RESPIRATORY SYSTEM

Adapted from bblearn.mb

WINNIPEG SCHOOL DIVISION

Name: _________________________________________________________

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Did you know that you can survive weeks without food and days without water, but only

a few minutes without oxygen?

Cells need oxygen to release energy from food. Without this energy, the cells are not

able to carry out their functions.

The process of respiration helps ensure that the body gets the energy it needs for its

functions. Respiration involves the inhaling and exhaling of air, the exchange of gases

between cells and the environment surrounding them, and the chemical reactions in

which oxygen is used to release energy from food.

In this module, you will study the structure and function of the human respiratory system

as well as some of the disorders and diseases that affect this system. You will also

learn about the biochemistry of respiration and the importance of respiration to

homeostasis in the body.

Introduction to Lesson 1:

Respiration

As we studied in the last module, digestion is the process by which food is broken down into smaller parts so that the body can use them to provide energy and build and nourish cells. The process of producing energy from food is called cellular respiration.

Humans need a continuous supply of oxygen for cellular respiration. They must also get rid of excess carbon dioxide, the poisonous waste product of this process. The process of respiration supports cellular respiration by constantly supplying oxygen and removing carbon dioxide. The oxygen we need is derived from the Earth's atmosphere, which is 21% oxygen. This oxygen in the air is exchanged in the body by the respiratory surfaces in the lungs.

Gas Exchange

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Lesson Overview

Following is a list of topics covered in this lesson.

• Respiration • Breathing • Gas Exchange • Cellular Respiration • Other Functions of the Respiratory System

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

o Define the terms respiration and gas exchange. o Distinguish between external respiration, internal respiration and cellular

respiration. o List four conditions required for gas exchange across a membrane.

Respiration and Gas Exchange

When you hear the word respiration, you probably think of breathing. However, breathing is just part of the respiratory process in humans. Respiration is defined as the exchange of oxygen and carbon dioxide between an organism and its external environment.

The respiratory system, including the lungs, brings air into the body. The oxygen in the air travels from the lungs through the bloodstream to the cells in all parts of the body. The cells use the oxygen for cellular respiration and give off carbon dioxide as a waste gas. The waste gas is carried by the bloodstream back to the lungs to be eliminated or exhaled. The lungs accomplish this vital process - called gas exchange - using an automatic and quickly adjusting control system.

In the course of a single day, an amazing 8,000 to 9,000 liters of breathed-in air meet 8,000 to 10,000 liters of blood pumped in by the heart through the pulmonary artery. The lungs relieve the blood of its burden of waste and return a refreshed, oxygen-rich stream of blood to the heart through the pulmonary vein.

Learning Outcomes

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Respiration in humans can be divided into three steps:

1. Breathing 2. Gas Exchange 3. Cellular Respiration

Breathing is the proces

s by which oxygen is taken from the external environment and carbon dioxide is expelled to the external environment. Breathing involves both inhalation and exhalation. These movements allow the body to take in the oxygen it requires and dispose of carbon dioxide. You will study the process of breathing in the next lesson when we learn about the structure of the human respiratory system.

Gas exchange is the process of transferring oxygen from the air into the body and transferring carbon dioxide from the blood out of the body. Gas exchange takes place at a respiratory surface - a boundary between the external environment and the interior of the body.

Gases cross the respiratory surface by diffusion – the movement of a substance from an area of higher concentration to an area of lower concentration. Single-celled organisms can exchange gases directly across their cell membrane. However, the slow diffusion rate of oxygen relative to carbon dioxide limits the size of single-celled organisms. Simple animals that lack specialized exchange surfaces have flattened, tubular, or thin shaped body plans, which are the most efficient for gas exchange. However, these simple animals are small in size.

Large animals cannot maintain gas exchange by diffusion across their outer surface. They have developed a variety of respiratory surfaces that all increase the surface area for exchange, thus allowing for larger bodies. In humans, this respiratory surface is found in specialized structures called lungs.

A respiratory surface is covered with thin, moist epithelial cells that allow oxygen and carbon dioxide to exchange. Those gases can only cross cell membranes when they are dissolved in water or an aqueous solution.

There are a number of conditions necessary for gas exchange across a membrane. These are:

• a concentration gradient • a large surface area • a thin permeable surface • a moist exchange surface

The Three Stages of Respiration

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Gas exchange occurs both externally and internally in humans. External respiration is the exchange of gases across the respiratory surface between the air sacs (alveoli) in the lungs and the blood. Internal respiration is the exchange of gases between the blood and individual cells in the tissues.

You will study the structures involved with these processes in lesson 3.

Cellular Respiration

Cellular Respiration or aerobic respiration involves the use of oxygen to break down glucose and produce energy in the cell. This process occurs in the mitochondria of cells. Cellular respiration is a series of chemical reactions that converts the chemical energy of foods into energy that can be used by cells (ATP). Carbohydrates, usually in the form of glucose, are the most useable source of energy.

The Chemical Equation for Cellular Respiration:

C6H12O6 + 6O2 ----> 6H2O + 6CO2 + Energy (ATP)

Glucose Oxygen Water Carbon Dioxide

Other Functions of the Respiratory

System

The lungs are internal organs. However, they are constantly exposed to our external environment. With each breath, a host of foreign substances enter our bodies -- pollens, dust, viruses, bacteria, animal dander, tobacco smoke, and other chemicals spewed into our atmosphere by smokestacks and automobile tailpipes. In addition to gas exchange, the lungs and the other parts of the respiratory system have important functions. These include:

• Warming or cooling air to proper body temperature • Moisturizing inhaled air for necessary humidity • Protecting the body from harmful substances by coughing, sneezing, filtering

or swallowing them, or by alerting the body through the sense of smell • Defending the lungs with:

1. cilia - microscopic hairs along the air passages

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2. phlegm (mucous) - a moving carpet of phlegm collects dirt and germs inhaled into the lungs and moves them out to be coughed up or swallowed

3. macrophages - scavenger cells in the lungs that literally eat up dirt and germs invading the lungs

1. Define the term

respiration.

2. List and describe the three steps of respiration in humans.

3. What are the four conditions necessary for gas exchange across a respiratory surface?

4. Why do humans require a specialized system for gas exchange?

5. Differentiate between external and internal respiration.

6. Describe how the human respiratory system prepares the air for gas exchange and protects the body from harmful substances.

Your respiratory system is made up of a pair of lungs, a series of passageways into

your body, and respiratory surfaces for gas exchange. The respiratory system is unique

in that the internal organs that are part of this system – the lungs are exposed to the

external environment.

In the last lesson, you studied the process of gas exchange and the need for a

specialized system for this purpose in humans. You also learned the differences

between external, internal and cellular respiration. In this lesson, you will study the

structure and function of the human respiratory system, including the mechanics of

breathing. You will also measure your own lung capacities.

