The cough reflex is a defense mechanism essential to life…
Coughing is a common, somewhat perplexing complaint with a variety of causes. It’s a symptom — not a disease. Coughing can be a reaction to “cold air” or it can make the clinician suspicious of cancer. It can appear to be the only presenting symptom or in association with illnesses such as asthma and bronchitis.
This reflex acts as a gatekeeper preventing stomach contents, harmful irritants and foreign bodies from gaining access to the lungs. It also forcefully removes excessive mucus and unwanted substances from the lungs and breathing passages.
THE COUGH REFLEX
The purpose of the reflex is to prevent aspiration and keep the respiratory tract’s “runway” clear, free of foreign matter and excess mucus, so we can breathe normally.
The larynx, wind pipe (trachea) and bronchi of the lungs are so sensitive that any irritation to these areas initiates the cough reflex. This irritation sends a signal to the medullary brain center that starts a sequence of events.
First, the reflex begins with an inspiration of air. Second, the vocal folds of the larynx shut tightly to seal off the air within the lungs. Third, the abdominal muscles and expiratory muscles of respiration contract forcefully causing the pressure in the lungs to rise significantly. Fourth, the vocal folds are suddenly forced opened. The compressed air from the lungs travels upwards across the windpipe, through the larynx and out of the mouth with or without solid or liquid contents from these structures. The air is expelled at a velocity that exceeds the highest speed limits in the United States.
TRIGGERS
Various factors can affect the cough reflex. Some of the triggers are mechanical, such as foreign bodies or cancer. Certain spices can trigger a cough. Medications, (e.g. ACE inhibitors) can result in coughing. Others triggers might be infectious in nature or secondary to inhaling irritating gases such as cigarette smoke. Certain medical conditions can compromise the reflex and prevent it from doing its job well.
IMPAIRMENT OF THE COUGH REFLEX
Patients who have undergone surgery are particularly vulnerable to a diminished cough reflex. Both the type of surgery and the surgical anesthesia affect the cough reflex, as do narcotic medications given post operatively for pain.
After surgery, patients may experience pain when inhaling or upon coughing. These patients cough less and are subject to lung infections. But there are other conditions that can compromise the cough reflex. Disorders such as emphysema, COPD, cerebral palsy and myasthenia gravis are just a few examples that can hinder the cough reflex.
Coughing has been both a simple and challenging problem to diagnose and manage… However, the more precise the diagnosis, the more focused the treatment, the more likely a favorable outcome. The cough reflex is vital to our wellbeing. We can’t live long without it!