Respiratory

Chapter 30: Respiratory Tract Infections, Cancers, and Childhood Illnesses

What is the Respiratory Tract?

• The respiratory tract helps us breathe and is divided into two main parts:

  • Upper respiratory tract: Includes your nose, throat (oropharynx), and voice box (larynx).

  • Lower respiratory tract: Includes your lower breathing tubes (airways) and lungs.

• Both parts work together for proper breathing.

Common Breathing Infections

• Common cold

• Sinus infection (Rhinosinusitis)

• Flu (Influenza)

• Pneumonia (lung infection)

  • (See Table 30.1 for more)

• Tuberculosis (TB)

• Fungal lung infections

What Affects Infection Symptoms?

• How an infection shows up depends on:

  • The part of the respiratory tract affected (e.g., nose vs. lungs).

  • How severe the infection is.

  • The person's age and overall health.

How Do You Catch a Common Cold?

• Colds are viral infections of the upper respiratory tract, caused by many viruses, including:

  • Rhinoviruses

  • Parainfluenza viruses

  • Respiratory syncytial virus (RSV)

  • Coronaviruses

  • Adenoviruses

• Fingers are the main way colds spread through touching contaminated surfaces then your face.

• The virus usually gets into your body through:

  • Breathing in droplets from coughs and sneezes.

  • The lining of your nose (nasal mucosa) and the surface of your eyes (conjunctival surface).

Quiz Question #1

• The most common port of entry for cold viruses is:
  
  A. inhalation
  
  B. small cuts
  
  C. food
  
  D. conjunctival surface of the eyes
  
  E. fingers

Rhinitis and Sinusitis (Inflammation)

• Rhinitis: Means inflammation of the nasal lining (inside your nose).

• Sinusitis: Means inflammation of the sinuses (air-filled spaces in your skull).

Types of Sinuses

• Paranasal sinuses: These are air-filled spaces in your skull that connect to your nasal cavity through small openings called ostia.

  • Maxillary sinus: Located below your eye socket and above your hard palate. Its opening makes drainage difficult.

  • Frontal sinuses: Located in your forehead, opening into the middle part of your nasal cavity.

  • Sphenoid sinus: Located behind your eyes, near your pituitary gland. It drains into the top part of your nasal cavity.

  • Ethmoid sinuses: A group of 3 to 15 small air cells on each side of your nose, with their own drainage paths.

Types of Sinus Infections (Rhinosinusitis)

• Acute rhinosinusitis:

  • Can be caused by viruses, bacteria, or both.

  • Lasts from 5-7 days up to 4 weeks.

• Subacute rhinosinusitis:

  • Lasts from 4 weeks to less than 12 weeks.

• Chronic rhinosinusitis:

  • Continues for more than 12 weeks.

Allergic Sinusitis (Allergic Rhinosinusitis)

• What it is: Often happens with hay fever (allergic rhinitis). The lining of the nose changes like in other allergies.

• Symptoms: Stuffy nose, itchy/burning nose, sneezing often, headache in the forehead, and watery snot.

• Treatment: Medications like oral antihistamines (for allergies), nasal decongestants (to clear stuffiness), and intranasal cromolyn (to prevent allergy symptoms) are used.

Types of Flu Viruses (Influenza)

• Type A:

  • The most common and severe type.

  • Can infect many animals and causes the worst illnesses.

  • Divided into subtypes based on two surface markers: Hemagglutinin (H) and Neuraminidase (N).

• Type B:

  • Only affects humans.

  • Not divided into subtypes.

Antiviral Medicines for Flu

• Amantadine

• Rimantadine

• Zanamivir

• Oseltamivir

Types of Flu Shots (Vaccinations)

• Trivalent inactivated influenza vaccine (TIIV):

  • The older type, given as a shot.

  • Developed in the 1940s.

• Live, attenuated influenza vaccine (LAIV):

  • Newer type (approved in 2003), given as a nasal spray.