Lesson 1 Questions

Introduction to Lesson 2:

The Human Respiratory System

Learning Outcomes - Lesson

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

• Identify from a model, diagram, or specimen and describe the function of the following structures of the human respiratory system:

o lungs o diaphragm

o pleura o interpleural fluid

o nasal cavity o pharynx

o epiglottis o larynx

o vocal cords o trachea

o bronchi o bronchial tubes

o alveoli

• Explain how the structure of alveoli are related their function. • Illustrate and explain the mechanics of breathing in humans, including the role of

the diaphragm and intercostal muscles in the changing volume and pressure of the chest cavity.

• Measure respiration rate and lung capacities, i.e. tidal volume, expiratory reserve volume and vital capacity.

Lesson 2 Overview

Following is a list of topics covered in this lesson.

• Human Respiratory System • Mechanics of Breathing • Defense Mechanisms

Human Respiratory

System

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As you studied in the last lesson, breathing is the process by which oxygen in the air is brought into the lungs and into close contact with the blood. The blood absorbs the oxygen and carries it to all parts of the body. At the same time the blood gives up waste matter (carbon dioxide), which is carried out of the lungs with the air breathed out.

The first step in the process of respiration involves taking air into your body through your nose or mouth. Air flows into the pharynx, passes the epiglottis, through the larynx and into the trachea. Let’s look at a diagram of the respiratory system to identify the location of these structures.

The nasal cavity (nose) is the usual entrance for outside air into the respiratory system. The nostrils lead to open spaces in the nose called the nasal passages. The nasal passages serve as a moistener, a filter, and to warm up the air before it reaches the lungs. The hairs in the nostrils prevent various foreign particles from entering. Different air passageways and the nasal passages are covered with a mucous membrane. Many of the cells

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which produce the cells that make up the membrane contain cilia. Others secrete a type a sticky fluid called mucous. The mucous and cilia collect dust, bacteria, and other particles in the air. The mucous also helps in moistening the air. Under the mucous membrane there are a large number of capillaries. The blood within these capillaries helps to warm the air as it passes through the nose.

The sinuses (frontal, maxillary, and sphenoidal) are hollow spaces in the bones of the head. Small openings connect them to the nose. The functions they serve include helping to regulate the temperature and humidity of air breathed in, as well as to lighten the bone structure of the head and to give resonance to the voice.

Air also enters through the oral cavity (mouth); especially during heavy exercise and in people who have a mouth-breathing habit or whose nasal passages may be temporarily obstructed.

The adenoids are lymph tissue at the top of the throat. When they enlarge and interfere with breathing, they may be removed. The lymph system, consisting of nodes (clumps of cells) and connecting vessels, carries fluid throughout the body. This system helps to resist body infection by filtering out foreign matter, including germs and producing cells (lymphocytes) to fight them.

The tonsils are lymph nodes in the wall of the throat (pharynx) that often become infected. They are also part of the germ-fighting system of the body.

The pharynx (throat) collects incoming air from the nose and mouth and passes it downward to the windpipe (trachea).

The epiglottis is a flap of tissue that guards the entrance to the trachea (the glottis), closing when anything is swallowed that should go into the esophagus and stomach.

The larynx (voice box) contains the vocal chords. When the air leaves the pharynx it passes into the larynx. The larynx is constructed mainly of cartilage, which is a flexible connective tissue. The vocal chords are two pairs of membranes that are stretched across the inside of the larynx. As the air is expired, the vocal chords vibrate. Humans can control the vibrations of the vocal chords, which enables us to make sounds.

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The trachea (windpipe) is the main passage leading from the pharynx to the lungs. The trachea is a tube approximately 12 centimeters in length and 2.5 centimeters wide. The trachea is kept open by rings of cartilage within its walls. Similar to the nasal passages, the trachea is covered with a ciliated mucous membrane. Normally, the cilia move mucous and trapped foreign matter to the pharynx. After that, they leave the air passages and are normally swallowed. Smoking stops the cilia from moving. Just one cigarette slows their motion for about 20 minutes. The tobacco smoke increases the amount of mucous in the air passages. When smokers cough, their body is attempting to dispose of the extra mucous.

The trachea divides into the two main bronchi – right bronchus and left bronchus, one for each lung, which subdivide into each lobe of the lungs. These, in turn, subdivide further into bronchioles. Bronchioles have a branching design similar to a bunch of grapes.

The lymph nodes of the lungs are found against the walls of the bronchial tubes and trachea.

The ribs are bones supporting and protecting the chest cavity. They move to a limited degree, helping the lungs to expand and contract.

The right lung is divided into three lobes, or sections. The left lung is divided into two lobes. Each lobe is like a balloon filled with sponge-like tissue. Air moves in and out of the lobes through a branch of the bronchial tube.

The pleura are the two membranes, actually one continuous one folded back on itself, that surround each lobe of the lungs and separate the lungs from the chest wall. The interpleural fluid is located between the two layers and functions to reduce the friction between the lungs and the chest cavity during breathing.

The bronchial tubes are lined with cilia (like very small hairs) that have a wave-like motion. This motion carries mucous (sticky phlegm or liquid) upward and out into the pharynx, where it is either coughed up or swallowed. The mucous catches and holds much of the dust, germs, and other unwanted matter that has invaded the lungs.

The diaphragm is the strong wall of muscle that separates the chest cavity from the abdominal cavity. By moving downward, it creates suction in the chest to draw in air and expand the lungs.

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The alveoli (plural of alveolus) are the very small air sacs that are the destination of air breathed in. Each bronchiole ends in these tiny air chambers that look like a bunch of grapes. It is estimated that each lungs contain about 300 million alveoli. Their total surface area would be about 100 square meters. That is 40 times the surface area of the skin. The walls of the alveoli, which are only about one cell thick, are the respiratory surface. They are thin, moist, and are surrounded by capillaries. The capillaries are small blood vessels that connect arteries and veins. They are imbedded in the walls of the alveoli. Blood passes through the capillaries, brought to them by the pulmonary artery and taken away by the pulmonary vein to the heart. While in the capillaries the blood gives off carbon dioxide through the capillary wall into the alveoli and takes up oxygen from the air in the alveoli. Once the blood reaches the heart, arteries carry oxygenated blood to the body cells while veins carry deoxygenated blood back to the heart.

Smoking makes it difficult for oxygen to be taken through the alveoli. When the cigarette smoke is inhaled, about one-third of the particles will remain within the alveoli.

The forcing

of air into and out of the lungs by breathing movements is necessary to increase the exchange of gases with the environment. The diffusion of oxygen from the external atmosphere into the nose, through the several parts of the respiratory system, and through to the alveoli would be too slow to supply a large, active organism with enough oxygen for its needs or rid the body of waste carbon dioxide rapidly enough.

