Coughing is a familiar, yet complex reflex action that functions to clear material from the airway. It protects the airway from irritants, saliva, or foreign particles that may have been inhaled (aspirated), and secretions, cellular debris, and microbes generated by the lungs or bronchial tree. Coughing can be involuntary; a reaction to inhaling a foreign particle or wayward food particle, or voluntary, intentionally taking a deep breath to clear mucus from the throat.
Maintaining a clear airway is important, and coughing is a primary means to that end. Because ALS is a disease resulting in decreased muscle strength and paralysis, a person’s ability to voluntarily or involuntarily cough is affected. Muscles that assist the diaphragm in providing adequate ventilation include the diaphragm, the primary muscle of ventilation; the muscles between the ribs, and the muscles between the sternum and head. In addition, the muscles of the mouth and throat (bulbar) which are responsible for speech and swallowing may be affected; resulting in the inability to open, close or protect the glottis, which is the opening between the vocal cords).
Coughing consists of three phases:
- an inhalation,
- a forced exhalation against a closed glottis and
- a violent release of air from the lungs following the opening of the glottis, usually accompanied by a distinctive sound.
Each of these phases of a cough requires the use of specific muscles:
- the diaphragm and muscles between the ribs are often used to inhale a big breath
- the throat muscles close the glottis while the diaphragm and chest muscles exert increased pressure
- upon opening of the glottis, the force of the air being expelled carries particles and secretions upward.
Coughing is a reaction to protect food, fluids, secretions, or particles from entering the windpipe, or allow items to “go down the wrong tube”. Coughing also assists in clearing secretions from the lower airway, preventing the pooling of secretions in the air sacs (alveoli) which may interfere with adequate exchange of oxygen and carbon dioxide between the lungs and blood. Deep breathing and coughing help maintain adequate ventilation. Maintaining a clear airway decreases the risk of pneumonia.
Persons living with ALS often have difficulty generating a strong cough due to inability to take a deep breath and weak exhalation and swallowing muscles. Lack of physical mobility or decreased fluid intake can result in shallow breathing and thickened secretions, increasing the efforts needed to adequately clear the airway.
Several techniques can help to increase deep breathing and forceful coughing. Breath stacking is an exercise whereby a person takes a series of small breaths without exhaling until the lungs are full, holds the breath briefly, then expels the air with a cough.
Mechanical Hyperinflation is similar to breath stacking however incorporates the use of a self-inflating resuscitator bag and mask or mouthpiece to provide deep breaths. A caregiver can assist with this procedure.
Automatic Mechanical cough assist devices such as the Philips CoughAssist™ or Hill-Rom Vital Cough™ helps those with an ineffective cough by breathing through a mouthpiece or mask, the device gradually applies positive pressure to insure a deep breath, then shifts to negative pressure to assist with pulling secretions upward, simulating a deep natural cough.
Appropriate sleeping and seating positioning, diet and safe swallowing techniques all assist in decreasing the work of breathing and maintaining a clear airway. Medications and therapeutic procedures can decrease oral or bronchial secretions, and respiratory support devices can assist in maintaining adequate lung volumes. Consult your physician or respiratory therapist for additional information related to decreasing your work of breathing, maintaining a clear airway and incorporating breathing exercises or cough therapy into your daily regimen.
The ALS Association thanks and acknowledges Cynthia Knoche, RRT for sharing her time and expertise on this factsheet.