Pneumonia (Lung Infection)

• Definition: An inflammatory disorder that affects the lung structures, including the tiny air sacs (alveoli) and small breathing tubes (bronchioles).

• Causes:

  • Infectious: Bacteria and viruses.

  • Noninfectious: Like stomach fluids accidentally breathed into the lungs.

What Makes Pneumonia Develop More Easily?

• Strong germs (highly virulent organisms).

• A large amount of germs breathed in (large inoculum).

• Weakened body defenses (impaired host defenses).

How Pneumonia is Grouped (Classifications)

• Based on where you got the infection:

  • Community-acquired pneumonia (got it outside a hospital).

  • Hospital-acquired pneumonia (got it in a hospital).

• Based on the patient's immune system:

  • Pneumonia in people with weakened immune systems.

Tuberculosis (TB)

• Caused by a bacterium called Mycobacterium tuberculosis.

  • This bacterium has a waxy outer coating that makes it hard to kill.

• TB can infect almost any organ, but it mostly affects the lungs.

• The body's immune cells (macrophages) try to attack it, which can unfortunately destroy lung tissue.

• A cell-mediated immune response in your body helps fight the bacteria and causes a reaction in the tissue.

Forms of Tuberculosis

• M. tuberculosis hominis (Human TB):

  • Spreads through the air when people with active TB cough or sneeze (droplet nuclei).

  • More common in crowded living areas.

• Bovine tuberculosis (Cow TB):

  • Caused by drinking milk from infected cows.

  • Starts in the digestive system.

  • Almost gone in North America and other developed countries.

Positive TB Skin Test: What it Means

• A positive tuberculin skin test means your body has had an immune reaction, showing:

  • You were previously infected with M. tuberculosis.

  • Your body has an immune response to the bacteria.

  • Important: A positive test does not mean you have active TB disease right now.

Fungal Infections of the Lung

• Lab Tests for Diagnosing Histoplasmosis (a type of fungal infection):

  • Cultures (growing the fungi in a lab).

  • Fungal stain (looking at fungi under a microscope).

  • Antigen detection (finding parts of the fungi).

  • Serologic tests (checking your blood for antibodies against the fungi).

Fungi: Types and How They Spread

• Yeasts: Round-shaped fungi that reproduce by budding (like a small bump growing off the main cell).

• Molds: Form long, thread-like structures called hyphae, which branch out and produce spores.

• Dimorphic Fungi: These fungi are special because they can exist in two forms:

  • They grow as yeasts at body temperature ($37^ ext{o} ext{C}$).

  • They grow as molds at room temperature ($25^ ext{o} ext{C}$).

• How Fungi Spread: Mainly by breathing in their spores.

Cancer of the Lung

What Causes Lung Cancer?

• Smoking (the biggest cause).

• Exposure to asbestos (a type of mineral).

• Family history (familial predisposition).

Types of Lung Tumors (Cancers)

• Primary lung tumors: Start in the lung (about 95% of cases).

• Secondary tumors: Spread to the lung from cancer elsewhere in the body (called metastasis).

• Small cell carcinoma (SCLC) (around 15% of lung cancers):

  • Made of small, round to oval cells.

  • Highly aggressive and spreads quickly.

• Non-small cell lung cancer (NSCLC) (around 85% of lung cancers):

  • This group includes different types:

    • Squamous cell lung carcinoma: Strongly linked to smoking.

    • Adenocarcinoma: This, along with squamous cell, makes up 90% of NSCLC.

    • Large cell carcinoma: Has large, polygonal cells and tends to spread early.

Quiz Question #2

• Why are the lungs a common site for secondary tumor development?
  
  A. Due to the highly vascular nature and small capillaries
  
  B. Due to the fragility of the cells
  
  C. Due to the rapid replication of type I alveolar cells
  
  D. Due to dumb luck

How Lung Cancer Shows Up (Manifestations)

• Symptoms from the lung or nearby areas: Like a cough or chest pain.