Ordinarily, breathing movements are involuntary; they proceed without thinking about it. They also continue when a person is sleeping or unconscious. This is necessary because the body does not store oxygen, and more than momentary cessation of breathing can be lethal. It is possible to exercise voluntary control over breathing. A person can hold his/her breath, or breathe more deeply or more shallowly than usual, but he/she soon tires of this, involuntary control takes over.

Breathing consists of two processes, inspiration and expiration. It is largely controlled by the diaphragm, a large muscle separating the thoracic cavity from the abdominal cavity. When relaxed, the diaphragm is dome-shaped, bulging upward into the thoracic cavity.

Inspiration

During inspiration, the diaphragm contracts and flattens. Acting in unison with the diaphragm are the intercostal muscles, which are attached to the 12 pairs of ribs

Mechanics of Breathing

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encircling the thorax. At the same time that the diaphragm contracts, the rib muscles also contract, moving the ribs slightly upward and forward. These actions increase the volume of the chest cavity. As the thorax expands, the pleura, which is firmly attached to the thoracic wall and diaphragm, moves outward and downward with them. This causes the elastic lungs to expand. This increase of volume lowers the air pressure in the alveoli to below atmospheric pressure (creating a vacuum). Because air always flows from a region of high pressure to a region of lower pressure, it rushes in through the respiratory tract and into the alveoli. This is called negative pressure breathing.

Expiration

Reversing the steps of an inhalation produces expiration. When the diaphragm relaxes, it assumes its maximum curvature and pushes upward. At the same time, the intercostal muscles relax, allowing the ribs to move downward and backward. Both of these movements push against the pleura. The chest cavity decreases in size, and the air pressure outside the lungs rises above that of the external air. This forces air out of the lungs in expiration or exhaling of air.

The diagram below illustrates this process.

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Figure 4.2.2 Mechanics of Breathing

(http://www.stemnet.nf.ca/~dpower/resp/exchange.htm#Breathing)

Try placing your hands on your chest as you breathe. Do you notice the movements discussed above while you are inhaling and exhaling?

Measure your own respiration rate (breaths/minute) at rest and after 1 minute of vigorous activity. What differences do you observe?

Defense Mechanisms and Other

Interesting Things

Coughing is a reflex action in response to irritation of the throat, trachea, lungs or pleural membrane. It can also be caused by nervousness, or it can be voluntary. There is a rapid contraction of the chest and diaphragm muscles causing a sharp

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intake of air. The epiglottis closes as the chest and diaphragm muscles relax. This causes a build up of air pressure inside. The epiglottis suddenly opens and the air blows out carrying the irritating particles with it. The main function is to protect the lungs from harmful particles that may be inhaled.

Sneezing is the sudden expulsion of air through the nose. Irritation of the lining of the nasal cavity usually stimulates the sneezing action. The air is taken in by normal breathing and then interrupted. The opening to the mouth is closed off by the soft palate and air is forced out through the nose carrying the irritating particles with it. During a sneeze, the heart stops momentarily.

Hiccoughing is the result of stimulating the vagus nerve. The impulse is carried to a center in the spinal cord which relays it to the diaphragm. It causes an involuntary contraction of all or part of the diaphragm forcing air out of the lungs. The sudden closing of the epiglottis as air is drawn into the chest produces the sound. Hiccoughs can be caused by eating too fast, drinking too much alcohol, and by irritating diseases of the digestive system, heart, and lungs.

Yawning is a combination of psychological and physical reactions resulting in an involuntary stretching of the mouth accompanied by a large intake of air. The air is then exhaled as the mouth closes. It may be the result of a decrease in breathing rate due to tiredness, boredom, or drug action. Since the body requires more oxygen there is a sudden intake of air in the form of a yawn.

Snoring is the result of vibrations of the soft palate in the mouth while sleeping.

Lung Capacity

A singer with a well-trained voice can hold a single note for over 30 seconds. To do this, the singer must be able to hold a relatively large amount of air in his or her lungs and release it in a slow, controlled manner. This ability is determined, in part, by the singer's vital capacity.

A person's vital capacity is the maximum amount of air the person can forcibly exhale after the largest possible inhalation of air. Vital capacity is also measured as the sum of three volumes of air: the tidal volume; the inspiratory reserve; and the expiratory reserve.

The tidal volume is the amount of air inhaled or exhaled during normal, quiet breathing. The inspiratory reserve volume is the amount of air that can be

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forcefully inhaled after normal inhalation. The expiratory reserve volume is the amount of air that can be forcibly exhaled after normal exhalation.

Lesson 2

Exercise

1. Describe the features of the nasal cavity that moisten, clean, and warm the air as it passes through this cavity on its way to the lungs.

2. How is food prevented from entering the lungs?

3. What is the function of cilia in the respiratory tract? How are the cilia affected by cigarette smoke?

4. How does the structure of the larynx allow humans to make sounds?

5. Trace the path of an oxygen molecule from your nose to a body cell. List each structure that it passes.

6. Describe the mechanics of breathing in humans.

7. List and explain the different lung capacities.

8. Differentiate between sneezing and hiccoughing.

Introduction to the Chemistry of

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Have you ever tried to hold your breath for as long as you can?

Little children often express their anger this way. You can not do so indefinitely.

Eventually, the body’s involuntary mechanisms take over and start the breathing

movements. Special chemical receptors in the brain and bloodstream detect increases

in carbon dioxide and decreases in oxygen, triggering the breathing process.

In this lesson, you will explore the chemistry of respiration, including the homeostatic

mechanisms involved in breathing control. You will also study the relationship between

metabolism and carbon dioxide production.

Outcomes for Lesson 3

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

• Describe the negative feedback mechanisms (chemoreceptors and the medulla oblongata) responsible for the control of breathing in humans.

• Predict the effects of varying blood levels of carbon dioxide, oxygen, and carbon monoxide on breathing rate.

• Describe the role of hemoglobin in transporting oxygen and carbon dioxide in the blood.

• Explain how hemoglobin maintains homeostasis in the body by buffering against pH changes in the bloodstream.

Lesson 3

Overview

Following is a list of topics covered in this lesson.

• Regulation of Breathing • Control of Breathing • Gas Exchange and Transport • External Respiration • Internal Respiration

Respiration

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Regulation of Breathing

The ability of the body to adjust and maintain the levels of oxygen and carbon dioxide is a good example of homeostasis (the maintenance of a constant internal environment). As we studied in the last lesson, breathing movements are controlled by the diaphragm and intercostal muscles. These muscles are stimulated by nerve impulses from the brain. This system of brain, nerves, lungs, and muscles constitutes one of the many negative feedback mechanisms that maintain homeostasis in the human body.

The respiratory center is located in the medulla oblongata of the brain (located at the back of the brain). The medulla is connected to the respiratory muscles (diaphragm and intercostal muscles) by motor neurons. A set of sensory neurons conducts impulses from the lungs to the respiratory center.

