Lung and Respiratory Diseases

Overview

Definition

Pulmonary medicine deals mainly with diseases involving the lungs and breathing. Since the lungs are closely linked to proper functioning of other body systems (such as the heart and kidneys), pulmonologists are often asked to evaluate patients with many different types of illnesses. In order to understand the types of disorders that can affect the lungs, it is first helpful to consider how the breathing system is put together and how it normally works.

Makeup of the Respiratory System

The respiratory system includes everything from the nose to the smallest parts of the lungs. Most people breathe through their nose, and the nose is particularly good at warming and moisturizing air on its way to the lungs. The breathing tubes branch away from the digestive system at the epiglottis (a piece of cartilage located at the back of the tongue which prevents food or liquids from entering the airway). The biggest breathing tube is the trachea, commonly referred to as the windpipe. The trachea divides into smaller tubes known as bronchi, in much the same manner as a tree trunk divides into branches. These bronchi continue dividing, becoming smaller and smaller until they lead to the areas where gas exchange itself occurs: the alveoli.

Lungs

Makeup of the Respiratory System

Aveoli

Alveoli are very small (they cannot be seen by the naked eye) and resemble grape clusters in appearance, when looked at under a microscope. Each "grape", or alveolus, consists of a sack of air surrounded by tiny blood capillaries (the blood vessels that connect the smallest arteries to the smallest veins). Deoxygenated blood (blood that has no oxygen) is pumped by the right side of the heart into the capillaries of the alveoli. After gas exchange has occurred, the blood is returned to the left side of the heart. From there, it is pumped to the rest of the body. In addition to the upper airway and lungs themselves, the respiratory system includes a variety of cells that perform specific tasks such as fighting infections and keeping the gas exchange areas open, as well as muscles, cartilage and nerves that are necessary to actually get air moving in and out.

Normal Lung Function

People must breathe to survive. Breathing serves two main purposes: getting oxygen into the body, so it can be used by cells to help create energy (respiration), and removing carbon dioxide from the body that is formed as a result of energy consumption (ventilation). In both cases, the lungs perform these actions by providing a large area by which air can come into contact with blood and gas exchange (oxygen in, carbon dioxide out) can occur. It is often estimated that the average adult's gas exchange area, if spread out flat, would cover a tennis court! Breathing itself is controlled by special areas of the brain and, for the most part, occurs without conscious effort. The body has additional cells that sense times when oxygen levels are low (an effect that can be brought on by high altitudes while mountain-climbing) or when carbon dioxide levels are high. The brain responds to these changes in oxygen levels by increasing breathing. Thus, breathing is a tightly regulated process, and keeps the energy-transforming processes of the body running smoothly.

Blood Circulation

Lungs and disease

Needless to say, the gas exchange surfaces of the lungs are quite delicate, and they can be injured fairly easily (for example, by cigarette smoking). Pulmonologists (lung specialists) often group lung diseases into categories based upon the type of injury to the lung, and/or the particular function of the lung that has been affected. A typical breakdown is as follows:

Obstructive lung disease (such as emphysema, chronic bronchitis, asthma, and cystic fibrosis)
Restrictive lung disease (such as pulmonary fibrosis and sarcoidosis)
Lung cancers
Disorders of normal breathing
Lung infections
General pulmonary problems (such as cough, pleurisy, pulmonary blood clots)

Lung Tests and Evaluations

Usually the first step in evaluating an individual for lung disease is a good history and physical.

Important questions that a pulmonologist will likely ask are:

"How long has the problem been present?"

"Are symptoms noticeable all the time, only at certain times (like at night), or only with exercise?"

"Are there any other conditions present, like heart disease, which could be contributing to the problem?"

The pulmonologist will typically perform a thorough examination of the chest, searching for evidence of deformities, proper breathing patterns, and the absence of key indications of disease. A general examination of the rest of the body is also necessary to determine whether the problem is limited to the lungs or reflects a more generalized disease.

In many cases, a pulmonologist can make a reasonable diagnosis based upon history and physical examination alone. He/she may perform additional tests to:

- Confirm a clinical suspicion,
- Rule out a possible condition,
- Further evaluate a complex problem.

The additional tests may include routine and/or specialized blood tests, as well as imaging studies. The most common imaging studies include chest X-rays and CT scans, which allow some structures of the lungs inside the body to be seen. More recent developments in imaging, such as MRI and PET scanning, are also being used for specialized situations involving the lungs.

Occasionally, it is necessary for the pulmonologist to examine the lungs directly, either to look at areas that cannot be seen well on imaging studies and/or to obtain a sample of the cells that make up the lungs and breathing tubes. The method of examination used is usually bronchoscopy. Bronchoscopy involves passing a small fiberoptic instrument (a very fine, flexible glass rod that transmits light) into the lungs via the nose or mouth. This allows the physician performing the bronchoscopy to look at the inside of the larger breathing tubes. In addition, biopsies and other sampling procedures can be performed. Although the procedure is not typically painful, a light anesthetic is often given. In routine cases a bronchoscopy can be performed in less than an hour, and patients may be sent home the same day. Rarely, it is necessary to perform a more extensive procedure on the lungs, such as draining large fluid collections or obtaining a larger biopsy sample. In these cases, it may be necessary to enlist the help of a thoracic (chest) surgeon who can safely perform these procedures in the operating room.

Keeping Your Lungs Healthy

The lungs are vital organs and it is important to keep them in good physical shape. The following guidelines can help to promote the health of your lungs:

Avoid Smoking - Nothing ruins a good set of lungs like smoking. Smoking has been linked to lung cancer and diseases such as emphysema (a condition which destroys the tissues of the lungs). Therefore, avoid this unhealthy and potentially deadly habit. To learn more about the dangers of smoking click here.
Exercise regularly - Regular exercise improves the ability of the heart and lungs to supply the body with oxygenated blood, thus improving endurance.

Do not take your lungs for granted. If you keep your lungs in good shape, every other part of your body will thank you. Your heart and kidneys will function better and you will enjoy greater physical endurance.

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Last Reviewed: Mar 28, 2000

Stuart Green, MD
Assistant Professor of Medicine and Pathobiology
Pulmonary, Critical Care & Sleep Medicine
Department of Internal Medicine
College of Medicine
University of Cincinnati