Mechanism and Pathophysiology of Cough

The pathophysiology of cough can be summarized as a stimulus to the Cough Center. This generates an abrupt contraction response. This contraction results in a sudden expulsion of air, which is known as a cough.

What is cough?

Coughing is a defense mechanism of the body. A reflex whose purpose is to preserve gas exchange by expelling any harmful agents from the airways. Coughing is a nonspecific sign of various respiratory pathologies.It can be provoked voluntarily or involuntarily.

Involuntary coughing is always considered abnormal. Since coughing does not play a role in the physiological cycle of normal breathing, its presence is regarded as a pathophysiological phenomenon. Therefore, its presence should always be investigated.

Pathophysiology of cough.

The regulation of the cough reflex is controlled by the Cough Center. This area is located near the Respiratory Center in the Medulla Oblongata. This cough center is stimulated by what are called cough zones.

The cough zones include the tracheal mucosa, vocal cords, interarytenoid region, bronchial mucosa, pleura, and outside the respiratory tract, the external auditory canal and even the uterus.

Afferent pathway of cough.

A stimulus activates the sensory receptors of the cough zones, which through the nerves. Trigeminal, Glossopharyngeal, Vagus, and the Superior Laryngeal nerve. send a signal to the Cough Center. It is important to mention that themain afferent nerve in the pathophysiology of cough is the Vagus Nerve..

Efferent pathway of cough.

The Cough Center generates a response to the stimulus from the cough-sensitive areas. This response is sent via the nerves. Inferior Laryngeal, Phrenic Nerve, and Spinal Nerves. resulting in the mechanism of cough.

Cough mechanism.

Cough is a defense mechanism and a clinical symptom. The mechanism of cough is related to the pathophysiology of cough. The cough mechanism is the defensive response carried out by the Cough Center. This response, whose main objective is to eliminate the invading agent or foreign body, involves a strong muscular contraction followed by a sudden expulsion of air.

Phases of cough.

The cough mechanism consists of a total of 3 phases: Inspiratory, Compressing, and Expulsive. Each of these phases serves a function that helps protect the body from the agent or stimulus causing the cough.

Inspiratory phase.In this phase, there is an intake of air into the lungs before the cough itself. At this point, the vocal cords open to allow the air to enter.

Compression phaseIn this phase, there is a contraction of the thoracoabdominal muscles by the spinal nerves. The glottis also contracts via the inferior laryngeal nerve. Both stimuli are responses from the Cough Center.

Expulsion phaseThis phase occurs just as the compression phase ends. The palate elevates to close the communication with the nasal cavities, and there is a sudden opening of the glottis. This is followed by a rapid expulsion of air, which is stimulated by a sudden contraction of the diaphragm, which is activated by the phrenic nerve.

The characteristic sound of the cough is due to the abrupt passage of air being expelled through the vocal cords.

Classification of cough.

Since cough is a clinical symptom present in multiple diseases, determining whether it is acute, subacute, or chronic allows for the segmentation of its possible causes. If combined with its specific characteristics according to the type of cough, a probable diagnosis of the cause can be obtained.

According to its duration, cough can be classified into 3 distinct variants:

• Acute: This lasts less than 3 weeks.
• Subacute: This lasts between 3 weeks and 8 weeks.
• Chronic: Also called persistent cough, this lasts more than 8 weeks.

It is important that in any patient over 10 years old with a cough lasting more than 15 days (respiratory symptomatic), tuberculosis is ruled out.

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