During inspiration, the respiratory center sends a nervous impulse to the respiratory muscles that causes them to contract. This inflates the lungs. The expansion of the lungs initiates impulses in the sensory neurons that extend from the lungs to the brain. These impulses inhibit the breathing center, which then ceases to send impulses to the respiratory muscles. No longer stimulated, these muscles relax, and the lungs deflate in an expiration. The deflated lungs stop stimulating the sensory neurons which then stop sending impulses to the respiratory center of the brain. No longer inhibited, the respiratory center once again sends out nerve impulses that stimulate the respiratory muscles, and the process repeats.

Normal breathing

usually supplies enough oxygen to meet the body’s needs and removes carbon dioxide as fast as it is formed. Occasionally, however, carbon dioxide may begin to accumulate in the blood or oxygen concentration may fall -- two changes that often occur simultaneously. Either of these conditions increases the rate and/or the depth of breathing. It should be noted that the body is more sensitive to the carbon dioxide concentration in the blood than to the oxygen concentration.

As discussed above, breathing rate is mainly controlled by the respiratory center in the brain. The respiratory centre monitors the carbon dioxide level in the blood. Oxygen levels are monitored by chemoreceptors in the aorta and the carotid arteries.

When carbon dioxide is dissolved in the blood, it reacts with water to form carbonic acid, which then ionizes to form a bicarbonate ion and a hydrogen ion:

CO2 + H2O H2CO3 ----> H2CO3 HCO3- + H+

Control of the Breathing Rate

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Carbon Water Carbonic Carbonic Bicarbonate Hydrogen

Dioxide Acid Acid Ion Ion

As more carbon dioxide enters the blood, the hydrogen ion concentration rises. The high concentration of hydrogen ions rather than the dissolved carbon dioxide gas stimulates breathing. The high hydrogen ion concentration in the blood stimulates the respiratory center in the brain, which then sends impulses to the respiratory muscles and the breathing rate is increased.

Neurons with endings (chemoreceptors) in the aorta and the carotid arteries are sensitive to oxygen concentration. These neurons monitor the blood continuously, and when the oxygen concentration begins to fall, they also stimulate the respiratory center in the brain.

Effects of Environment on

Breathing Rate

If you have ever hiked in the high mountains, you have probably noticed how much faster and deeper you breathe at higher elevations than at lower elevations. That is because there is less oxygen in the air at higher elevations than at lower elevations. You need to take in more air to obtain the same amount of oxygen as at lower elevations.

People native to high altitudes have adapted to their environment by having more alveoli and blood vessels in their lungs than people native to low altitudes. They also have a higher red blood cell count (70% of the blood volume instead of the normal 45 to 50%).

Gas Exchange and

Transport

As discussed in the last lesson, the trachea forks into the right and left bronchi, one leading to each lung. Each bronchus, in treelike manner, branches into smaller tubes, the bronchioles, which divide repeatedly into alveolar ducts. These ducts end in numerous grapelike clusters, the alveolar sacs, each of which contains several pockets, the alveoli. Although the alveoli of the lungs are small, they are so numerous (three hundred million per lung) that if they were to be opened up, their total surface area in an adult would be 100 square meters. This area is approximately the size of a tennis court or 40 times the external body surface area (2 square meters). It is across these 100 square meters of delicate alveolar surface that all our oxygen is absorbed.

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A network of capillaries surrounds each alveolus. Their thin walls, like the alveolar walls, are only one cell thick. Thus, the blood passing through the capillaries is separated from the air in the alveolus by only two cells. At this point, the partnership between the respiratory system and the circulatory system comes into effect. The respiratory system has brought oxygen molecules to the exchange site in the alveoli. Oxygen will diffuse across the membranes, enter the bloodstream and be transported to the cells and tissues, which require oxygen for their activities. Carbon dioxide, a waste product of cellular respiration, will diffuse from the body cells into the capillaries and be transported back to alveoli and be exhaled from the body. The diagram below illustrates this relationship.

Figure 4.3.1 Alveolar Sacs

(Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com))

G

as

exchan

ge in

an alveolus takes place by diffusion across the moist membrane of the alveolus and the

capillary walls. About 18% to 20% of the air is oxygen, which is a much higher

External Respiration

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concentration of oxygen than that found in the blood. Due to these differences in

concentration, the oxygen diffuses from the alveoli to the blood in the capillaries. At the

same time, waste carbon dioxide diffuses from the blood into the alveoli due to a higher

concentration of carbon dioxide in the blood than in the air in the alveoli.

Internal Respiration

As the oxygen laden blood passes through the body into the capillaries adjacent to the body cells, the reverse action takes place. This process is called internal respiration. Because of the oxidation of food nutrients constantly going on within the cells (cellular respiration), the cells' supply of oxygen is quickly depleted while the by-product of food oxidation, carbon dioxide, builds up. This condition causes the oxygen to diffuse from the bloodstream into the cells, while the carbon dioxide leaves the cells and enters the bloodstream.

Oxygen must constantly be replenished in the body cells through the respiratory and circulatory systems as it cannot be stored by the body. Oxygen is absolutely essential in the cells, where it combines with food molecules, producing the energy needed to maintain the body functions.

Neither ext

ernal respiration nor internal respiration could take place without the blood that flows in the circulatory system. It is the blood that carries the oxygen to the cells of the body and accepts the carbon dioxide from the cells and delivers it to the lungs for exhalation.

Most of the oxygen diffusing into the bloodstream becomes bound to iron-containing hemoglobin molecules within the red blood cells. Each molecule of hemoglobin is capable of carrying four molecules of oxygen. An average human red blood cell contains 280 million molecules of hemoglobin. Accordingly, a single red blood cell, with fully saturated hemoglobin molecules, can transport about one billion oxygen molecules. Only a small fraction (less than 3 percent) of the total oxygen remains freely dissolved in the plasma. The combination of oxygen with hemoglobin allows for the transportation of as much as sixty times the amount oxygen as could be carried if the oxygen were solely in solution in the plasma.

The chemical combination of hemoglobin and oxygen is reversible. Hemoglobin associates with oxygen in the capillaries of the lungs to form the bright red oxyhemoglobin and dissociates from the union with oxygen in the capillaries of the body tissues to form the dark purplish deoxyhemoglobin. The amount of oxygen carried by hemoglobin depends upon the concentration (partial pressure) of oxygen. At

Oxygen Transport

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the normal concentration of oxygen in the arteries, 97% of the hemoglobin is combined with oxygen. The reactions below illustrate these processes.

