The Cough Mechanism
The following series of actions occur when a patient coughs:
- Deep inspiration occurs.
- Glottis closes and vocal cords tighten.
- Abdominal muscles contract and diaphragm elevates, causing an increase in intrathoracic and intro abdominal pressures.
- Glottis opens.
- Explosive expiration of air occurs.
- A cough may be reflective or voluntary.
- In the normal individual, the cough pump is effective to the seventh generation of bronchi. (There are a total of 23 generations of bronchi in the tracheal bronchial tree.)
- Ciliated epithelial cells are present up to the terminal bronchiole and raise secretions from the smaller to the larger airways in normal individuals.
1. Decreased inspiratory capacity because of:
- Acute lung disease.
- Rib fracture.
- Trauma to the chest.
- Recent thoracic or abdominal surgery.
- High spinal cord injury.
- Anterior horn cell disease (Guillain–Barre syndrome).
Inability of the patient to forcibly expel air as the result of:
- Spinal cord injury above.
- Myopathic disease and weakness such as muscular dystrophy.
- Critical illness that causes excessive fatigue.
- Chest wall or abdominal incision.
- General anesthesia and intubations.
- COPD (chronic obstructive pulmonary disease) such as chronic bronchitis, which is associated with a decreased number of ciliated epithelial cells in the bronchi.
- Cystic fibrosis.
- Chronic bronchitis.
- Pulmonary infections such as pneumonia.
Because an effective cough is an integral aspect of airway clearance, a patient must be taught the significance of an effective cough, how to produce an efficient and controlled voluntary cough, and when to cough.
- Evaluate the patient’s voluntary or reflexive cough.
- Place the patient in a relaxed and comfortable position for deep breathing and coughing.
- Sitting or leaning forward is usually the best position for coughing.
- The patient’s neck should be slightly flexed to make coughing more comfortable.
- Teach the patient controlled diaphragmatic breathing, emphasizing deep inspiration.
- Demonstrate a sharp, deep, double cough.
- Demonstrate the proper muscle action of coughing (contraction of the abdominal).
- Have the patient place the hands on the abdomen and make three buffs with expiration to feel the contraction of the abdominal.
- Have the patient practice making a K sound to experience tightening the coval cords, closing the glottis, and contracting the abdominal.
- When the patient has put these actions together, instruct the patient to take a deep but relaxed inspiration, followed by a sharp double cough. The second cough during a single expiration is more productive.
- Use an abdominal binder or Glossopharynegal breathing in selected patients with inspiratory or abdominal muscle weakness to enhance the cough, if necessary.
- Precautions, Never allow the patient to suck air in by gasping, because it.
- Increases the work (energy expenditure) of breathing and the patient fatigues more easily.
- Tends to increase turbulence and resistance in the airways and may lead to increased bronchospasm (further construction of airways).
- May push mucus or a foreign object deep into air passages.