Cough overview

# Overview
A cough is a sudden, often repetitive, spasmodic contraction of the thoracic cavity, resulting in a violent release of air from the lungs, and usually accompanied by a distinctive sound. A cough by itself is not a complete diagnosis but rather a symptom of an underlying condition, despite this, it accounts for one of the most common indications for visits to the general practitioners and family physicians with a good proportion of these cases resulting in a pulmonology referral.
Coughing is an action the body takes to get rid of substances that are irritating the air passages. The act of coughing can be triggered by a myriad of conditions physiologic and otherwise, A cough is mostly initiated to clear a buildup of phlegm within the trachea. Coughing can also be triggered by a bolus of food entering the trachea and other parts of the respiratory tree rather than the esophagus due to a failure of the epiglottis. During the management of cough the duration is an important tool utilized by the clinicians; and when presented with a history of frequent or chronic coughing the presence of an underlying disease should be suspected. In non-smoking patients with a normal chest X-ray, chronic cough in 93% of these patients' cohort can be attributed to  asthma, heartburn or post-nasal drip. Other causes of chronic cough include chronic bronchitis and medications such as ACE inhibitors. Coughing can happen voluntarily as well as involuntarily.
The uncleanness of most cases of cough with regard to etiology, duration, and other precipitating symptoms coupled with the lack of a universal guideline for quantifying cough results in variability during its assessment. Thus, a thorough evaluation should be done to isolate the etiology of the patient's cough when they present, and before initiating therapy for symptomatic relief.

# Classification
The accepted classification of cough is that of the ACCP(American college of chest physicians).Cough is classified into 3 types depending on its duration.
- Acute cough: last less than 3 weeks
- Sub-acute cough: last between 3 and 8 weeks.
- Chronic cough: last longer than 8 weeks.

# Pathophysiology
The act of coughing is a vital one that leads to the mucociliary clearance of excess secretions from the airway and other parts of the respiratory tree.Cough occurs via a complex neurophysiologic cough reflex arc.

# Causes
There are various causes of cough,the most common causes are:
- Allergic Rhinitis
- Asthma
- Bronchiectasis
- Gastroesophageal Reflux Disease (GERD)
- Post-nasal drip
Cough causes can also be classified according to the organ system, see the segment on cough causes for details.

# Differentiating Cough from other Diseases
Making a differential diagnosis when a patient presents with a cough can be challenging however when the clinician asks about the other associated symptoms such as fever, vomiting, night sweats, weight loss, sputum production, and quantity, smoking history, drug use and most importantly the duration of the cough, making a differential diagnosis becomes less challenging.See the segment on Cough differential diagnosis for an extensive overview of the various differential diagnosis of cough.

# Cough Risk Factors
Cough is a protective reflex, however, some factors can increase one's risk of having a cough.
- Allergies.
- Smoking.
- Air pollution due to aerosolized chemicals, dust, smoke, etc.
- Uncontrolled Bronchial asthma & other chronic diseases.

# Cough natural history, complications, and prognosis
The various complications associated with cough can be categorized according to systems involved also, Cough complications can also be acute or chronic. See the segment on Cough natural history, complications, and prognosis.

# Cough diagnostic study of choice
There is no single diagnostic study of choice for the diagnosis of cough.

# History & Symptoms
A detailed cough history should cover the following:
- Onset of symptoms.
- Dry vs Productive cough.If productive, sputum content, color, amount, etc.
- Duration.
- Exacerbating/relieving factors.
- Previous episodes.
- Frequency.
- Drug use eg:ACEIs

## Other associated cough symptoms includes
- Fever.
- Chills and Rigor.
- Weight loss.
- wheezing.
- Associated hemoptysis
- Post nasal dripping
- Allergy history
- Smoking history
- Environmental or Occupational exposure to air pollutants.

# Physical examination
Once an in-depth history is taken from the patient, a detailed physical examination consisting of inspection, palpation, percussion, and auscultation should be done when evaluating coughing patients.

# Cough laboratory findings
Some laboratory test used when evaluating cough are:
- Complete blood count
- CRP
- Nasopharyngeal swab
- Sputum analysis & culture

# Chest x ray
Chest X-rays are a go-to investigative tool used by most clinicians when evaluating cough. Despite the routine use of CXR when evaluating cough, the most common causes of cough in the general population such as Gerd, Asthma and Post nasal drip cannot readily be diagnosed by CXR.

# CT
The use of a high resolution CT may identify pulmonary parenchymal lesions/diseases that were not readily picked up by CXR in patients with chronic cough.

# MRI
The use of MRI in the diagnosis of cough is particularly useful when red flags are noted during the detailed medical history and physical examination of the patient.

# Other imaging studies
- Bronchoscopy.
- Sinus imaging.

# Treatment
Treatment of cough depends on its etiology. Cough treatment is mostly medical with the use of cough syrups, antibiotics, modifying lifestyle, etc. The use of surgery limited to few cases refractory to medical therapy. See the chapter on Cough medical therapy and Cough surgery for a detailed algorithm on cough treatment.

# Cough primary prevention
Avoiding smoking, areas with air pollution, and proper hand hygienic practices can prevent one from acquiring cough due to other causes.

# Cough secondary prevention
There are no established guidelines for the secondary prevention of cough.