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Pharmacology for Nurses

23.2 Introduction to the Lower Respiratory System

Pharmacology for Nurses23.2 Introduction to the Lower Respiratory System

By the end of this section, you should be able to:

  • 23.2.1 Describe the structure and function of the lower respiratory system.
  • 23.2.2 Discuss common conditions that affect the lower respiratory system.

The lower respiratory system, shown in Figure 23.4, consists of several organs including the trachea, bronchi, bronchioles, and alveoli, which together make up the lungs.

A diagram of a torso shows the organs of the lower respiratory system. Starting from the neck and working down, the organs are the trachea, which has lymph nodes on it. Below the trachea are the right lung, which consists of the upper, middle, and lower lobe, and the left lung, which consists of an upper and lower lobe. Bronchi are web-like structures that branch out in each of the lungs, eventually becoming bronchioles. At the end of each bronchiole are alveoli, which are connected to arteries and veins. Below the lungs is the diaphragm.
Figure 23.4 The lower respiratory system starts at the trachea and includes the lungs. (credit: modification of work from Anatomy and Physiology 2e. attribution: Copyright Rice University, OpenStax, under CC BY 4.0 license)

Lung Structure and Function

The lower respiratory tract consists of these structures:

  • Trachea (windpipe): This carries inhaled air into the lungs.
  • Lungs: These include the bronchi, bronchioles, and alveoli. Air enters the lungs for oxygen and carbon dioxide to be exchanged.
    • Bronchi: Major air passages that branch off from the trachea
    • Bronchioles: The smallest airways in the lungs

The lungs are air-filled organs on either side of the thorax. The right lung consists of three lobes, and the left lung consists of two lobes. Air travels from the larynx to the trachea, which is lined with smooth muscle and elastic tissue. Cartilage supports the airway and prevents collapse. The air then flows into branches called bronchi. The bronchi divide into smaller bronchioles until they become microscopic. At the end of the bronchioles are alveoli. Alveoli are microscopic air sacs where oxygen from the air is absorbed into the blood. Carbon dioxide travels from the blood to the alveoli so that it can be exhaled.

The function of the lungs can be assessed in a variety of ways. Assessing a client’s respiratory rate can provide an insight into proper function. A normal respiratory rate for an adult should be 12–20 breaths per minute. Pulmonary function tests (PFTs) determine how well the lungs work. They measure how much air goes into and out of the lungs, how much air goes from the lungs to the blood, and how well the lungs work during exercise.

Lower Respiratory Conditions

Some of the most common lower respiratory conditions are asthma and chronic obstructive pulmonary disease (COPD), which includes emphysema and chronic bronchitis.


Asthma is a condition in which airways swell and become narrow. The airways may also produce extra mucus. The combination of these characteristics can make breathing difficult and cause coughing and wheezing (a whistling sound) when breathing out. Asthma often causes clients to feel short of breath. (Mayo Clinic, n.d.-a).

Asthma symptoms can vary from person to person and in severity. Clients may present with:

  • Shortness of breath
  • Chest tightness or pain
  • Wheezing (inspiratory and expiratory)
  • Sleep problems due to the previous symptoms

Symptoms can be worsened by respiratory viruses such as influenza. They also can be triggered by exercise, occupational exposure to chemicals or dust, and allergens such as pollen or mold. Asthma cannot be cured, but it can be treated and its symptoms controlled.

Diagnosis of asthma is made utilizing PFTs as described previously, typically spirometry, after a client has exhibited symptoms.

Preventing asthma attacks and long-term control are the main goals of treatment. Asthma is often treated with inhaled corticosteroid and inhaled bronchodilators. For treatment of acute asthma attacks, inhaled short-acting bronchodilators and anticholinergic agents such as ipratropium are often used (Mayo Clinic, n.d.-a).

Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a group of conditions that cause the blockage of air flow and result in breathing issues. It includes emphysema and chronic bronchitis (discussed in the following sections). The main cause of COPD is tobacco smoke; other causes include air pollution, family history, and certain respiratory infections like pneumonia (Centers for Disease Control and Prevention, 2021).


Emphysema is characterized by shortness of breath. In clients with emphysema, the alveoli are damaged and do not work properly. Because of this damage, when the client exhales, old carbon dioxide–rich air becomes trapped and reduces room for fresh, oxygen-rich air. Emphysema is a progressive disorder. As time goes on, the inner walls of the alveoli become weak and rupture. This creates large air spaces in the lungs, which reduce the surface area of the lungs and how much oxygen reaches the bloodstream (Mayo Clinic, n.d.-b).

Symptoms of emphysema get progressively worse and include:

  • Shortness of breath
  • Wheezing
  • Chronic cough

Many clients do not have symptoms for years, but eventually they may notice difficulty breathing during normal everyday activities.

Because smoking is the biggest risk factor for emphysema, smoking cessation is the most common preventative measure.

Emphysema is diagnosed through a client history, images such as x-rays, and pulmonary function tests.

Emphysema cannot be cured, but there are treatments that can decrease symptoms and slow the progression of the disease. Bronchodilators, inhaled corticosteroids, and, if needed, antibiotics are utilized. Many clients may need supplemental oxygen to ensure proper blood oxygen levels (Mayo Clinic, n.d.-b).

Chronic Bronchitis

Chronic bronchitis is a type of COPD characterized by inflammation and irritation of the bronchial tubes. This causes mucus buildup and difficulty moving air into and out of the lungs.

Chronic bronchitis is usually caused by exposure to irritants over a long period. In the United States, cigarette smoking is the main reason for this disorder (Johns Hopkins Medicine, 2019).

Symptoms of chronic bronchitis include:

  • Frequent coughing
  • Wheezing
  • Shortness of breath
  • Tightness in the chest

Although there is no cure for chronic bronchitis, it is possible to manage symptoms, slow disease progression, and improve quality of life. Nonpharmacologic treatments include lifestyle changes such as quitting smoking, increasing physical activity, and having a healthy diet.

Pharmacological therapy often includes bronchodilators, inhaled corticosteroids, and antibiotics if bacterial infection is suspected (Johns Hopkins Medicine, 2019).


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