LRTI Flashcards
What is present throughout the lower respiratory tract?
Mucus, cilia, immune cells and commensal organisms are present throughout the LRT.
Where can LRTI occur?
LRTI can occur at every level of the respiratory tract
what is tracheitis?
Tracheitis = rare, viral or bacterial infection of the trachea, often overlaps with laryngitis.
Often affects young children, if not treated quickly it can lead to life threatening complications.
What is bronchitis?
Bronchitis = LRTI affecting the bronchi, may be acute or chronic
what is bronchiolitis?
Bronchiolitis = infection of the bronchioles, usually in children under 2 yrs, viral, usually RSV
What is pneumonia?
Pneumonia = LRTI affecting the alveoli, may be lobar or multifocal
How common and what is a lung abscess?
How can they develop?
Lung abscess = liquefactive necrosis of lung tissue and formation of cavities containing necrotic debris/ fluid often caused by aspiration.
They are rare, lung abscess can be bronchogenic ( from aspiration, inhalation and airway damage) and haematogenic-dissemination from other infected sites.
What can a pleural infection lead to?
pleural infection = pleural effusion (build up of fluid between the two pleural layers around the lung) –> infection –> empyema (pus filled pocket within the pleural space).
which type of pathogen is the most likely to cause a pleural effusion?
What is pleural effusion secondary to pneumonia called?
Describe the three stages from infection within the lungs to empyema development.
Bacteria are the pathogens responsible for the majority of pleural effusion from infectious causes.
Pleural effusion secondary to pneumonia is termed paraneumonic effusion
First stage in exudative phase pleural fluid accumulates from increased pulmonary interstitial fluid traversing visceral pleura and due to increased permeability of the pleural capillaries from inflammation
If infection within the lung continues, bacteria may be able to pass through the visceral pleura into the plerual cavity and infect this space. This is called the fibropurulent stage.
Empyema is the third stage of pleural effusion spectrum, is defined as frank pus in the pleural cavity.
How can LRTI be classified?
Classified either by 1) location of infection 2) by cause
What are some of the causes of LRTI?
(think causative classifications)
- Infective exacerbation of COPD (chronic bronchitis and emphysema)
- Community acquired pneumonia (CAP) = usualyl due to organisms that are common and sensitive to first line antibiotics
- Hospital acquired pneumonia (HAP) = possibly due to organisms that are rare and resistnt to first line antibiotics
- Atypical pneumonia = due to uncommon organisms (e.g. pertussis)
- Secondary pneumonia = bacterial pneumonia following virtal LRTI
- Aspiration pneumonia = due to aspirating drinks, secretions etc..
- Opportunistic LRTI = due to immunodeficiency or immunosuppression
What agent is most likely to cause acute bronchitis?
What agent is most likely to cause chronic bronchitis?
What are typical microbes that cause bronchitis?
Acute bronchitis mostly viral causes
Chronic bronchitis mostly bacterial
Typical microbes:
Viral –> Rhinovirus and influenza
Bacterial –> Streptococcus pneumoniae
Haemophilis influenzae
Other causes –> possibly underlying airway damage
What microbes are involved in pneumonia (typically)?
Whats a possible underlying cause?
Microbes –> influenza virus
Streptococcus pneumoniae
Staphylococcus aureus
Possibly underlying immunocompromised
What does tuberculosis cause?
What are the different classifications of the disease it can cause?
Tuberculosis causes bronchopneumonia w/ w/out haemoptysis
Note: bronchopneumonia = foci of consolidation (pus in alveoli and adjacent air passages) scatted in one or more lobes of one or both of the lungs.
Lobar pneumonia = actue inflammatin in one lobe of the lung
interstitial pneumonia = pneumonia within tissue inbetween the alevoli, also called interstitial pneumonitis.
What are the specific risk factors for LRTI?
- Extremes of age –> younger children and older adults
- Stress and starvation
- Immunocompromised host –> LRTI more common w HIV
- Compromised barries to infection:
- smoking increases mucus production yet reduces ciliary action
- smoking related damage to resp tissues (Bronchitis)
- viral LRTI damages resp tissues –> leads to bacterial LRTI
- Depletion of commensal organisms by anti microbial tx
- malformations (rare) and obstructions (e.g. tumours)
- Iatrogenic (tracheostomy, bronchoscopy)
Describe the pathogenesis of LRTI?
Access –> Resp tract is open to environment
Adherence –> pathogenic organisms have receptors for respiratory tissues
Invasion –> damaged resp tissues help invasion
Multiplications –> good nutritional environment for microorganisms
Evasions –> immune cells are present, damaged tissues help evasion
Resistance –> some bacteria causing LRTI have multi drug resistance
Damage –> causes bronchitis , pneumonia, septicaemia etc
Transmission –> easily passed out in resp. secretions
What are the specific clinical features of Bronchitis?
pathology
symptoms
signs
investigations
how common is sepsis?
Bronchitis
Pathology –> infection and inflammation of airways
Symptoms –> dysponea, cough, sputum and wheeze
Signs –> fever, tachypnoea, crackles and wheeze
Investigations –> hypoxia (possibly), normal CXR (usually)
Sepsis = uncommon