Lungs

O2 + Hb -------> HbO2

Oxygen Deoxyhemoglobin Oxyhemoglobin

Tissues

HbO2 -------> O2 + Hb

Oxyhemoglobin Oxygen Deoxyhemoglobin

Carbon monoxide poisoning is directly related to oxygen transport in the blood. Carbon monoxide (CO) competes with oxygen for the active sites on the hemoglobin molecules. Unfortunately, CO combines more readily than oxygen. As more and more CO molecules combine with hemoglobin, less and less oxygen is carried to the tissues, eventually leading to oxygen starvation and cell death.

Carbon Dioxide Transport

Carbon dioxide is carried in the bloodstream in several forms. About 9% remains in solution in the plasma. A further 27% is attached to vacant carrier sites on hemoglobin molecules that have just emptied their oxygen into the tissues. About 67% of the carbon dioxide combines with the water in the plasma to form carbonic acid. As discussed earlier in the lesson, this acid dissociates into bicarbonate ions (HCO3

-) and hydrogen ions (H+).

Tissues

CO2 + H2O ---------> H2CO3 -------> HCO3- + H+

Carbon Water Carbonic Bicarbonate Hydrogen

Dioxide Acid Ion Ion

As you learned in module 1, hydrogen ion concentration lowers the pH of solutions, creating an acidic environment. This acidic environment can create problems for enzyme function. This is where hemoglobin performs its second function. The hemoglobin combines with the excess hydrogen ions in the blood, controlling the pH and acting as a buffer to maintain homeostasis.

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tissues lungs

Hb + H+ ---------> HHb ---------> Hb + H+

Deoxyhemoglobin Hydrogen Buffer Deoxyhemoglobin Hydrogen

Ion Ion

The bicarbonate ions are carried back to the lungs in the blood plasma. Once the blood reaches the lungs, the hydrogen ions dislodge from the hemoglobin and join with the bicarbonate ions to form water and carbon dioxide.

Lungs

HCO3- + H+ --------> H2CO3 ------------> CO2 + H2O

Bicarbonate Hydrogen Carbonic Carbon Water

Ion Ion Acid Dioxide

The carbon dioxide diffuses across the alveolar membranes and is then exhaled. The diagrams below illustrate this process.

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Figure 4.3.2 Carbon Dioxide Transport

(Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates

(www.sinauer.com) and WH Freeman (www.whfreeman.com))

1. a) How

do CO2 and O2 levels in the blood regulate breathing movements?

b) Explain how these mechanisms are a good example of homeostasis.

2. a) What effect does high altitude have on breathing?

b) How have people that live in high altitudes adapted to their environment?

3. Explain how the structure of the alveoli allows them to perform their function.

4. Explain how carbon monoxide acts as a poison.

Lesson 3 Exercise

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5. Describe how oxygen and carbon dioxide are transported in the blood.

6. Other than transporting oxygen, what other important function does hemoglobin perform?

Introduction to Lesson 4 -

Disorders and Diseases of the

Respiratory System

Our lungs are amazing machines that can supply large amounts of oxygen to our blood. Sometimes the lungs don't work as well as they should. This can be because of a disease, allergies, or other inherited conditions. In the last three lessons, you have studied the structure and function of the human respiratory system. In this lesson, you will study some of the disorders and diseases that affect the respiratory system. You will also participate in a case study/debate related to smoking and lung cancer.

Outcomes for Lesson 4

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

• Describe the cause, symptoms, and treatment of the following disorders of the respiratory system:

o lung cancer o emphysema o chronic bronchitis o asthma

Over 3 million Canadians must cope with serious respiratory diseases - asthma, emphysema, lung cancer, chronic obstructive pulmonary disease (COPD), influenza,

Disorders and Diseases of the

Respiratory System

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pneumonia, bronchitis, tuberculosis (TB), cystic fibrosis, and respiratory distress syndrome (RDS). These diseases affect people of all ages. While in the past, lung cancer has affected primarily men, the increase in smoking among women in the past 50 years has resulted in the increased incidence and prevalence of this disease among women.

Respiratory diseases, including lung cancer, exert a great economic impact on the Canadian health care system. Costs include hospitalization, physician visits and drugs. They also include the less visible or indirect expenses associated with disability and mortality, which may be even more significant.

Some common disorders and diseases of the respiratory are discussed on the following pages.

Lung cancer is now one of the best known and most feared of all diseases. Every year the numbers of Canadians diagnosed with lung cancer increase. Although other substances such as asbestos and coal tar products can cause lung cancer, at least 85% of the disease is related to smoking.

What is Cancer?

Cancer is a disease in which abnormal cells in some organ or tissue go out of control, growing and increasing in number. Normal cells reproduce themselves throughout life, but in an orderly and controlled manner. Normal growth occurs, worn out tissues are replaced and wounds heal. When cells grow out of control and form a mass, the mass is called a tumor. Some tumors grow and enlarge only at the site where they began and these are referred to as benign tumors. Other tumors not only enlarge locally but also have the potential to invade and destroy the normal tissue around them and to spread to distant parts of the body. Such tumors are called malignant tumors, or cancer. Distant spread of a cancer occurs when malignant cells detach themselves from the original (primary) tumor, are carried to other parts of the body through the blood or lymphatic vessels and establish themselves in the new site as an independent (secondary) cancer. A tumor that has spread in this manner is said to have metastasized and the secondary tumor (or tumors) is called a metastasis.

Smoking and Lung Cancer

As cigarette smoking is the major cause of lung cancer today, it is important to understand how it affects the lungs. Smoking causes lung cancer in two ways. First of all smoke inhalation damages the normal cleansing processes by which the lung protects itself from injury. The tube-like structures (bronchi) which conduct inhaled air to the lung tissue are lined with a single layer of cells on which lies a protective coating of mucous. Hair-like cilia on these cells beat in rhythmic fashion to move the mucous continually upwards from the lung, removing any inhaled particles which have been

Lung

Cancer

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trapped in the sticky mucous. The effectiveness of this cleansing mechanism is destroyed very quickly by smoke inhalation because the cilia disappear and the lining thickens in an attempt to protect the delicate underlying tissues from damage.

When these changes have occurred, the lung can no longer keep itself clean. Consequently, cancer-producing agents in the cigarette smoke remain trapped in the mucous on the surface lining of the airway long enough to pass into the cells before these substances can be removed by coughing, the only cleansing mechanism which remains. Once within the body, these chemicals, or their products, can alter the nature of the cells slowly and progressively until cancer develops.

The risk of lung cancer increases with the total amount of exposure. In cigarette smoking, several factors are involved in determining the actual exposure, including the duration of smoking, the number of cigarettes smoked and the depth of inhalation. Contrary to previous theories, women who share the same smoking history as men also share the same, or higher, risk. The person at greatest risk is one who has smoked for many years (e.g., over 20 years), who has averaged more than 20 cigarettes per day and who has inhaled freely. For this person the risk may be increased by as much as 15-30 times compared to that of a non-smoker. Starting smoking early makes it possible for a person to have smoked heavily for at least 20 years by the age of 35.

