of respiratory weakness is less well known but equally relevant: the accumulation of bronchial secretions. In a healthy bronchial system, a thin layer of secretions is constantly produced to moisten the inhaled air and remove inhaled dust. The bronchial secretions are transported from the fine branches of the bronchi toward the main bronchi and from there to the trachea and larynx. When the bronchial secretions reach that point, they are “diverted” unnoticed from the larynx into the esophagus and swallowed.
This transport process of bronchial secretions requires adequate ventilation of the lungs and specific pressure conditions (expiratory pressure). In ALS, not only inhalation but also exhalation—and thus the generation of the necessary expiratory pressure—is reduced. The consequence of impaired exhalation is reduced transport of bronchial secretions and their accumulation in the bronchial system, a condition known as “secretion retention.”
As secretions accumulate, the airways narrow, making breathing (which is already impaired) more difficult. If a bronchus becomes completely obstructed, airflow into the bronchial segment is interrupted, and the area of lung tissue beyond it is cut off from gas exchange (atelectasis). In addition to increased respiratory effort and reduced gas exchange, the accumulation of secretions is associated with an increased risk of infection. The secretions serve as a “breeding ground” for bacterial and viral pathogens. Secret retention is therefore associated with the risk of bronchitis (inflammation of the bronchi) or pneumonia (lung inflammation).
Due to its various adverse effects, the effective removal of bronchial secretions is one of the most important treatment goals in ALS. The set of measures aimed at preventing and removing excess bronchial secretions is referred to as “secretion management.”
The most important method for removing bronchial secretions is the “cough assistant” (mechanical insufflator-exsufflator, MIE). Using the cough assistant several times a day produces an “artificial cough” that helps clear bronchial secretions and counteracts the adverse effects of secretion retention (labored breathing, reduced ventilation, risk of infection).
In addition to the cough assist device, mask ventilation is another treatment that helps clear secretions. Ventilation therapy supports lung aeration and the clearance of bronchial secretions. Mask ventilation primarily facilitates inhalation (inspiration), whereas the cough assist device affects both components of breathing: inhalation (inspiration) and exhalation (expiration).
However, the limitation of the cough assist device is that its use is restricted to a few inhalation and exhalation cycles, whereas mask ventilation can be used for several hours. Therefore, combining both treatment methods—mask ventilation with daily use of the cough assist device—is the most effective “secretion management” strategy.