Respiratory Tract Infections – Treatment & management. Self Learn Series 18

By definition, Respiratory tract infection is said to occur when pathological bacteria are present in the respiratory tract and are producing the symptoms of an infection. Rspiratory tract infections include conditions such as bronchitis, diphtheria, influenza (flu), colds, croup, pneumonia, sinusitis, legionnaires’ disease, severe acute respiratory syndrome (SARS), tuberculosis and whooping cough. There is, usually, a build-up of pus and fluid (mucus) and the airways become swollen, making it difficult for you to breathe. Most of the symptoms of respiratory tract are due to these occurances.

This article is about respiratory tract infectons in adults and it is written with the aims of reducing the prevelence of respiratory tract infections and on how to manage them.

Anatomy of the Respiratoy System.

The human respiratory system is made up cell, tissues and organs which are involved in the interchange of gases and consists of the nose, pharynx, larynx, trachea, bronchi and lungs. The organs of the Upper respiratory tract include tne nose, nasal cavity, ethmoidal air cells, frontal sinuses, maxillary sinus, larynx and the trachea. All of these parts are shown in the diagram 1, below. The organs of the lower respiratory tract include the lungs, the bronchi and the alveoli.

Each student is expected to know the different parts of the Respiratory system because there will be times when an infection will be localised. When this happens, the symptoms are not necessarily systemic.

Figure 1. Diagramatic Representation of Human Respiratory Tract.

Physiology of the Respiratory Tract.

Physiology is the study of the functioning of living organisms or their constituent tissues or cells. Physiology is usually considered separately from anatomy which has already been discussed above. High powered microscopes made it clear that structure and function were inseparable at the cellular and molecular level. An understanding of biochemistry is fundamental to physiology. Physiological processes are dynamic; cells change their function in response to changes in the composition of their local environment, and the organism responds to alterations in both its internal and external environment. Many physiological reactions are aimed at preserving a constant physical and chemical internal environment.

Breathing (External Respiration)

Breathing consists of two phases, inspiration and expiration. During inspiration, the diaphragm and the intercostal muscles contract. The diaphragm moves downwards increasing the volume of the thoracic (chest) cavity, and the intercostal muscles pull the ribs up expanding the rib cage and further increasing this volume. This increase of volume lowers the air pressure in the alveoli to below atmospheric pressure. 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, changing the pressure inside thelunsg relative to the pressure of the outside atmosphere. In contrast to inspiration, during expiration the diaphragm and intercostal muscles relax. This returns the thoracic cavity to it’s original volume, increasing the air pressure in the lungs, and forcing the air out.

When a breath is taken, air passes in through the nostrils, through the nasal passages, into the pharynx, through the larynx, down the trachea, into one of the main bronchi, then into smaller broncial tubules, through even smaller broncioles, and into a microscopic air sac called an alveolus. It is here that external respiration occurs. Simply put, it is the exchange of oxygen and carbon dioxide between the air and the blood in the lungs. Blood enters the lungs via the pulomanory arteries. It then proceeds through arterioles and into the alveolar capillaries. Oxygen and carbon dioxide are exchanged between blood and the air. This blood then flows out of the alveolar capillaries, through venuoles, and back to the heart via the pulmanory veins.

Figure 2: Alveoli of Lungs where gas exchange takes place.

Transport of Oxygen

In the loading and unloading of oxygen, there is a cooperation between these four haem groups. When oxygen binds to one of the groups, the others change shape slighty and their attraction to oxygen increases. The loading of the first oxygen, results in the rapid loading of the next three (forming oxyhaemoglobin). At the other end, when one group unloads it’s oxygen, the other three rapidly unload as their groups change shape again having less attraction for oxygen. This method of cooperative binding and release can be seen in the dissociation curve for haemoglobin. Over the range of oxygen concentrations where the curve has a steep slope, the slighest change in concentration will cause haemoglobin to load or unload a substantial amount of oxygen. Notice that the steep part of the curve corresponds to the range of oxygen concentrations found in the tissues. When the cells in a particular location begin to work harder, e.g. during exercise, oxygen cincentration dips in that location, as the oxygen is used in cellular respiration. Because of the cooperation between the haem groups, this slight change in concentration is enough to cause a large increase in the amount of oxygen unloaded.

Figure 3: External Respiration at cellular level takes place in the alveoli (shown in diagram above).

As with all proteins, haemoglobin’s shape shift is sensitive to a variety of environmental conditions. A drop in pH lowers the attraction of haemoglobin to oxygen, an effect knownas the Bohr shift. Because carbon dioxide reacts with water to produce carbinic acid, an active tissue will lower the pH of it’s surroundings and encourage haemoglobin to give up extra oxygen, to be used in cellular respiration. Haemoglobin a notable molecule for it’s ability to tranport oxygens from regions of supply to regions of demand.

Internal Respiration – Definition.

All of the body’s tissues need oxygen but have to get rid of the carbon dioxide. The blood carries oxygenated blood throughout the body and exchanges oxygen and carbon dioxide with the body’s tissues. Internal respiration is defined as the exchange of gasses between the blood in the capillaries and the body’s cells.