• Symptoms from cancer spread: Effects due to the cancer spreading to other parts of the body.

• Paraneoplastic syndromes: Problems not caused by the tumor itself, but by substances the tumor makes, affecting hormones, nerves, or connective tissues.

• General symptoms: Like not wanting to eat (anorexia) and losing weight.

Quiz Question #3

• Which of the following involves infection of the entire respiratory tract?
  
  A. Common cold
  
  B. Pneumonia
  
  C. Tuberculosis
  
  D. Cancer

Breathing Problems in Children

Stages of Lung Development in a Baby

• Embryonic period: The very early stage where basic lung structures begin to form.

• Pseudoglandular period: Lungs look like glands, and branching airways develop.

• Canalicular period: Airways become wider, and blood vessels start to get closer to future air sacs.

• Saccular period: Primitive air sacs (saccules) form.

  • Surfactant: A substance made during this stage that reduces surface tension in the lungs, helping to keep the tiny air sacs (alveoli) open and prevent collapse when breathing.

• Alveolar period: Most mature air sacs (alveoli) develop, continuing after birth.

Common Breathing Problems in Newborns

• Respiratory distress syndrome (RDS): Lungs aren't fully developed, often lacking enough surfactant.

• Bronchopulmonary dysplasia (BPD): Chronic lung disease often seen in premature babies who needed breathing support.

Upper Airway Infections in Children

• Viral croup: Causes a barking cough and noisy breathing (stridor).

• Spasmodic croup: Similar to viral croup but often comes on suddenly, usually at night.

• Epiglottitis: A serious infection causing swelling of the flap that covers your windpipe, which can block breathing.

Lower Airway Infections in Children

• Acute bronchiolitis: A common viral infection in infants that causes inflammation in the small airways.

Warning Signs of Breathing Failure in Babies and Children (See Chart 30.1)

• Fast breathing.

• Using extra muscles to breathe (exaggerated use of accessory muscles).

• Retractions (skin sucking in around ribs or sternum with each breath).

• Nasal flaring (nostrils widening with each breath).

• Grunting sound during breathing out.

COVID-19 Infection

Who is Most at Risk?

• The highest risks are for:

  • People over 60 years old.

  • Those with ongoing health conditions (like heart disease, diabetes), obesity, cancer, and weakened immune systems.

  • (See Chart 30.2 for more details).

How COVID-19 Progresses (Pathogenesis)

• COVID-19 typically goes through phases:

  • Incubation phase: Time from infection to symptoms (no symptoms yet).

  • Symptomatic phase: When symptoms like fever, cough, and fatigue appear.

  • Pulmonary phase: Symptoms worsen, often affecting the lungs directly, potentially leading to pneumonia.

What COVID-19 Looks Like (Clinical Manifestations)

• Symptoms vary a lot from person to person.

• (See Table 30.3 for a list of symptoms).

How COVID-19 is Diagnosed

• Based on your patient history (what you tell the doctor) and symptoms.

• Confirmed by lab and imaging tests, such as:

  • CT scans (imaging of the chest).

  • Nucleic acid amplification tests (NAATs): These tests look for the virus's genetic material.

  • Serologic assays: These tests look for antibodies in your blood to see if you've been infected.

• PCR tests (a type of NAAT) are considered the most accurate for diagnosing COVID-19.

How COVID-19 is Managed

• Mild cases:

  • Managed at home with rest, fluids, fever reducers, and isolation.

  • Antiviral medicines might be used.

• Severe cases:

  • Need hospitalization.

  • May involve oxygen therapy, ventilator use (breathing machine), and plasma transfusions.

  • Medications like corticosteroids, IL-6 receptor blockers, and antivirals may be given.

• Prevention/Treatment:

  • Vaccinations are available to lower the severity and spread of the disease.