The person who has smoked only pipes or cigars and never cigarettes, tends to "puff" rather than inhale freely, and therefore has less risk of developing lung cancer than a cigarette smoker, although it is an increased risk compared to a non-smoker's. It is important to realize that it doesn't do much good for cigarette smokers to switch to pipes and cigars. Unfortunately, once the habit of inhalation has been learned as a cigarette smoker, the individual who switches tends to continue inhaling when smoking either pipes or cigars. Indeed, the total smoking exposure may actually be increased by this change.

Other forms of inhaled pollutants, particularly repeated industrial exposures, may increase the risk for the smoker, although they can also affect the non-smoker. This effect has been noted in exposure to the following agents: asbestos, chromium, nickel coal tar products and radon (a radioactive gas).

The risk of developing lung cancer has been increased 50 times for asbestos workers who also smoke in comparison with the risk in the non-smoking general population. In comparison the risk for a non-smoking asbestos worker is only 5 times greater than the risk in the non-smoking general population. Both non-smokers and smokers must therefore avoid work where there is a risk from airborne asbestos.

A series of studies have now shown that non-smoking spouses are at increased risk of lung cancer from prolonged exposure to the smoke produced from the cigarettes of their spouse. The greatest risk, approximately twice the normal low risk in non-smokers, comes from the exposure to spouses who smoke 20 or more cigarettes a day at home. Prolonged exposure to the smoke of others, in for example, the working environment,

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also increases risk, and this increase may apply not only to non-smokers, but to smokers as well. Particularly at risk are young children, as it has already been demonstrated that children exposed to the smoke of their parents have increased risk of respiratory infection and it has even been suggested that mothers of unborn children exposed to the smoke of others, have a greater frequency of low birth weight infants than mothers not so exposed. Health Canada figures estimate that every year at least 330 non-smokers die from lung cancer due to exposure to secondhand smoke.

Detection and Diagnosis

Regardless of the type of lung cancer, the complaints noted by the patient are very similar. Since the tumor is a foreign object in the airway, a repetitive cough develops in an attempt to dislodge it. This chronic cough may damage the surface of the tumor so that blood appears in the sputum. In addition, glands are also stimulated by the irritation of the smoke inhalation and produce increased amounts of mucus which must be coughed up.

At a later stage, the growing tumor may also completely obstruct an airway so that infection develops behind this obstruction, resulting in the signs and symptoms of pneumonia. Usually people with lung cancer complain of increased cough, fever, and sometimes chest pain. Because the obstruction prevents the effective clearing of secretions from the involved lung, the symptoms persist even if antibiotics bring the infection itself under control.

The development of these complaints demands investigation in the attempt to detect the cancer at the earliest possible moment.

Diagnostic Techniques

Once cancer is suspected, there are several techniques of investigation that can be pursued.

• Sputum can be collected and examined microscopically for the presence of malignant cells which have sloughed from the surface of the tumor. Adequate and careful sampling is required.

• Bronchoscopic examination of the airway is sometimes undertaken. In this examination the doctor passes a tube through the mouth or nose into the airways subdivision of each lung. When the obstructing tumor can be seen, a small piece of the tumor can be removed through the bronchoscope for examination under the microscope. Brushings and washings can also be taken from a suspect area for subsequent examination.

• Needle biopsy-When the tumor cannot be reached by the bronchoscope and diagnosis has not already been established, a fine needle can be introduced through the chest wall directly into the tumor with x-ray guidance. A small sample is taken of the tissue and then examined microscopically.

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• Mediastinoscopy-Since it is essential that the specific nature of the tumor be clearly established before deciding how best to treat it, additional information can be obtained by making a short incision just above the breast bone down to the airway (trachea). A tube is passed through the incision downward alongside the airway to inspect the lymph nodes near the lungs. This procedure is called a mediastioscopy. If abnormalities are noted, biopsies can be obtained for examination.

• Computerized Axial Tomography (CAT) Scans are used to help a physician diagnose the presence and extent of any cancer in the lung. During this painless procedure, a narrow x- ray beam is directed by a computer to revolve around the chest area. Within seconds, thousands of bits of information are fed into the computer which converts the data into an image.

• And finally, if all other measures have failed to establish a working diagnosis, a small opening can be made in the chest (mini-thoracotomy) through which the tumor can be directly examined and material obtained for diagnostic purposes.

Treatment

Once the diagnosis has been established, the decision regarding appropriate treatment must be made. The doctor treats the whole person and not the disease alone. Therefore, the same treatment is not necessarily used for all people with cancer.

Lung cancers are not all alike and patients themselves differ widely in their resistance to the development and spread of the cancer. Some cancers grow and spread rapidly and aggressively whereas others grow slowly, not spreading until very late in the development of the tumor. Similarly, some patients can reject spreading tumor cells and also maintain effective control of the local growth while others cannot. Therefore, the doctor decides whether the tumor is one which is best treated surgically, by radiation, by the use of drugs (chemotherapy), or by a combination of these measures.

If the tumor is localized so that surgery is advisable, about 30-35 per cent of the people who have lung cancer will be alive and well five years after a successful operation. Radiotherapy is considered a better method of controlling the primary tumor when it cannot be removed completely or when the patient's health indicates that surgery would be inadvisable.

The use of drugs, or chemotherapy, has in the past been used when there is evidence that the tumor has spread to other parts of the body. More recently, chemotherapy has been shown to be particularly helpful in the treatment of the small cell variant of lung cancer and an increase in long term survivals is now being reported following this form of treatment. However, overall, when all people with cancer of the lung are considered, it is obvious that prevention through smoking cessation is the best solution.

Emphysem

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Emphysema is a slowly progressing (chronic) destruction of the lungs which makes breathing very hard to do. Persons with emphysema are, for the most part, males between 50 and 70 years old. Women get emphysema,

too, but so far, not as often as men. However these statistics are changing as women are starting to smoke more, and at an earlier age. A very high percentage of the people who have emphysema smoke cigarettes and have been heavy smokers for many years. Frequently, they live in areas where air pollution is a constant problem.

Some people are born with a lack of a substance called alpha-1 antitrypsin. This makes them more likely than others to get emphysema and at an earlier age.

How it Attacks

A person with emphysema doesn’t develop the disease suddenly. It comes on gradually. He or she has probably had several very bad colds each winter for the past few years, each accompanied by a heavy cough, and often with chronic bronchitis. The cough often persists between colds and becomes chronic. The symptom that usually brings the patient to the doctor is that he or she has begun to feel short of breath on exertion in morning or evening or both. The patient may think he or she has asthma or heart disease.