Causes of Respiratory Tract Infection.

Chest infections are due to any of the following organisms;

• A virus
• Bacteria
• Mycoplasma (a special kind of bacteria/yeast).

Chest infections affect people of all ages and both the sexes. Young children and the elderly are most at risk, as well as people who are ill. Smokers, HIV positive clients and patients who have low white cell counts are high risk patients and sometimes a chest infection can be fatal for these people.

Signs and Symptoms

Pneumonia is more common in winter and spring. It can strike suddenly or come on slowly over a few days. The symptoms will depend on your age, the cause and severity of the infection, and any other medical problems you may have. Symptoms include:

• Fast or difficult breathing. In the hospital setting this is often called tachypnoea (fast breathing) or dyspnoea (difficulty in breathing)
• Coughing with brown or green coloured phlegm. This sort of secretions indicates that the patient’s chest is really infected seriously and medical attention should be sought.
• Fever (sweating, shivering, chills). An elevated temperature that the patient’s body is suffering from generalised invasion by bacteria, viruses or moulds.
• Feeling unwell. This is a non-specific sign but many patients complain of feeling tired and drained of energy.
• Blue colour around the lips (cyanosis). This is an extreme situation. If a patient is blue around the lips, he needs to be given oxygen immediately, as long as he is not suffering from COPD.
• Stomach pain – Non-specific symptom, of limited value in the diagnostic procedure.
• Chest pain – This indicates that the patient is severely infected and he needs medical attention. The pain could be from exhaustion, pleurisy or respiratory distress.
• Headaches. These may or may not be present.
• General aches and pains
• Loss of appetite. This is probably due to a lack of oxygen and low level of energy which is available.
• A child may vomit, have diarrhoea, and be irritable or lethargic. If the patient is a child, he/she should be taken to the hospital for treatment, as soon as possible.

Home Management of a Chest Infection.

Generally speaking, if you have a bacterial chest infection, you should start to feel better 24 to 48 hours after starting on antibiotics. This may not be the case if the infection you have is resistant to the antibiotics you are taking. You may have a cough for days or weeks. For other types of chest infections, the recovery is more gradual. You may feel weak for some time and need a longer period of bed rest.

Be guided by your doctor, but general self-care suggestions include:

• Take your medication as directed. Even if you feel better, finish the course of antibiotics which were prescribed specifically for you.
• Drink plenty of fluids – The fluids help to loosen secretions and to cough out the bacteria.
• Rest for a few days. The infection is a stress to your body system. Resting will make you feel better and help you to recover sooner. In the long run, it is a good thing.
• Prop yourself up on a couple of pillows to sleep – it will make it easier to sleep.
• Most of the published literature states that you should stop smoking, at least until you feel better, in my opinion, this is the best time to give up smoking, for good.
• Use an incentive respirometer to keep your lungs open. This will actually help cough up some of the secretions which have been building up in the passages.
• Contact your local doctor if you have any concerns or questions.
• Go straight to your local doctor or the nearest hospital emergency department if you (or your child) have trouble breathing, have a high fever or feel worse.
• Call or page the on call physician if the saturation of the patient you are looking after is deteriorating.

Prevention:

Individauls who are physically fit seldom get chest infections except from very virulent strains of bacteria. This usually happens when their fluid status, their nutritional or respiratory status is compromised in one way or another.

Vaccines are available to reduce the risk of some types of chest infection. Some groups like the elderly and people with chronic conditions can be vaccinated against one of the most common types of bacterial pneumonia every five years. A different vaccine is used for children. The elderly and people with chronic conditions are advised to have a flu vaccination every year before winter comes. See your doctor for more information.

A chest infection affects your lungs, either in the larger airways (bronchitis) or in the smaller air sacs (pneumonia). Most chest and lung infections can be treated in the home, sometimes a hospital admission and ventilation may be necessary.

It is likely that your own immune system will deal with the infection, as most chest infections are caused by a virus. However, antibiotics are sometimes needed to assist with recovery. If your doctor does not prescribe an antibiotic, you should not worry about it. He is of the opinion that your “chest infection” is viral or one which is not sufficiently virulent and that you are strong enough to deal with it.

The elderly and people with chronic conditions are advised to have a flu vaccination every year before winter comes and pneumococcal vaccine every five years.

If you are a hospital employee, you will be advised to be vaccinated. This is because you are going to be maximally exposed to bacteria when you are needed most. That is the time you are most likely to fall sick. Your employer does not want you to be sick when your services are most needed.

Figure 4: Servo Ventilator – a Breathing Machine

Last but not least, if your system does not cope, you may end up on breathing machine. You will then be sedated, a tube (ETT) will be inserted in your bronchus and you will be placed on a breathing machine for a few days. When you recover, you will be wheened off the machine. A ventilator is shown in the diagram five, above.

Students are reminded that it is beyond their scope of practice to diagnose and treat patients. Only registered physicians can diagnose and treat patients.