The upper respiratory tract consists of the oral cavity (mouth), the nasal cavity (the nose), the pharynx and the larynx. As well as providing smell and speech the upper respiratory tract ensures that the air entering the lower respiratory tract is warm, damp and clean. The lower respiratory tract includes the trachea, the right and left primary bronchi and the constituents of both lungs. The trachea (or windpipe) is a tubular vessel that carries air from the larynx down towards the lungs. The trachea is also lined with pseudostratified ciliated columnar epithelium so that any inhaled debris are trapped and propelled upwards towards the oesophagus and pharynx to be swallowed or expectorated. The trachea and the bronchi also contain irritant receptors, which stimulate coughs, forcing larger invading particles upwards. The bronchi are the main airways in the lungs, which branch off on either side of the windpipe (trachea). They lead to smaller and smaller airways inside the lungs, known as bronchioles. The walls of the bronchi produce mucus to trap dust and other particles that could otherwise cause irritation. The nasal cavity is also lined with a mucus membrane made
from pseudostratified ciliated columnar epithelium, which contains a network of capillaries and a plentiful supply of mucussecreting goblet cells.
Pathophysiology
Cells that line the airways in the lungs normally produce mucus as part of the body’s defence mechanism against bacteria, viruses and other foreign particles. The mucus traps these particles, and tiny hair‐like projections in the airways (called cilia) sweep the dirty mucus up and out of the lungs. Many of the bronchi develop chronic inflammation with swelling and excess mucus production. The inflammation causes a change in the lining cells of the airways to varying degrees. Many cells that line the airway lose the function of their cilia (hairlike appendages that are capable of beating rapidly), and eventually the ciliated cells are lost. Cilia perform the function of moving particles and fluid (usually mucus) over the lining surface in such structures as the trachea, bronchial tubes and nasal cavities, to keep these hollow structures clear of particles and fluids. These ciliated cells that help in clearance of secretions are often replaced by socalled goblet cells. This group of cells secretes mucus into the airway. The warm moist environment of the airway, along with the nutrients in the mucus, are an excellent medium for growing bacteria. The mucus often becomes infected and discoloured from the bacterial overgrowth and the body’s inflammatory response to it. The inflammation, swelling and mucus frequently and significantly inhibit the airflow to and from the lung alveoli by The muscles that surround some of the airways can be stimulated by this airway irritation. This muscular spasm, also known as bronchospasm, can result in further airway narrowing.
In chronic bronchitis, more mucus than normal is constantly produced. This causes a build‐up of excess mucus that the cilia are unable to clear from the lungs. Exacerbating this is the fact that the cilia become dysfunctional and are less efficient at expelling mucus from the lungs. The build‐up of mucus narrows the airways and provides havens for bacteria to thrive, leading to more frequent
and serious lung infections, and even more mucus production. In chronic bronchitis there is a long‐lasting cough and mucus production. The airways in the lungs become swollen and produce more mucus.
Signs and symptoms
Cough and sputum production are the most common symptoms; they usually last for at least three months and occur daily. The intensity of coughing and the amount and frequency of sputum production varies from patient to patient. Sputum may be clear, yellowish, greenish or, occasionally, blood‐tinged. Since cigarette smoke is the most common cause of chronic bronchitis, it should not be surprising that the most common presentation is so‐called smoker’s cough. This is characterized by a cough that tends to be worse on getting up and is often productive of discoloured mucus in the early part of the day. As the day progresses, less mucus is produced. The person may also present with wheezing, and dyspnoea often occurs.
Management
The key point with regards to the management is to avoid the triggers that cause chronic bronchitis. For patients with an acute exacerbation of chronic bronchitis, therapy with short‐acting agonists or anticholinergic bronchodilators should be administered during the acute exacerbation. In addition, a short course of systemic corticosteroid therapy may be given and has been proven to be effective. Smoking causes bronchoconstriction and paralyses the cilia, the tiny, protective hairs that line the airways. Because cilia are important in removing irritating substances and particles from the lungs, damage to them results in difficulty or an inability to remove secretions. Smokers are also more susceptible to lung infections, which are a common problem for people with chronic bronchitis. Unless contraindicated, patients should be advised to have flu vaccines yearly. Patients with CB are prone to chest infection and thus when they have flu they are at risk of developing a chest infection. Advise on simple measures such as getting plenty of rest, drinking lots of fluids, avoiding smoke and fumes, and possibly getting a prescription for an inhaled bronchodilator and/or cough medicines.
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