Causes of Emphysema

It is believed that emphysema often is a late effect of chronic infection or irritation of the bronchial tubes. When the bronchi become irritated, some of the airways may be obstructed, trapping air in the lung beyond them. Or the walls of the tiny air spaces may tear, for various reasons. The small blood vessels in the walls disappear. Less contact between blood and air results.

If infection or irritation continues or is repeated for a long time and the stretching and destruction of the walls of the air spaces goes on, the lungs as a whole may become enlarged, at the same time becoming less efficient in exchanging oxygen for carbon dioxide. Enlarged lungs are what give the disease its name, emphysema (which is a Greek word meaning "Inflation").

Cigarette smoking contributes to the destructive processes that end up as emphysema.

Effects of Emphysema

Emphysema may begin with only a slight morning and evening inconvenience in breathing. Next, a short walk may be enough to bring on an attack of breathlessness. It may reach a point where every breath requires a major effort. The changes of emphysema also interfere with the passage of blood through the small blood vessels of the lung. As interference grows, the heart must work harder to pump blood. The heart

a

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may enlarge under the strain and eventually give out. This type of heart failure is often an end result of emphysema.

Treatment

The emphysematous patient must stop smoking to retard progression of the disease. Doctors may prescribe various bronchial dilating medications to treat an asthmatic component that often co-exists with emphysema. Antibiotics are helpful for acute chest infections. Some patients benefit from oxygen therapy, either when exercising or on a nearly continuous basis.

For the few patients suffering alpha-1 antitrypsin deficiency, weekly infusions of alpha-1 antitrypsin are available. These infusions are very expensive and it is not yet known if progress of this rare form of emphysema can be reduced by using this therapy. Physicians may emphasize the importance of regular exercise to maintain physical fitness and even refer a patient with emphysema to a respiratory rehabilitation program.

Prevention

At this time, doctors do not know how to prevent emphysema. Continuing research is being conducted to find answers to many questions about this disease. But they do know that cigarette smoking is a definite cause, and that cutting out smoking can avoid damage for many who would otherwise develop the disease. Controlling air pollution can also help.

Modern medicine can usually slow down the progress of emphysema if patients are treated early. It is always the doctor’s immediate concern to clear up any infection or irritation of a patient’s respiratory system, because these things set up a possible starting place for emphysema.

Chronic

Brochitis

The bronchi are air passages connecting the windpipe (trachea) with the sacs of the lung (alveoli) where oxygen is taken up by the blood. Bronchitis is an inflammation of the bronchi causing excessive mucous production and swelling of the bronchial walls.

Many people suffer a brief attack of acute bronchitis with fever, coughing and spitting when they have a severe cold. Chronic bronchitis, however, is the term applied when this coughing and spitting continue for months and return each year, generally lasting slightly longer each time. Undue breathlessness on exertion is eventually noticed, due to obstruction to air flow in the air passages caused by

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swelling of the bronchial wall and the presence of mucous that cannot be cleared.

What Causes Chronic Bronchitis?

Cigarette smoking is the most important cause of chronic bronchitis which rarely occurs in the non-smoker. Environmental pollution may contribute to the development of chronic bronchitis. Some smokers are resistant to the development of chronic bronchitis, but as yet there is no way of predicting which smokers will not develop chronic bronchitis. The decreased incidence of chronic bronchitis among women probably reflects the difference in smoking habits between the sexes. As these differences have diminished we are seeing an increasing incidence of chronic bronchitis in women.

Chest infections seem to occur more frequently in patients with chronic bronchitis. Inhaled tobacco products impair the ability of the lungs to combat infections. The excessive mucus associated with chronic bronchitis is ideal for bacteria to breed.

What does Chronic Bronchitis feel like?

Initially, it begins as a "smoker’s cough" – the expectoration of small amounts of phlegm each morning. It is usually worse in the winter time and when the person has a head cold. In these early phases of chronic bronchitis, the person may lead an entirely normal life, including vigorous sports. Sensitive breathing tests, however, can indicate the beginning of irreversible damage to the lung even at this stage.

The cough becomes more frequent during the day time and even at night, disturbing sleep. The patient then notices that activities previously tolerated well, cause shortness of breath and perhaps some wheezing. As the disease progresses, shortness of breath may be caused by very ordinary activities such as getting dressed in the morning or having a bath.

The patient with advanced bronchitis may be unable to walk or climb stairs without supplemental oxygen. He or she may be confined to a chair or bed because of shortness of breath and the type of heart failure which may develop in the late stages of this disease. Minor chest infections in patients with severe chronic bronchitis may require intensive treatment in hospital. As the disease is not rapidly fatal, it becomes an important cause of disability and the annual cost of this disease in terms of time lost from work, disability pensions and medical therapy may approach one hundred million dollars annually in Canada.

Treatment

The best treatment for chronic bronchitis is prevention which means no smoking. Once chronic bronchitis is established, smoking cessation does not cure the disease. The cough of chronic bronchitis will diminish within weeks of smoking cessation and usually disappears entirely within three months. Obstruction to air flow caused by swelling of the walls of the bronchi persists, although medications to dilate the bronchi (bronchodilators) may diminish the breathlessness.

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The important point to remember is that patients with chronic bronchitis who continue to smoke continue to deteriorate relatively rapidly. Smoking cessation will stop this rapid deterioration and there may actually be a slight improvement in the ability to lead a normal life.

Many physicians prescribe antibiotics for acute chest infections which may shorten their duration and help prevent pneumonia. Annual vaccinations against influenza and a once only vaccination against bacterial pneumococcal pneumonia may help prevent the pulmonary complication of infections in chronic bronchitis.

The sufferer from chronic bronchitis should avoid excessive dust and fumes although under normal circumstances, the contribution of atmospheric pollution to chronic bronchitis is extremely small.

Regular exercise is even more important for patients suffering chronic bronchitis than for healthy individuals. Exercise does not improve the ability of the lungs to take up oxygen, but the effects of physical fitness on the cardiovascular system will compensate somewhat for the impaired lung function. The result of physical fitness in the patient suffering from chronic bronchitis is a lessening in breathlessness on exercise.

Chronic bronchitis is basically a preventable disease being rare in the non-smoker. It is never too late to stop smoking. The patient with chronic bronchitis can be treated with better results in the early stages of the disease.

Asthm

a

Asthma is a chronic lung condition. It is characterized by difficulty in breathing. People with asthma have extra sensitive or hyperresponsive airways. The airways react by narrowing or obstructing when they become irritated. This makes it difficult for the air to move in and out. This narrowing or obstruction can cause one or a combination of wheezing, coughing, shortness of breath, chest tightness

This narrowing or obstruction is caused by airway inflammation (meaning that the airways in the lungs become red, swollen and narrow) and bronchoconstriction (meaning that the muscles that encircle the airways tighten or go into spasm)

Two factors provoke asthma:

a) Triggers

Triggers irritate the airways and result in bronchoconstriction although they do not cause inflammation and therefore do not cause asthma. The symptoms and bronchoconstriction caused by triggers tend to be immediate, short-lived, and rapidly reversible. The airways will react more quickly to triggers if inflammation is

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already present in the airways.

