Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease impacting nerve cells in the brain and spinal cord, known as motor neurons. These motor neurons control voluntary muscle movement throughout the body, including muscles essential for breathing. The degeneration of these nerve cells leads to muscle weakness and atrophy, affecting the respiratory system. Respiratory involvement is a serious aspect of ALS progression, impacting an individual’s ability to breathe effectively.
How ALS Impacts Breathing
ALS primarily affects the motor neurons that transmit signals from the brain to muscles, including those responsible for respiration. The diaphragm, a large dome-shaped muscle beneath the lungs, serves as the primary muscle for inhalation. Intercostal muscles, located between the ribs, also assist in expanding the chest cavity during breathing. As motor neurons degenerate in ALS, the signals to these muscles weaken, leading to their weakening and wasting.
This weakening of the diaphragm and intercostal muscles impairs the body’s ability to draw air into the lungs and expel it effectively. The chest wall cannot expand fully, and the lungs cannot inflate to their normal capacity, resulting in reduced lung volumes, such as forced vital capacity (FVC). This restrictive pattern of breathing means less oxygen enters the bloodstream and less carbon dioxide is removed, leading to a buildup of carbon dioxide in the body over time. Respiratory function can decline, requiring increasing support as the disease advances.
Recognizing Respiratory Symptoms
Weakness in the respiratory muscles due to ALS can manifest through several signs. Individuals might experience shortness of breath, particularly during physical activity or when lying flat, a condition known as orthopnea. Lying down can make breathing more difficult because the diaphragm must work harder against gravity and abdominal contents.
A weak cough is another common symptom, occurring because the muscles needed for a forceful expulsion of air are compromised. This diminished cough effectiveness makes it challenging to clear mucus and secretions from the airways, increasing the risk of respiratory infections. Other indicators include frequent sighing or yawning, difficulty speaking loudly or projecting the voice, and changes in sleep patterns. Morning headaches and daytime fatigue can also signal insufficient breathing during sleep, as carbon dioxide levels rise overnight.
Managing Respiratory Challenges
Managing respiratory challenges in ALS involves various strategies to support breathing and maintain airway clearance. Non-invasive ventilation (NIV), such as BiPAP (Bilevel Positive Airway Pressure) machines, is a common intervention. These devices deliver pressurized air through a mask to help individuals take fuller breaths and exhale carbon dioxide more effectively, particularly during sleep. NIV can alleviate symptoms, improve quality of life, and extend survival.
Techniques and devices for managing secretions are also used. A mechanical cough assist device helps simulate a natural cough by delivering a large volume of air and then rapidly reversing airflow to pull secretions from the lungs. Portable suction machines can then remove excess mucus and saliva from the mouth and throat, especially when swallowing becomes impaired. Maintaining good oral hygiene and pulmonary hygiene helps prevent respiratory infections. Speech-language pathologists also play a role by assisting with swallowing difficulties, as impaired swallowing can indirectly affect respiratory health by increasing the risk of aspiration.