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Lower respiratory tract infection

Lower respiratory tract infection is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lower respiratory tract infection rather than just read about it. In short: Lower respiratory tract infection (LRTI) is a term often used as a synonym for pneumonia but can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, coughing and fatigue.

Lower respiratory tract infection — main illustration
Lower respiratory tract infection — illustration

Key takeaways

  • Lower respiratory tract infection belongs to biology; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Lower respiratory tract infection to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Lower respiratory tract infection from memory before moving on to harder problems.

Reference excerpt

Lower respiratory tract infection (LRTI) is a term often used as a synonym for pneumonia but can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, coughing and fatigue. A routine chest X-ray is not always necessary for people who have symptoms of a lower respiratory tract infection. Influenza affects both the upper and lower respiratory tracts. Antibiotics are the first line treatment for pneumonia; however, they are neither effective nor indicated for parasitic or viral infections. Acute bronchitis typically resolves on its own with time. In 2015 there were about 291 million cases. These resulted in 2.74 million deaths down from 3.4 million deaths in 1990. This was 4.8% of all deaths in 2013. The World Health Organization has reported that, in 2021, "Lower respiratory infections remained the world's most deadly communicable disease other than COVID-19, ranked as the fifth leading cause of death." However, the number of deaths caused has decreased by around 13% from 2000 to 2021.

Bronchitis

Bronchitis describes the swelling or inflammation of the bronchial tubes. Additionally, bronchitis is described as either acute or chronic depending on its presentation and is also further described by the causative agent. Acute bronchitis can be defined as acute bacterial or viral infection of the larger airways in healthy patients with no history of recurrent disease. It affects over 40 adults per 1000 each year and consists of transient inflammation of the major bronchi and trachea. Most often it is caused by viral infection and hence antibiotic therapy is not indicated in immunocompetent individuals. Viral bronchitis can sometimes be treated using antiviral medications depending on the virus causing the infection, and medications such as anti-inflammatory drugs and expectorants can help mitigate the symptoms. Treatment of acute bronchitis with antibiotics is common but controversial as their use has only moderate benefit weighted against potential side effects (nausea and vomiting), increased resistance, and cost of treatment in a self-limiting condition. Beta2 agonists are sometimes used to relieve the cough associated with acute bronchitis. In a recent systematic review it was found there was no evidence to support their use. Acute exacerbations of chronic bronchitis (AECB) are frequently due to non-infective causes along with viral ones. 50% of patients are colonised with Haemophilus influenzae, Streptococcus pneumoniae, or Moraxella catarrhalis. Antibiotics have only been shown to be effective if all three of the following symptoms are present: increased dyspnea, increased sputum volume, and purulence. In these cases, 500 mg of amoxicillin orally, every 8 hours for 5 days or 100 mg doxycycline orally for 5 days should be used.

Pneumonia

Pneumonia occurs in a variety of situations and treatment must vary according to the situation. It is classified as either community or hospital acquired depending on where the patient contracted the infection. It is life-threatening in the elderly or those who are immunocompromised. The most common treatment is antibiotics and these vary in their adverse effects and their effectiveness. Pneumonia is also the leading cause of death in children less than five years of age in low income countries. The most common cause of pneumonia is pneumococcal bacteria, Streptococcus pneumoniae accounts for 2/3 of bacteremic pneumonias. Invasive pneumococcal pneumonia has a mortality rate of around 20%. For optimal management of a pneumonia patient, the following must be assessed: pneumonia severity (including treatment location, e.g., home, hospital or intensive care), identification of causative organism, analgesia of chest pain, the need for supplemental oxygen, physiotherapy, hydration, bronchodilators and possible complications of emphysema or lung abscess.

Causes

Typical bacterial Infections:

Haemophilus influenzae Staphylococcus aureus Klebsiella pneumoniae Atypical bacterial Infections:

Legionella pneumophila Mycoplasma pneumoniae Chlamydophila pneumoniae Chlamydia psittaci Parasitic infections:

Respiratory cryptosporidiosis Viral infections:

Adenovirus Influenza A virus Influenza B virus Human parainfluenza viruses Human respiratory syncytial virus Severe acute respiratory syndrome coronavirus (SARS-CoV) Middle East respiratory syndrome coronavirus (MERS-CoV) Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Aspiration pneumonia

Prevention Vaccination helps prevent bronchopneumonia, mostly against influenza viruses, adenoviruses, measles, rubella, streptococcus pneumoniae, haemophilus influenzae, diphtheria, bacillus anthracis, chickenpox, and bordetella pertussis. Specifically for the children with low serum retinol or who are suffering from malnutrition, vitamin A supplements are recommended as a preventive measure against acute LRTI.

… excerpt ends here. Continue reading the full article.

Illustrations

Lower respiratory tract infection illustration
Lower respiratory tract infection: Deaths from lower respiratory infections per million persons in 2012: .mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}  24-120  121-151  152-200  201-241  242-345  346-436  437-673  674-864  865-1,209  1,210-2,085
Deaths from lower respiratory infections per million persons in 2012: .mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}  24-120  121-151  152-200  201-241  242-345  346-436  437-673  674-864  865-1,209  1,210-2,085
Lower respiratory tract infection: Disability-adjusted life year for lower respiratory infections per 100,000 inhabitants in 2004:[18]  no data   less than 100   100–700   700–1,400   1,400–2,100   2,100–2,800   2,800–3,500   3,500–4,200   4,200–4,900   4,900–5,600   5,600–6,300   6,300–7,000   more than 7,000
Disability-adjusted life year for lower respiratory infections per 100,000 inhabitants in 2004:[18]  no data   less than 100   100–700   700–1,400   1,400–2,100   2,100–2,800   2,800–3,500   3,500–4,200   4,200–4,900   4,900–5,600   5,600–6,300   6,300–7,000   more than 7,000

Worked examples

Example 1 — a first encounter with Lower respiratory tract infection

Start with the simplest possible case. Write down what Lower respiratory tract infection claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lower respiratory tract infection before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lower respiratory tract infection ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lower respiratory tract infection

In research
Lower respiratory tract infection appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Lower respiratory tract infection in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Lower respiratory tract infection is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acute lower respiratory infections, Infectious diseases, so understanding it makes those chapters shorter.
In everyday life
Look for Lower respiratory tract infection outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Lower respiratory tract infection in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Lower respiratory tract infection means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Lower respiratory tract infection out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lower respiratory tract infection in simple terms?

Lower respiratory tract infection (LRTI) is a term often used as a synonym for pneumonia but can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, coughing and fatigue.

Why does Lower respiratory tract infection matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lower respiratory tract infection?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lower respiratory tract infection.

Tags

  • Acute lower respiratory infections
  • Infectious diseases

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