Common triggers of bronchoconstriction include everyday stimuli such as cold air, dust, strong fumes, exercise, inhaled irritants, emotional upsets, and smoke.

Smoke acts as a very strong trigger. Second-hand smoke has been shown to aggravate asthma symptoms, especially in children. The effects of one cigarette linger in the home for 7 days, and therefore it is very important to provide a smoke-free home for all children. In fact, some health care workers feel that smoking in a home where there is a child with asthma is a form of child abuse. Children should not be exposed to a polluted environment over which they have no control.

b) Causes or Inducers

In contrast to triggers, inducers cause both airway inflammation and airway hyperresponsiveness and are recognized as causes of asthma. Inducers result in symptoms which may last longer, are delayed and less easily reversible than those caused by triggers.

The most common inducers are allergens and respiratory viral infections.

Allergens

Inhalant allergens are the most important inducer or cause of inflammation and airway hyperresponsiveness. Probably 75-80% of young asthmatics are allergic. The most common inhaled allergens include pollen (grasses, trees and weeds), animal secretions (cats and horses tend to be to the most allergen causing), molds, and house dust mites.

Exposure to an allergen (e.g. cat secretions) may cause immediate symptoms such as wheeze or cough. This occurs because airways are hyperresponsive and react by tightening. These symptoms can easily be relieved by a bronchodilator (such as Ventolin®). However, about 4 and 7-8 hours after exposure to the secretion, a late response occurs which is caused by the inflammation. This inflammation develops over time. Because of the late response, it is often difficult for the patient and physician to identify what is actually causing the asthma.

Respiratory Viral Infections

In children, respiratory viral infections may cause deterioration in his or her asthma. A respiratory viral infection is probably one of the most common causes of asthma. In some cases, the influenza vaccine is indicated. This may help to prevent respiratory complications that can occur from developing influenza. This vaccine is contraindicated for those individuals who have an allergy to eggs.

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Diagnosis

Making a correct diagnosis is extremely important: if asthma is correctly diagnosed it can be treated appropriately. The diagnosis of asthma involves the following:

1. Detailed history which would include: � family history of asthma, allergies, hay fever, eczema; children will

have a greater chance of developing the above if there is a family history of allergies and asthma

� child's medical history including: � when parents first noticed the child developed breathing

problems; history of nasal stuffiness (rhinitis), itchy eyes (allergic conjunctivitis) and eczema, which are common accompaniments to asthma, and hives (urticaria).

� history of recurrent and persistent cough following a cold, frequent colds, croup, seasonal changes (i.e. worse in the spring and fall), exercise limited by breathing problems, waking at night with symptoms.

� school absences, emergency room visits (hospitalizations) � environmental history

2. Physical examination: i.e. listening to the lungs with a stethoscope; examination of nasal passages etc.

3. Chest x-ray may be done once to exclude the possibility of breathing problems being caused by something other than asthma.

4. Blood tests and sputum studies may be done. 5. Allergy prick skin testing: Skin tests can confirm the presence or absence of

allergies; they must, however, be correlated to the history of symptoms. 6. Spirometry is a breathing test which measures the amount and rate at which air

can pass through airways; if the airways are narrowed because of inflammation it will be more difficult for air to pass through the airways. This will result in changes in spirometry values. With children under the age of five years, generally this test is not indicated because there is a certain amount of effort and cooperation required. However, this is a very dependable method of making a diagnosis. Any difficult or troublesome asthma should be confirmed objectively by performing spirometry.

7. Challenge tests: Exercise challenge tests and methacholine inhalation tests are procedures used most frequently in clinical laboratories to evaluate airway responsiveness.

8. Differential diagnosis: Other possible causes of shortness of breath, wheeze, cough and chest tightness must be investigated in order to rule these out. i.e. such as heart disease, other lung conditions.

9. A trial use of asthma medications: If asthma medications are taken and improvement in symptoms is seen this further supports the diagnosis of asthma.

Because of the variability of symptoms (meaning symptoms can become worse and improve over time), a diagnosis cannot always be made immediately.

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Managing Asthma

The consensus of asthma specialists is that the best way to manage asthma is to have the individual actively involved in his or her own treatment.

1. Education

Patient education is an important area where asthma treatment can be improved. Asthma is common and controllable. Asthma is a disease that is variable, meaning that symptoms may get worse and may improve over time. Because of this variability it is often necessary to review and change the treatment. In order to enhance the patient-physician relationship, the patient must be familiar with the following:

� Nature of the disease; identifying provoking factors � Nature of medications and side effects � Proper technique of using devices � Goals of treatment � Early recognition of worsening control � Written Action Plan � Asthma Diary Form

The patient with this type of knowledge can communicate to the physician in order to work out an appropriate treatment plan. The goals of treatment should be understood and agreed upon by both the physician and the patient.

2. Environmental Control

Environmental control should always be initiated along with taking the appropriate medications. If exposures to inducers are avoided, less medication is required.

It is not always easy to identify what inducer is making the asthma worse. It often means reviewing the history of symptoms carefully i.e. keeping track of the symptoms.

Controlling the inside and outside environment at home and in school, should be considered for those people who have identified allergies. For example:

o House dust mites: Dust mites are small parasites that live off the dead skin that we shed. Decrease exposure by enclosing mattress and box spring in plastic and washing all bed sheets and blankets in hot water once a week.

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o Pets: If allergic to pets, animals should not be allowed in the house; this can include animals such as dogs, cats, gerbils and birds. People with identified animal allergies should not care for the pet.

o Smoke: No smoking in the home should be allowed at any time. o Mold: Remove the mold wherever and whenever mold is found. Bleach

can be used for this. The source of mold should be eliminated. o High humidity: Increased moisture in the home can encourage mold

growth and house dust mites, which require greater than 50% humidity to survive. Humidifiers, if not cleaned properly, can grow bacteria and produce a residue which some people find irritating to their lungs.

o Pollens: It may be necessary to avoid playing outside during times of high pollen counts. Pollen counts are usually greater in hot, dry and/or windy weather and usually between 4-10 AM. Camping and raking leaves will expose the person to pollens.

3. Medications

Drugs and devices used in the treatment of asthma include:

o Anti-inflammatories o Bronchodilators o Inhalation Devices

There are many other diseases or disorders that you may be interested in investigating. Please discuss this possible research with your teacher/tutor-marker.

Lesson 4

Exercise

Briefly describe the following disorders/diseases of the respiratory system. Include: a) Description of the disease/disorder b) Symptoms c) Causes d) Treatment

1. Emphysema

2. Lung Cancer

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3. Asthma

4. Bronchitis